| The structural problem exposed by earthquake is carefully researched on the basis of large numbers of seismic damage pictures of structure and data files collected by housing forensic expert team of Guangdong province, which carried out structural appraisal work of wenchuan county. Through the study of seismic damage on structure of wenchuan county, many building stairwells are found to be seriously damaged to indicate the previous design is not safe without considering the impact of stairwell on the main structure. The performance of stairs in seism and the impact of stairwell on the main structure are necessary to be seriously researched and considered by civil engineering. As a whole the theory and research work of this aspect is in preliminary stage in our country. A lot of works are needed to be carried out. The main research content of this paper is listed as bellows:(1) The seismic statistics and characteristics of structure in wenchuan town are studied according to the built year and functions and structure style. Then typical damaged structure is processed to make structural back checking and calculation analysis. Combined the seismic damage characteristics of house, the suggestion to ensure earthquake resistance in aseismic fortification zone could be put forward.(2) The break law of structure in wenchuan town was summarized from different aspects to further recognize the aseismic mechanism of the building structure. Then the basic law of collapse under microseism for house in mountains is bring forward to reflect and advance our seismic provisions.(3) The calculation model of frame construction, which contains stairwell, is established and analyzed based on ETABS finite element analysis software. Then the calculation results are compared with traditional model without considering stairwell effects to understand influence of stair on the dynamic characteristics and overall deformation of frame construction. The relationship between stair rigid effects and structural lateral stiffness and layer numbers of frame construction are found out based on these comparisons. With time history analytical method applied, the acceleration and speed and displacement of model top layer are compared between model with stairwell and traditional model to accurately reflect the impact of stairs on the framework in detail. Four different stairwell arrangement models of frame construction are established and compared to get the influence law of stairwell on frame construction.(4) The strained condition of gangboard under horizontal seismic load and the impact of stair on beam,column and other members of frame construction are researched in detail. The stress distribution of gangboard is analyzed briefly to get stress distribution law under seismic action. The reinforcement area design and strained condition of staircase columns are compared between model with stairwell and traditional model to understand the impact of staircase on beam,column and other members of frame construction. And some aseismic design proposals are put forward. |
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