Research On The Method Of Performance Based Energy Dissipation Design For Irregular Structures

With the widely use of energy dissipation technology in irregular building structure design,most conventional method for damping energy dissipation design is repeated to meet the performance and economic requirements using time-history analysis.The purpose of this study is to put forward a new method for irregular structure to fast and efficient energy dissipation design and performance evaluation.The main result of the work undertaken and major achievements include:1. A new method for irregular structure is given to energy dissipation design. The convention method of Kasai for energy dissipation design based on the performance curve of damper can clearly quantify structural damping effect, but this method is only applicable to regular structure’s damping design.Based on the Chinese code response spectrum, damping ratio correction coefficient is deduced, The method of Kasai is implemented a major improvement, which Include:(1)The establishment of an initial allocation of a new damping system parameters;(2) Based on the theory of the random vibration and optimization;(3) The development of a new new procedure combining SAP2000API finite element software and genetic algorithms is bring forward to quickly and synchronously optimize the number, location and parameters of dampers in different story of irregular structure. Thereby, the application of Kasai is expanded to energy dissipation design in irregular structures.2. During the pushover process, the structure with the velocity dependent dampers is not dynamically, so the influence of dampers would not be able to be considered.A pseudo static analysis method is proposed in this investigation. The elastic time-history analysis and the pushover analysis are combined to infer the real responses of structure under rare earthquake. This new method is an approximate method, it is based on not only the assumptions of pushover analysis method, but also the following assumptions:(1)Assuming that the structure load pattern under rare earthquake is proportional to maximum story acceleration load calculated by elastic time-history analysis; (2) The target displacement of structure is assumed to be similar to the structure displacement calculated by elastic time-history analysis; (3)The damper in structure can be simulated by a bar element with a plastic hinge.3. A method of inter-story capacity spectrum based on the pseudo static elastic-plastic analysis mentioned above is given to evaluate performance of the irregular structure’s absorption design. If a seismic design is evaluated in a timely manner, this design is guaranteed. Capacity spectrum method can be used to study the performance of the nonlinear deformation to evaluate the seismic performance of structure under excitation of earthquake.However, capacity spectrum method is based on the structural capacity curve of the displacement vs base shear. The seismic performance of irregular structure is controlled by the deformation of the weak story. With convention capacity spectrum method, it will bring large error for vertical irregular structure by seismic performance of equivalent system. According to the characteristics of vertical irregular structure under earthquake, considering the dynamic characteristics of different reaction stage, taking the floor as the research object, the seismic performance assessment of the inter-story capacity spectrum method is given for vertical irregular structure, which can not only identify the the weak story, but also evaluate the seismic performance of each story in irregular structure.4. A complete procedure of design-evaluation-redesign is established and confirmed for the design of energy dissipation and evaluate the performance of the irregular structure based on modified Kasai method and inter-story capacity spectrum method. The application of this method is also performed in practical engineering (irregular frame structure, irregular frame shear wall structure) and the corresponding verification of the analytical results, further reflect the method in irregular superiority of seismic design of structure. It can quickly get the optimal design scheme, the realization of "private reservations " performance based seismic design of irregular structure, target, and can get the response of the structure under rare earthquake is in a relatively short period of time, such as the development of the plastic hinge situation, story displacement, force of damper and weak story in the structure. If irregular structure plastic performance evaluation cannot achieve the performance goal, it will be redesigned that the energy dissipation in irregular structure based on modified Kasai method, until achieving performance goals.