Seismic Performance Analysis Of Frame Structures With Stainless Steel Bars And HRB500 Steel Bars

Using stainless steel bars in concrete structures could improve the durability of concrete structures in harsh environments and reduce maintenance costs.At present,the mechanical properties of reinforced concrete components with stainless steel bars have been studied at home and abroad,but little research has been done on integral seismic performances of the frame structure with stainless steel bars under rare earthquakes.So far,the strength of stainless steel bar is equivalent to that of HRB500 MPa steel bar,but the elastic modulus of stainless steel bar is lower.Therefore,it needs to be confirmed that how do integral deformation performances of the structure and ductility demands of the components change,which are replaced HRB500 steel bars by stainless steel bars?This paper studied from two aspects of the component experiment and the integral structure simulations.A reinforced concrete column with stainless steel bars has been experimented under low-cycle repeated loading.Analysis the effect of the axial compression force ratio on seismic performances of columns by comparing two columns with different axial compression ratios.In addition,the displacement ductility coefficients between reinforced concrete columns with stainless steel bars and HRB500 steel bars under the same conditions are compared.A frame structure with HRB500 steel bars is designed according to requirements of the code,and design the frame structure with stainless steel bars according to the same reinforcement conditions,because of the equal strengths of stainless steel bar and HRB500 steel bar.Perform-3D is used to carry out bidirectional rare seismic actions of the two structures in zone of earthquake intensity 8(0.3g).Compare differences in intergral deformation responses of the two structures and ductility demands of the beam and column.And analyze differences of seismic performances between the two structures.The main conclusions are as follows:(1)Within a certain range,increasing the axial compression force ratio would reduce the ultimate displacement drift and displacement ductility coefficient of the column,and accelerate the speed of stiffness degradation of the column with stainless bars when the reinforcement ratio and other conditions are certain.The displacement ductility coefficient of the column with stainless steel bars is lower than that of the column with HRB500 steel bars when their stirrup characteristic and other conditions are same.The deformation and displacement ductility coefficient of the reinforced concrete column with stainless steel bars can meet requirements of earthquake resistance under the standard of the displacement ductility coefficient being 3.0 when the axial compression force ratio is not more than 0.3.(2)Regularities of integral deformation rections of the frame structure with stainless steel bars are similar with those of the frame structure with HRB500 steel bars.The integral stiffness of the frame structure with stainless steel bars is lower but the deformation is larger.The maximum roof displacement and maximum story drift of the structure with stainless steel bars are increased when compared with those of the structure with HRB500 steel bars,and maximum story drifts of the two structures are less than 1/50 which is the limit of Chinese code.The bottom shear force and stiffness of the structure with stainless steel bars are slightly smaller.(3)Plastic hinge ratios of the beam and column with stainless steel bars are higher than those of components with HRB500 steel bars,and demands of the curvature ductility of the beam and column with stainless steel bars are generally small at same positions.however,the maximum plastic drift ratios of the beam and column with stainless steel bars are higher.Both demand distributions of the maximum curvature ductility and plastic drift ratio of the beam and column of the two structures conform to lognormal distribution.Compared with ductility demads of the components with HRB500 steel bars,demands of the curvature ductility of the beam and column with stainless steel bars are reduced at the same guaranteed rate,while demands of the plastic drift ratio are increased under three situations of considering only the uncertainty of ground motion,considering two types of uncertainties of ground motion and model quality and considering four types of uncertainties given by American code.(4)Demands of the curvature ductility and plastic drift ratio of the beam and column of the two structures are higher when consider more uncertainties,and design requirements of the beam and column are higher.In order to make the frame structure with stainless steel bars has more safety margin in region 8,it is suggested to consider two types of uncertainties of ground motion and model quality when analyze demands of the curvature ductility and plastic drift ratio of components in high intensity zone.