jS. Saibabu , V. Srinivas, Saptarshi Sasmal, N. Lakshmanan, Nagesh R. IyerCSIR, Structural Engineering Research Centre, CSIR Camp

cast posegmeunderen is lverall p

aper presents the experimental investigations carried out in laboratory envi-ronment on a scaled model of a simply supported precast post-tensioned box-girder bridge deck that

the superstructure is built in segments. The segments can becast-in situ or precast depending upon the situation. The concep-tion, development, and worldwide acceptance of segmental con-struction in the eld of prestressed concrete segmental bridgesrepresent one of the most interesting, and important achieve-

tal bridges are favourable alternatives for long spans and forconstruction in areas where minimal disruption of the environ-ment is required.

In segmental construction, required quantities of precast units(or segments) are manufactured under controlled factory condi-tions and then transported with conventional carriers to the con-struction site. At the site, the segments are lifted into place onthe superstructure, assembled and then tied together using post-tensioning in the sequential order as designed. The overall stiffnessof the girder becomes less and less by the attachment of number ofsegments continuously [1].

Corresponding author. Tel.: +91 44 22549181; fax: +91 44 22541508.E-mail addresses: ssb@serc.res.in (S. Saibabu), srinivas@serc.res.in (V. Srinivas),

Construction and Building Materials 38 (2013) 931940

Contents lists available at

Construction and B

evsaptarshi@serc.res.in (S. Sasmal).Segmental box girderPrestressScaled modelCyclic loadPerformance evaluationEpoxy joint, Dry jointEpoxy-sand mortar mixBinders and llers

is cast using segmental construction method. Performance of box-girders with dry and epoxy joints isevaluated under static and cyclic loading. It is observed from the results that the exural strength ofdry jointed specimen is less than the epoxy joint due to high concentration of rotation and deectionat individual joints of segmental girder. Upto design load, segmental box girder specimen with dry andepoxy joints behaved like monolithic beam. However, it is found from the study that rst joint openingload of the dry jointed specimen is 27% less than the epoxy jointed specimen due to lack of resistance totension between the joints. Due to high concentration of rotation and deection at individual joints in thedry jointed specimen, the maximum load and failure load are 8.6% and 16.7% less than that of the epoxyjointed specimen. The study will help in understanding the role of type of joint and the material used onthe performance of the segmental bridges.

2012 Elsevier Ltd. All rights reserved.

1. Introduction

Segmental construction for bridges is a concept in which

ments in civil engineering. Segmental bridges are recognized asa solution to many bridge problems with superior durability,low life cycle costs and quality control readily achieved. Segmen-Keywords:need for investigation on tbecomes necessary. This ph i g h l i g h t s

" Investigation on a scaled model of pre" Performance of epoxy and dry jointed" Performance of segmental box girders" Flexural strength of dry jointed specim" Studying the role of type of joint on o

a r t i c l e i n f o

Article history:Received 2 May 2012Received in revised form 30 August 2012Accepted 21 September 2012Available online 3 November 20120950-0618/$ - see front matter 2012 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.conbuildmat.2012.09.068us, Taramani, Chennai 600 013, India

st-tensioned box-girder bridge deck.ntal box girder under monotonic loading.cyclic loading.ess than the epoxy segmental girder.erformance of the segmental girder.

a b s t r a c t

A large number of post-tensioned prestressed concrete segmental bridges are being constructed world-wide. Use of different materials and shear keys will have varying effects on the performance of segmentalgirders even during the service load. The type of joints, quality of joint, degree of mechanical actions andthe joint materials will contribute to the variation in the behaviour of the segmental girders. Hence, the

he epoxy jointed segmental box girder and dry jointed segmental box girdergirders under monotonic and cyclic loading

Performance evaluation of dry and epoxy

journal homepage: www.elsll rights reserved.ointed segmental prestressed box

SciVerse ScienceDirect

uilding Materials

ier .com/locate /conbui ldmat

were started in the seventies. Limited numbers of investigations

of the same conguration. Very often, joints are lled with materi-

Builals like epoxy, cement mortar, etc. Joints can be of various typessuch as cast-in-place, dry packed, grouted or match cast [9,10].

Construction of precast segmental girders with dry joints iscommon and popular due to its simplicity in construction. Since,there is no bonding agent to provide structural continuity; no ten-sile stress can be transferred across the joint. Therefore, segmentsare directly contacted without any ller maternal. Flexural designof dry jointed segmental girder is based on serviceability criteriaand it is made sure that concrete at the bottom most bre of thebridge is always under compression. All joints in the girders are de-signed for shear loads as that is followed for any section in mono-lithic constructions. Shear keys and its friction between the jointsurfaces provides resistance to the applied shear load. Thoughthe performance of the dry joints in segmental construction ishighly inuenced by environmental factors, dry joints are stillopted in many occasions because the technique does not needthe usage of epoxy and temporary prestress; moreover it reducesthe time and cost of the construction as well. On the other hand,though cost intensive, epoxy jointed bridge girders are preferredin many occasions due to its better structural conguration, dura-bility and performance point of view.

2.1. Epoxy jointed segmental box girder (EJSBG)were carried out for understanding of the structural behaviour ofsegmental girder, especially under cracking and under ultimateload conditions [27]. Segmental girders are generally more sus-ceptible to cyclic load. These repetitive loads increases stresses insteel and concrete which can create fatigue damage in the respec-tive materials, reduce bond strength between joints, and lead tosubstantial increase in crack widths and deections [8].

The segmental joints can be constructed and erected either byusing an epoxy layer between the segments or in a dry condition.Segmental concrete bridges with external prestressing and dryjoints are associated with a span-by-span construction process thatis thought to be the fastest of its type. Generally, it is not essentialto apply any epoxy resin between the joint faces of the segments,but in many cases it is adopted so. It is precisely the subject matterof the present work to study the performance of externally pre-stressed segmental bridges with epoxy resin joints and with re-sin-free dry joints subjected to static and cyclic loading. In thepresent study, experimental investigations were carried out forthe purpose to provide a better understanding on the behaviourof dry and epoxy joints in segmentally constructed precast post-tensioned bridge girders.

2. Overview on segmental bridge construction

In segmental bridge construction, the overall behaviour is dif-ferent from that of monolithically constructed bridges specicallywith respect to deformation aspects both in the pre-cracking andin the post-cracking phase. Behaviour of segmentally erected boxgirders is more complicated than that of monolithically con-structed girders because of preformed cracks at the joints for thefull cross section starting from the zero load stage. This becomesfurther complicated in the post cracking stage due to concentrationof cracks at the segmental joints and nonlinear behaviour of con-crete and steel at higher level of stresses. Segmental girder withmultiple shear keys and adequate prestress across the joint willclosely reproduce the behaviour of the monolithic concrete sectionStudies on the post-cracking behaviour of box-girder bridges

932 S. Saibabu et al. / Construction andIn EJSBG, epoxy resin is used for joining the precast segments.Thickness of epoxy joint varies from 1.0 mm to 3.0 mm. In the li-quid state, the epoxy acts simultaneously as a lubricant, whichfacilitates easy joining the segments. In the cured state, the epoxyfunctions as a sealer to protect the post-tensioning tendons, andtransmits shear forces. The adhesive strength of the epoxy can beassumed to be greater than the ultimate strength of the concrete.

Based on the experimental investigations on segmental con-crete girders with bonded tendon as reported by Rabbat andSowlat [11], it was observed that the girders failed in a exuralmode under cyclic load where simultaneously concrete crushedin the compression zone and strands fractured in the tensile zone.Buyukozturk and Bakhoum [12] carried out tests to assess theshear strength and deformation behaviour of precast segmentalbridge joints which includes at and keyed joints, without epoxywith the required level of prestressing, and with the epoxy. Itwas found that the strength of joints with epoxy is consistentlyhigher than that of dry joints and the failure of the joints withepoxy was found to be very sudden and brittle. Zhou et al. [13]studied the shear capacity of segmental joints which are at, singleand multiple-keyed, with and without epoxy. It was observed thatthe stress level increases as conning pressure is increased andshear strength of epoxy joint is consistently higher than dry joints.Failure in the joint with epoxy was more brittle than dry joints. Theaverage shear strength for a key in multiple-keyed dry joints wasalways found to be less than those in single-keyed dry joints dueto imperfections in tting of keys. Issa and Abdalla [14] examinedthe shear capacity of epoxy-jointed single keys using cold-weatherand hot-weather epoxy types. It was observed that the failuremode of all shear-key specimens is fracture of concrete along thejoint with shearing of the key. The hot-weather epoxy specimensshowed better shear capacity in comparison to the cold-weatherepoxy specimens. It was also concluded that implementing AASH-TO procedures result in conservative estimates of the shearstrength of the single keyed joint since it neglects the contributionof the epoxy and underestimates the strength of the key itself.Megally et al. [15,16] conducted large-scale experimental investi-gations to study the seismic performance of joints of segmentalbridge superstructures. It was observed that opening of an epoxybonded joint occurs due to cracking of the concrete cover adjacentto the joint rather than opening of the epoxy joint.

2.2. Dry jointed segmental box girder (DJSBG)

Hewson [17] outlined the design and construction aspects asso-ciated with dry-jointed bridge decks including the advantages anddisadvantages encountered in the construction. The exural andshear strength of dry joint was observed to be less than the epoxyjoint due to high concentration of rotation and deection at indi-vidual joints of segmental girder. Takebayashi et al. [18] conducteda full-scale destructive test of a precast segmental box girderbridge to investigate the behaviour of precast segmental box girderbridges with dry joints and external tendons. Turmo et al. [19]studied the behaviour of segmental bridges with dry joints of con-crete panels with and without steel bres under shear, at serviceand ultimate limit states with different levels of prestressing. Thetests showed that, even though all the keys of the panel are pro-fusely cracked, the joint was still capable of transmitting load. Also,from tests on the panels, it was concluded that the use of steel brereinforced concrete (SFRC) does not increase the shear capacity ofthe panel joints. Algora et al. [20] presented an experimentalinvestigation of the structural behaviour of dry jointed externallyprestressed segmental bridge beams under combined stresses, i.e.bending, shear and torsional stresses. From the experimentalinvestigations, it was found that the presence of torsion in beams

ding Materials 38 (2013) 931940reduces the vertical load and vertical deection at the onset of non-linearity, failure load and further, it would alter the failure mecha-nism. Nonlinear nite element analysis with joints having multiple

shear keys, different geometries and material properties were con-ducted by Romback [21], Romback and Abendeh [22] to proposemore realistic design models for the joints.

It was observed from the earlier studies that the use of differentmaterials and keys will have varying effects on the behaviour ofsegmental girders even during the service load. The type of jointsand the joint materials will contribute to the variation in thebehaviour of the segmental girders. However, investigation onthe performance evaluation of the segmental box girder bridgesusing epoxy- and dry-jointed segmental box girder subjected tocyclic loading is very limited and discrete. Further, the discussionon important structural behaviour parameters such as strengthand stiffness degradation, stress development in tendon and crush-ing and cracking strain in critical regions under different displace-ment limits are extremely limited. In view of this, experimentalinvestigations on performance evaluation of joints in a scaled mod-el of segmentally constructed prestressed box girder bridge hasbeen carried out in the present study. Both the types of joint asmentioned above are studied in detail under monotonic and cyclicloading. Details of test specimens, instrumentation setup and testprocedure are described followed by the responses such as deec-

A typical segmental prototype bridge superstructure of 30 m span is designed

box girder and dry jointed segmental box girder. In the scaled bridge, six segments

3.1.1. General dimensions and characteristicsThe test specimens have an overall dimension of 5000 mm length and 500 mm

depth. Geometric details of segments of test specimen and shear key details areshown Fig. 2. It consists of 4 numbers of 750 mm long by 500 mm deep precastbox mid segments (S2, S3, S4, and S5) with two end segments of 1000 mm length(S1, and S6). The end segments consist of a solid portion of 500 mm and box portionof 500 mm length. The thickness of top ange, bottom ange and the web is 75 mm.The top and bottom width of each segment is 1080 mm and 600 mm, respectively.The box segment consists of inclined webs with two trapezoidal shape shear keysin each web Fig. 2b. The depth and width of each key is 100 mm and 50 mm respec-tively. The mid-block segments are designed for self weight and impact loads thatmay developed during shifting from site to laboratory. The reinforcement detailsare shown in Fig. 3. PVC pipe of 40 mm diameter was kept at 140 mm from bottomand at centre of end block for inserting post-tensioning bar.

3.1.2. Materials composition and propertiesThe properties of constituent materials were characterized and the mix propor-

tion of 1:1.38:2.74 (cement: ne aggregate: coarse aggregate) with water/cementratio of 0.45 for M45 grade concrete was arrived after trial mixes. The average com-pressive strength value of the trial mix is 36.92 MPa and 50.4 MPa after 7 days and28 days respectively. Similarly, average split tensile strength of 100 mm diameterand 200 mm height cylinders after 7 days and 28 days is 2.37 MPa and 4.18 MParespectively.

3.1.3. Specimen construction

ts o

000

100vat

000

10800

e

sec

S. Saibabu et al. / Construction and Building Materials 38 (2013) 931940 933were joined together by using a straight prestress tendon. The details of the speci-men and the material properties are discussed in the following sections.

Precast Segmen 1.6 m lengthExternal Tendons

10500 10

3Ele

250 thick flange

6

250 thick flang

crosswith box shape segments using external tendons as shown in Fig. 1. The tendonsare trapezoidal proled with 10 m of straight tendon length at centre of span. Itwas designed for span by span construction method. The critical location of the pro-totype structure for positive bending under dead loads and live loads is found to beapproximately at mid span. The test specimen for the present experimental inves-tigation is a scaled model of the central middle third of prototype span in which thetendons are horizontal. The scaling of the model is done in such a way that the con-crete stresses of the model are nearly equal to the stresses of prototype structure attransfer and at service stage.

3.1. Details of test specimen

Two test specimens have been prepared, one each for epoxy jointed segmentaltion, strain, strength, and energy dissipation. under monotonic andcyclic loading.

3. Experimental investigation on scaled model of a precast post-tensionedsegmental bridge deckFig. 1. Geometric details of prototype girdThe segments were cast with match casting method. For EJSBG, a layer ofepoxy-sand mortar mix, about 23 mm thick, was applied on the mating surfacessegment. The epoxy mortar consisting of binder and ller is used to join the seg-ments. The binder had Araldite GY257 and Aradur 140 at ratio of 1:0.5. Quartz sandwas used as ller. The epoxy mortar had a binder-to-ller ratio of 1:2.5. It has spe-cic gravity of 2.0. Compressive strength of the epoxy mortar varies from 80 to100 MPa. Temporary external compression of about 0.28 MPa was applied thoughtwo jacks operating simultaneously on the web of segment until mortar oozedout along the perimeter. The compressive force was kept for 24 h for curing ofepoxy. This process was followed up to assembling of the segment. In the DJSBG,the segments are dry jointed by pushing the segments with hydraulic jack simulta-neously until the gap closed between the segments.

After assembling all the segments in order, designed prestressing force of780 kN was applied with central hole prestressing jack to a single high strengthsteel rod of 36 mm diameter which is inserted through the hole provided in the seg-ments at constant eccentricity of 140 mm as shown in Fig. 4. Stresses developed attop and bottom of box girder after transfer of prestress is observed to be 0.96 MPaand 9.18 MPa respectively.

3.2. Instrumentation setup

The girder was placed in simply supported condition where roller support atone end and hinge support at other ends were used and the loading was arrangedfor four-point bending condition as shown in Fig. 5. MTS actuator of 500 kN capacitywas xed on a reaction frame of 2000 kN capacity which was anchored to the strong

fTest Zone

10500

0ion

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350 thickweb

tion

er. Note: All dimensions are in mm.

S3S2

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Hinge

DistributionBeam

Test Floor

Pedestal

Test specimen(Semental box girder)

Actuato

J1 J2

934 S. Saibabu et al. / Construction and Buil45test oor. To measure concrete deformation at maximum bending moment loca-tion, LVDTs were placed horizontally at the top of joints. To measure crack width

5000Dial gaugeLVDTAll dimensions are in mm

(a) Elevation of t

75

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Cross section of segment

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Fig. 2. Details of the scaled mod

600

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{a} 6mm dia @ 65mm c/c

{b} 6mm dia @ 74mm c/c

(c} 6mm dia @ 130 mm c/c

{d} 6mm dia @ 90 mm c/c

Fig. 3. Reinforcement details of mid segment.S6S5S4

1000750

140C

r

Prestresstedon

LJ3 J4 J5

ding Materials 38 (2013) 931940or joint opening at bottom of joints, LVDTs were placed horizontally at the bottomof joints. Deections were monitored with dial gauges of 50 mm measuring capac-ity under the loading points and at mid span. The distance between the loadingpoints is 2250 mm. To measure vertical slip of the segmental joint in the shear zone,two dial gauges were placed on either of side of the joint. The least count of the dialgauges is 0.01 mm. The instrumentation details can be seen in Fig. 2a.

3.3. Static and cyclic load test

The purpose of the static load test is to study the elastic behaviour of the spec-imen up to service load before starting the cyclic load test. Loading was applied bythe actuator at the centre of distributor beam. The applied load is gradually in-creased up to rst cracking load at an increment of 22.5 kN. Both deections andstrains are measured during the static test.

Segmental girders are generally susceptible to cyclic load due to trafc. Thisrepetitive loading and unloading causes changes in stresses and creates fatiguedamage in the steel and concrete materials; reduces bond properties at the inter-face between joints, and lead to substantial increase in crack widths and deec-tions. Segmental girders subjected to cyclic loading may suffer from excessive

est set up

PVC duct of 50mm dia

125

500 250 250

75

75

50

Elevation of end segment

425

75

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50

50 60

2550255025502560

Elevation of shear keys

of a segments

el of segmental box girder.

cracking and deections. Experimental investigations on the behaviour of segmen-tal girders subjected to repeated loading have shown that the deection and crackwidth of segmental concrete girders increase with the number of load repetitions.The cyclic loading is applied in deection control actuator at the rate of 1 mm perminute. The upper and lower limits were kept constant during each cyclic loading.The deection limits are chosen to produce tensiontension cyclic stresses in theunbonded strand at the tension zone and compressioncompression repetitivestresses in the concrete at the compressive zone. One set of loading and unloadingis dened as one cycle. The specimens are subjected to cyclic load after the appli-cation of static loading up to rst cracking stage. A set of four loading cycles areconducted at each deection increment of 4.0 mm, until specimen reached to thefailure state. Applied load corresponding to each induced deection is measured.

4. Observations on the response of EJSBG and DJSBG

The responses are measured during static and cyclic loading for

4.2. Response under cyclic loading

Crack opening at different deection levels are shown for EJSBGin Fig. 8a and b. Fig. 9a shows the loaddeection hysteresis at midspan. From the gure, a drastic loss of stiffness can be found be-

S. Saibabu et al. / Construction and Building Materials 38 (2013) 931940 935the deections at mid and one-fourth spans as well as strains at thetop and bottom of girder at each joint. The observed responses arediscussed below.

4.1. Response under static loading

For EJSBG, rst crack is noticed at a load of 405 kN, in the exurezone at bottom of joints J2 and J4. The cracks are developed due toexceeding of the exural tensile strength of specimen compared tothe tensile strength of epoxy mortar after decompressed. Openingof the joints occurred in the concrete adjacent to the epoxy layerbetween the bonded precast segments, rather than in the epoxylayer itself. The measured crack width at rst crack location is0.001 mm. No cracks are observed at other places of test specimen.The measured deection was recovered fully after unloading. Thecracks are completely closed after unloading. No residual deec-tion and strains are recorded which shows that the specimen isin the elastic stress range. Based on the elastic theory, deectionof 4 mm is computed under the load of 405 kN which is well cor-roborated with the results obtained from the experiment (asshown in Fig. 6). Loaddeection curve at mid-span is linear withincreasing applied load up to the designed load of 360 kN. Mea-sured deection at different span lengths is shown in Fig. 7a. It isclear from the gure that under higher deection, local deforma-tion (in central segment) has also taken place which cannot be seenin lower deection magnitudes.

Static load test on the DJSBG is conducted similar to that usedfor the EJSBG. No sign of distress is observed in the test specimenup to the service load of 286.5 kN. First joint opening had occurredat bottom of J2 in constant bending zone at 296 kN load and it isclosed after unloading. The calculated rst cracking load is in goodagreement with the experimental value (as shown in Fig. 6). Themeasured deection is fully recovered and cracks are completelyclosed after unloading. No cracks are observed at other places oftest specimen. Fig. 7b shows the deection prole of dry jointedFig. 4. Application of external prestress (a) through centraspecimen under static load. The gure depicts that unlike the spec-imen with epoxy joint, under various deection magnitudes,deection prole is nonuniform and this observation is more pre-dominant in central segment. Further, it is also found that dryjointed specimen shows un-symmetric deection prole whereasthe epoxy jointed specimen provides a smooth and uniform deec-tion prole till failure. Deections envelop of epoxy and dry jointedspecimens under static load test is compared in Fig. 7c. It is worthmentioning that, both at quarter and mid span, deection under agiven load level is always more in dry jointed specimen than thatobserved in epoxy jointed specimen. As stated earlier, variationof deection at two quarter spans is considerably less in case ofepoxy jointed specimen. From Fig. 7c, it is evident that rate of stiff-ness degradation with damage (in form of cracks or opening up ofjoints) is much faster than that noted in epoxy jointed specimen.Further, from the response of the specimens under static load, itis to note that (i) up to design load, segmental box girder specimenwith dry and epoxy joints behaved like monolithic beam, and (ii)rst joint opening load of the dry jointed specimen is 27% less thanthat of the epoxy jointed specimen due to lack of resistance to ten-sion between the joints.Fig. 5. Experimental test setup.l hole jack and (b) measurement of external prestress.

yond the displacement level of 10 mm. The cyclic deection pro-les on EJSBG are shown in Fig. 9b. It is clear that after the crackopening at the joints, nonlinearity in the deection response is dis-tinct. Joint opening at joint J2 at 12 mm deection and the joint atfailure load for DJSBG is shown in Fig. 10a and b respectively. Rela-tion between the applied loads to each cyclic deection at midspan of DJSBG is shown in Fig. 11a. It is important to note thatthe stiffness degradation due to cyclic load is much more than thatobserved from EJSBG. However, stiffness of the structure at lowerdeection range is more than EJSBG as evident from the initial stiff

nature of loaddeection behaviour. Deection envelop of DJSBGunder cyclic loading is shown in Fig. 11b. It is important to notethat the EJSBG is susceptible to nonlinear behaviour under higherdeection level but concentrated to a local region at middle ofthe span whereas the deection prole of DJSBG shows that thenonlinearity is not conned to middle zone, rather it is uniformlydistributed. Comparison of loaddeection behaviour of dry- andepoxy-jointed specimens at maximum displacement level for eachload cycle is presented in Fig. 12. It can be stated that the load car-rying capacity under different levels of deection is less in DJSBGas that been found from EJSBG. It can also been inferred that theductility offered by the whole system (area under the curve) is con-siderably more in case of EJSBG than that obtained from DJSBG. En-ergy dissipation (as shown in Fig. 13a) and strength envelop (asshown in Fig. 13b) of the box girder with epoxy and dry joint arealso studied. Energy dissipation capacity of the specimens are cal-culated by integrating the entire area in the loaddisplacementcurve for each displacement cycle. Applied load from the actuatorrequired to produce the deection in each cycle is assigned as thestrength of the specimen. Though, after a large deection, both thejoints showed (Fig. 13a) the similar magnitude of energy dissipa-tion, at the initial level (up to a deection level of 25 mm) dryjointed specimen showed considerably more energy dissipationin comparison to that obtained from the epoxy jointed bridge.The study on energy dissipation versus deection would providethe information on the resilience of the structure. It is evident thata structure with high energy dissipation capacity would indirectlyreect the inherent ductility in the structural system. Further, thestrength degradation rate (calculated as the reduction in strengthin two consecutive cycles) with higher magnitude of deection is

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936 S. Saibabu et al. / Construction and Building Materials 38 (2013) 9319400

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(c) Comparison oFig. 7. Deection behaviour of epoxy and dry jointed specimens under static load test. [N22.5 in 1.]0

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ote: Marks on deection proles are in 22.5 kN increment in each step starting with

BuildS. Saibabu et al. / Construction andobserved to be higher in dry jointed specimen. It is found that (asshown in Fig. 13a and b), both the joints perform almost similarunder higher displacement demand (with opening in joints)whereas in lower levels of displacement, dry jointed girder showeda considerable increase in energy dissipation compared to epoxyjointed girder. Since, the dry joint is prone to open even at mediumdisplacement levels, it provides more energy release due to rota-tion. Further, strength envelop shows that epoxy jointed bridgeprovides more strength than the dry jointed bridge under any levelof displacement. It is easy to understand that the epoxy does alsoprovide extra bonding strength to the segments. But, the present

(a) At J3 at 18mm deflectionFig. 8. Crack open

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Fig. 9. Performance of EJSBG under deection. [Note: Marks on deection prolesare in 4 mm increment in each step starting with 4 mm in 1.]study underscores that the magnitude of improvement due toepoxy jointed segments is not considerable.

4.2.1. Stress, strain and crack width under cyclic loadDevelopment of tendon stress under different deection level is

shown in Fig. 14a. The stress in the bar is increased by 16.62% fromthe initial stress due to increase in deection up to 12 mm. It isimportant to note that with further increase in deection (from12 mm to 47 mm), stress in tendon is increased by only 7% whichclearly depicts that the structural integrity (load transfer mecha-nism between tendon and concrete) is deteriorated. The stress inthe bar increases due to compression in concrete. Stress in thebar decreases further due to crushing of concrete and reductionin the load carrying capacity. Total increase in stress is 54% of re-serve stress available in the bar. The increase in concrete compres-sive strains at top of mid joint with increase in deection is shownin Fig. 13b. It is found that compressive strain developed in con-crete due to bending increases linearly, up to 0.0027 strain whichcorresponds to deection of 18 mm. Under higher deection de-mand, non-linear in the straindeection behaviour is found dueto decrease in load carrying capacity of girder and starting of thecrushing of concrete. Compressive strain of 0.0136 is measuredat failure load.

Crack widths (joint openings) which are computed from themeasured deformations at the joints are presented in Tables 1and 2 for EJSBG and DJSBG respectively. It is observed from the ta-bles that crack width increases with the increase in the deectionof beam. First crack occurred at bottom of joints which are located

(b) At J3 at 24mm deflectioning for EJSBG.

ing Materials 38 (2013) 931940 937near to the loading points. Initial depth of crack is 75 mm and it isequal to the thickness of bottom ange. All the cracks are closedafter unloading due to effect of prestressing until the maximumload of girder. Crack widths varied from 0.10 mm to 19.0 mmand its length increased from 75 mm to up to depth of girder i.e.500 mm. From the tables, it is observed that, new cracks areformed at other joints after decrease in maximum load of girderand bending of the specimen. The joint J4 in EJSBG and joint J2 inDJSBG are widened more than the other joints and propagated intothe compression zone.

4.2.2. Comparative performance of the joints under cyclic loadAs the segmental girder had no reinforcement across the joint,

the tensile stresses are concentrated along the prestressing steelin the constant bending moment zone rather than distributedthrough the total length of the girder. The crushing of the concreteis considered as a total collapse of structure for the simply sup-ported beam. Failure of the specimen with epoxy joint (EJSBG) un-der cyclic loading is found to be at 388 kN when the concrete is

Building Materials 38 (2013) 931940938 S. Saibabu et al. / Construction andcrushed at the extreme compression zone above the segmentaljoint followed by large deection and opening segmental joint(Fig. 8). The maximum load and maximum deection is found tobe more than 1.5 times that at service load. The deection andthe maximum crack width measured on the EJSBG specimen underrepeated loading are found to increase with the number of load cy-cles. The width of crack at joints is found to be varied from 0.1 mmto 19 mm and its depth also varied from 75 mm to 500 mm. Stressin the unbonded tendon is also increased up to 115 MPa. The cyclicload at the deections varies from 4 mm to 47 mm and the appliedload varies from 83% to 85% of maximum cyclic load. It shows thatthe girder had reserve strength of above 83% of the maximum load

(b) Joint opening at J2 at 24mm(a) Joint opening at J2 at 12mmFig. 10. Crack opening for DJSBG.

0

50

100

150

200

250

300

350

400

450

Load

(kN

)

Deflection (mm)

1

2

3

4 65 7 89

1110

(a) Load- deflections at mid span

0

5

10

15

20

25

30

35

40

45

0 5 10 15 20 25 30 35 40 45 50

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Def

lect

ion

(mm

)

Span (mm)

1

2

3

4

6

5

7

8

9

10

(b) Deflection profiles of DJSBG under cyclic loading

Fig. 11. Performance of DJSBG under deection.

Fig. 12. Loaddeection behaviour of dry and epoxy jointed specimens at maxi-mum displacement level for each load cycle.

0

200

400

600

800

1000

1200

1400

1600Ene

rgy

diss

ipat

ion

(kN

mm

)

Deflection (mm)

For Epoxy Jointed BridgeFor Dry Jointed Bridge

(a) Energy dissipation

050

100150200250300350400450500

0 5 10 15 20 25 30 35 40 45 50

0 5 10 15 20 25 30 35 40 45 50

Stre

ngth

(kN

)

Deflection (mm)

For Epoxy Jointed BridgeFor Dry Jointed Bridge

(b) Strength degradationFig. 13. Cyclic response of the segmental bridge with dry and epoxy joints.

after subjected to the cyclic deection. The applied load at thedeections increases from 4 mm to 12 mm, varies from 83% to100% of the maximum load of the specimen. Further, the appliedload decreases from 98% to 85% of the maximum load as the deec-tions increases from 12 mm to 47 mmwhich shows that the girderhad always reserve strength of above 83% of the maximum loadafter subjected to the cyclic deection.

For the specimen with dry joint (DJSBG), rst joint (J2) whichwas opened during static test is reopened at the same load andsame deection of cyclic load. It was completely closed afterunloading. During cyclic displacement loading, joints at other loca-tions are also opened. All opening are propagated vertical into thecompression zone and closed after unloading. Deection increasedfrom 4 mm to 16 mm and corresponding load is also increased by20% which shows girder had sufcient reserve strength after crack-ing. From 16 mm deection onwards up to failure (47 mm), corre-sponding loads were decreased by 15%. This indicates a decrease inthe rigidity and stiffness of the girder while increasing deectionsand with the number of load repetitions. The segment to segmentjoints in the constant bending moment zone were subjected to sig-nicant repeated openings and closure under cyclic loading with-out failure up to the ultimate load. Specimen failed due tocrushing of top ange above the segmental joint J2 in the constantbending moment zone. The failure load is found to be 323 kN at47 mm cyclic deection. The cracking load and ultimate load isfound to be 1.03 times and 1.46 times the design load in the dryjointed segmental beam. Ratio of ultimate load to cracking loadis 1.41. The applied load at the deections increases from 4 mmto 16 mm, varies from 71% to 100% of the maximum load of thespecimen. Further, the applied load decreases from 98% to 77% ofthe maximum load as the deections increases from 16 mm to

600

650

700

750

800

850

900

Stre

ss in

tens

on (M

Pa)

Deflection (mm)

For Epoxy Jointed BridgeFor Dry Jointed Bridge

(a) Deflection vs stress in tendon

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 5 10 15 20 25 30 35 40 45 50

0 5 10 15 20 25 30 35 40 45 50

Com

pres

sive

str

ain

at to

p (x

10-2

)

Deflection (mm)

For Epoxy Jointed BridgeFor Dry Jointed Bridge

(b) Deflection vs strain at top of jointFig. 14. Comparison of stress and strain variation of epoxy and dry jointedspecimens.

Table 1Showing crack width and depth of EJSBG.

Def. (mm) Load (kN) Joint-1 J1 Crack at J2

Dp (mm) Wi (mm) Dp (mm) Wi (mm)

4 383 0 0 75 0.1358 431 0 0 75 0.173

12 459 0 0 150 0.19318 448 150 0.134 150 0.19324 424 300 0.256 300 0.63231 416 425 0.279 300 0.88037 413 425 0.323 300 3.03343 402 425 0.379 300 4.54647 388 425 0.404 300 7.289

Depth of crack (Dp), and width of crack (Wi) at each cyclic load at the Joint-1 (J1), Joint-2S4S5, and S5S6 respectively.

Table 2Showing crack width and depth of DJSBG.

Def. (mm) Load (kN) Crack at J1 Crack at J2

Dp (mm) Wi (mm) Dp (mm) Wi (mm)

4 294 0 0 75 0.1008 339 0 0 75 0.173

12 376 0 0 150 0.19318 417 150 0.134 150 0.19324 408 300 0.256 300 0.63228 392 425 0.279 300 0.88032 365 425 0.323 300 1.03336 341 425 0.379 300 6.54640 323 425 0.404 300 10.289

Depth of crack (Dp), and width of crack (Wi) at each cyclic load at the Joint-1 (J1), Joint-2S4S5, and S5S6 respectively.

S. Saibabu et al. / Construction and Building Materials 38 (2013) 931940 939Crack at J3 Crack at J4 Crack at J5

Dp (mm) Wi (mm) Dp (mm) Wi (mm) Dp (mm) Wi (mm)

0 0.436 75 0.135 0 00 0.590 75 0.173 0 00 0.925 150 0.193 0 0

300 1.764 150 0.193 150 0.166425 2.685 300 0.734 300 0.198425 4.258 300 0.977 425 0.266425 6.756 300 3.650 425 0.365500 11.253 300 4.678 425 0.398500 18.469 300 8.267 425 0.540

(J2), Joint-3 (J3), Joint-4 (J4), and Joint-5 (J5) between segments S1S2, S2S3, S3S4,

Crack at J3 Crack at J4 Crack at J5

Dp (mm) Wi (mm) Dp (mm) Wi (mm) Dp (mm) Wi (mm)

0 0 75 0.135 0 00 0 75 0.173 0 00 0.110 150 0.193 0 0

300 0.153 150 0.193 150 0.166425 0.625 300 0.734 300 0.198425 2.842 300 0.977 425 0.266425 4.423 300 3.650 425 0.365500 10.251 300 4.678 425 0.398500 15.022 300 8.267 425 0.540(J2), Joint-3 (J3), Joint-4 (J4), and Joint-5 (J5) between segments S1S2, S2S3, S3S4,

44 mm. It shows that the girder had always reserve strength ofabout 71% of the maximum load after subjected to the cyclicdeection.

It was observed from the results that (i) the exural strength ofdry jointed specimen is less than the epoxy joint due to high con-centration of rotation and deection at individual joints of segmen-tal girder, (ii) behaviour of dry jointed specimen is similar to thebehaviour of epoxy bonded specimen at failure, (iii) due to highconcentration of rotation and deection at individual joints inthe dry jointed specimen, the maximum load and failure load are

the girder. Two stage and match cast method was applied for cast-ing of trapezoidal box shape precast segments. Performance of the

the experiments will be useful to the bridge designer to check theperformance of the segmental girder at different load levels.

Acknowledgements

The paper is published with the permission of the Director,CSIR-SERC, Chennai, India. The technical support and help renderedby Shri. R. Jayaraman, Chief Scientist (Retired) and the team of

Eng Struct 2008;30:17119.

940 S. Saibabu et al. / Construction and Building Materials 38 (2013) 931940test specimen consisting of epoxy and dry joints were studied un-der static and cyclic loading. Static loading was applied to get therst crack, then monotonically increasing cyclic load (displacementcontrol) was applied to the specimens up to failure load. Both testspecimens was found to be performed well similar to the mono-lithic beam up to ultimate load. Repeated loading and unloading re-sulted in opening and closing of the joints between two segments,which result in loss of stiffness of joint and crushing of concreteabove the joint at mid span and found that the phenomenon ismuch severe in dry jointed specimens. It was observed from thepresent study that the segmental box girders with epoxy jointshowed better performance than the dry jointed segmental box gir-der due to additional tensile strength in the joint region. Neverthe-less, dry jointed bridges are preferred in some cases due toenvironmental constraints or site requirements. The load- deec-tion behaviour (under cyclic load), strength degradation, stiffnessdeterioration and stress development in tendon, etc. obtained from8.6% and 16.7% less than that of the epoxy jointed specimen, (iv)segment to segment joints undergone signicant repeated open-ings and closures during cyclic loading test without failure, (v) Per-manent deformations of both specimens under cyclic loading arealmost equal up to the maximum load. But the deformation ofdry jointed specimen is less than epoxy jointed specimen at thefailure load, (vi) under cyclic load test, failure was initiated bycrushing of the top ange above the segmental joint in the constantbending moment zone, after repeated loading cycles in both thespecimens, (vii) In both the specimens, the load carrying capacityof the specimens dropped gradually with increased displacementin the post-peak range due to decrease in the stiffness, (viii) theshear keys did not fail up to the failure load of specimen in boththe specimens as keys were designed for ultimate load. Relativevertical sliding between precast segments is very less, and (ix) boththe test specimens showed signicant deection and joint openingbefore failure.

5. Concluding remarks

Experimental investigations were carried out on a scaled modelof precast post-tensioned concrete segmental box girder to evalu-ate the performance of epoxy and dry segmentsegment joints ofStructural Testing Laboratory of CSIR-SERC is acknowledged.

References

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Performance evaluation of dry and epoxy jointed segmental prestressed box girders under monotonic and cyclic loading1 Introduction2 Overview on segmental bridge construction2.1 Epoxy jointed segmental box girder (EJSBG)2.2 Dry jointed segmental box girder (DJSBG)

3 Experimental investigation on scaled model of a precast post-tensioned segmental bridge deck3.1 Details of test specimen3.1.1 General dimensions and characteristics3.1.2 Materials composition and properties3.1.3 Specimen construction

3.2 Instrumentation setup3.3 Static and cyclic load test

4 Observations on the response of EJSBG and DJSBG4.1 Response under static loading4.2 Response under cyclic loading4.2.1 Stress, strain and crack width under cyclic load4.2.2 Comparative performance of the joints under cyclic load

5 Concluding remarksAcknowledgementsReferences