Simulation Study Of Bottom Collapse Of Reinforced Concrete Frame Structure In High Intensity Area

Reinforced concrete frame structure is one of the most widely used structure type which is used in many schools,shopping malls,railway stations and other public facilities,therefore,the seismic damage of frame structure is concerned widely.The collapse of the structure for huge casualties and economic losses caused by earthquake is the most important reason,which there is the most serious damage in the high intensity area.Therefore,it is important to summarize and analyze the failure mode and mechanism of the structure from the numerical simulation of the frame structure in the high intensity area,and to lay the foundation for the seismic design and disaster reduction of the high-intensity zone frame structure.The relevant research is carried out and as follows.First,the damage and disaster situation of the frame structure in several major earthquakes are presented from the earthquake damage site investigation and damage picture of reinforced concrete frame structures,and the current research of the frame structure collapse is summarized.From the damage of the Chi-Chi earthquake,the Kobe earthquake and the Wenchuan earthquake and other major earthquakes.It can be seen that,the destruction of the high-intensity area of the frame structure is found firstly at the top of the bottom storyed column,and then the bottom of structure is overall collapsed.At present,there are two types of research on the collapse of frame structure on the overseas and domestic study field: one is the study of the overall performance and structural component level of the structure;the other is the study of ground motion characteristic,especially the near-field pulse ground motion.The numerical simulation is an important method to study the seismic response of structure.Considering the effect of on large strain,large displacement and contact collision in LS-DYNA software during the collapse simulation of frame structures,the analysis model of reinforced concrete frame structure is built by this software,selected the Wenchuan earthquake in the actual damage of the two reinforced concrete frame structure and by using the analysis models,the seismic response of two reinforced concrete frame structure is analysised and the destruction of the state and collapse process of the frame structure in the high intensity area are obtained.Compared with the actual earthquake damage,the validity and reliability of the models are verified.In order to study the influence of different types of ground motion records on the structural response,the ground motion records with different amplitudes are input respectively.The results showe that the response of the ground motion is effected by the amplitude of the ground motions.Two near-field ground motions and two far-field ground motions are input for the history analysis.By the comparison analysis,it shows that the structural response under far-field ground motions are very different from those under the near-field ground motions,and the damage is more serious under the near-field ground motion.Two near-field non-pulsed ground motions and two near-field pulsed ground motions are input for time history analysis.The comparative analysis shows that the structural response under the pulsed ground motion is obviously increased.In order to study the hysteretic energy consumption requirement of elasto-plastic single-degree-of-freedom system under seismic load,a number of different near-far field ground motions are input respectively,and the hysteretic energy dissipation time history analysis of single-degree-of-freedom system is carried out.There is a significant difference in the hysteresis energy demand of single-degree-of-freedom system under ground motions.By the comparison analysis hysteretic energy consumption of near-field ground motion is needed highly.The concept of hysteretic energy dissipation velocity spectrum of single-degree-of-freedom system is proposed,and the influence of different parameters on hysteresis energy dissipation velocity spectrum is analyzed from both seismic characteristics and structural characteristics.The results show that the hysteretic energy consumption requirement of the system is influenced obviously by the strength and site conditions of near-far field and ground motion,and hysteretic energy dissipation velocity spectrum is influenced obviously by the damping ratio of single-degree-of-freedom system.In order to further study the effect of different types of ground motion on the energy consumption of reinforced concrete frame structures,the results show that the energy dissipation of the structures under the near-field ground motion and far-field ground motion is obviously different,and there is a higher demand for the hysteresis energy under the near-field ground motion The results show that there is a difference in the energy dissipation of the structure under the action of pulsed ground motion and non-pulsed ground motion,and the demand for hysteresis energy consumption of the frame structure is higher than that of the pulsed ground motion.The collapse model of energy based on the double standard of energy and the maximum displacement is established,which the damage level of the frame structure is reflected by the interaction of energy and displacement,and to a certain extent the reason of the collapse of the structure are also obtained.by the results a basis for better considering the characteristics of ground motion in structural design and implementing energy-based structural seismic design is provided.