| With the rapid development of China's modernization,the height and irregularity of many high-rise buildings exceed the limits of Chinese codes.In China,however,the traditional seismic design method are generally based on the bearing capacity and constructional measures to ensure structural ductility,which has certain limitation and cannot meet the requirements of seismic design for out-of-codes high-rise building.The practical results show that the performance-based seismic design is more suitable for the out-of-codes high-rise buildings,and it is critically important that how to obtain reliable elastic-plastic performance under strong earthquake.Therefore,it is the main trend in modern society that how to apply the performance-based seismic design theory and method to the analysis of irregular out-of-codes structures.The irregular office building in Huichang,Jiangxi is analyzed in this paper,which are partial discontinuity in the 2nd floor,and partial setback in the 15 th and 16 th floor,irregular torsion and the centroid eccentricity of the main tower and large chassis exceed 20% of the length of the chassis(belonging to the single tower offsetting)and so on.On the base of performance-based seismic theory and method,the seismic performance of out-of-codes structures is analyzed here.The main content as follows:(1)At first,the paper conduct a transfinite discriminant analysis for each irregular feature,and then reasonably confirm the performance objectives of structure and performance level of each component.Using PKPM and Midas building software establish two different mechanical models for the comparison of CQC and elastic time history analysis under minor earthquakes,and conduct analysis of elastic and unyielding under medium earthquake,and verify whether it meet the corresponding expected performance level.(2)The norm,technical specification for concrete structures of tall building,merely makes a brief discussion on the method of elastic-plastic analysis at the aspects of height and irregularity.The height of the irregular building is lower than the specification limits(150 meters),the static elastic-plastic method(Push-over method)can be used to analyze the performance under the strong earthquake,but the domestic and foreign studies show that the Push-over method in the flat and vertical structure of several irregular structures to obtain a reasonable approximation results still need to further verify.So in this paper,EPDA is used to select 3 seismic waves for dynamicelastic-plastic analysis,and compared with the Push-over method at the aspect of the top displacement,the displacement deformation needs,the plastic hinge damage.By comparing the applicability and error between Push-over method and dynamic elastic-plastic method in details for multiple irregular structures,thus obtains these performance indicators such as reliable elastic-plastic deformation,stress state and damage situation,and then puts forward some reference for the seismic design of this kind of building.(3)Finally,this paper aims at the situation that the centroid eccentricity of the main tower and large chassis is more than 20% of the length of the chassis(belonging to the single tower offsetting)will lead to the podium complex torsion effect to further analyse.First of all,it conducts the complex stress analysis of the skirt floor,then research the relationship between the tower and podium by establishing model respectively,and finally changes its eccentricity by adding different shear wall at corner of the podium form three optimization schemes.By studying the relationship between the performance of each scheme,it can propose optimization scheme of such irregular structure in the process of seismic design.Eventually,the project managed to achieve the performance objective by taking appropriate strengthening measures,and further verify that performance-based seismic design concept is more convincing for the out-of-codes high-rise building. |
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