Prestressed Steel Reinforced Concrete Frame Applied to Outer-jacketing Structure and its Restoring Force Model Based on IDARC

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1 Research Jornal of Applied Sciences, Engineering and Technolog 6(11): , 013 ISSN: ; e-issn: axwell Scientific Organization, 013 Sbmitted: November 7, 01 Accepted: Janar 07, 013 Pblished: Jl 5, 013 Prestressed Steel Reinforced Conete Frame Applied to Oter-jacketing Strctre and its Restoring Force odel Based on IDARC Jing Ji, Wen-f Zhang, Chao-qin Yan, Dan Yang and Fei Xing 1 School of Civil Engineering, Northeast Petrolem Universit, Daqing , China Heilongjiang Ke Laborator of Disaster Prevention, itigation and Protection Engineering, Daqing, China Abstract: A new stle of frame strctre made p of encased H-shape steel prestressed conete composite beams and angle-steel conete colmns with 4 or 8 angle-steels is pt forward and joint constrctions of the frame are given in detail. This frame is fit for reconstrcting the existing bilding sing oter-jacketing strctres for storadding. On the basis of analzing application of PARK trilinear restoring force model in IDARC analsis software, recommended restoring force models of beams and colmns of prestressed steel reinforced conete frame based on IDARC in seismic response analsis are given as well as the method regarding frame joint as rigid region. It provides basis for elastic-plastic seismic response analsis of prestressed steel reinforced conete frame applied to oter-jacketing strctre for stor-adding. Kewords: Angle steel conete colmn, IDARC, oter-jacketing strctre for stor-adding, prestressed steel reinforced conete frame, restoring force model INTRODUCTION At present, with the transition of China s constrction indstr from primaril new constrction to new and retrofit constrction, the reconstrction of the existing bilding sing oter-jacketing strctres for stor-adding has alread become one of the hot isses in China's cit constrction (Zheng et al., 005). This std constrcts a new stle of frame strctre made p of encased H-shape steel conete composite beams and angle-steel conete colmns, if necessar, the beams for frame can be exerted prestressing effect. The frame strctre can bear self-weight in the process of the constrction and it is convenient for laot and anchorage of prestressing tendons, so it is sitable for the reconstrction of the existing bilding sing oterjacketing strctres for stor-adding. Restoring force models of encased H-shaped steel prestressed conete composite beam and angle steel conete composite colmn are the fondation of elastic-plastic seismic response analsis of the frame strctre b IDARC. In view of the little research of restoring force characteristics of angle steel conete colmn, so it is sggested that reinforced conete colmns replace angle steel conete colmn when the restoring force model is established. The restoring force model of frame beams is established according to two stages for the prestressing tendons of encased H-shaped steel conete composite beam. THE SELECTION OF OUTER-JACKETING STRUCTURE SYSTE Combined with oter-jacketing reconstrction project of Sifenhe Qingn market, the idea of the constrction phase self-spporting floor was pt forward (Zheng et al., 005), that is, dring the constrction self-weight of frame beams and constrction loads are beared b the prestressed steel trss and in-service phase the added loads are taken b oter-jacketing framework. The floor sstem can not onl bear new constrction loads and ensre the normal se of original bilding in the constrction process, bt also achieve the integration of force strctre and constrction measres, so saving investment and redcing constrction period can be achieved. However, althogh the self-spporting floor sstem dring the constrction phase has been applied in several projects, some problems still exist. B composite frame instead of conete frame, oter-jacketing strctres for stor-adding can be constrcted faster and the constrction period will be redced, at the same time, it can be avoided that constrction load is transmitted to the original roof dring the constrction phase. However, becase the original hosing generall is wider, so it is necessar to exert prestressing to steel frame composite beam or steel reinforced conete beam. If solid-web steel reinforced conete colmns and beam are adopted, it is difficlt to arrange and anchor prestressed tendons. Corresponding Athor: Jing Ji, School of Civil Engineering, Northeast Petrolem Universit, Daqing , China 045

2 Fig. 1: Conete colmn with for angle-steels K 0 Fig. 4: Skeleton crve Fig. : Conete colmn with eight angle-steels (a) Angle steel conete colmn role, bt also it is eas to chisel awa smaller protective laer conete and weld a variet of small components. The area of for angle steels with a wide of 00 mm and a thickness of 4 mm is roghl eqivalent to 76ø5 steel bar, so it is feasible that angle steel conete colmns are adopted as oter-jacketing strctre frame colmn. According to the principle of the same area, constant netral axis and strong, angle steel conete colmns with for angle steels and eqivalent reinforced conete colmn are shown in Fig. 3, it can be seen from Fig. 3, angle steel is sed instead of steel bar in the oter-jacketing frame colmn, this method solve the thorn problem, that is, it is difficlt for longitdinal reinforcement to laot at the beamcolmn joints PARK THREE LINEAR RESTORING FORCE ODEL IN IDARC (b) Eqivalent reinforced conete colmn Fig. 3: Sections of two kinds of colmns Therefore we recommend that oter-jacketing prestressed steel reinforced conete frame is formed b H-shape steel prestressed conete composite beam as frame beam and the angle steel conete colmn made of 4 or 8 angle steel as frame colmn, H-shape steel throgh the gap in the angle steel. The oss-section view of the colmn with for and eight angle steels is shown in Fig. 1 and respectivel. The longitdinal angle steel of colmn is welded with horizontal stirrps to form the spatial steel skeleton; it can share external loads with constraint conete. There is no more longitdinal reinforcement otside the angle, so the conete protective laer of angle steel skeleton can be redced and is roghl the same as ordinar reinforced conete colmn. Not onl can the lever arm of the angle steel inease to make the colmn pla a greater 046 At present, three linear restoring force models which are pt forward b Park et al. (1987) are recognized as the most comprehensive model, this model can better consider the pinch effect and strength and stiffness degradation phenomenon and it is applied to the strctral nonlinear analsis program IDARC. The ke of the program application is that the restoring force model of the strctral members is accratel reflected. Restoring force model of strctral members in the IDARC program incldes the skeleton crve and hsteretic rles, the skeleton crve can be achieved in two was: one is that the skeleton crve is determined b the program throgh inptting the axial force, stress-strain relationship of longitdinal reinforcement and conete, sectional reinforced area, distance of the centre of the steel bar to oss-sectional srface, the diameter of the stirrp, stirrp spacing and constraint effect (Valles et al., 1996); the other is that skeleton crve of strctral members restoring force model is inpt directl b calclating, the skeleton crve is shown in Fig. 4. and stand for forward and reverse acking

3 Fig. 5: Stiffness degradation dring nloading moment and the corresponding ack crvatre; and stand for forward and reverse ield moment and the corresponding ield crvatre; and stand for forward and reverse the limit bending moment and the corresponding ltimate crvatre. Above anone manner is adopted to form skeleton crve for restoring force model, the hsteretic rles of restoring force model need to be determined. Hsteretic rles inclde stiffness degradation, strength degradation, slip degradation and hsteretic mode. The hsteretic rles of different constrction members can be simlated realisticall b setting the stiffness degradation parameters (α), strength degradation parametersm (β 1, β ), the slip degradation parameters (r) and selection of hsteretic mode. The phsical meanings of degradation parameters, calclation formla and the hsteretic mode are as follows: Fig. 6: Strength degradation Fig. 7: Slip and pinch degradation α / / = Stiffness degradation parameter, αε[,00] / = Forward and reverse initial elastic stiffness = Forward and reverse nloading stiffness degradation coefficient Stiffness degradation: Stiffness degradation of strctral members restoring force model at nloading stage is often referred as the stiffness degradation. The initial stiffness line is reverse extended to a point that the vertical ordinate is α and nloading line point to the point ntil it is intersected with axis, then reverse loading line point to the maximal point which is previosl reached. If the previos maximm point is in elastic range, it will point to the ack point. Forward stiffness degradation diagram is shown in Fig. 5. Calclation formla of forward and reverse nloading stiffness degradation coefficient is as follows: R / k K / / cr / / / 0 cr (1) Strength degradation: Strength degradation is sed to desibe the phenomenon which skeleton crve of strctral members redces nder cclic loading, forward strength degradation is shown in Fig. 6. The formla is as follows: 1 / 1 / / max / 1 H () H lt where, / = The ield bending moment after forward and reverse degradation / = Forward and reverse initial ield bending / moment = Forward and reverse maximm crvatre that where, / hsteresis loop reached = Forward and reverse ield bending moment / / = Forward and reverse limit crvatre = Forward and reverse the nloading point β 1 = The degradation parameter based on the bending moment dctilit / = Forward and reverse the nloading point B = The degradation parameter based on the crvatre energ; β 1, β [0.01,1] 047

4 K 0 Res. J. Appl. Sci. Eng. Technol., 6(11): , (a)yield towards method K (b) Vertex towards method Fig. 8: Hsteretic modes in IDARC H H lt = Absorbed energ b complete hsteresis loop = Energ which the hsteresis loops forward and reverse the ltimate bending moment point and limit crvatre point exist can absorb withot an degradation Pinch and slip degradation: Pinch and slip degenerac phenomenon will be prodced in restoring force model of strctral member becase the conete ack and close. In Park model, parameter γ is sed to desibe slip degradation and forward slip degradation is shown in Fig. 7. It can be seen from the Figre, when γ is eqal to 1, no slip degradation. r and r are the bending moment and crvatre vales corresponding to the first segment end point for considering ack effect and the phsical meaning of other smbols are the same with above meaning. Hsteresis mode: Two kinds of hsteretic mode are provided in IDARC restoring force model of members, the are ield toward method with considering the slip effect and vertex toward method withot considering slip effect (Valles et al., 1996) and both are shown in Fig represent the process of hsteresis and the smbols phsical meaning are same with above ones. Forward load stiffness which is 8-9 process is shown in Fig. 8, it is determined respectivel according to the 048 ield toward method and vertex toward method. Reverse loading stiffness as 4-5 process is determined according to the following method, if the previos largest point in elastic range, then it will point to ack point, on the contrar it can be determined b the ield toward method and vertex toward method. RESTORING FORCE ODEL OF ANGLE STEEL CONCRETE COLUN BASED ON IDARC Determination of the skeleton crve: In IDARC, skeleton crve can be bilt b first wa based on the constittive relationship of materials for reinforced conete colmn. From Fig. 3, angle steel conete colmns which are adopted in this std can be regarded as reinforced conete colmn, therefore, according to the first wa the skeleton crve of angle steel conete colmns is bilt. Skeleton crve can be determined b IDARC program and the restraint effect are relevant to tpe of stirrps in the section. The vale is shown in literatre (Valles et al., 1996). Constittive relation ship of conete and steel in IDARC is shown in literatre (Valles et al., 1996). Determination of the for parameters and hsteretic mode: In IDARC, the for parameters in hsteretic rles of restoring force model of member were respectivel given for different degradation cases and the corresponding vales, the for different degradation cases were severe degeneration, medim degradation, slight and no degradation. In IDARC, it is recommended that medim degeneration can be sed for the for parameters of the restoring force model of the reinforced conete colmn. In this std, the angle steel conete colmn can be regarded as reinforced conete colmn and meet the above reqirements, therefore, medim degradation can be sed for the for parameters of restoring force model, the corresponding vales is 10, 0.3, 0.15, 0.5. The ield toward method considering the slip effect is adopted in hsteretic mode. RESTORING FORCE ODEL OF COPOSITE FRAE BEA BASED ON THE IDARC Determination of the skeleton crve: In IDARC, skeleton crve of H-shape steel prestressed conete composite frame beam can not be given directl based on the constittive relationship of steel, conete, steel bar and prestressing tendon. In view of this, we se the second wa to establish skeleton crve of the composite frame beam. For the prestressed reinforcement of H-shape steel prestressed conete composite frame beam, it can be considered in two stages: the first stage is from tension to the effective prestressing σ pe, the idea of this stage is prestressing force is eqivalent for external loads and is

5 H H I B G Ap= 7PS Ap1= 3PS Fig. 9: Determination of ield point sing crrent ield moment method applied to the strctre. The second phase is prestressed reinforcement is eqivalent for non prestressed reinforcement of tensile ield stress for f p -σ pe and providing resistance together with additional configration steel bar for the members. This std sed plane section assmes and sectional strip method, reckoned in the affection of axial force generated b the tensioning prestressed reinforcement and the role of framework beam conete flange, compiled the calclation program for momentcrvatre relationship ( crve) of the H-shape prestressed conete composite beam arbitrar osssection and then the forward and reverse ack moment and the corresponding crvatre vale, the forward and reverse the ltimate moment and crvatre vales on arbitrar oss-section skeleton crve can be obtained b the process. The forward and reverse acking moment corresponds to the moment when the conete on the pper and lower edge of the conete frame beam was plled acking. The experimental reslts of steel conete beams loaded propert in literatre (Zhang, 005; sallem et al., 010) show that it is not big difference between the load of the steel conete beam when the conete is shed and peak load, so the bending moment and the corresponding crvatre when pper and lower edge conete of frame beam reached the ltimate compressive strain was designated as forward and reverse the limit bending moment and the ltimate crvatre. The forward and reverse ield moment and corresponding crvatre vales are determined according to the general ield moment method and it is shown in Fig. 9. Tangent was made throgh the origin point O of - crves and intersected with the horizontal line which is throgh horizontal ltimate bending moment G point at the H point; vertical was made from H point and intersected crve - at I point; O and I were linked, then extended and intersected with HG at H, vertical was made from H point and intersected crve - at B point, B point was ield point, its level ordinate is the ield crvatre and the vertical ordinate is ield bending moment, reverse similarl Fig. 10: Section of encased H-shape steel prestressed conete composite frame beams at spport Determination of for parameters and hsteretic mode: It is the cial link for desibing the restoring force model for H-shape steel prestressed conete composite frame beam in the IDARC, that for parameters and the hsteretic model is accratel determined. The stiffness degradation parameters are most important, so the detailed desiption is shown as follows: Unloading stiffness degradation coefficient calclation formla of members restoring force model in IDARC is shown in formla (1), for forward nloading stiffness degradation coefficient, the followings can be obtained from the Fig. 6: ( )( ) cr cr (3) where, phsical significance of,, cr,, and cr are the same as the former. We will handle above eqation into nloading stiffness degradation coefficient formla (1), When α is a fixed vale, the nloading stiffness degradation coefficient is the fnction of, it is recorded as fnction 1. Unloading stiffness degradation coefficient formla of solid-web steel conete frame beam restoring force model is given in Literatre (Xe and Zhao, 000), that is: of R 0.85 ( / ) v (4) k cr The sggested vale of v is 0.6. R k is also fnction and is recorded as fnction. It is reqired in cr literatre (Xe and Zhao, 000) that steel section size of solid-web steel conete frame beam and frame beam oss section size shold be similar and coordinate. While In this std the H-shape steel conete composite frame beam is Coincide with the above reqirements, therefore, the H-shape steel conete composite frame beam nloading stiffness degradation coefficient formla is taken as fnction. B selection the two fnction crves abot Rk are in

6 Table 1: Data of skeleton crve for section Point (N/m) (m -1 ) (N/m) (m-1) (n/m) (m-1) Vale 3.6e5-5.7 e5.4 e-4-3.5e-4.5e6 -.5e6.7e-3-3.e-3 3.e6-3.3e6 8.5e-3-9.8e-3 (a) Forward (b) Reverse Spport section skeleton crve and is calclated b compter program, the ield point data is determined b general ield moment method. Based on the fnction, forward and reverse nloading stiffness degradation coefficient crve of the above section restoring force model is shown as crve 1 in Fig. 11a and b. Based on the fnction1, in IDARC, when is.5, 4 and 6, the forward and reverse nloading stiffness degradation coefficient crve of the section restoring force model is shown as crve, 3 and 4 in Fig. 11a and b. From Fig. 11 we can see, forward and reverse nloading stiffness degradation coefficient crve is good agreement with nloading stiffness degradation coefficient crve1 which based on fnction, when is eqal to.5. It is known that solid-web steel conete frame beam P-Δ hsteretic crve is plmp and spindle-shaped (Chen, 011), skeleton crve strength degradation is relativel slow, therefore, the strength degradation parameters β 1, β of above frame beam arbitrar oss section restoring force model can be respectivel selected slight degradation and sliding degradation parameters γ are considered to no degradation in the IDARC. The frame beam shown in Fig. 11 is accordance with the reqirements for solid-web steel conete frame beam, so the strength degradation parameters β 1, β and γ of spport section restoring force model can be taken as 0.15, 0.08, 1 respectivel. Vertex toward method withot considering slip effect is sed in hsteretic mode. Fig. 11: Stiffness degradation coefficient crves of frame beams good agreement. Similarl, the above two fnction crves for reverse nloading stiffness degradation coefficients are in good agreement throgh selection the same. Forward and reverse nloading stiffness degradation coefficient of restoring force model of H-shape steel prestressed conete composite frame beam can be desibed in IDARC program throgh selecting accratel α vale. Spporting section of H-shape steel prestressed conete composite frame beam in one-laer top of an oter-jacketing strctre is shown in Fig. 10. We take it for an example to illstrate how to select stiffness degradation parameter. Frame beam medioprestressed Reinforcement (Ap1 = 3 PS) is arranged b single parabolic link, Upper prestressed reinforcement (Ap = 7 PS) is arranged b three parabola links. The data shown in Table 1 are the date which correspond to forward and reverse directions ack point and extreme point of the frame beam 050 PROCESSING ON JOINT REGION OF OUTER- JACKETING FRAE IN IDARC In IDARC, In order to show framework node area, Colmn and beam interchange are need to give domain area length, Colmn domain area length take half of the beam section height, beam domain area length take half of the Colmn section height. CONCLUSION This std constrcted a tpe of frame strctre with H-shape prestressed conete composite beams as the frame beams and angle steel conete colmns eqipped with 4 or 8 angle steel as frame colmns, then the strctral form of frame nodes is given. The frame strctre is sitable for the reconstrction of the existing bilding sing oterjacketing strctres for stor-adding. Based on the IDARC, restoring force models of H- shape prestressed conete composite frame beam and angle steel conete are proposed.

7 Becase the span of oter-jacketing frame is larger, the original roof cannot bear oter-jacketing constrction loads, so frame beams constrction load is borne b H-shape steel beam (or prestressed H-shape steel beam) throgh hanging formwork constrction technolog. In service stage, the follow-p load is borne b H-shape steel prestressed conete composite beams. The restoring force models of H-shape steel prestressed conete composite beams on the two stages are needed to std. ACKNOWLEDGENT Project (0134) spported b Special Scientific Research Fnd of the Doctoral Program of Higher Edcation in 01 Year (The New Teacher Class); Project (15110) spported b the Heilongjiang Provincial Department of Edcation Science and technolog research of China; Project ( ) spported b The National Natral Science Fondation of China. REFERENCES sallem, Y., H. Kassem, F. Jacqemin and A. Poito, 010. Experimental std of the indced residal stresses dring the manfactring process of an aeronatic composite material. Res. J. Appl. Sci., Eng. Technol., (6): Park, Y.J., A.. Reinhorn and S.K. Knnath, IDARC: Inelastic damage analsis of reinforced conete frame-shear-wall strctres. Technical Report NCEER , State Universit of New York at Bffalo, NY, pp: Valles, R.E., A.. Reinhorn, S.K. Knnath, C. Li and A. adan, IDARC D version 4.0: A program for inelastic damage analsis of bildings. Technical Report NCEER , State Universit of New York at Bffalo, pp: Xe, J.Y. and H.T. Zhao, 000. Elastoplastic analsis of seismic responses for steel reinforced conete frame model. J. Bild. Strct., 1(4): Zhang, Q.X., 005. Experiment and analsis of flexral properties of encased steel-conete composite beam..a. Thesis, in Engineering, pp: Zheng, W. Z., Y. Wang, T. Li and J. Tan, 005. Thoghts and nderstanding of remodelling of adding stores arond existing bilding. Ind. Cons., 35(4): 1-5. Chen,.Y., 011. Elastic-plastic seismic response analsis of oter-jacketing prestressed conete frame..a. Thesis, in Eng., pp: