Study On Seismic Behavior Of Reinforced Concrete Frame Structure With Multiple Central Reinforcement

In order to meet the service requirements of a subway station building in Lanzhou,the structure is selected as a long-span reinforced concrete frame structure,and the frame column adopts the form of multiple central reinforcement.Taking the actual project as an example,the experiment and numerical simulation of multiple central reinforcement joints are carried out,and the nonlinear time history analysis of the frame structure with multiple central reinforcement columns is further carried out.The anti-collapse performance of the structure is evaluated.The main research work is as follows:(1)The effects of axial compression ratio and column shear span ratio on the seismic performance of multiple central reinforcement joints are considered in the experimental study.The experimental results show that the plastic hinge failure occurs at the beam end of the joints.There is no identifiable damage in the core area of the joint,which shows the characteristic of "strong node weak component".The higher the axial compression ratio is,the higher the horizontal bearing capacity is,the better the energy dissipation is,the greater the stiffness of the specimen is,but the faster the stiffness degradation rate is,the worse the ductility is.The larger the shear span ratio is,the lower the horizontal bearing capacity is,the worse the ductility is,the smaller the stiffness of the specimen is,but the fuller the hysteretic loop is,and the better the energy dissipation capacity is.(2)Based on the existing constitutive model of concrete,the method of calculating the constitutive relation of each layer confined concrete under the form of multiple central reinforcement is proposed,and the element model and its parameter determination method are discussed in detail.The finite element analysis model of multiple central reinforcement joints is established.The simulation results show that the numerical results are in good agreement with the experimental results.The proposed constitutive relation calculation method and parameter determination method can be used to analyze the mechanical behavior of multiple central reinforcement members.(3)The time history analysis of the complex frame structure with multiple central reinforced columns is carried out.Compared with the conventional frame structure,thedisplacement response and internal force response of the structure under rare and extremely rare earthquakes are analyzed.The results show that the use of multiple central reinforcement in frame columns can reduce the displacement response of the structure and improve the stiffness of the structure,which is more conducive to meeting the earthquake-resistant target of "no collapse under maximum consider earthquake".By analyzing the development process of plastic hinge of complex frame structure,it is found that the weak link of the complex frame structure is the third floor,the failure process is that the failure at the end of the beam is ahead of the end of the column,and the failure at the end of the column and the end of each story is remarkable.The seismic response characteristics of "strong column-weak beam" are shown,and the layer yield failure occurs in the third and fourth layers of the structure.(4)On the basis of incremental dynamic analysis and seismic vulnerability analysis method,the collapse resistance of the complex frame structure is further evaluated.The results show that the structure can meet the target of three-level aseismic fortification criterion and has certain safety reserve,the vulnerability curve of collapse and damage increases slowly,and the probability of sudden collapse of structure is low.The structure can resist rare earthquakes effectively,and it still has a high anti-collapse ability under the action of extremely rare earthquakes.