Performance Analysis Of The Existing Structure With Additional Early Yield-type Side Force Resistant System

The new code for seismic design of buildings GB50011-2010provides China’s major cities and towns of earthquake intensity, the basic design earthquake acceleration and seismic design group. Compared to old Specification,some areas’s earthquake intensity is raised. Suffered as a major earthquake disaster in Wenchuan,Beichuan,Dujiangyan and other regions from7degrees upwards to8degrees. With the improvement of earthquake intensity, structural seismic design considerations will be enhanced. So now a lot of normal use of the building structure does not meet the new seismic requirements specification.Re-construction is bound to consume a large amount of manpower, material and financial resources, resulting in unnecessary waste. Therefore,reinforcement to take reasonable measures to the existing structure become an imperative road.Currently, the main seismic reinforcement method to do a direct reinforcement of the component, an additional branch of the internal system, set the isolation layer. Compared to other methods,mode of additional lateral force branch system is simple form, easy construction and reinforce good performance.Already,this method shows wide range of applications in the field of seismic reinforcement. Characteristics of the branch system for the study itself, but also become the focus of the study. A large number of research data show that, due to the mechanical properties, component connections, construction technology and economic conditions and other factors, the strength of the branch system may not meet the requirements of the new norms of fortification intensity.The accurate prediction of the real dynamic response under earthquake of the existing structures with additional branch system of side force resistant is necessary for the performance-based seismic design method of structures.The affect of Insufficient strength of the branch system on structural earthquake response is studied. Research methods of simplified equivalent are used based on time-history analysis under specific intensity to study the infulence of early yielding of the branch system on structural earthquake response.The results show that,with long periods, maximum relative displacement of structure and maximum earthquake undertaked by the original structure will be reduced by decreasing branch system yield strength coefficient after branch system yielded. Reversely,with short periods, maximum relative displacement of structure and maximum earthquake undertaked by the original structure will be increased by decreasing branch system yield strength coefficient.