| The structure supported by foundation with different horizontal levels (abbreviated as SSFDH in the paper below), which is widely built in mountain cities, is a typical kind of structure built on slope. Such kind of buildings in a community located in Dujiangyan had damaged heavily during the 5.12 Wenchuan Earthquake 2008. The facts are that the specialties in such structures haven't been full understanding, and the structure designing is lack of the guides of relevant codes, and the theoretical research fall behind the demands of engineering construction.Based on the achievements of previous researches about the seismic behaviors of SSFDH, this paper aims to research the dynamic characteristics and anti-overturning behaviors for the purposes of providing a theoretical basis to the design work and the code compiling. The main contents are as below:①offering the simplified model based on the frame structure in SSFDH;②analyzing the influence to the dynamic characteristics when changing storey stiffness, storey mass and storey numbers and other factors;③analyzing the difference of contribution to the earthquake responses among the upper storeys and lower storeys under the same mode shape;④studying the stress distribution of basement subjected to the lateral load action;⑤discussing the special problems and studying the rules of SSFDH on anti-overturning behaviors. It can be concluded as follows by studying and analyzing in this paper:①There exist significant differences in dynamic characteristics between SSFDH and regular structures by analyzing the dynamic characteristics of simplified model with variation of storey mass, stiffness and storey numbers. The differences become significant while the lower storey stiffness is weaker, lower storey mass and storey numbers are larger. In addition, this paper provided the influence laws to natural period, mode shapes and related properties such as modal participation factors and modal participating mass ratios when changing the influence factors above.②The same mode shape contribute differently to the earthquake response between the upper storeys and the lower storeys. The fundamental mode shape mostly affects the upper storeys while the higher modes mainly affect the lower storeys.③The Chinese codes require the modal participating mass ratios must achieve 90% at least computing and analyzing the structure subjected to earthquake action. For the lower storeys of SSFDH, it might be omit the higher modes'contribution if doing this when designing so that leading to unsafety. The ratio is insufficient for SSFDH.④According to the study on the basement stress distribution, the guidelines in current Chinese codes aren't suitable for SSFDH in anti-overturning. It suggests checking anti-overturning behavior when designing SSFDH. This paper provides the moment computing method of both overturning and anti-overturning. The earthquake dynamic earth pressure have to be considered for SSFDH which lower storys contact with slope.⑤By analyzing the anti-overturning behavior of SSFDH, it is more unfavorable than the two regular structures which based on the different horizontal levels. Besides, the more stories, the less bays in the lower level, the more unfavorable in the anti-overturning behaviors for SSFDH.
|
PDF Full Text Request