Antiseismic Performance Analysis Of Lushan Middleschool Frame Structure Teaching Building

In China today, reinforced concrete frame structure has been widely used in schools, hospitals, residences, office buildings and other personnel-intensive buildings for its flexible space layout, light weight, good integrality, easy construction and some other advantages. The codes for structural design in our country consider frame structure infilled walls as non-structural element, recommend using lightweight infilled wall materials, and take no account of the effects between infilled walls and frame structure, but only multiply by reduction factor of 0.6 to 0.7 when calculate the natural vibration period of frame structure. In recent years, a large number of frame structures suffered destruction in the strong earthquakes because of the unreasonable consideration of infilled walls, and these caused a high number of casualties and great property losses. Therefore, the consideration of frame structure infilled walls needs to be further improved on the basis of the existing codes requirements.In addition, studies show that the most serious damage area is the near-fault in the earthquake. By the impact of fault rupture directivity effect, the ground motion velocity time history and displacement time history present high-intensity pulse, which is the main cause of the near-fault structure failure. At present, the study about velocity pulse mostly concentrate on the relationship among the pulse period, pulse peak value and the seismic source parameter, and the failure mechanisms of different types of structures under the action of velocity pulse ground motion. But the earthquake intensity index of velocity pulse needs to be further researched when study the near-fault structure seismic. At present, the most widely used earthquake intensity index in seismic analyses and structural designs is PGA in our country, but the structure seismic damages in recent strong earthquakes show that PGA is not an appropriate earthquake intensity index in the near-fault.This paper mainly takes Lushan middle school frame structure teaching building as the analysis object, combines with its damage characteristics in Lushan earthquake, at April 20, 2013, and performs numerical simulation on the building with large-scale non-linear finite element software ABAQUS. Mainly analyses the seismic damage performances about main load-bearing structures and infilled walls of the frame structure teaching buildings, which take different density and stiffness infilled wall materials, under the action of different earthquake intensity. The analysis shows that the floor displacement of a frame structure, which seismic precautionary intensity is seven, is larger when the infilled walls material is fired common brick than it is porous brick under the action of low earthquake intensity, and is larger when the infilled walls material is porous brick than it is fired common brick under the action of high earthquake intensity. The main purpose of the analyses is to point out that the choice of frame structure infilled walls material is unreasonable in the current structural design codes, and suggest choosing the high density and stiffness infilled wall materials when the potential earthquake action is small(0.2g and below) in this area, and choosing the low density and stiffness infilled wall materials when the potential earthquake action is large(0.2g above) in this area.This paper mainly takes Lushan middle school frame structure teaching building as the analysis object, and performs time-procedure analysis on the building in elastic stage and plastic stage under the action of multiple velocity pulse ground motions. The analysis shows that, under the action of velocity pulse, the correlation between the PGA(PGV) and the seismic response of structures is preferably when the frame structure works in elastic behavior, and the correlation between the PGV(PGD) and the seismic response of structures is preferably when the frame structure works in plastic behavior. Considering comprehensively, the correlation between the PGV and the seismic response of structures is preferably in the near-fault. The main purpose of the analyses is to point out that the earthquake intensity index used in seismic analyses and structural designs in our country is not appropriate, and suggest choosing PGV as the earthquake intensity index in the near-fault.