The behavior of connection between precast panels is important as it controls the failure
mode of the shear wall. Therefore, it is aimed to test the behavior of different type of precast
panel connections in this study. One monolithic reference model and two precast panel models
having different horizontal connection details were produced. The behavior of connections was
tested under reversed-cyclic lateral loads. It was concluded that welded connections can be
designed in high and normal ductility levels

Kaplan, Hasan

Solak, Adem

Tama, Yavuz Selim

Yılmaz, Salih

Epoka University

32nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.Seismic Behavior of Welded Precast Panel ConnectionsAdem Solak1, Yavuz Selim Tama2, Salih Yılmaz3, Hasan Kaplan21 Pamukkale University, Institute of Natural Sciences, Denizli, Turkey2Pamukkale University, Department of Civil Engineering, Denizli, Turkey3 İzmir Katip Çelebi University, Department of Civil Engineering, İzmir, TurkeyABSTRACTThe behavior of connection between precast panels is important as it controls the failuremode of the shear wall. Therefore, it is aimed to test the behavior of different type of precastpanel connections in this study. One monolithic reference model and two precast panel modelshaving different horizontal connection details were produced. The behavior of connections wastested under reversed-cyclic lateral loads. It was concluded that welded connections can bedesigned in high and normal ductility levels.Keywords: Seismic Strengthening, External Shear Wall, Precast Panel ConnectionINTRODUCTIONStrengthening of the structures with deficient seismic performance is a significant subjectfor many countries. Numerous methods were developed to strengthen existing buildings. RCinfill walls, jacketing, and steel shear walls are some of them. These methods are both introducessome difficulties for construction and need building’s to be out of service. Besides, these are alsotime-consuming and expensive [1]. The use of external shear walls for strengthening of existingbuildings was developed to overcome these difficulties. The studies on external shear wallapplications in parallel to facades [2] and those in vertical to facades [3, 4] are available inliterature. In these studies, external shear walls were produced as cast-in-place and connection tothe existing structure was provided by adhesive anchors. In multi-storey structures, there areseveral difficulties in the application of cast-in-place construction of external shear walls.On the other hand, the strengthening made with precast members provides ease ofapplication. Several studies were conducted for the use of precast members for the strengtheningof buildings [5-9]. Although, the application of precast panels from outside of the buildingsprovides a considerable ease of application, the production of panels in multi-piece becomes anecessity with increasing heights of buildings. In the literature, there are several studies in thesubject of horizontal panel connections of Precast RC Panel walls [10-12]. Besides these studies;in previous earthquakes, it was seen that prefabricated panel systems show good performance[13-17].In this study, external shear walls were produced as precast panels. Panel connections weredesigned for one-face only to simulate the real case. In this context, two precast panel specimenshaving different horizontal connection details and one reference specimen without anyconnections were prepared. The models were tested under reversed-cyclic lateral loads.32nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.EXPERIMENTAL STUDYSpecimensThis study consists of three models. The reference model (RM) and panel models with twodifferent connection types were constructed in one-third scale. Labeling and description ofmodels are given in Table 1. Dimensions and detailing of the specimens are given in Figure 1.Table 1 Experimental ModelsModel Name Panel-Panel Connection Type DescriptionRM Without connection- onecasting Reference modelWHC1 Models with welding andconjunctionU-cross sectioned steel componentswhich are dry in horizontal with clampand steel sheet supported conjunctionWHC2 Conjunction with U-cross sectioned,steel, dry in horizontal componentsFigure 1 Reinforcement details of the reference modelPanels were produced in two pieces for WHC1 (Welded Connection in Horizontal) model.At the panel ends, where connections are to be realized, cold formed U sections having athickness of 5 mm which are made of A36 steel. Longitudinal reinforcements of the shear wallswere welded to the internal surfaces of these steel end section (Figure 2). During the assembly,32nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.these end sections were welded with fillet weld. Furthermore, steel plate (A36) havingdimensions of 100.200 was welded to both end sections. For all welding works, weld thicknesswas 3.0 mm. All connections were formed with electric arc welding by alkali electrodes.Figure 2 Schematic view of WHC1 and WHC2 models and connection details.WHC2 (Welded Connection in Horizontal ) model has the same properties as WHC1model except that it has no connection plates, welded over U-end sections. Connection wasprovided by welding U-end sections from one side (Figure 2).MaterialsIn the production of specimens, ready-mix concrete with maximum grain size of 16 mmwas used. Mean concrete compressive strength of each model is given in Table 2 for 28th day andthe day of experiment.Table 2 Mean concrete compressive strength of test modelsExperimentelementfc (MPa)(Mean compressive strength)32nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.28 Days Experiment DayRM 42.42 50.23WHC1 42.42 50.23WHC2 36.09 41.81Moment and Shear Capacity of ConnectionsIn this study welded connections were used. In WHC1 and WHC2 models, connection ofpanels was provided by welding. Shear and moment capacity of connections and the shear wallare calculated without considering material safety factors. Those capacities are compared withdesign forces in Table 3. When the panel reaches its moment capacity at the bottom end, thedesign moment (Mdc) at the connection level, which is located at 700 mm height should besmaller due to linear moment distribution throught the wall height. That reduction is carried outfor the calculation of Mdc. It is seen that connections are considerably safe against shear forces.However, critical effects which define the safety of connections are flexural forces.Table 3 The sufficiency of sectioning force and moment capacities of connection regionsSpecimenMoment capacityof the wallMr (kNm)Design momentfor the connectionMdc (kNm)Design shearforce for theconnectionVdc (kN)Momentcapacity of theconnectionMrc (kNm)Shearcapacity oftheconnectionVrc (kN)RM116.19No connection40.77No connectionWHC1 87.65 141.59 809.13WHC2 91.03 404.56Test SetupExperimental studies were conducted in Pamukkale University Earthquake and StructuralTechnologies Research Laboratory. Within this study, specimens were tested under reversed-cyclic loading applied from top of the panel walls. Overview of loading system is given in Figure3. Sliding supports were used at the top of panels to prevent the out of plane-behavior ofspecimens (Figure 3).32nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.Figure 3 Overview of test setup and placement of data acquisitionDisplacement transducers were placed to the same places for each model (Figure 3).Curvature measurements were performed for three different regions. The average curvaturemeasurements were carried out in the region with lengths of 200 mm, 300 mm, and 350 mmfrom the bottom. The third region where the last measurement was done also covers theconnection.Lateral movement and rotation of base were prevented. Some displacement transducerswere used to measure whether there has been any sliding in the interface between panel and rigidbase. In RM model in the experimental study and in all other experiment models, it was seen thatthere is not a sliding formation in the elements which provide connection in panel base. Loadmeasurements in the experimental study were done with the load cell placed between piston andpanel. Reversed cyclic loading was applied to the specimens.TEST RESULTSAll experiments within this study were performed as displacement controlled. Experimentcycles were started with +5 mm and continued up to +/- 100 mm peak displacement dependingon the stability of specimens. The deformations and damages on specimens were inspected aftereach step.Reference Model (RM)RM was tested under reversed-cyclic loading. Damage conditions of panel at the momentsof 0.5 %, 1 %, 2 %, and 3.3 % lateral sway were given in Figure 4.32nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.0.5% 1.0% 2.0% 3.3%Figure 4 Observed damages at different sway levels for RMAs a result of the experiment, bending and shear cracks were observed in the first 180 cm-and mostly in first 60 cm- height of the panel wall. RM element exhibited a ductile behavior andno loss in load-bearing capacity is observed up to + 99 mm peak displacement. After theexperiment, maximum base shear force and moments are found to be 43.26 kN and 118.96 kNmrespectively. Moment-curvature hysteresis for 1st, 2nd, and 3rd regions and force-displacementcycles are given in Figure 5. It was seen that nonlinear behavior mostly formed at the firstregion.32nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.Figure 5. Moment-Curvature and Force-Displacement hysteresis for RMWHC1 ModelIn WHC1 model, experiment started with +5 mm and ended with –70 mm peakdisplacement. A clear capacity loss started at the displacement level of 42.03 mm in the pushdirection of WHC1 model and maximum base shear force and moment were found to be 39.25kN and 107.94 kNm respectively. After the experiment, the damages of panel at the sway of 0.5%, 1 %, 2 %, and 3.3 % are given in Figure 6.32nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.0.5% 1.0% 2.0% 3.3%Figure 6 Observed damages at different sway levels for WHC1No damage formation was observed in the welds connecting WHC1 panels. Althoughflexural cracks were widely seen throughout the panel, at –70 mm peak displacement, panelreached to the collapse after crushes around the connection and failure in reinforcements.Moment-curvature hysteresis for 1st, 2nd, and 3rd regions and force-displacement cycles aregiven in Figure 7. In first measurement region, some plastic deformations were observed andpanel reached its flexural capacity. However, in contrast to RM, no plastic deformations wereoccurred in second region, where curvature has changed linearly. When the panel reached 40 mmtop displacement, connection failed and it was subjected to a significant capacity loss. Due tothis damage, a rapid curvature increase was observed while moment decreases in the connectionregion. Due to the increased top displacement because of damage occurred in the connection, thedemand for curvature in the panel base has decreased. Final curvature values were measured as0.04 rad/m and 0.01 rad/m for the first and second regions respectively; while that in theconnection region increased to 0.02 rad/m. Although, nonlinear curvature is not observed in thisregion for RM, curvature increase arose with significant capacity loss in case of welded-connection. Flexural behavior at the connection was considerably brittle. However, this brittlebehavior happened due to break of connection between reinforcement bars and the end plate. It isclear in Figure 6 that there is no damage in welds between panel connection plates.32nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.Figure 7 “Moment- Curvature” and “Force-Displacement” curves for WHC1WHC2 ModelFor this specimen, similar damage pattern was observed with RM. No damage wasobserved in the welds which connect panels. WHC2 model shows a ductile behavior likeReference Model. A clear capacity loss was formed at 80.92 mm top displacement in the pulldirection. Maximum base shear force and maximum moment were found to be 39.25 kN and106.32 kNm respectively. The damage schemas at the sway levels of 0.5 %, 1 %, 2 %, and 3.3 %are given in Figure 8.32nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.0.5% 1.0% 2.0% 3.3%Figure 8. Observed damages at different sway levels for WHC2Moment-curvature hysteresis for 1st, 2nd, and 3rd regions and force-displacement cycles aregiven in Figure 9. Nonlinear behavior was not observed in the connection region. Curvatures inthe 1st and 2nd region still continued to increase after yielding of longitudinal reinforcements.Plastic curvatures were observed in the first 500 mm of panel height. Nonlinear behavioroccurred throughout this height and panel reached the collapse mode with rebar failure in thepanel base and concrete crushes. Due to well-performance of the connection, panel exhibited aductile behavior (Figure 9).Figure 9. “Moment- Curvature” and “Force-Displacement” curves for WHC2CONCLUSIONSIn scope of this study, it is aimed to investigate the behavior of precast panels connected toform a strengthening shear wall. A reference monolithic model and two panel models were testedunder reversed-cyclic loads.Reference model behaved in a ductile manner and a plastic hinge is formed at the bottomof the wall. The plastic damages were concentrated mostly in the 200 mm height of the model. Ithas a displacement ductility of 7.07.Precast panels were connected with welded connections to form a similar geometry withthe reference model. WHC1 model failed under cyclic loading. WHC2 has a similar ductility to32nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.that of the reference specimen. Although, WHC1 suffered from the connections, it could reachthe flexural capacity at the bottom. Some damages were experienced at the bottom of this model;however its ductility was not as high as reference model and WHC2.In design stage, shear and flexural capacity of connections were both checked. Flexure wasthe dominating criteria for the design of the connections. It is concluded that precaststrengthening panels can be connected with welded end plates. However, the designer should beaware of the ductility of the connections. Welds between end plates and reinforcements as wellas welds between connection plates should satisfy enough shear and flexural capacity and assurehigh quality of construction.AcknowledgementThis study was supported by The Scientific and Technological Research Council of Turkey(TUBITAK) under project number 110M340. Authors acknowledge Suat Tasdelen and IbrahimKayalı for helping in drawings.REFERENCES[118] Kaplan, H. and Yılmaz S. (2012) Seismic strengthening of Reinforced concrete buildings.Earthquake-Resistant Structures - Design, Assessment and Rehabilitation. Chapter 16,ISBN 979-953-307-680-4.[119] Kaplan, H. Yılmaz, S. Çetinkaya, N. and Atımtay E. (2011) Seismic strengthening of RCstructures with exterior shear walls. Indian Academy of Sciences.,36(1), 17–34.[120] Kaplan, H. Nohutcu, H. Çetinkaya,N. Yılmaz, S. Gönen, H. and Atımtay E. (2009) Seismicstrengthening of pin-connected precast concrete structures with external shear walls anddiaphragms. PCI J, 54(1), 88-99.[121] Kaltakçı, M. Y. Öztürk, M. and Arslan M. H. (2010) An experimental investigation forexternal RC shear Wall applications. Nat. Hazards Earth Syst. Sci.: 1941-50.[122] Yüzügüllü Ö. (1979) Strengthening of reinforced concrete frames damaged by earthquakeusing precast panel elements. TUBITAK  Project No.MAG-494.[123] Frosch, RJ. Wanzhi, L. Jirsa JO. and Kreger ME. (1996)  Retrofit of non-ductile moment-resisting frames using precast infill wall panels. Earthquake Spectra 12(4), 741-760.[124] Baran, M. and Tankut, T. (2011) Experimental study on seismic strengthening of RCframes by precast concrete panels. ACI Struct. J, 108(2), 227-237.[125] Yılmaz, S. Tama, YS. and Kaplan, H. (2010)  Design and construction of external precastshear walls for seismic retrofit. 14th European Conference on Earthquake EngineeringOhrid, Macedonia, 1238.[126] Yılmaz, S. Çetinkaya, N. Nohutcu, H. Çalışkan, Ö. and Çırak, İF. (2010) ExperimentalInvestigation of anchors in external strengthening shear walls. TUBİTAK ProjectNo.107M572.[127] Soudki, KA. Jeffrey, SW. Rizkalla, SH. and Bruce B. (1996) Horizontal connections forprecast concrete sheare wall panels under cyclic shear loading. PCI J 41(3), 64-80.32nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.[128] Soudki, KA. Rizkalla, SH. and LeBlanc B. (1995) Horizontal connections for precastconcrete sheare walls subjected to cyclic deformations part 1: mild steel connections. PCI J40(4), 78-96.[129] Soudki, KA. Rizkalla, SH. and Diakiw RW. (1995) Horizontal connections for precastconcrete sheare walls subjected to cyclic deformations part 2: prestressed connections. PCIJ 40(5), 82-95.[130] Polat, U. Göktepe, S. and Gürses E. (2000) Behavior and Seismic Rehabilitation ofPrefabricated Frame and Panel Wall Structural Systems. Proceedings of 10th Symposiumon Prefabrication, İstanbul, Turkey, 117-126.[131] Sachanski, S. (1978) Earthquake resistance of precast structures. Proc. of the 6th Europeanon earthquake engineering. Dubrovnik, 3-28.[132] Hashim, MSAW. and, Sinan, YHS. (1991) Prediction of Ultimate Shear Strength ofVertical Joints in Large Panel Structures. ACI Structural Journal, 88-S25.[133] Booth, E. (1994) Concrete structures in earthquake regions, design and analysis. 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Seismic Behavior of Welded Precast Panel Connections

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Seismic Behavior of Welded Precast Panel Connections

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