Analysis Of Typical Seismic Damage Of Two Categories Of Structures

In recent years, earthquakes occur frequently, which makes a great contribution to the loss of life and public property. The major threat caused by earthquakes is the destruction of the civil engineering. Thus, it is of great importance to analyze and summarize the typical earthquake damage and failure mechanism of kinds of structures. It also plays a very important role in taking much more reasonable structural seismic measures to reduce the loss. Therefore, this paper collects seismic damage materials of two typical structures in the Ninger Earthquake, the Great Wenchuan Earthquake and the Yushu Earthquake. The first category is the multistory brick masonry structure with spacious rooms, permeate transverse; the other one is RC frame structure with upside-soft and heavy roof. Their failure mechanisms are discussed. Major work and conclusions of this paper are listed as follows:1. Seismic damage of multistory brick masonry structure with spacious room and permeate transverse show the seriously shear inclined cracks with brick blocks scattered. For further study on the mechanism of seismic damage to this kind of the structure, this paper uses the fine finite element method, which conducts seismic response analysis contrast of normal room and multistory brick masonry structure with spacious room of the practical seismic damage material, uses the index of the wall average shear bearing capacity reserve coefficient to effecting structural seismic capability. The results show that:(1) Numerical results show that the average wall reserve coefficient of the wall of structure with normal room is larger than that of the structure with spacious room. For the latter, under the excitation of medium earthquake (fortification intensity is 7 degree), the average reserve coefficient of its inner longitudinal walls is less than 1, which is obviously lower than that of outer longitudinal wall and cross wall. The numerical results are in accordance whit practical seismic damage.(2) The arrangement of spacious room should not be used in brick masonry structure. The mortar with higher strength or tie reinforcements is usually utilized in masonry structures with large transverse span in order to improve seismic bearing capacity of inner longitudinal wall. 2. There are many RC archaize frame structures with heavy roof, upside-soft and separated arrangements of frame column in this country. There is a heavy destruction in this kind of structure in earthquake. The investigation of the seismic damage shows that there are 2 major types of damage: the columns placed in top storey are sheared severely along the bottom edge of beam; connections of beam, column and infill wall is distributed with through cracks. To discuss the seismic response and seismic performance of this kind of structure, three models are set up: the model of prototype structure; the model of prototype structure with light-weighted roof; the model of prototype structure with reasonable adding frame columns placed in transverse wall of top storey. Meanwhile, we use the equivalent strut model to simulate infill walls to consider the influence of infill walls. The time history of typical earthquake waves is used as input excitation. The calculated shear force is compared with shear bearing capacity of the column. The results show that:(1) The earthquake force of top-level is relatively large with big roof load. In addition, due to upside-soft of top-level, the earthquake force only shared by both sides column and infill walls. Under the excitation of earthquake, the cracks are distributed in upper position of infill walls. At the section with distributed cracks, the earthquake force is undertaken by the frame column, while, at other sections (between the bottom and first crack section), the frame column and infill wall co-work with the earthquake force. The shear failure is apt to occur in the former.(2) Numerical analysis demonstrates that under the action of earthquake, the shears force of columns placed in up storey of the prototype structure is larger than their shear bearing capacity, which the arrangements of light-weighted roof and reasonable placed frame column in transverse wall of up storey benefit reducing. This shear force: the light-weighted roof reduce the seismic action, which is helpful to reduce the shears force of frame column; the reasonable placed frame column in transverse wall make sure that the columns and the wall in up storey could better co-operate to resist the seismic load.(3) Suggestions are given in this paper. Roof with light-weighted materials should be arranged reasonably, too. Both of the measures benefit the improvement of the seismic performance of the structure.Results of this paper can be referenced to improve the seismic performance of related building structures.