Numerical Analysis of a Reinforced Concrete Slab-Column Connection Subjected to Lateral & Vertical Loading

Transcription

1 , Mrch 15-17, 2017, Hong Kong Numericl Anlysis of Reinforced Concrete Slb-Column Connection Subjected to Lterl & Verticl Loding Mostfiz Emtiz, A.S.M. Aluddin Al Azd, H. M. Shhin b nd Sultn Al Shfin c Abstrct Abstrct Reinforced concrete flt slbs re widely used becuse of its economicl nture. Flt slb structures show significnt vulnerbility under lterl nd verticl seismic loding s punching sher filure my occur in the joints of slb nd column. In this reserch, finite element nlyses hve been crried out to predict how much seismic loding flt slb-column connection cn endure. The vulnerbility of the flt slb-column connection is checked through the nlyses. The finite element nlyses hve been conducted with ABAQUS softwre becuse of its wide mteril modeling cpbility nd customiztion property. Elstoplstic CDP model is used mteril modelling for the reinforced concrete. It is found tht thickness of the slb, reinforcement rtio, usge of bent brs, high strength mterils re the importnt fctors in punching sher filure in the slb-column connection. Index Terms ABAQUS, Finite Element Anlysis, Punching Sher Filure, Seismic Loding, Stress Anlysis. R I. INTRODUCTION ECENTLY mny experimentl works hs been done on reinforced concrete structures subjected to seismic loding. Strengthening of both modern nd ging infrstructure is essentil becuse of recent erthquke ctivities. In this pper we wnt to focus on reinforced concrete slb-column connection subjected to lterl seismic loding t the top nd verticl seismic loding t the bottom of the column. Mny experiments hve been performed to understnd the behvior of the connection of building. Performing experiment for flt slb-column connection subjected to seismic loding requires more time nd money. Such n experiment ws performed by Robertson & Johnson [1] to determine the punching sher filure for slb-column connection. In tht experiment, six specimens were used. And for ech specimen experimentl setup ws prepred nd the specimens were subjected to lterl loding. In this reserch, we hve nlyzed the specimen one nd pplied both verticl nd horizontl seismic loding. A.S. Genikomsou nd M.A. Polk (2014) studied with the Mnuscript received August, 2016; revised October 10, This work ws supported in prt by the Islmic University of Technology. F. A. Author hs completed B.Sc. in Civil Engineering from Islmic University of Technology (phone: ; e-mil: sjl105@iutdhk.edu, mostfiz.emtiz@gmil.com). S. B. Author is with Islmic University of Technology, Gzipur, Dhk, Bngldesh. He is now professor of the Deprtment of Civil & Environmentl Engineering, Islmic University of Technology, Dhk, Bngldesh (e-mil: shhin@iut-dhk.edu). T. C. Author is working with the Civil & Environmentl Engineering Deprtment, Islmic University of Technology, Gzipur, Bngldesh, (emil: shfin1@iut-dhk.edu). problem tht cn occur in flt slbs, re high stresses in the slb-column connection re tht cn result in punching sher In this pper, 3-D nlysis of the reinforced concrete slb with the finite element softwre ABAQUS using the dmge-plsticity model is presented. The simultions of the reinforced concrete slb re compred to the behvior of specimen tht hs been tested t the University of Wterloo. This study involves the investigtion on the punching sher behvior of reinforced concrete slbcolumn connections without sher reinforcement. Tomsz Jnkowik, Tomsz Lodygowski (2005) presents method nd requirements of the mteril prmeters identifiction for concrete dmge plsticity constitutive model. The lbortory tests, which re necessry to identify constitutive prmeters of this model hve been presented. Two stndrd pplictions hve been shown tht test the constitutive model of the concrete. The first one is the nlysis of the three-point bending single-edge notched concrete bem specimen. The second presents the four-point bending single-edge notched concrete bem specimen under sttic lodings. Fig.1. Exmple of Punching Sher filure in the buildings due to erthquke. Jun Chen, Chengxing Xu, nd Xueping Li (2012) pointed out the seismic behvior of frme connections composed of specil-shped concrete-filled steel tubulr columns nd steel bem, finite element nlyses were performed using ABAQUS compred ginst experimentl dt. In our reserch we minly focused on the punching sher filure on slb-column connection subjected flt slb to seismic loding. filure occurs due to stress or high loclized forces on reinforced concrete slbs. In reinforced concrete, flt slb structures this occurs t column support point. filure due to seismic loding hs been common phenomenon in recent erthqukes. Reserch ctivities in this field re reltively less.

2 , Mrch 15-17, 2017, Hong Kong II. MATERIAL MODELING A. Concrete dmge plsticity Model In the reserch of Genikomsou et l (2014) [2] it is sid tht, the concrete dmge plsticity model is continuum, plsticity-bsed, dmge model, which ssumes two min filure mechnisms: the tensile crcking nd the compressive crushing. The model uses the yield function proposed by Lubliner et l. (1989) [3] nd modifiction by Lee nd Fenvs (1998) [4]. s 2743mm*3048mm. And the column size is plced s 254mm*254mm. And the height of the column is plced s 1524mm. A. Reinforcement Modeling Reinforcement of both slb nd column hs cted s the embedded element. The bottom slb reinforcements re plced t #10@356mm, #10@203mm, #10@152mm, #10@256mm & #10@356mm long the width of the slb nd #10@356mm, #10@203mm, #10@152mm, #10@256mm & #10@356mm long the length of the slb. The top slb reinforcements re extended to one third of the slb. The top slb reinforcements re plced t #10@152mm long the width of the slb nd #10@152mm, #10@127mm, #10@127mm & #10@152mm long the length of the slb. Four rebr re used in column nd no tie brs re used. #20 reinforcement is used s the column reinforcement. B. Mteril property for slb & Column concrete TABLE I PROPERTY FOR SLAB AND COLUMN CONCRETE Property Vlue Fig. 2. CDP Model for compression & tension. B. Linier Elstic Plstic Model The mteril returns to its originl shpe when the lods re removed. Strin in these mterils is smll nd stress is proportionl to strin. Fig. 3. Liner elstic plstic model. III. SPECIMEN MODELING A. Slb-Column Joint Modeling An interior slb-column connection hs been creted using the co-ordinte system where the whole connection cted s the host element for the reinforcements. Concrete dmge plsticity type model hs been used here. Slb is plced with the thickness of 114mm nd slb size is plced Density (kg/mm 3 ) Young Modulus (MP) Poison s Rtion 0.23 Diltion Angle 38 Eccentricity 0.1 FB0 / FC K 0.67 Viscosity Prmeter Yield Strength 44 (Compressive) Yield Strength (Tensile) 2.2 Frcture Energy (N/mm) 0.09 C. Mteril properties for reinforcement Rebr s density is 7.75E-6 kg/mm 3 And Young modulus MP. Poison rtio ws tken 0.3. T3D2 element hs been used. Truss elements re rods tht cn crry only tensile or compressive lods. They hve no resistnce to bending; therefore it cn be modeled s truss. D. Meshing Every prt ws individully meshed for finite element nlysis. Mesh size 10mm is used in the host element nd 10mm is used in the embedded element. T3D2 elements re used. Totl number of element is 12,656. Totl number of node is 16,846. Totl number of vribles in the model is 50,538. IV. STRESS DISTRIBUTION A. Stress Distribution Anlysis for Different Loding Cses For the loding cse 1 punching sher occurs t the criticl perimeter ccording to ACI code where the top of the column is subjected to 1000 Hz of seismic loding. The criticl perimeter is locted t distnce of d/2 from the fce of the column. The mximum sher stress t criticl column

3 , Mrch 15-17, 2017, Hong Kong is necessry to determine whether punching sher filure will occur or not. Stress distribution nlysis hs been done for vrious cses to find out the mximum stress t criticl perimeter. t the bottom of the column in verticl direction. Von mises & stress distribution nlysis is done for n element situted in criticl prmeter of the flt slb. Fig 4. Meshing & Modeling of the slb-column joint, reinforcement. Fig 6. Contour plot of the slb column connection & Element t the criticl prmeter for Mximum stress distribution curve for cse-1 Fig 5. Seismic loding t the top nd bottom of the column. B. Von & Stress Distribution For the loding cse 1 it is considered tht the top of the column is subjected to 1000 Hz of seismic loding in the horizontl direction. Von mises & stress distribution nlysis is done for n element situted in criticl prmeter of the flt slb. For the loding cse 2 it is considered tht the top of the column is subjected to 2000 Hz of seismic loding in the horizontl direction. Von & stress distribution nlysis is done for n element situted in criticl prmeter of the flt slb. For the loding cse 3 it is considered tht the top of the column is subjected to 1000 Hz of seismic loding in horizontl loding & 1000 Hz of verticl Loding Fig. 7. Mximum stress distribution curve for cse-2

4 , Mrch 15-17, 2017, Hong Kong t the end of the column. TABLE II EXAMPLE OF THE CONSTRUCTION OF ONE TABLE. Cses Stress Distri butio n Ultimt e stress N/mm 2 Concret e stress N/mm 2 Sher Rtio Chnce of occurring filure Fig. 8. Mximum stress distribution curve for cse Crck my develop & Crck my develop & punching sher imminent Fig. 9. Mximum stress distribution curve for cse C. Comprison with ACI Code A vlue of 1.0 for the sher rtio would indicte tht the connection is on the verge of punching sher filure ccording to the ACI Building Code. The concrete sher stress is limited to the smllest of three concrete stress equtions given in ACI 318 section VI. Conclusions Sher rtio is the rtio of ultimte sher stress for the criticl perimeter & concrete sher stress. If the rtio is 1 or greter thn 1 then punching sher filure occurs. V. RESULTS AND DISCUSSIONS The results of the nlysis hve been summrized in Tble II. As from ACI building code it hs been estblished tht if sher rtio 1 then punching sher filure will occur. From the tbulted chrt it is seen tht punching sher filure occurred for slb-column connection subjected to 2000 Hz of cyclic loding lterlly t the top of the column nd combintion of 2000 Hz of cyclic loding t the top of the column lterlly nd 2000 Hz of cyclic loding verticlly In this model Von stress nd stress distribution hs been checked t the slb-column connection. It hs been observed tht it is possible to determine the behvior of slb-column connection subjected to seismic loding. To minimize the effects of seismic loding the following should be tken into considertion Increse the thickness of the slb, Increse the reinforcement rtio, Usge of bent brs, Usge of high strength mterils. REFERENCES [1] Robertson nd Johnson, (2004), NON-DUCTILE SLAB-COLUMN CONNECTIONS SUBJECTED TO CYCLIC LATERAL

5 , Mrch 15-17, 2017, Hong Kong LOADING, 13th World conference on Erthquke Engineering, Vncouver, B.C., Cnd, Pper No-143. [2] Genikoumsou & Polk(2014), Finite Element Anlysis of Reinforced Concrete Slb - Column Connection using ABAQUS, Structures Congress 2014 ASCE [3] Lee, J., nd Fenves, G. L. (1998). Plstic-Dmge Model for Cyclic Loding of Concrete Structures. Journl of Engineering Mechnics, 124(8), [4] Lubliner, J., Oliver, J., Oller, S., nd Onte, E. (1988). A plsticdmge model for concrete. Interntionl Journl Solids Structures, 25(3), [5] ] Roylnce (2001), Finite Element Anlysis, Deprtment of mteril science nd engineering, Msschusetts Institute of Technology, Cmbridge, MA [6] ABAQUS (version 6.10), June 2010 ABAQUS user s mnul. [7] ACI. Building Code Requirements for Structurl Concrete (318-99) nd Commentry (318R-99). Americn Concrete Institute Committee 318, ACI, Frmington Hills, Michign, 1999.