Collapse Simulation Of Frame Structures Based On Rate-dependent Materials

The reinforced concrete frame structure is one of the most common structural forms adopted by China's civil buildings.Its seismic researches of elastic and inelastic responses under frequent earthquake and strong earthquake are relatively mature at present.However,The form and corresponding failure mechanism of collapses under ground motion with mega peak acceleration are still insufficient.In the high-magnitude earthquakes that occurred in recent years,cases of severe damage or even collapse of the frame structure have occurred frequently.Therefore,it is of practical significance to analyze the collapse process of the frame structure and study the collapse mechanism of the frame structure.Based on the Abaqus and Vumat subroutine,secondary development on the concrete and steel constitutive model was carried out.Through the material subroutine,the failure of the reinforced concrete material is simulated,the collapse of the structure is realized,and the results of simulation are discussed.The details are as follows:1.Based on the Abaqus/explicit dynamics analysis module,the pressure damage model in HJC constitutive model and the tensile damage model based on fracture energy are referenced,and the corresponding yield surface function and flow law are combined to construct the new concrete constitutive model related to steel strain rate.For the metal Johnson-Cook constitutive model related to steel strain rate,the correction in yield surface for domestic steel bars was carried out.And selection of material parameters for Johnson-Cook damage model applied to beam elements was simplified.2.The finite element model of the concrete column and a plane frame is established in the Abaqus/explicit analysis module,the numerical simulation analysis of the pseudostaticcollapse experiment completed by Tsinghua University in 2011 was implemented.By comparing the published test results,it is shown that the numerical simulation results have been well restored from the overall hysteresis curve to the local damage of the frame.The comparison results also show that using solid element to simulate the concrete and simulating the steel bar with the beam element are reasonable and effective for reinforced concrete frame structure,as it can intuitively reflect the damage form and the local damage of the structure.The comparsion also verified the correctness of the constitutive subroutine.3.Based on the element deletion in FEM,seismic collapse simulations of a four-story reinforced concrete frame structure under the actions of Wenchuan Wolong seismic wave with a peak acceleration of 400gal/600gal/800gal/1000 gal were carried out.The results show that in the bottom column,the column with larger axial compression ratio will be destroyed first.At the same time,the horizontal ground motion damage to the bottom column is mainly reflected in the column foot,and the vertical ground vibration damage to the bottom column is mainly reflected in the upper part of the column.4.Using the other four classic ground motion data,the collapse damage analysis under the peak acceleration of 1000 gal ground motion is carried out.The influence of vertical ground motion on the failure and collapse results of structures under fixed horizontal PGA is compared and analyzed.The analysis shows that under the action of the fixed peak acceleration of 1000 gal weak horizontal ground motion.,the greater the vertical peak acceleration of the ground motion,the smaller the lateral displacement of the structure,and the more serious the damage of the upper part of the frame structure column,the beam-column joints and the floor part.