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Review ArticleA Review of Precast Concrete Beam-to-Column ConnectionsSubjected to Severe Fire Conditions

Noor Azim Mohd Radzi Roszilah Hamid Azrul A Mutalib and A B M Amrul Kaish

Department of Civil Engineering Faculty of Engineering and Built Environment Universiti Kebangsaan Malaysia UKMBangi 43600 Selangor D E Malaysia

Correspondence should be addressed to Roszilah Hamid roszilahukmedumy

Received 27 May 2020 Revised 10 November 2020 Accepted 16 November 2020 Published 30 November 2020

Academic Editor Chiara Bedon

Copyright copy 2020 Noor Azim Mohd Radzi et al (is is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Fire exposure can have a significant impact on the structural integrity and robustness of precast concrete beam-to-columnconnections Given the importance of fire safety in the design of a structure it is critical to understand the damage that may occurin the event of a fire to be able to prevent the building from collapsing No comprehensive study has been carried out to determinethe effects of fire on semirigid and pinned concrete beam-to-column connections Most studies focused on the impact of exposureof rigid concrete beam-to-column connections to high temperatures(is paper is a comprehensive review of the literature on theperformance of precast concrete beam-to-column connections under fire conditions(e key areas in this review are the moment-rotation-temperature characteristics and fire effect on precast concrete beam-to-column connections (is paper focuses pri-marily on the case studies of real fires large-scale fire tests computer simulations and analytical models fire resistance tests on theconnection elements and assessment and rehabilitation of fire-damaged precast concrete (e paper also discusses the currentissues and possible challenges

1 Introduction

(e precast concrete frame structure developed by theconstruction industry has resulted in high production effi-ciency better product quality and low labour intensity[1ndash6] (e mechanisation and standardisation of prefabri-cation methods have made the production of concrete el-ements sustainable [7ndash9] Connections are critical inensuring structural integrity adequate strength energydissipation stiffness and ductility of the designed precastconcrete structures [1 7 10 11] Connections must fulfilvarious design and performance criteria including flexibilityin resisting the ultimate design force production efficiencyand good in-service structural behaviour of the componentsand satisfy the requirements for fire safety and durability andaesthetically pleasing [1 12 13]

Depending on their stiffness precast concrete beam-to-column connections are classified as pinned or rigid connec-tions Connections with low stiffness are classified as pinned

connections and those with high stiffness are fixed connectionsHowever precast concrete beam-to-column connections areoften not fully rigid or perfectly pinned because they exhibitsemirigid behaviour [14 15] (ese connections have an in-termediate stiffness between fully rigid and perfectly pinned andcan partially transmit stress [14 16] Even though they havefinite stiffness and moment resistance these connections areusually weaker than the connected elements [17] Semirigidconnections give more realistic and reliable results and are moreeconomical [18]

(e failure of connections during natural and human-made disasters has an adverse impact on precast structuresPrecast concrete structures have a relatively low integrityand are more vulnerable to progressive collapse than thetraditional cast-in-place concrete structures [9] (e designof precast structures must take into account the occurrenceof a fire as it is one of the accidental actions [11 19]Structural fire design is critical in ensuring the general firesafety of buildings [20] Exposure to fire could considerably

HindawiAdvances in Civil EngineeringVolume 2020 Article ID 8831120 23 pageshttpsdoiorg10115520208831120

reduce the strength and stiffness of a building [21] Severefires in large buildings are rare and unpredictable incidentsbut can cause catastrophic loss of life and property damageand affect the structural integrity and robustness of buildings[20 22] (e construction of safer buildings can reduce therisks of loss of life and property in the event of fire [20]

(ere are reports of actual fire incidents involvingprecast buildings [23ndash26] (e postfire condition of thesebuildings indicates that the structures sustained seriousdamage because of the failure of the beam-column con-nections and collapsed However the reasons for the failureof the precast beam-to-column connections exposed to hightemperatures are not known (e research that comparedthree different methods of precast concrete beam-to-columnconnections (dry semidry and wet) at elevated tempera-tures [3] was not able to determine the mechanical prop-erties of the connections postfire Most research focused onrigid connections under moment-resisting frame systemsparticularly the top reinforcement continuity in a ductileconnection at the support [22 23 27ndash29]

Besides the established impacts of fire on reinforcedconcrete such as explosive spalling cracking reducedcompressive strength of the concrete (fcu) and reduced yieldstrength of the reinforcement (fy) [30ndash32] the postfiremoment-rotation (M-θ) characteristics of semirigid con-nections are not yet understood During a fire the momentcapacity (M) rotational capacity (θ) and rotational stiffness(S) of semirigid connections are adversely affected by thechange in modulus of elasticity (E) andmoment of inertia (I)[33] (e changes are caused by the lower strength of thematerials and the cross section of the structure Also themoment-rotation characteristics are affected by the postfireeffect on the connection elements in precast structures suchas bearing pad grout bolts and welds

Connections must be protected with concrete or groutand enclosed in or sprayed with fire-resistant materialsbecause fire exposure could weaken precast concrete beam-to-column connections Connections must be given thesame protection as the components and frame of a structureStructural engineers are responsible for ensuring thestructural safety of the precast component connection aswell as the compliance of the joint functional requirementssuch as fire safety and thermal insulation [4]

(ere are many questions concerning the exposure ofprecast buildings to fire Some of the questions are thesemirigid behaviour of precast concrete beam-to-columnconnections under severe fire conditions the capability ofconnections under increased rotation and reduced momentcapacity the effect of fire-damaged reinforced concrete onthe strength and stiffness of the semirigid connections andthe moment-rotation-temperature characteristics at elevatedtemperatures

(is article presents a comprehensive review of thebehaviour of precast concrete beam-to-column connectionsunder fire conditions It will also discuss connection per-formance in terms of the moment-rotation-temperaturecharacteristics and the effect of fire on precast concretebeam-to-column connections (e primary focus of thisarticle is the case studies of real fires large-scale fire tests

computer simulations and analytical models fire resistancetests on connection elements and assessment and rehabil-itation of fire-damaged precast concrete Finally this paperexplores the critical issues and challenges faced by theconstruction industry and gives recommendations for futureresearch

2 Moment-Rotation-TemperatureCharacteristics of Precast Concrete Beam-to-Column Connections

(e connection of a precast concrete beam-to-columnconnection is semirigid because of its rotational behaviour atthe joint (e connection rotates when a moment is inducedthrough the application on a load (e rotational charac-teristics of the connections are a moment-rotation rela-tionship (e moment-rotation-temperature relationship ofa connection is established when the connection is exposedto fire In general the full moment-rotation-temperatureconnections in a fire consist of a moment-rotation at am-bient temperature and a rotation-temperature at hightemperatures [34] (e critical properties of a precastconcrete beam-to-column connection are dependent on themoment-rotation characteristics of the connection in-cluding the beam end moment capacity rotational stiffnessrigidity and fixity factor (c) [12]

21 Classification of Semirigid Connection (ere are twoeffective methods for classifying semirigid connections[11 14] Figure 1 [11] shows the beam-line method (emoment-rotation shown in Plot 1 is for a rigid connectionwith complete rotational continuity while Plot 2 shows apinned connection with no moment resistance (e semi-rigid connections in Plots 3 4 and 5 tend to exhibit thebehaviour of a connection in a precast concrete structuredepending on the type of connection(e beamrsquos moment ofresistance (MR) and relative pin-beam end rotation (θR) atthe support is given by

MR wL

2

12(kNm) (1)

θR wL

3

24EI(rad) (2)

where w is uniform distribution load (kNm) L is the spanlength of the beam (m) E is the modulus of elasticity of theconcrete (σε) ((FA)(ΔLL)) (MPa or Nmm2) and Iis the moment of inertia for a rectangle concrete beam

(bh312) (mm4)However the simplified moment-rotation relationship

in Figure 2 was developed for practical applications and toobtain reliable results [14] Mylim is the yielding momentand Mu is the flexural strength moment of the connectionSecant rotational stiffness (Rsec) is used in a linear analysisthat considers the nonlinearity response of the connection inthe moment-rotation curve Secant rotational stiffness is asafe approximation for representing the behaviour of con-nections in a global analysis of structural stability

2 Advances in Civil Engineering

(e second method for classifying semirigid connectionsuses the connection classification system shown in Figure 3[11] (is system consists of five distinct zones Zone I and Vrepresents pinned connections and rigid connections re-spectively Zone II represents semirigid connections withlow strength (014lt cle 040) Zone III represents semirigidconnections with moderate strength (040lt cle 067) andZone IV represents semirigid connections with highstrength (067lt cle 090) (e equation for Monfortonrsquosfixity factor [13] is given by

c 1 +3EI

SEL1113888 1113889

minus 1

(3)

where L is the span length of the beam (m) E is the modulusof elasticity for concrete (σε) ((FA)(ΔLL)) (MPa orNmm2) I is the moment of inertia for rectangle concretebeam (bh312) (mm4) and SE is the rotational stiffness(kNmrad)

Equations (2) and (3) clearly show that the modulus ofelasticity and moment of inertia of a structure are critical in

1

3

4

5

2

MR = 12

M

θ

Failure of connection

Rigid

Pinned

Semirigid

M

M = 0

M

θ

wL2

θR = 24EIwL3

Beam-line

Figure 1 Moment-rotation relationship beam-line method [11]

M

θ (rad)

Secant Moment-rotation curve

Yielding reinforcementSecant rotational stiffness

Ductility factorarctg

Rsec = θy

Mylim

μ = θy

θuθy

θuRsec

Mu

Mylim

Figure 2 Simplified moment-rotation relationship [14]

Advances in Civil Engineering 3

the classification of beam-to-column connection Anychange that reduces the strength of the materials and crosssection of structures affects the moment capacity rotationalcapacity rotational stiffness and fixity factor of semirigidconnections

22 e Moment-Rotation-Temperature Relationship ofSemirigid Connection Refs [34ndash37] described the moment-rotation-temperature relationships for beam-to-column

connections Most of the studies focused on steel structuresHowever the fundamental relationship is also applicable toconcrete structures Observations of fire-damaged structuresand fire tests showed that simple connections could resistsignificant moment even at large deformations (e fol-lowing modified RambergndashOsgood equation [35] was usedto represent the moment-rotation-temperature data ob-tained from experimental fire tests

empty M

A+ 001

M

B1113874 1113875

n

minus for a one minus stagemoment minus rotation curve

empty empty1 +M minus M1( 1113857

A1+ 001

M minus M1( 1113857

B11113890 1113891

n1

minus for a two minus stagemoment minus rotation curve

(4)

where Oslash is the joint rotation (rad) Oslash1 is the rotation atwhich the beam flange comes into contact with the column(rad) M is the moment capacity (kNm) M1 is the momentcapacity corresponding to Oslash1 A and A1 are the stiffness ofthe joints B and B1 are the strength of the joints and n andn1 are the sharpness of the curve

Figure 4 shows the moment-rotation-temperature curvesfor both stages of moment-rotation behaviour [35 36] (efigure shows reduced moment-rotation curves with increasingtemperatures (e parameters representing the jointrsquos stiffnessand strength showed similar characteristics in that the valuesfor both parameters decrease with rising temperatures fol-lowing the strength reduction factors of structural steel pre-sented in the design codes Further test by Rahnavard and(omas [37] on various types of steel connection (boltedendplate bolted cover plate bolted tee and welded cover plate)showed a change in the behaviour of the moment capacity aswell as stiffness as the temperature increased from 20 to 300degC

(e moment-rotation-temperature relationships for aconcrete structure are influenced by the fire effects on thereinforced concrete structure including deflection crackingspalling loss of stiffness and strength and loss of rein-forcement strength Figure 5 shows the types of fire damageobserved in semirigid conditions (e change in the prop-erties of a concrete structure as a result of exposure to hightemperatures affects the moment capacity rotational ca-pacity rotational stiffness and fixity factor of semirigidconnections

Spalling is the breakaway of a layer of concrete from thesurface as a result of the high internal steam pressure fromwater vaporisation [30 38 39] Spalling can be categorised asaggregate spalling explosive spalling surface spalling andcornersloughing-off spalling as shown in S1 S2 and S3Explosive spalling is the most severe form of spalling and ischaracterised by the burst-out of concrete pieces that areaccompanied by a sudden release of energy and loud sounds

Zone I Zone II Zone III Zone IV Zone V

05 EIL 2 EIL 6 EIL 25 EIL

EC3

limit

EC3

limit

00010203040506070809101112131415

Nor

mal

ised

mom

ent o

f rot

atio

n

02 0301 06 0700 04 09 1005 08Fixity factor γ

Mspan

MR 2 + γ3 ndash 15γ=

MEMR 2 + γ

3γ=

θEθR 2 + γ

3γ= 1ndash

Figure 3 Connection classification system [11]


[40] In a standard building fire spalling starts at a tem-perature of between 250 and 420degC depending on theheating rate and concrete properties [41] Prefabricatedconcrete structures constructed using high-strength con-crete (HSC) have a higher risk of severe explosive spallingDespite the high strength and excellent durability of thisconcrete its low permeability proves to be a disadvantage athigh temperatures

(e structural performance of reinforced concretestructures is influenced primarily by spalling which causesloss of material smaller cross-sectional areas (∆d) andexposure of the reinforcing steel to excessive temperaturesas shown in Section 1-1 [30 38 39 41] Researchers haveelucidated the critical role of spalling in reducing the fireresistance of a structure [42 43] (e adverse effect on fireresistance occurs at the beginning of the spalling processwhere the dismantlement of large pieces of concrete from thesurface exposed to fire reduces the thickness of concretecover and cross-sectional area and thus exposes the rein-forcements to fire However the impact on fire resistance isless severe in the late stages of a fire when the spallinggenerally causes the breaking up of thin layers of concreteand minor dislodgement of the surface Minor gradual re-duction of the surface layer may continue after the fire hasstopped burning

(e thermal conductivity of concrete is dependent on thetype of aggregates used in the concrete (e use of cathoderay tube (CRT) waste as aggregates in the production ofconcrete produces concrete with excellent fire resistance attemperatures of up to 600degC [44] Nanosilica is a material

with advanced pozzolanic properties and can act as amicrofiller in cement It can also enhance the hydration ofconcrete material by increasing its pozzolanic activity [45]Innovative fireproof concrete containing high volumes of flyash with colloidal nanosilica (HVFANS) can be used aspassive fire protection in high-risk structures [45 46] (ehigh-strength mortar produced through the incorporationof a high amount of fly ash and colloidal nanosilica andexposure to a temperature of 700degC has a comparable re-sidual strength as the control cement mortar specimensbefore its exposure to high temperatures [47ndash49]

During a fire concrete experiences a permanent loss ofstiffness and strength which is known as thermal damage andthermal decohesion respectively [40] (e chemical com-position and physical structure of a concrete change con-siderably as a result of dehydration and high-temperatureresponse [40] Georgali and Tsakiridis [38] demonstrated thegeneral condition of concrete that have been exposed tovarying temperatures as shown in Figure 6 (e colour of theconcrete remained unchanged when exposed to a tempera-ture of up to 300degC (e colour of the concrete changes fromgrey to pink as the temperature increases(e colour changedfrom pink to red when the temperature is between 300 and600degC to whitish-grey at 600 to 900degC and whitish-grey tobuff at 900 to 1000degC (e pink discolouration is due to thepresence of an iron compound in the fine or coarseaggregates

(e deterioration of mechanical properties in terms ofthe yield strength and modulus of elasticity of steel rein-forcements during a fire is a critical factor affecting the

Extrapolation

20degC

200degC

400degC

500degC

600degC

700degC

0

5

10

15

20

25

30

35

40M

omen

t (kN

m)

20 40 60 80 1000Rotation (milirads)

(a)

0

Curves at 100degC intervals

20degC 100degC

20

40

60

80

100

Mom

ent (

kNm

)20 40 60 80 1000

Rotation (milirads)

(b)

Figure 4 Moment-rotation-temperature curves (a) one-stage and (b) two-stage [35 36]


Symbol Descriptions

S1

S2

S3

C1

C2

C3

Aggregate spalling

Surface spalling

Explosive spalling

Flexural cracking

Interface cracking

Shear cracking

S1S2

S3

C2

C3

Loss of fcu

Loss of fy

Fire exposure

M

θ

P (kN)

∆d

θ

d

b

1-1

1

C1

1

Figure 5 Different forms of fire damage observed in semirigid conditions (concrete nib)


performance of concrete structures (e concrete cracking(flexural interface and shear) as shown in C1 C2 and C3and concrete spalling during a fire exposes the steel rein-forcement to high temperatures (e close distance of theconcrete surface to the steel reinforcement may causedamage or collapse of the concrete structure during a fireSteel reinforcements must be protected from exposure to atemperature greater than 250 to 300degC depending on thetype of reinforcement [20] since steel with low carboncontent exhibits ldquoblue brittlenessrdquo at temperatures between200 and 300degC [50] A review of the literature [3 23 51 52]revealed that steel reinforcements begin to lose yield andultimate strength at 200degC and 300degC respectively Exposureto temperatures higher than 400degC could cause a consid-erable expansion of the reinforcements Exposure to highertemperatures of up to 700degC results in a 20 reduction ofload-bearing capacity At temperatures higher than 800degCthe tensile strength of the reinforcements is significantlylower

(e combination of the above fire damages causes amarked deterioration of the beam-to-column connectionFurther exposure to high temperature weakens both theconcrete and the reinforcement (e tension reinforce-ment tends to slip due to the cracking of top joints (evalues of modulus of elasticity and moment of inertia aremarkedly reduced (e continuous deflection at themidspan of the beam caused a larger rotation whichreduces the moment capacity of the joint (e reducedmoment-rotation curve results in lower rotational stiff-ness and lower fixity factor As a consequence the beam-to-column connection tended to collapse and overturnand failed despondently

3 The Effect of Fire on Precast Concrete Beam-to-Column Connections

Beam-to-column connections are essential part of precastskeletal frames Exposure of beam-to-column connectionsto extreme fires produces a destructive force that can causestructural deterioration Tables 1ndash5 present the findings ofinvestigations on the behaviour of concrete beam-to-col-umn connection exposed to high temperatures (e casestudies comprise a real fire large-scale fire tests computersimulations analytical models fire resistance tests on theconnection elements and assessment and rehabilitation offire-damaged precast concrete (is section will providegreater insight into the effects of fire on precast concretebeam-to-column connections in terms of descriptionsmethods parameters and limitations

31Case Studies of aReal Fire Table 1 lists the case studies ofreal fires of precast structures namely a plant in Turkey [23]a factory in Poland [25] and a production hall in Serbia [26]Even though there are many case studies focused on real fireevents there is no report on the precast structures Most ofthe studies focused on conventional structures that haverigid connections

311 Cotton read Plant Kahramanmaras Turkey [23](e plant was constructed in 1997 using 450mmtimes 450mmprecast concrete columns and 350mmtimes 1270mm L-shapedprecast concrete girders (e precast concrete columns wereconnected with the precast concrete girders using visiblecorbels as shown in Figure 7 (e information on the

Other possible physical effectsTemperature

40degC

300degC

550degC575degC

900degC

800degC

None

Surface crazing

Deep crackingPop outs over chert or quartz aggregate particles

Powdered light colored dehydrated paste

Spalling exposing not more than 25 percent ofreinforcing bar surface

300degC

600degC

950degC

Concrete colour

Buff

Black throughgray to buff

Pink to red

Normal

Figure 6 Visual evidence of the temperature to which concrete has been heated [38]


method used to connect the two components is not available(e concrete is a mixture of riverbed aggregates andPortland cement having a compressive strength of 25MPaAll precast structural members have a 15mm concrete coverAll precast concrete structural members do not have fireprotection (e colour of the deformed concrete samplesindicates that the fire burned for more than two hours andthe temperature is estimated to be around 800 to 900degC

(e methods used in the case study include visual ex-amination and observation tensile test on the reinforce-ment ultrasonic pulse velocity test concrete coring andscanning electron microscope (SEM) (e damage sustainedby the internal column was more severe than that experi-enced by the external column because of the internal walls

between the two columns (e spalling of the concrete coverexposed the transverse reinforcements (e colour of theaggregates changed to pink or red (e yield and rupturestrength of the steel reinforcement were lower than thevalues stated in the standard (e matrix of the concrete andthe binding between the concrete and steel was destroyed

Consequently some of the structural members were notable to carry the applied load and collapsed(e bottom partof the columns and ground floor slab sustained heavydamage where the bottom part of the girders (tension zone)sustained most of the damage (e spalling of concreteexposed the steel reinforcements to high temperatureswhich caused a reduction in the strength and yield of thereinforcements (is resulted in the formation of large

Table 1 Case studies on real fires

Author yearand ref no Descriptions Methods Parameters Limitations Conclusions

Kose et al(2006) [23]

Cotton thread plantKahramanmaras Turkey(2003) containing precastconcrete column and girder

(i) Visualexamination andobservation(ii) Tensile test onreinforcement(iii) Ultrasonictest and concretecoring(iv) Scanningelectronmicroscope

(i) Concretespalling(ii) Aggregatecolour(iii) CaO layer(iv)Reinforcementtensile strength(v) Concretecompressivestrength(vi) Concretecracking

(i) (ermal behaviourof the beam-to-column connection athigh temperature(ii) Level oftemperature duringthe fire(iii) Compressivestrength of heavilydamaged concrete(iv) Rehabilitationsolution

(i) Corbel was used toconnect the column to theprecast concrete girder(ii) Several beam-to-column connections havefailed(iii) Due to concretespalling at hightemperature steelreinforcement lost theirstrength leads to thecollapse of the girder

Wroblewskiet al (2016)[25]

Personal care productfactory Poland (2012)

containing precast columnand precast posttensioned

girder

(i) Visualexamination andobservation(ii) Tensile test onprestressingreinforcement(iii) Scanningelectronmicroscope

(i) Columnverticality(ii) Girderdeflection(iii) Concretecracking(iv)Reinforcementcorrosion(v) Prestressingreinforcementstrength(vi) Concretespalling(vii) Concretemicrostructure

(i) (ermal behaviourof the beam-to-column connection athigh temperature(ii) Rehabilitationsolution

(i) Corbel was used toconnect the column to theprecast concrete girder(ii) Column inclined andcurved due to thermalelongation of the roofgirder(iii) Several beam-to-column connections havetotally failed(iv) High temperaturereduced prestressing forceand increased thedeflection of the girder

Radonjaninet al (2016)[26]

Production hall buildingNovi Sad Serbia (2013)

containing precast concretecolumn and precast beam

(i) Visualinspection onphysical effects(ii) Dimensionmeasurement(iii) Concretecoring(iv) Tensile teston reinforcement(v) Geodeticsurvey

(i) Columnverticality(ii) Concretespalling(iii) Aggregatecolour(iv) Concretecracking(v) Concretecompressivestrength(vi)Reinforcementtensile strength

(i) Constructionmethod of beam-to-column connection(ii) Temperature andduration of the fire

(i) Beam-to-columnconnection exhibited acrumbling of concrete(ii) Precast beam memberwas rotated and tend todecline(iii) Two possiblerehabilitation solutionsinclude removal thedamaged surface andretrofit


cracks at the bottom of the girders and loss of bond betweenthe concrete and the steel (e girders were not able to carrythe applied load and collapsed

312 Personal Care Product Factory Poland [25] (efactory was constructed in 1968 with reinforced concretecolumns (400mmtimes 400mm C16 concrete grade) fixed tothe foundation footings (18mtimes 6m column grid) post-tensioned roof girders (180m span 140m high C30 con-crete grade 1500MPa grade steel four 12 Oslash 5mm tendonsT sections of chords with 200mmtimes 300mm bottom and300mmtimes 200mm top) and reinforced concrete thin-walledribbed roof panels supported on the girders (6m span C20concrete grade 25mm thick 300mm high) as shown inFigure 8 (ere was no fire suppression system in the part ofthe facility where the fire occurred (e information on themethod used to connect both components is not available

(e methods adopted in the report are the same asthose adopted in the study by Ref [23] including visualexamination and observation tensile test on prestressingreinforcement and SEM observation (e damage to the

structure is extensive (e marked reduction of the load-bearing capacity rendered the factory unusable (ecolumns were inclined and curved due to the thermalelongation of roof girders and panels and the horizontalaction of the collapsing roof girders (ere was crackingon the lower surface of the columns (e temperatureincrease and the accelerated relaxation of high-strengthsteel reduced the prestressing force which in turn in-creased the deflection and width of the joints in thebottom chords of the girders (e corrosion of the exposedprestressing reinforcement in the damaged anchoragezones and the open joints reduced the load-bearing ca-pacity of the girders (e completely uncovered anchoragezones of the prestressing steel or the cracked and brokenconcrete cover accelerated the corrosion of the steelelements

(e fire began in the precast concrete frames (com-partments C and E) which collapsed several hours after thefire started even though the fire burned the longest in thesecompartments Although some of the structural damage tocertain parts of the building occurred in the early stages ofthe fire (less than one hour) the concrete frame hall where

Table 2 Large-scale fire tests


Panedpojamanet al (2016) [53]

Precast concrete cantilever beamconnected to precast concretemiddle beam by a welded platejoint with different fire protectionmethods

(i) Load test(ii) Fire test usinggas burner(standard firecurve EN 1991-1-2 or ASTM E119for 120min)

(i) Failurepatterns(ii) Loadresistances(iii) Load-deflectioncurves(iv) Load-rebarstrain curves(v) Load-steelplate straincurves

(i) Postfire effect tothe concretestructure(ii) Internaltemperaturedistribution data(iii) Momentcapacity rotationalcapacity therotational stiffnessand the fixity factor

(i) (e fire resistancedurations were 66 113gt120 andgt 120minfor the specimenswithout fireprotection with thinplaster with thickplaster and withsealant respectively(ii) (e beam enddeflection graduallyincreased with fireduration and increasedsignificantly at failure

Teja et al (2019)[3]

Precast concrete cantilever beamconnected to precast concretecolumn with three differentconnectionsmdashmonolithic hybridand corbel

(i) Load test(ii) Fire test usinggas burner(constanttemperature400degC for 60min)

(i) Load-displacementcurves(ii) First crack(iii) Ultimatecrack(iv) Toughness

(i) Internaltemperaturedistribution data(ii) Exposure tostandard fire curveEN 1991-1-2 orASTM E119(iii) Boundarycondition for topand bottom column(iv) Postfire effect tothe concretestructure(v) Moment-rotation-temperaturecharacteristics therotational stiffnessand the fixity factor

Corbel connectionshowed betterperformance in termsof toughnesscompared tomonolithic and hybridconnection


the fire originated did not collapse until several hours later(e collapse of the central part of the building and thepushing out of the outer parts caused significant damage tothe posttensioned roof girders reinforced concrete slabsand columns (e foundation footings remained intact

313 Production Hall Novi Sad Serbia [26] (e buildingwas constructed using precast concrete columns and precastfaccedilade beams with concrete grade C3545 (e informationon the size of the members and the method used to connectthe members is not available However the figure given bythe researcher shows that the end of the precast faccedilade beamis discontinuous and is seated on top of the precast columnwhich caused the faccedilade beam to rotate and decline Detailedinformation on the fire intensity is not available Figure 9shows the general view of the building after the fire

(e methods used in the report include visual inspectionof the physical effects dimension measurement concretecoring tensile test of the reinforcement and geodetic survey(e major interior parts with installations roof coveringsand facade cladding as well as the complete roof-bearingstructure were destroyed during the fire (e precast col-umns and precast facade beams suffered severe damage Adetailed visual inspection revealed the following defects anddamages (1) insufficient protective concrete layer (2) roughconcrete surface (3) spalled fallen or burnt concreteprotection layer (4) change in the colour of the concretesurface (5) crumbling and burnt concrete protective layerwith the aggregate grains showing a colour change (6)crumbly longitudinal column edges (7) net-like fissures onthe surface of the elements (8) horizontal cracks along thestirrups (9) horizontal cracks due to flexion of the columns(10) vertical cracks and gaps along the column edges (along

Table 3 Computer simulations and analytical model


Reis et al(2009) [54]

Fire damage to precastprestressed concretedouble-tee beam in aparking structure

Analytical model(i) Materials engineeringphase (in-place andlaboratory testing)(ii) Load-testing phase(verify load-carryingcapacity)

(i) Concretespalling(ii) Aggregatecolour(iii) Concretecracking(iv) Pulse velocity(v) Elasticmodulus(vi) Splittingtensile strength(vii) Midspandeflection-loadcurves(viii) Crackingmoment

(ermalbehaviour of thebeam-to-columnconnection at hightemperature

(e analytical modelconfirmed(i) General findings of theevaluation programpertinent to the midspandeflections and the loadtesting(ii) Means of comparing thedeflection response with thetest findings

Pessiki andBayreuther(2013) [55]

Fire damage to precastconcrete double-teebeams pocketedspandrels walls andinverted-tee girders

Computational fluiddynamics program for aseries of vehicle fires andthe resulting fire loads

(i) Maximumcombustion gastemperature(ii) Maximumprestressing steeltemperature(iii) Gastemperature timehistories(iv) Temperaturedistributions


(i) Geometry of structurehave a significant effect onthe movement ofcombustion gases in thestructure(ii) Fires cause greaterincreases in prestressingsteel temperatures andreduced the steel strength


Personal care productfactory Poland (2012)containing precastcolumn and precastposttensioned girder

(i) Fire DynamicsSimulator ver 5 forthermal condition inbuilding(ii) Lusas for thermalcondition in structuralelements and mechanicalanalysis of the entirestructural

(i) (ermalcondition inbuilding(ii) Temperaturedistribution instructuralelements


(i) (e extent of fire in timeand space and thetemperatures reached thestructure resisted the firevery effectively(ii) (e computational fluiddynamics and globalmechanical analyses giveonly a rough estimation ofthe real fire and structurebehaviour due to shortageof precise information andnumerical data on the fire


the main reinforcement) (11) broken spalled and fallenconcrete along the edge of the columns (12) impaired ad-hesion between the concrete and reinforcement (13) ex-posed reinforcement and (14) local mechanical damage ofthe concrete in places where interior elements were fixedTwo possible repair solutions were analysed namely repairof the precast concrete columns and removal of the existingprecast concrete columns and replacing themwith new ones

32 Large-Scale Fire Tests Most large-scale fire tests wereconducted on monolithic concrete beam-to-column con-nection [21 22 28 65ndash67] Only a few investigations werecarried out on precast concrete beam-to-column connec-tions as shown in Table 2 [3 53] However the large-scalefire tests on the monolithic concrete beam-to-columnconnection were beneficial as further references andguidelines Many studies performed large-scale fire tests onsteel and composite structures due to the greater fire risk ofsteel and composite structures(ese studies investigated thedifferent sources of heat including natural fire large-scalefurnace small-scale furnace gas burner and flexible ceramicpad (FCP) [68] Most large-scale fire tests on monolithic

concrete beam-to-column were conducted on cantileverbeam setup with a furnace or gas burner placed at the jointarea [3 22 53 66 67] However in the method adopted byRaouffard and Nishiyama [28] the full-length beam issupported by columns at the ends

Panedpojaman et al [53] conducted a large-scale fire teston precast concrete beam-to-column connection to inves-tigate the moment capacity and fire protection performanceof the welded plate joint for precast members exposed tohigh temperature as shown in Figure 10 In this case asimilar welded connection can be designated to the precastbeam-to-column connection (e researchers investigatedfour types of joints (1) joints without fire protection (2)joints protected with 15mm thick mortar plaster (2) jointsprotected with 40mm thick mortar plaster and (4) jointsprotected with 19mm thick intumescent sealant (especimens were exposed to fire from below for up to120min Due to the limitation of laboratory testing this firewas specified as a parametric fire following the specificationsin EN 1991-1-2 which is a realistic range for office or housefire (is fire curve is slightly less severe than the standardfire curve in EN 1991-1-2 or ASTM E119 (e parametersinvestigated in the test include failure patterns load

Table 4 Fire resistance test on the precast connection elements


Zhang et al(2018) [56]

Tensile behaviour ofhalf-grouted sleeveconnection at elevatedtemperatures

(i) Groutedspecimens andsingle rebarsunder statictension atdifferenttemperatures(ii) Furnace test(iii) Tensile test

(i) Grout compression strength(ii) Grout vertical expansionratio(iii) Failure modes(iv) Ultimate tensile force andyield tensile force(v) Ultimate elongation(vi) Yield elongation(vii) Ductility factor(viii) Elastic modulus

(i) (ermaleffect whenembedded inconcrete withconcrete spalling(ii) Exposure tohighertemperaturegt600degC(iii) Full-scalebeam with half-grouted sleeveconnectionexposed to fire

(i) At normaltemperature halfgrout sleeves exhibitedtwo types offailuremdashrebar fractureand rebar pull-out(ii) At elevatedtemperature thefailure mode andrebar breakpointlocation were changedat 600degC


Mechanical behaviourof postfire half-groutedsleeve connectioncovered by concrete

(i) Single rebargrouted rebarwith cover andgrouted rebarwithout concretecover(ii) Furnace test(iii) Tensile test

(i) (e propertiesmdashstrengthelongation ductility andelastic modulus(ii) (e failuremechanismmdashelongationbonding slip influence ofconcrete cover and bondingbehaviour

(i) Exposure tohighertemperaturegt600degC(ii) Full-scalebeam with half-grouted sleeveconnectionexposed to fire

Postfire tensileproperties of the half-grouted sleeveconnection wereobviously affected bythe peak temperatureand the concrete cover


Fire protection of thewelded platejointmdashwithout any fireprotection withmortar plaster andwith intumescentsealant of 1 cmthickness


(i) Deflection(ii) Failure mode(iii) Plate failure(iv) Spalling(v) Cracking

(i) Postfire effectto the concretestructure(ii) Internaltemperaturedistribution data

(ick plaster was thebest alternative forpreventing jointdamage To reduce thecost flexible sealant isrecommended


Table 5 Assessments and rehabilitations of fire-damaged concrete structure

Stages Methods Descriptions Author Ref

(A) Assessments

Nondestructive andlaboratory and load testing

(i) Ultrasonic pulse velocity and radiographic exposures tolocate tendons(ii) Concrete cores to determine the flexural strength ofconcrete and dynamic Youngrsquos modulus of elasticity and airpermeability index

Dilek and Dileket al [58 59]

Visual inspection (i) Control design of the built-in concrete and reinforcement(ii) Geodetic survey

Radonjaninet al [26]

Visual inspection and on-site material tests Residual strength on damaged concrete and reinforcing Ha et al [60]

Nondestructive testing Residual durability properties of core extraction Aseem et al [61]Methods and materials

(B)Rehabilitations

(i) Variant I (repair of columns)(ii) Variant II (removal of existing and concreting the new columns)


(i) Replacement of slab(ii) Retrofit girders and beam(iii) Surface treatment of columns and walls(iv) Steel beams and deck plates

Ha et al [60]

(i) Carbon fibre-reinforced polymer(ii) Glass fibre-reinforced polymer(iii) Normal strength concrete(iv) Fibre-reinforced concrete(v) Ferrocement(vi) Epoxy resin mortar(vii) High-performance concrete

Zahid et al [62]

(i) Section enlargement method(ii) Steel wrapping strengthening(iii) Externally bonded reinforcement

Zhou andWang [63]

(i) Externally bonded reinforcement(ii) Fibre-reinforced polymers(iii) Bolted side plating(iv) Jacketing with high- and ultra-high-performance concretes or mortars(v) Damaged concrete replacement

Ma et al [64]

Figure 7 General view of the plant after the fire [23]


resistances load-deflection curves load-rebar strain curvesand load-steel plate strain curves

During the fire test the higher deflection at the beam endcaused a separation of the cantilever beam joint and mainbeam (ermal damage and expansion caused the fire-re-sistant plaster to crack and break off (e plate swelled andthe upper edge of the plate split (e mechanical degradationof the plate reduced the moment capacity of the joint(e fireresistance duration of the specimens without fire protectionwith thin plaster with thick plaster and with sealant is 66113 gt120 and gt120min respectively (e fire-resistantsealant has good flexibility and remains intact when exposedto fire which allows it to cover and protect the joint Based onthese findings thick plaster seems to be the best option inpreventing joint damage Nonetheless the application of thickplaster may not be feasible due to its high cost(us the use offlexible sealant as a fire protection material is recommendedfor welded plate joints

Teja et al [3] used the cantilever beam method identicalto that used by Refs [22 67] to investigate the performanceof precast hybrid and corbel connections exposed to high

temperatures shown in Figure 11 (e specimens were ex-posed to a constant fire temperature of 400degC provided by agas burner for 60 minutes(e hybrid connection consists ofa cleat angle with two stiffeners on both edges and a smallstiffener in the middle (e beam reinforcement was linkedto the cleat angle using arc welding in the vertical face andthen cast in a mould Another plate was welded at the centreof the main reinforcement of the column and cast Aftercuring both specimens were joined using a bolted con-nection (e corbel connection was formed by a precastconcrete beam supported on a precast concrete columncorbel (e gaps between the rebar and concrete were filledwith grout A cleat angle with stiffeners on either side wasprovided towards the top of the beam (e cleat angle wassimultaneously anchored vertically into the beam andhorizontally into the column that restrains the upward-lifting of the beam Grout was applied in the vertical in-terface to increase the rotational flexural stiffness andflexural strength capacity of the connections(e parametersinvestigated in the test include load-displacement curve firstcrack ultimate crack and toughness

(a) (b)

Figure 8 Factory condition after the fire (a) inclined and curved columns and deformed roof girders and (b) collapsed roof [25]

(a) (b)

Figure 9 General view of the building after the fire (a) appearance of the objects after the fire and clearing of the ground and (b) beamrotation (tends to decline) [26]


(e result of the fire test showed that the specimen withcorbel connection has the best performance in terms of jointtoughness (e first crack at the ultimate load for corbelconnection (53) is less than those for monolithic (55)and hybrid (58) connections However the displacementat the first crack for corbel (56) is higher than those formonolithic (28) and hybrid (37) connections

33 Computer Simulations and Analytical ModelsComputer simulations and analytical models are used tovalidate experimental findings and improve engineeringrecommendations Many studies have been conducted onsteel beam-to-column connection to determine the mo-ment-rotation-temperature relationships [34ndash37] as de-scribed in Section 2 Among the finite element simulationprograms used to make the simulations are ABAQUSVULCAN ADAPTIC DIANA and ANSYS However nocomprehensive study has been carried out on the precastconcrete beam-to-column connection under high-tem-perature conditions as shown in Table 3 Most studiesfocused on precast prestressed slabs [54 55 69] and firedynamics simulation of precast building [25]

Reis and Mata [54] and Pessiki [55] developed an an-alytical model for fire-damaged double tees in a parkingstructure to evaluate the fire damage sustained by precast

prestressed concrete members of the parking structure (eanalytical model used by Reis and Mata [54] includes thematerials engineering phase (in-place and laboratory test-ing) and load-testing phase (verify load-carrying capacity)(e parameters involved in the analytical model includeconcrete spalling aggregate colour concrete cracking pulsevelocity elastic modulus splitting tensile strength midspandeflection-load curves and cracking moment (e analyticalmodels confirmed the findings of the experimental programon midspan deflection load testing the significant effect ofthe structurersquos geometry and the strength of prestressingsteel

Reference [55] used a computational fluid dynamics(CFD) computer program to perform an analysis Heat fluxhistories were used as the input to determine the temper-ature rise in the prestressing strand of the double-tee floormembers (e increased prestressing steel temperatureswere used to estimate the reductions in steel strength (eparameters in the analytical model are maximum com-bustion gas temperature maximum prestressing steeltemperature gas-temperature time history and temperaturedistribution (e result showed that the geometry of astructure has a significant effect on the movement ofcombustion gases in the structure Fires have significantlyincreased prestressing steel temperature and reduced steelstrength

(a) (b)

Figure 10 (a) Electric welding of a welded plate joint and (b) experimental setup [53]


(e dynamics simulation study of the precast buildingusing the CFD computer program (Fire Dynamics Simulatorver 5) by Ref [25] showed the extent of fire in time andspace and the temperatures reached and that the structurewas able to resist the fire very effectively(e CFD and globalmechanical analyses gave a rough estimation of the real fireand structure behaviour due to the lack of accurate infor-mation and numerical data on the fire

A comparison with previous studies on computersimulations of monolithic concrete beam-to-column con-nection shows that the computer simulations performed byKodur and Shakya [69] on a precast prestressed concretehollow-core slab at a high temperature are congruent withthe predicted temperature and the test data(e hollow-coreslabs were able to resist the fire for 95 minutes because of theinfluence of the load concrete cover thickness and core sizeHowever the failure of a precast prestressed concrete hol-low-core slab in the fire is due primarily to the degradationof moment capacity or increased deflection as well as the

limiting temperature on the unexposed surface (ese pa-rameters are influenced by the temperature rise in the slabsand the corresponding loss of strength and modulus of theprestressing strand

Annerel and Taerwe [29] modelled internal and externalthermal restraints to investigate the behaviour of concretebeam-column connections exposed to ISO 834 fire Resultsshowed that the vertical cracks in the concrete elementcaused by the internal thermal restraint did not extend to thebottom surface of the heated beam External thermal re-straint was observed with the gradual development of plastichinges and increasing shear force that occurred well beforethe fire resistance stated in EN 1992-1-2 is attained (ermaldeformation may cause cracking in the building elementsthat are not directly exposed to the fire Additional rein-forcement concrete cover and insulation can be provided tostrengthen the structure

Kodur and Agrawal [70] assessed the residual capacityof fire exposed reinforced concrete beams (e researchers

Grout

Cleat angle withstiffeners anchored

Corbel rebar

(a)

Cleat angle withstiffeners

Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell

Beam column specimen

Burner

(c)

Figure 11 (a) Corbel connection (b) hybrid connection and (c) experimental setup [3]


examined the material properties of the reinforcing steeland concrete under three conditions (1) structural re-sponse in ambient condition (2) thermomechanical re-sponse during fire exposure and (3) postfire residualresponse after the beams have cooled down(e assessmenttook into account the load level specific fire scenariosboundary conditions and plastic deformation of thebeams In contrast with the simplified cross-sectionalanalysis taking into account the temperature-dependentstrain hardening properties of steel reinforcement and thetension stiffening properties of concrete gives a more re-alistic prediction of the residual capacity Large irrecov-erable plastic deformation may remain in the fire exposedreinforced concrete beams and higher residual deforma-tions reduced the postfire residual capacity of the rein-forced concrete beams (e reinforced concrete beamsanalysed in this study retained about 60 to 70 of theirultimate room temperature capacity for different para-metric fire exposure scenarios with a distinct cooling phase

Eid et al [66] performed a theoretical analysis of thebehaviour of reinforced concrete beam-column connectionsexposed to fire by considering the effect of reinforcementratio the number of stirrups on reinforced concrete con-nection and the duration of the fire (e experimentalprogram also determined the heat distribution in reinforcedconcrete beam-to-column connections by measuring thetemperature at different points In contrast to the experi-mental results finite element analysis is a more efficientmethod for predicting the structural behaviour of reinforcedconcrete beam-to-column connection (e theoretical re-sults are in good agreement with the experimental results

34 Fire Resistance Test on the Precast Connection Elements(e fire resistance of connection elements is a critical factorin the design of precast connections (e connection ele-ments in precast structures comprise bearing pads groutbolts and welds Generally the connection elements transfercompressive stress through direct contact or the insertion ofa material [71] (e direct contact method is rarely used dueto the low-tension strength and fragile behaviour of theconcrete Researchers have investigated the performance ofhalf-grouted sleeve and welded connection at elevatedtemperatures [53 56 57] as shown in Table 4 Howeverthus far no extensive study has been carried out on the firebehaviour of bearing pads bolts and welds [71ndash75]

Half-grouted sleeve connections (HGSC) are often usedto join rebars in precast concrete structures Zhang et al [56]and Zhang et al [57] performed a furnace test and tensile testto investigate the mechanical behaviour of postfire half-grouted sleeve connection covered with concrete at elevatedtemperatures (ey found that the tensile properties of half-grouted sleeve connections are directly affected by tem-perature (e compressive strength of the grouts and thebonding length decreased at 600degC (e half grout sleevesexhibited two types of failure (1) rebar fracture and (2) rebarpull-out due to bonding failure (e failure mode and lo-cation of rebar breakpoint may change at elevatedtemperatures

(e strength of a welded connection is dependent on thequality of metal-to-metal contact Welded connections mustbe protected from fire Panedpojaman et al [53] investigatedthe fire protection of the welded plate joint(e load test andfire test in this research were carried out using a gas burner(standard fire curve EN 1991-1-2 or ASTM E119 for120min)(e researchers found that the flexibility of sealantfire protection makes it suitable for covering and protectingwelded connections Even though thick plaster is the bestmethod for preventing joint damage its utilisation is notcost-effective (erefore the use of flexible sealant is rec-ommended for protecting welded plate joints from fire

Bearing pads are essential in precast concrete connec-tions to provide a uniform distribution of contact stress overthe bearing areas and allow relative movement between theprecast concrete elements to prevent cracking at the con-nection area El Debs et al [71] stated that alternativematerials fabricated using styrene-butadiene latex-modifiedcement mortar polymeric fibres and lightweight aggregate(vermiculite) could be used as bearing pad due to theirexcellent compression strength and low elasticity modulusAccording to El Debs et al [72] the optimum amount offibre should be used to enhance the capacity of the bearingpad to accommodate surface irregularities (e performanceof glass fibres subjected to concentrated load is superior tothat of polyvinyl alcohol fibres Poor positioning of thebearing pad over the reinforced concrete corbel could causepremature failure of the structure [74]

(e advantages of bolt connections are their reliabilityconvenience and rapid assembly Bolt connections are ofteninstalled together with steel plates and rubber layers [75]Guo et al [76] asserted that high-strength bolt connectionsplay a critical role in the initial structure stiffness and haveconsiderable influence on the dynamic response of astructure because it is the primary lateral resistance com-ponent Bolt connections must be perfect for reducingstructural acceleration response According to Zhong et al[75] precast specimens with bolt connections have almostthe same ultimate bearing capacity and failure mode asmonolithic cast-in-place specimens

35 Assessment and Rehabilitation of Fire-Damaged PrecastConcrete Many building structures that have experiencedsevere fire have been repaired and put back into service [20]However postfire structures that are heavily damaged andhave collapsed cannot be put back into service [23] (eirload-bearing capacity has been considerably reducedmaking them unusable A thorough assessment showed thatfire-damaged precast concrete structures could be repairedor strengthened and therefore do not have to be demolishedand reconstructed Researchers have assessed and even re-habilitated fire-damaged precast concretes [26 58 59] (eyfocused on the precast prestressed double-tee concrete of aparking structure and the precast components (beam andcolumn) of a factory building Currently there is no com-prehensive research on the rehabilitation of fire-damagedprecast concrete beam-to-column connections A previousin-depth discussion on this subject focused on the


assessment and rehabilitation of fire-damaged precast andmonolithic concrete structures as shown in Table 5

Investigators have carried out a comprehensive inves-tigation of the fire damage sustained by precast concretebeam-to-column connections and found that unlike theexternal columns the internal columns were severelydamaged [23] Similarly the bottom part of the beams andgirders suffered heavy damage (e concrete layer spalledand exposed the reinforcement to a high temperature[23 26] which caused the reinforcements to lose theirstrength and yield(e colour of concrete changed to pink orred [23 26] Some of the structural members were no longerable to carry the applied load and collapsed [25] (ere arevertical and horizontal cracks on the structures [26]

Dilek [58] and Dilek et al [59] conducted nondestructivetesting (NDT) and load and laboratory testing to assess thefire damage sustained by the precast prestressed concretemembers of a parking structure Ultrasonic pulse velocityand radiographic exposures were used to locate the tendonsbefore removing the cores Concrete cores from the sampleswere examined to determine the flexural strength dynamicYoungrsquos modulus of elasticity and air permeability index ofthe concrete Radonjanin et al [26] performed a visualinspection to assess the fire damage sustained by the precastconcrete of a factory (e researchers also developed acontrol design of the built-in concrete and reinforcementconducted a geodetic survey and made a conclusion on thestate of the structure

As a comparison the assessment of fire-damagedmonolithic concrete was used Ha et al [60] made a visualinspection of the damaged structures and this was followedby a finite element analysis and on-site material tests of theconcrete core cylinders and rebar coupons to determine thedegree of neutralisation in the remaining structure (especimens of damaged concrete and reinforcing bars weretested to determine their residual strengths Aseem et al [61]assessed the residual durability properties of the reinforcedconcrete structural column and shear walls using an NDTand determined their residual mechanical properties usingcore extraction tests (e results of microstructural andthermal analyses were used to develop a framework forestimating the exposure temperatures of the variousstructural units

Radonjanin et al [26] proposed two possible methodsfor rehabilitating fire-damaged precast concretes variant I(repair of columns) and variant II (removal of existingcolumns and concreting new columns) Both methodspredicted that the severely damaged faccedilade beams have to beremoved Ha et al [60] recommended replacing the slabswith new ones and retrofitting the girders and beams (esurface of the columns and walls could be treated and do notrequire structural retrofitting Given the tight constructionschedule and the complexity of the rehabilitation work theresearchers recommended for the steel beams and deckplates to function as temporary slabs during the rehabili-tation period and as permanent supplementary slabs afterthe rehabilitation work is completed

Zahid et al [62] recommended using materials such ascarbon fibre-reinforced polymer glass fibre-reinforced

polymer normal strength concrete fibre-reinforcedconcrete ferrocement epoxy resin mortar and high-performance concrete for repairing a structure (e ma-terial selected for repair work must be compatible with thesubstrate or base material to ensure an effective repairZhou and Wang [63] used section enlargement steelwrapping strengthening and externally bonded rein-forcement methods to repair fire-damaged reinforcedconcrete columns (e section enlargement method wasparticularly effective in improving the structural bearingcapacity stiffness and stability of the compressed mem-bers (e steel jacketing prevented concrete spalling whileincreasing the ultimate load capacity According to Maet al [64] the suitable methods for repairing fire-damagedconcrete structures are externally bonded reinforcementnear surface-mounted fibre-reinforced polymers boltedside plating jacketing with high-performance and ultra-high-performance concretes or mortars and replacementof the damaged concrete

36 Conclusion of the Previous Studies (e following con-clusions are drawn based on the summary of the studiespresented in Tables 1ndash5 In the case study of a real fire theresearchers were unable to determine the thermal behaviourof the beam-to-column connection at high temperatures thetemperature during the fire the residual compressivestrength of heavily damaged concrete and the solution forrehabilitation In the large-scale fire tests the researcherswere unable to determine the postfire effect on the concretestructure the moment-rotation-temperature characteristicsrotational stiffness and fixity factor in the semirigidconnections

Concerning the computer simulations and analyticalmodels the researchers were unable to determine thethermal behaviour of the beam-to-column connection athigh temperatures (e researchers were unable to use theresult of the fire resistance test on the precast connectionelements to explain the thermal effect of HGSC by con-sidering the concrete spalling and exposure to tempera-tures gt600degC (e researchers were also unable todetermine the fire performance of bearing pads and boltsat elevated temperatures Regarding the assessment andrehabilitation of fire-damaged precast concrete nocomprehensive research has been carried out on theprecast concrete beam-to-column connections

4 Issues

41 e Effect of Fire on Semirigid Concrete Beam-to-ColumnConnections Unlike the effect of fire on steel structures thefire effect on semirigid concrete beam-to-column connec-tions has not been extensively explained (ere is an urgentneed to understand the moment-rotation-temperaturecharacteristics of semirigid concrete beam-to-column con-nections at elevated temperatures Currently the focus toensure fire protection of mechanical connection is onlygiven in the design stage However designers are veryconcerned with the thermal behaviour of the semirigid


concrete beam-to-column connections under severe fireconditions(e continuously increasing rotation at the jointdiminishing moment capacity small cross section andmaterial deterioration reduced the capability of connectionsto preserve a structurersquos integrity strength energy dissi-pation stiffness and ductility

As mentioned earlier this review paper is concernedwith whether the effects of fire on rigid connections andsemirigid connections are comparable A rigid connection isa frame system that can resist moment and is constructedusing a monolithic concrete cast in place with the continuityof top reinforcement in a ductile connection at the supportwhereas in semirigid connection joint flexibility is takeninto account (e method for constructing semirigid con-nections is different from that used for rigid connectionsHidden concrete corbels have precast elements such asbearing pads dowel bars and grout between the joints (edry semidry and wet methods can be used to constructsemirigid connections and take into consideration the effectof fire on these elements Two of the most common types ofsemirigid connections (welded plate connection and billetconnection) are constructed using separate elements

Depending on the flexural stiffness of the connection themaximum elastic bending moment of semirigid connectionoccurs at the support or midspan (provided that thesemirigid end connections have the same flexural stiffnesscapacity) between the pinned and rigid support beam andpermits a reduction in the beam material (e optimumconnection allows just enough end rotation to balance be-tween the end moment and midspan moment Exposure tosevere fire will cause changes in the bending momentdiagram

42 e Effect of Fire on Pinned Concrete Beam-to-ColumnConnections (ere is currently no detailed description ofthe effect of fire on pinned concrete beam-to-columnconnections Previous studies focused on the effect of fire onthe bottom surface of precast members such as hollow-coreslab [69 77ndash79] prestressed girder [80] and prestressedbeam [81ndash83] that have simple connections Althoughconcrete exhibits good performance under compression itsperformance under tension is not satisfactory Concretemust be able to resist the tensile stress caused by fire and thebending force from applied loads that can cause crackingand ultimately failure

Determination of the effect of fire on pinned connectionsmust take into consideration two factors the installation of aprecast beam with a pinned joint condition without amoment at the support and the simply supported precastroof beam with no slab Both connections have a smallstiffness that can be classified as pinned However the lit-erature review showed that the interlocking effects of infillgrouting and shear friction could cause the development ofsmall moments of resistance which rapidly disappear duringservice and make the connection ldquopinnedrdquo

(e high temperature during a fire may cause midspandeflection and overturn precast beams as have been ob-served in real fire incidents [23 25 26] (is reaction allows

for rotation at the end of the beam It is critical to understandthe effect of midspan rotation beam overturning and beamend rotation on beam support and precast elements such asbearing pad dowel bar and the grout between the joints(econcrete at the edge of the corbel and the top of the columnmay spall and expose the steel reinforcements to hightemperatures which consequently reduce the strength of thereinforcements and prevent the pinned connection fromtransferring the shear and axial force

43 e Effect of Fire on Precast Connection Classification(e classification of precast beam connections depends onthe value of the beamrsquos moment of resistance and relativepin-beam end rotation in the moment-rotation curve Asevere fire can reduce the material strength and cross sectionof a structure (ese changes affect the values of modulus ofelasticity and moment of inertia of the structure which inturn reduce the moment capacity rotational capacity ro-tational stiffness and fixity factor of semirigid connections

It is possible to reduce the moment-rotation curve fromclose to that in Plot 1 (rigid connection with no rotation) andapproach the curve in Plot 2 (pinned connection with nomoment resistance) (refer to Figure 1) In this case semirigidis an intermediary behaviour between fully rigid and perfectpinned connections that partially transmits the stress andhas a certain degree of rotational stiffness When thishappens the primary concern is the overall structuralbuilding analysis(e connection whether it is designed as arigid semirigid and pinned connection requires a differentshear force and bending moment diagram during thestructural design Structures with insufficient reinforceddesign may fail

44 Fire Test on Semirigid andPinnedConnections (ere is adegree of uncertainty in the fire tests used for semirigid andpinned concrete beam-to-column connections Most large-scale fire tests for monolithic concrete beam-to-columnconnection use a cantilever beam setup and a furnace or gasburner at the joint area (e tests adopted the concept of anideal beam-to-column connection under no lateral ther-mally induced thrust and no moment redistribution influ-ence by removing the midsection of the reinforced concretebeam and turning it into two separate reinforced concretecantilever beams [22] (is raises the question of whethersimilar fire test methods can be used for semirigid andpinned connections

In Figure 1 the moment at the semirigid connection issmaller than the moment at the rigid connection while thepinned connection produces minimal moment resistanceFor this reason the cantilever beam method may besuitable for semirigid connections with a certain degree ofmoment reduction (e simply supported method is moresuitable for pinned connections because of the significantrotation at the beam end Previous studies have used asimilar method on hollow-core slabs [69 77ndash79] pre-stressed girders [80] and prestressed beams [81ndash83] withsimple connections Fire tests must consider the essentialcriteria of the beam-to-column connections including


connection stiffness transfer of force between membersrestoring force characteristics and equivalent or superiorserviceability durability and fire safety

Fire tests on semirigid and pinned connections mustconsider the effect of the reduced scale of specimens Areview of the literature shows that the specimens for rigidconnections are one-half to one-third smaller than theactual structure Also the issues surrounding the testsincluding the different types of precast beam-to-columnconnection (corbel hidden-corbel bolted endplate) effectsof loading (static or cyclic) the inclusion of reinforcementand differences in concrete properties must be taken intoaccount

Another concern with fire tests is the residual strengthmethods used to determine the effect of fire on semirigid andpinned concrete beam-to-column connections Previousstudies applied a static or cyclic load to the beam-to-columnconnection specimens and exposed the specimens to a fire ina large-scale furnace (e custom-made large-scale furnaceused in beam-to-column connection tests is different fromthe standard large-scale furnace and not readily available(us there is a need to develop alternative testing methodsIn the past the residual strength methods were employed toinvestigate the postfire behaviour of concrete at elevatedtemperatures Standard size concrete cube specimens wereprepared and burned in the furnace without a load Simi-larly the specimens for beam-to-column connection wereburned in a normal large-scale furnace and separately testedunder standard static or cyclic loading

45 Rehabilitation of Fire-Damaged Semirigid and PinnedConnections At present there is no in-depth investigationand description of rehabilitation of fire-damaged semirigidand pinned concrete beam-to-column connections In thisregard three critical factors must be taken into consider-ation (1) rehabilitation of fire-damaged precast concretestructure (2) rehabilitation of precast concrete elementsand (3) performance of the postrehabilitated precast con-nection (e fire-damaged precast structure will be repairedstrengthened partially demolished or completely demol-ished and reconstructed

Table 5 presents a summary of the assessment and re-habilitation of fire-damaged concrete structures Moststudies focused on the connections and joints betweenprecast structures(e semirigid and pinned connections areconnected by vertical and horizontal components while theprecast elements are protruding reinforcements bearingpads grouts bolts and welds(emethods for rehabilitatingnormal structures are different from those for rehabilitatingprecast structures

(e precast elements of precast structures damaged in afire must be rehabilitated Engineers must understand thepossible failure modes and the critical aspect of the jointsbecause different materials react differently during a firedepending on the exposure temperature (e rehabilitationof fire-damaged elements has to be done using suitablealternative materials and methods and this includes thedesign installation and monitoring process (e

rehabilitated precast beam-to-column connections must beassessed to determine the performance under static or cyclicloading After completing the rehabilitation process engi-neers must make sure that the load-bearing capacity isadequate for future use

5 Challenges

Precast pinned connections are seldom used in regionswith high seismic activity because they cannot carrylateral and seismic loads in high-rise buildings Howeverthey are often used in low-rise buildings (e continuitybetween the beam and the column in the connection areacan improve the performance behaviour of the pinnedjoint as it acts as a rigid or semirigid connection Pre-viously most fire tests were conducted on rigid concreteconnections under cyclic loading Fire tests and computersimulations of semirigid and pinned precast concreteconnections under cyclic loading are a challenging task asthey have to take into account exposure temperature typeof connection construction method and materialproperties

Design for Deconstruction (DfD) is an increasinglypopular concept in civil engineering because the compo-nents of DfD buildings can be reused as a second life at theend of the service life of the first building Similarly Pre-fabricated Prefinished Volumetric Construction (PPVC) is anew advanced modular construction technology that fa-cilitates higher productivity in the construction industryAlthough the design takes fire protection into account(concrete cover and drywall partition) the effect of fire onthe connection between the beam and the column is stillunknown (ere is a need to perform large-scale fire testsand computer simulations on the actual specimens whichtake into account the event of a fire during installation andservice

(e most recent technologies in beam-to-column con-nection are prefabricated bolted beam-to-column connec-tion steel beam-to-column connection beam-to-columnwelded connection dry-type high-strength bolt connectionand exterior reinforced concrete column and steel con-nection Another type of connection used in the construc-tion industry is the composite connection where the steelbeam is cast with the concrete Tests should be carried out tounderstand the effect of fire on the new connection tech-nologies especially steel structures to ensure that the entirestructure is fire resistant (ese tests should aim to provide abetter understanding of the interaction between the bendingmoment and axial load in the heated internal joint after theloss of the column

With the availability of the different types of beam-to-column connections the design of the systems includingconnections beams and columns should be standardisedto ensure a reliable precast construction system (e use ofstandard components can reduce manufacturing costproduction error or erection error Standardisation canalso reduce inconsistencies and improve quality andmanufacturing efficiency


6 Conclusions

(e global precast concrete market is forecast to grow in thefuture (e precast industry is currently undergoing rapidexpansion because of its high production efficiency betterproduct quality and low labour intensity (e design of astructure must meet the fire safety requirement for precastbuildings to keep pace with the rapid progress Designengineers must consider accidental actions including theeffects of fire Beam-to-column connections are the mostimportant connections in precast skeletal frames Exposureto an extreme fire produces destructive forces within thebeam-to-column connections that cause structural deteri-oration as observed in the recent fire accidents throughoutthe globe (e following conclusions are drawn from thereview of precast concrete beam-to-column connectionsunder fire conditions

(1) Precast concrete beam-to-column connections areclassified (rigid semirigid and pinned) using themoment-rotation relationship beam-line methodand connection classification system

(2) (e moment-rotation-temperature relationships forprecast concrete beam-to-column connection areinfluenced by the effects of fire on the reinforcedconcrete structure including deflection crackingspalling loss of stiffness and strength and rein-forcement strength loss

(3) (e change in the properties of concrete structure asa result of exposure to high temperatures affects themoment capacity rotational capacity rotationalstiffness and fixity factor of the semirigidconnections

(4) (e case studies of fire effect on precast structuresshowed that the beam-to-column connections sus-tained severe damage Some of the main structuralmembers were not able to carry the applied load andcollapsed (eir load-bearing capacity was consid-erably compromised making them unusable (esestudies explored the possibility of rehabilitating thestructures by repairing or demolishing and re-building the main structures

(5) Several studies investigated the effect of fire onprecast concrete beam-to-column connections (edifferent sources of heat used in large-scale fire testsare natural fire large-scale furnace small-scalefurnace gas burner and FCP (e tests were con-ducted on the cantilever and simply supportedbeams Among the investigated parameters are thefirst crack displacement toughness of the joints andfire protection

(6) (e fire resistance of connection elements (bearingpad grout bolt and weld) is a critical parameter inthe design of precast connections (e tensileproperties of half-grouted sleeve connections weredirectly affected by temperature (e quality ofmetal-to-metal contact determines the strength ofthe welded connections Alternative materials

fabricated from styrene-butadiene latex-modifiedcement mortar polymeric fibres and lightweightaggregates (vermiculite) can be used as bearing padsdue to the excellent compression strength and lowelasticity modulus of the materials High-strengthbolt connections play a critical role in the initialstructural stiffness and have a strong influence on thedynamic response of a structure

(7) (e main issues faced by the researchers are the lackof research conducted on the effect of fire onsemirigid and pinned concrete beam-to-columnconnections the effect of fire on the precast con-nection classification the level of uncertainty in firetests and the insufficient understanding of themethod for rehabilitating fire-damaged connections

(8) (e challenges faced by current researchers are theinadequate procedure for performing fire tests andcomputer simulations of semirigid and pinnedprecast concrete connections under cyclic loadingNew fire tests and computer simulations must bedeveloped to complement the concepts of DfD andPPVC (ere is also a need to standardise the designof connection systems to achieve a feasible precastconstruction system

Data Availability

No data were used to support the findings of the study

Conflicts of Interest

(e authors declare that they have no known conflicts offinancial interest or personal relationships that could haveappeared to influence the work reported in this paper

Acknowledgments

(e authors acknowledge the financial support from Uni-versiti Kebangsaan Malaysia through Research UniversityGrant (grant no GUP-2018-027) and laboratory facilitiesprovided by the Department of Civil Engineering Faculty ofEngineering and Built Environment Universiti KebangsaanMalaysia

References

[1] I Holly and I Harvan ldquoConnections in precast concreteelementsrdquo Key Engineering Materials vol 691 pp 376ndash3872016

[2] K W Ding and X Zhang ldquoLiterature review of precastconcrete frame structures in civil engineeringrdquo AdvancedMaterials Research vol 568 pp 3ndash6 2012

[3] C S Teja T S Moturu G Yaswanth Kumar H A KhanG Y Kumar and H A Khan ldquoEffect of fire on prefabricatedconcrete beam column `Connectionsrdquo International Journalof Recent Technology and Engineering vol 8 no 2pp 1433ndash1436 2019

[4] Y Rui ldquo(e review of problems in precast construction ac-tivitiesrdquo Journal of Social Science Research vol 2 pp 173ndash1762018


[5] A B Abd Rahman and W Omar ldquoIssues and challenges inthe implementation of industrialised building systems inMalaysiardquo in Proceedings of the 6th Asia-Pacific StructuralEngineering and Construction Conference (APSEC 2006)pp C-45ndashC-53 Kuala Lumpur Malaysia September 2006

[6] V Turai and A Waghmare ldquoA study of cost comparison ofprecast concrete vs Cast-in-Placerdquo International Journal ofAdvanced Engineering Research Application vol 2 no 2pp 112ndash122 2016

[7] W He Z Yinqi G Weijun and D Student ldquoA review ofprecast concrete building development in different countriesrdquoin Proceedings of 128th e IIER International Conferencepp 8ndash11 Auckland New Zealand October 2017

[8] M P GULHANE and S R S R Bhuskade ldquoReview onanalysis of precast concrete structurerdquo International Journalof Advance Engineering and Research Development vol 4no 04 pp 742ndash747 2017

[9] K Qian S-L Liang F Fu and Q Fang ldquoProgressive collapseresistance of precast concrete beam-column sub-assemblageswith high-performance dry connectionsrdquo EngineeringStructures vol 198 p 109552 2019

[10] H H Ghayeb H Abdul Razak and N H Ramli SulongldquoSeismic performance of innovative hybrid precast reinforcedconcrete beam-to-column connectionsrdquo Engineering Struc-tures vol 202 p 109886 2020

[11] K S Elliott Precast Concrete Structures CRC Press Taylor ampFrancis Group Boca Raton FL USA 2nd edition 2017

[12] Building and Construction Authority (BCA) Connections forAdvanced Precast Concrete System Building and ConstructionAuthority (BCA) Singapore Singapore 2018

[13] R Mokhtar Z Ibrahim M Z Jumaat Z A HamidA Hazim and A Rahim ldquoBehaviour of semi-rigid precastbeam-to-column connection determined using static andreversible load testsrdquo Measurement vol 164 p 108007 2020

[14] M M S Lacerda T J da Silva G M S Alva andM C V de Lima ldquoInfluence of the vertical grouting in theinterface between corbel and beam in beam-to-columnconnections of precast concrete structuresndashan experimentalanalysisrdquo Engineering Structures vol 172 no Maypp 201ndash213 2018

[15] FIB Bulettin 43 Structural Connections for Precast ConcreteBuildings International Federation for Structural ConcreteLausanne Switzerland 2008

[16] T Fatema ldquoStudy on connection between precast concretebeam and cast-in-situ column in prefabricated buildingframesrdquo Journal of Engineering and Applied Sciences vol 1no 1 pp 33ndash38 2006

[17] H Gorgun ldquoSemi-rigid behaviour of connections in precastconcrete structuresrdquo Ph D(esis University of NottinghamNottingham UK 1997

[18] M E Kartal H B Basaǧa A Bayraktar and M MuvafikldquoEffects of semi-rigid connection on structural responsesrdquoElectronic Journal of Structural Engineering vol 10 pp 22ndash352010

[19] S Mohammed and A Inamdar ldquoJoints and Connections inPrecast Concrete Buildingsrdquo International Journal of Scienceand Research (IJSR) vol 7 no 6 p 2017 2019

[20] A H Buchanan and A K Abu Structural Design for FireSafety Excelic Press LLC Lewes DE USA Second edition2017

[21] M M Raouffard and M Nishiyama ldquoResidual load bearingcapacity of reinforced concrete frames after firerdquo Journal ofAdvanced Concrete Technology vol 14 no 10 p 625 2016

[22] MM Raouffard andM Nishiyama ldquoFire response of exteriorreinforced concrete beam-column subassemblagesrdquo FireSafety Journal vol 91 pp 498ndash505 2017

[23] MM Kose H Temiz and H Binici ldquoEffects of fire on precastmembers a case studyrdquo Engineering Failure Analysis vol 13no 8 pp 1191ndash1201 2006

[24] J Gales L A Bisby and M Gillie ldquoUnbonded post tensionedconcrete in fire a review of data from furnace tests and realfiresrdquo Fire Safety Journal vol 46 no 4 p 151 2011

[25] R Wroblewski J Gierczak P Smardz and A Kmita ldquoFireand collapse modelling of a precast concrete hallrdquo Structureand Infrastructure Engineering vol 12 no 6 pp 714ndash7292016

[26] V Radonjanin M Malesev I Lukic S Supic andS Vukoslavcevic ldquo(e assessment and repair of the precastRC structure exposed to firerdquo Istrazivanja I Projektovanja ZaPrivredu vol 14 no 1 p 1 2016

[27] M M Raouffard ldquoStructural behavior of reinforced concreteelements and subassemblies under fire conditionsrdquo Ph D(esis) Kyoto University Kyoto Japan 2018

[28] M M Raouffard and M Nishiyama ldquoFire resistance ofreinforced concrete frames subjected to service load Part 1experimental studyrdquo Journal of Advanced Concrete Technol-ogy vol 13 no 12 pp 554ndash563 2015

[29] E Annerel and L Taerwe ldquoRobustness of a typical beam-column concrete structure exposed to firerdquo IABSE SymposiumReport vol 100 no 4 pp 210ndash216 2013

[30] S Deeny T Stratford R P Dhakal P J Moss andA H Buchanan ldquoSpalling of Concrete Implications forStructural Performance in firerdquo in Futures in Mechanics ofStructures and MaterialsmdashProceedings of the 20th Austral-asian Conference on theMechanics of Structures andMaterialsACMSM20 Toowoomba Queensland December 2008

[31] Z Huang I N W Burgess and R J Plank ldquoBehaviour ofreinforced concrete structures in firerdquo in Proceedings of the4th International Workshop on Structures in Fire p 561Aveiro Portugal January 2006

[32] I B Topccedilu and C Karakurt ldquoProperties of reinforced con-crete steel rebars exposed to high temperaturesrdquo ResearchLetters in Materials Science vol 2008 Article ID 8141374 pages 2008

[33] N Hashim and J Agarwal ldquoRotational stiffness of precastbeam-column connection using finite element methodrdquo IOPConference Series Earth and Environmental Science vol 140p 012128 2018

[34] V-L Tran ldquoMoment-rotation-temperature model of semi-rigid cruciform flush endplate connection in firerdquo Fire SafetyJournal vol 114 p 102992 2020

[35] K S Al-Jabri I W Burgess T Lennon and R J PlankldquoMoment-rotation-temperature curves for semi-rigid jointsrdquoJournal of Constructional Steel Research vol 61 no 3pp 281ndash303 2005

[36] K S Al-Jabri J B Davison and I W Burgess ldquoPerformanceof beam-to-column joints in fire-A reviewrdquo Fire SafetyJournal vol 43 no 1 p 50 2008

[37] R Rahnavard and R J (omas ldquoNumerical evaluation of theeffects of fire on steel connections Part 2 model resultsrdquo CaseStudies in ermal Engineering vol 13 p 100361 2019

[38] B Georgali and P E Tsakiridis ldquoMicrostructure of fire-damaged concrete A case studyrdquo Cement and ConcreteComposites vol 27 no 2 p 255 2005

[39] A M Gil B Fernandes F L Bolina and B F TutikianldquoExperimental analysis of the spalling phenomenon in precastreinforced concrete columns exposed to high temperaturesrdquo


Revista IBRACON de Estruturas e Materiais vol 11 no 4p 856 2018

[40] C Maraveas and A A Vrakas ldquoDesign of concrete tunnellinings for fire safetyrdquo Structural Engineering InternationalJournal of the International Association for Bridge andStructural Engineering (IABSE) vol 24 no 3 pp 319ndash3292014

[41] G A Khoury ldquoEffect of fire on concrete and concretestructuresrdquo Progress in Structural Engineering and Materialsvol 2 no 4 pp 429ndash447 2000

[42] M Hedayati M Sofi P A Mendis and T Ngo ldquoA com-prehensive review of spalling and fire performance of concretemembersrdquo Electronic Journal of Structural Engineeringvol 15 no 1 pp 8ndash34 2015

[43] M B Dwaikat and V K R Kodur ldquoFire induced spalling inhigh strength concrete beamsrdquo Fire Technology vol 46 no 1p 251 2010

[44] N N M Pauzi M Jamil R Hamid A Z Abdin andM F M Zain ldquo(e effects of using cathode ray tube (CRT)glass as coarse aggregates in high-strength concrete subjectedto high temperaturerdquo Journal of Material Cycles and WasteManagement vol 21 no 6 pp 1414ndash1425 2019

[45] F Omar S A Osman and A Mutalib ldquoNano-silica as the gomaterial on heat resistant tunnel liningrdquo IOP ConferenceSeries Materials Science and Engineering vol 342 no 1Article ID 012071 2018

[46] H Alhawat R Hamid S Bahroom and M H Mussa ldquoAreview on large-scale fire testing of concrete tunnel liningrdquoJournal of Engineering and Applied Sciences vol 14 no 9pp 2891ndash2897 2019

[47] R K Ibrahim R Hamid and M R Taha ldquoFire resistance ofhigh-volume fly ash mortars with nanosilica additionrdquoConstruction and Building Materials vol 36 p 779 2012

[48] R K Ibrahim R Hamid and M R Taha ldquoStrength andmicrostructure of mortar containing nanosilica at hightemperaturerdquo ACI Materials Journal vol 111 no 2 2014

[49] M H Mussa A A Mutalib R Hamid and S N RamanldquoDynamic properties of high volume fly ash nanosilica(HVFANS) concrete subjected to combined effect of highstrain rate and temperaturerdquo Latin American Journal of Solidsand Structures vol 15 no 1 2018

[50] S Iffat and B Bose ldquoA review on concrete structures in firerdquoInternational Journal of Civil Environmental StructuralConstruction and Architectural Engineering vol 10 no 22016

[51] I Fletcher S Welch J Torero R Carvel and A UsmanildquoBehaviour of concrete structures in firerdquo ermal Sciencevol 11 no 2 pp 37ndash52 2007

[52] M Ada B Sevim N Yuzer and Y Ayvaz Assessment ofDamages on a RC Building After a Big Fire AdvancedConcrete Construction Inc Sheridan CO USA 2018

[53] P Panedpojaman P Jina and S Limkatanyu ldquoMomentcapacity and fire protection of the welded plate joint forprecast membersrdquo Archives of Civil and Mechanical Engi-neering vol 16 no 4 pp 753ndash766 2016

[54] E M Reis and L A Mata ldquoAn analytical model for estimatingload-test deflections in fire-damaged precast prestressedconcrete membersrdquo PCI Journal vol 54 no 3 pp 129ndash1422009

[55] S Pessiki ldquoAnalytical investigation of vehicle fires in precastconcrete parking structuresrdquo PCI Journal vol 53 no 3pp 111ndash123 2013

[56] W Zhang X Deng J Zhang and W Yi ldquoTensile behavior ofhalf grouted sleeve connection at elevated temperaturesrdquo

Construction and Building Materials vol 176 pp 259ndash2702018

[57] W Zhang C He J Zhang W Yi and X Deng ldquoMechanicalbehavior of post-fire half-grouted sleeve connection coveredby concreterdquo Construction and Building Materials vol 201pp 218ndash231 2019

[58] U Dilek ldquoEvaluation of fire damage to a precast concretestructure nondestructive laboratory and load testingrdquoJournal of Performance of Constructed Facilities vol 19 no 1pp 42ndash48 2005

[59] U Dilek T Caldwell E F Sharpe Jr and M L Leming ldquoFiredamage assessment pre-stressed concrete double-tees atparking deckrdquo in Proceedings of the Congress (ASCE -American Society of Civil Engineers no 919 pp 247ndash258Honolulu HI USA March 2003

[60] T Ha J Ko S Lee S Kim J Jung and D-J Kim ldquoA casestudy on the rehabilitation of a fire-damaged structurerdquoApplied Sciences vol 6 no 5 p 126 2016

[61] A Aseem W Latif Baloch R A Khushnood andA Mushtaq ldquoStructural health assessment of fire damagedbuilding using non-destructive testing and micro-graphicalforensic analysis a case studyrdquo Case Studies in ConstructionMaterials vol 11 Article ID e00258 2019

[62] M M Zahid B A Bakar F Nazri M Ahmad andK Muhamad ldquoReview of repair materials for fire-damagedreinforced concrete structuresrdquo IOP Conference Series Ma-terials Science and Engineering vol 318 Article ID 0120232018

[63] J Zhou and L Wang ldquoRepair of fire-damaged reinforcedconcrete members with axial load a reviewrdquo Sustainability(Switzerland) vol 11 no 4 2019

[64] W Ma C Yin J Zhou and LWang ldquoRepair of fire-damagedreinforced concrete flexural members a reviewrdquo Sustain-ability vol 11 no 19 p 5199 2019

[65] L Bisby J Gales and C Maluk ldquoA contemporary review oflarge-scale non-standard structural fire testingrdquo Fire ScienceReviews vol 2 no 1 p 1 2013

[66] F Eid K Heiza andM Elmahroky ldquoBehavior and analysis ofreinforced self-compacted concrete beam column connectionsubjected to firerdquo American Journal of Science Engineeringand Technology vol 2 no 4 pp 132ndash140 2017

[67] K Heiza M Taha and M Soliman ldquoPerformance of rein-forced concrete beam column connections exposed to fireunder cyclic loadingrdquo e International Conference on Civiland Architecture Engineering vol 11 no 11 p 1 2016

[68] N A M Radzi R Hamid and A A Mutalib ldquoA review ofmethods issues and challenges of small-scale fire testing oftunnel lining concreterdquo Journal of Applied Sciences vol 16no 7 pp 293ndash301 2016

[69] V K R Kodur and A M Shakya ldquoModeling the response ofprecast prestressed concrete hollow-core slabs exposed tofirerdquo PCI Journal vol 59 no 3 pp 78ndash94 2014

[70] V K R Kodur and A Agrawal ldquoAn approach for evaluatingresidual capacity of reinforced concrete beams exposed tofirerdquo Engineering Structures vol 110 pp 293ndash306 2016

[71] M K El Debs A da Silva Ramos Barboza and A M MiottoldquoDevelopment of material to be used for bearing pad inprecast concrete connectionsrdquo Structural Concrete vol 4no 4 pp 185ndash193 2003

[72] M K El Debs L C Montedor and J B de Hanai ldquoCom-pression tests of cement-composite bearing pads for precastconcrete connectionsrdquo Cement and Concrete Compositesvol 28 no 7 pp 621ndash629 2006


[73] D Guan Z Guo C Jiang S Yang and H Yang ldquoExperi-mental evaluation of precast concrete beam-column con-nections with high-strength steel rebarsrdquo KSCE Journal ofCivil Engineering vol 23 no 1 pp 238ndash250 2019

[74] R C Neupane L Eddy and K Nagai ldquoInvestigation onstrengthening approaches adopted for poorly detailed RCcorbelsrdquo Fibers vol 5 no 2 pp 1ndash15 2017

[75] Y Zhong F Xiong J Chen A Deng W Chen and X ZhuldquoExperimental study on a novel dry connection for a precastconcrete beam-to-column jointrdquo Sustainability vol 11no 17 p 4543 2019

[76] W Guo Z Zhai Y Cui Z Yu and X Wu ldquoSeismic per-formance assessment of low-rise precast wall panel structurewith bolt connectionsrdquo Engineering Structures vol 181pp 562ndash578 2019

[77] A M Shakya and V K R Kodur ldquoResponse of precastprestressed concrete hollowcore slabs under fire conditionsrdquoEngineering Structures vol 87 pp 126ndash138 2015

[78] A Van Acker ldquoShear resistance of prestressed hollow corefloors exposed to firerdquo Structural Concrete vol 4 no 2pp 65ndash74 2003

[79] J V Aguado A Espinos A Hospitaler J Ortega andM L Romero ldquoInfluence of reinforcement arrangement inflexural fire behavior of hollow core slabsrdquo Fire Safety Journalvol 53 pp 72ndash84 2012

[80] M Garlock I Paya-Zaforteza V Kodur and L Gu ldquoFirehazard in bridges review assessment and repair strategiesrdquoEngineering Structures vol 35 p 89 2012

[81] N Kalaba P Bamonte and R Felicetti ldquoPrestressed membersunder natural fires a preliminary study on the residual be-haviourrdquo in 2015 Proceedings of the International Conferencepp 15-16 Dubrovnik Croatia October 2015

[82] S Baba S Michikoshi S Sakamoto and T Hirashima ldquoFireperformance of precast prestressed concrete beam withopeningsrdquo in Structures in Fire - Proceedings of the SixthInternational Conference SiFrsquo10 pp 157ndash164 East LansingMI USA June 2010

[83] N M Okasha and S Pessiki ldquoRestraint mechanisms inprecast concrete double-tee floor systems subjected to firerdquoPCI Journal vol 58 no 3 pp 95ndash110 2013


reduce the strength and stiffness of a building [21] Severefires in large buildings are rare and unpredictable incidentsbut can cause catastrophic loss of life and property damageand affect the structural integrity and robustness of buildings[20 22] (e construction of safer buildings can reduce therisks of loss of life and property in the event of fire [20]

(ere are reports of actual fire incidents involvingprecast buildings [23ndash26] (e postfire condition of thesebuildings indicates that the structures sustained seriousdamage because of the failure of the beam-column con-nections and collapsed However the reasons for the failureof the precast beam-to-column connections exposed to hightemperatures are not known (e research that comparedthree different methods of precast concrete beam-to-columnconnections (dry semidry and wet) at elevated tempera-tures [3] was not able to determine the mechanical prop-erties of the connections postfire Most research focused onrigid connections under moment-resisting frame systemsparticularly the top reinforcement continuity in a ductileconnection at the support [22 23 27ndash29]

Besides the established impacts of fire on reinforcedconcrete such as explosive spalling cracking reducedcompressive strength of the concrete (fcu) and reduced yieldstrength of the reinforcement (fy) [30ndash32] the postfiremoment-rotation (M-θ) characteristics of semirigid con-nections are not yet understood During a fire the momentcapacity (M) rotational capacity (θ) and rotational stiffness(S) of semirigid connections are adversely affected by thechange in modulus of elasticity (E) andmoment of inertia (I)[33] (e changes are caused by the lower strength of thematerials and the cross section of the structure Also themoment-rotation characteristics are affected by the postfireeffect on the connection elements in precast structures suchas bearing pad grout bolts and welds

Connections must be protected with concrete or groutand enclosed in or sprayed with fire-resistant materialsbecause fire exposure could weaken precast concrete beam-to-column connections Connections must be given thesame protection as the components and frame of a structureStructural engineers are responsible for ensuring thestructural safety of the precast component connection aswell as the compliance of the joint functional requirementssuch as fire safety and thermal insulation [4]

(ere are many questions concerning the exposure ofprecast buildings to fire Some of the questions are thesemirigid behaviour of precast concrete beam-to-columnconnections under severe fire conditions the capability ofconnections under increased rotation and reduced momentcapacity the effect of fire-damaged reinforced concrete onthe strength and stiffness of the semirigid connections andthe moment-rotation-temperature characteristics at elevatedtemperatures

(is article presents a comprehensive review of thebehaviour of precast concrete beam-to-column connectionsunder fire conditions It will also discuss connection per-formance in terms of the moment-rotation-temperaturecharacteristics and the effect of fire on precast concretebeam-to-column connections (e primary focus of thisarticle is the case studies of real fires large-scale fire tests

computer simulations and analytical models fire resistancetests on connection elements and assessment and rehabil-itation of fire-damaged precast concrete Finally this paperexplores the critical issues and challenges faced by theconstruction industry and gives recommendations for futureresearch

2 Moment-Rotation-TemperatureCharacteristics of Precast Concrete Beam-to-Column Connections

(e connection of a precast concrete beam-to-columnconnection is semirigid because of its rotational behaviour atthe joint (e connection rotates when a moment is inducedthrough the application on a load (e rotational charac-teristics of the connections are a moment-rotation rela-tionship (e moment-rotation-temperature relationship ofa connection is established when the connection is exposedto fire In general the full moment-rotation-temperatureconnections in a fire consist of a moment-rotation at am-bient temperature and a rotation-temperature at hightemperatures [34] (e critical properties of a precastconcrete beam-to-column connection are dependent on themoment-rotation characteristics of the connection in-cluding the beam end moment capacity rotational stiffnessrigidity and fixity factor (c) [12]

21 Classification of Semirigid Connection (ere are twoeffective methods for classifying semirigid connections[11 14] Figure 1 [11] shows the beam-line method (emoment-rotation shown in Plot 1 is for a rigid connectionwith complete rotational continuity while Plot 2 shows apinned connection with no moment resistance (e semi-rigid connections in Plots 3 4 and 5 tend to exhibit thebehaviour of a connection in a precast concrete structuredepending on the type of connection(e beamrsquos moment ofresistance (MR) and relative pin-beam end rotation (θR) atthe support is given by

MR wL

2

12(kNm) (1)

θR wL

3

24EI(rad) (2)

where w is uniform distribution load (kNm) L is the spanlength of the beam (m) E is the modulus of elasticity of theconcrete (σε) ((FA)(ΔLL)) (MPa or Nmm2) and Iis the moment of inertia for a rectangle concrete beam

(bh312) (mm4)However the simplified moment-rotation relationship

in Figure 2 was developed for practical applications and toobtain reliable results [14] Mylim is the yielding momentand Mu is the flexural strength moment of the connectionSecant rotational stiffness (Rsec) is used in a linear analysisthat considers the nonlinearity response of the connection inthe moment-rotation curve Secant rotational stiffness is asafe approximation for representing the behaviour of con-nections in a global analysis of structural stability



c 1 +3EI

SEL1113888 1113889

minus 1

(3)



1

3

4

5

2

MR = 12

M

θ


Rigid

Pinned

Semirigid

M

M = 0

M

θ

wL2

θR = 24EIwL3

Beam-line


M

θ (rad)




Rsec = θy

Mylim

μ = θy

θuθy

θuRsec

Mu

Mylim






empty M

A+ 001

M

B1113874 1113875

n



A1+ 001

M minus M1( 1113857

B11113890 1113891

n1


(4)







EC3

limit

EC3

limit

00010203040506070809101112131415

Nor

mal

ised

mom

ent o

f rot

atio

n

02 0301 06 0700 04 09 1005 08Fixity factor γ

Mspan


MEMR 2 + γ

3γ=

θEθR 2 + γ

3γ= 1ndash









Extrapolation

20degC

200degC

400degC

500degC

600degC

700degC

0

5

10

15

20

25

30

35

40M

omen

t (kN

m)


(a)

0


20degC 100degC

20

40

60

80

100

Mom

ent (

kNm

)20 40 60 80 1000

Rotation (milirads)

(b)



Symbol Descriptions

S1

S2

S3

C1

C2

C3

Aggregate spalling

Surface spalling

Explosive spalling

Flexural cracking

Interface cracking

Shear cracking

S1S2

S3

C2

C3

Loss of fcu

Loss of fy

Fire exposure

M

θ

P (kN)

∆d

θ

d

b

1-1

1

C1

1










40degC

300degC

550degC575degC

900degC

800degC

None

Surface crazing




300degC

600degC

950degC

Concrete colour

Buff


Pink to red

Normal









Kose et al(2006) [23]









girder






































Reis et al(2009) [54]














































(A) Assessments








(B)Rehabilitations




Ha et al [60]


Zahid et al [62]


Zhou andWang [63]


Ma et al [64]







(a) (b)


(a) (b)








(a) (b)








Grout


Corbel rebar

(a)


Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell


Burner

(c)





















4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References



























































































c 1 +3EI

SEL1113888 1113889

minus 1

(3)



1

3

4

5

2

MR = 12

M

θ


Rigid

Pinned

Semirigid

M

M = 0

M

θ

wL2

θR = 24EIwL3

Beam-line


M

θ (rad)




Rsec = θy

Mylim

μ = θy

θuθy

θuRsec

Mu

Mylim






empty M

A+ 001

M

B1113874 1113875

n



A1+ 001

M minus M1( 1113857

B11113890 1113891

n1


(4)







EC3

limit

EC3

limit

00010203040506070809101112131415

Nor

mal

ised

mom

ent o

f rot

atio

n

02 0301 06 0700 04 09 1005 08Fixity factor γ

Mspan


MEMR 2 + γ

3γ=

θEθR 2 + γ

3γ= 1ndash









Extrapolation

20degC

200degC

400degC

500degC

600degC

700degC

0

5

10

15

20

25

30

35

40M

omen

t (kN

m)


(a)

0


20degC 100degC

20

40

60

80

100

Mom

ent (

kNm

)20 40 60 80 1000

Rotation (milirads)

(b)



Symbol Descriptions

S1

S2

S3

C1

C2

C3

Aggregate spalling

Surface spalling

Explosive spalling

Flexural cracking

Interface cracking

Shear cracking

S1S2

S3

C2

C3

Loss of fcu

Loss of fy

Fire exposure

M

θ

P (kN)

∆d

θ

d

b

1-1

1

C1

1










40degC

300degC

550degC575degC

900degC

800degC

None

Surface crazing




300degC

600degC

950degC

Concrete colour

Buff


Pink to red

Normal









Kose et al(2006) [23]









girder






































Reis et al(2009) [54]














































(A) Assessments








(B)Rehabilitations




Ha et al [60]


Zahid et al [62]


Zhou andWang [63]


Ma et al [64]







(a) (b)


(a) (b)








(a) (b)








Grout


Corbel rebar

(a)


Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell


Burner

(c)





















4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References





























































































empty M

A+ 001

M

B1113874 1113875

n



A1+ 001

M minus M1( 1113857

B11113890 1113891

n1


(4)







EC3

limit

EC3

limit

00010203040506070809101112131415

Nor

mal

ised

mom

ent o

f rot

atio

n

02 0301 06 0700 04 09 1005 08Fixity factor γ

Mspan


MEMR 2 + γ

3γ=

θEθR 2 + γ

3γ= 1ndash









Extrapolation

20degC

200degC

400degC

500degC

600degC

700degC

0

5

10

15

20

25

30

35

40M

omen

t (kN

m)


(a)

0


20degC 100degC

20

40

60

80

100

Mom

ent (

kNm

)20 40 60 80 1000

Rotation (milirads)

(b)



Symbol Descriptions

S1

S2

S3

C1

C2

C3

Aggregate spalling

Surface spalling

Explosive spalling

Flexural cracking

Interface cracking

Shear cracking

S1S2

S3

C2

C3

Loss of fcu

Loss of fy

Fire exposure

M

θ

P (kN)

∆d

θ

d

b

1-1

1

C1

1










40degC

300degC

550degC575degC

900degC

800degC

None

Surface crazing




300degC

600degC

950degC

Concrete colour

Buff


Pink to red

Normal









Kose et al(2006) [23]









girder






































Reis et al(2009) [54]














































(A) Assessments








(B)Rehabilitations




Ha et al [60]


Zahid et al [62]


Zhou andWang [63]


Ma et al [64]







(a) (b)


(a) (b)








(a) (b)








Grout


Corbel rebar

(a)


Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell


Burner

(c)





















4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References
































































































Extrapolation

20degC

200degC

400degC

500degC

600degC

700degC

0

5

10

15

20

25

30

35

40M

omen

t (kN

m)


(a)

0


20degC 100degC

20

40

60

80

100

Mom

ent (

kNm

)20 40 60 80 1000

Rotation (milirads)

(b)



Symbol Descriptions

S1

S2

S3

C1

C2

C3

Aggregate spalling

Surface spalling

Explosive spalling

Flexural cracking

Interface cracking

Shear cracking

S1S2

S3

C2

C3

Loss of fcu

Loss of fy

Fire exposure

M

θ

P (kN)

∆d

θ

d

b

1-1

1

C1

1










40degC

300degC

550degC575degC

900degC

800degC

None

Surface crazing




300degC

600degC

950degC

Concrete colour

Buff


Pink to red

Normal









Kose et al(2006) [23]









girder






































Reis et al(2009) [54]














































(A) Assessments








(B)Rehabilitations




Ha et al [60]


Zahid et al [62]


Zhou andWang [63]


Ma et al [64]







(a) (b)


(a) (b)








(a) (b)








Grout


Corbel rebar

(a)


Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell


Burner

(c)





















4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References


























































































Symbol Descriptions

S1

S2

S3

C1

C2

C3

Aggregate spalling

Surface spalling

Explosive spalling

Flexural cracking

Interface cracking

Shear cracking

S1S2

S3

C2

C3

Loss of fcu

Loss of fy

Fire exposure

M

θ

P (kN)

∆d

θ

d

b

1-1

1

C1

1










40degC

300degC

550degC575degC

900degC

800degC

None

Surface crazing




300degC

600degC

950degC

Concrete colour

Buff


Pink to red

Normal









Kose et al(2006) [23]









girder






































Reis et al(2009) [54]














































(A) Assessments








(B)Rehabilitations




Ha et al [60]


Zahid et al [62]


Zhou andWang [63]


Ma et al [64]







(a) (b)


(a) (b)








(a) (b)








Grout


Corbel rebar

(a)


Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell


Burner

(c)





















4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References

































































































40degC

300degC

550degC575degC

900degC

800degC

None

Surface crazing




300degC

600degC

950degC

Concrete colour

Buff


Pink to red

Normal









Kose et al(2006) [23]









girder






































Reis et al(2009) [54]














































(A) Assessments








(B)Rehabilitations




Ha et al [60]


Zahid et al [62]


Zhou andWang [63]


Ma et al [64]







(a) (b)


(a) (b)








(a) (b)








Grout


Corbel rebar

(a)


Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell


Burner

(c)





















4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References
































































































Kose et al(2006) [23]









girder






































Reis et al(2009) [54]














































(A) Assessments








(B)Rehabilitations




Ha et al [60]


Zahid et al [62]


Zhou andWang [63]


Ma et al [64]







(a) (b)


(a) (b)








(a) (b)








Grout


Corbel rebar

(a)


Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell


Burner

(c)





















4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References



















































































































Reis et al(2009) [54]














































(A) Assessments








(B)Rehabilitations




Ha et al [60]


Zahid et al [62]


Zhou andWang [63]


Ma et al [64]







(a) (b)


(a) (b)








(a) (b)








Grout


Corbel rebar

(a)


Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell


Burner

(c)





















4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References





















































































































(A) Assessments








(B)Rehabilitations




Ha et al [60]


Zahid et al [62]


Zhou andWang [63]


Ma et al [64]







(a) (b)


(a) (b)








(a) (b)








Grout


Corbel rebar

(a)


Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell


Burner

(c)





















4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References






























































































(a) (b)


(a) (b)








(a) (b)








Grout


Corbel rebar

(a)


Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell


Burner

(c)





















4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References































































































(a) (b)








Grout


Corbel rebar

(a)


Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell


Burner

(c)





















4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References































































































Grout


Corbel rebar

(a)


Boltsembedded

(b)

Loading frame

Hydraulic jack

Load cell


Burner

(c)





















4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References












































































































4 Issues






















5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References













































































































5 Challenges






6 Conclusions











Data Availability




Acknowledgments


References


























































































6 Conclusions











Data Availability




Acknowledgments


References


























































































AReviewofPrecastConcreteBeam-to-ColumnConnections ... · `neNO `neNOO `neNOOO `neNOY...

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Transcript of AReviewofPrecastConcreteBeam-to-ColumnConnections ... · `neNO `neNOO `neNOOO `neNOY...