Analysis On Impact Of Stairs To Seismic Performance Of High-rise Frame Structure

Although stairs has been extensively utilized into the high-rise frame structure system, stairs structure as vertical and perpendicular traffic aisle of buildings, its significance in the high-rise architectural structures is self-evident. Many previous post-earthquake investigations have found that under the circumstances of many subject frame structure being complete, the structures of stairs (between stairs) suffered from serious destructions. Thus, the stairs which should have undertaken role of escaping, did not play the role of emergency evacuation-"safety when faced with natural disaster.After Yushu and Wenchuan Earthquakes, domestic specialists and scholars have issued a series of essays which illustrates that in the frame structure, the existence of stairs changes distribution of stiffness of overall structure which causes stress state and overall deformation of main structural element connecting to stairs to have obvious changes. Stairs have significant influence on spatial behavior of overall structure. Therefore, Ministry of Construction definitely regulates in Article 3.6.6 of the building seismic design codes (GB50011-2010) in July,2008: "Establishment of computational model, necessary simplified calculation and treatment should comply with actual conditions of structure and take the influence of components of stairs into consideration in calculation".This essay takes a building of ten layers of concrete frame structure as example and uses FEA design analysis software ETABS to establish six high-rise frame structure models with, without stairs and stairs in different positions. It also uses decomposition response spectrum method and time history method to calculate and analyze each model and get the result of influence of stairs to seismic performance of stairs to high-rise frame structure.Results showed that the stairs have greater influence on the natural vibration characteristics, overall deformation and frame structure internal force of high-level framework structure; the stress and overall deformation of staircase structural elements (staircase flight slab, staircase pillar, platform beam) are significantly changed under the effect of bi-directional horizontal earthquake action, meanwhile, the effect of earthquake action in staircase flight slab layout direction (Y) is greater than that of perpendicular to staircase flight slab layout direction (X); the change of stair position has greater influence on the natural vibration characteristics, overall deformation and stress condition of high-level framework structure; summarize research results and put forward targeted stair design suggestions.