基于性能的既有建筑防屈曲支撑抗震加固设计

对于抗震能力低、抗震构造措施普遍不满足现行规范的原非抗震设防区既有建筑,采用消能减震技术加固结构,通过性能化设计方法实现抗震加固目标,可以解决传统加固方法效率低、难以实施等难题。以原非抗震设防区某既有框架结构教学楼加固项目为例,介绍了采用耗能防屈曲支撑提高抗震性能的具体方法和既有建筑基于性能的抗震加固设计流程。结果表明:加固前结构单体中最大的扭转周期比达到了0.96,最大位移比为1.38, 加固后扭转周期比控制为0.84,最大位移比为1.20; 加固前结构小震下构件承载力基本满足要求,但扭转周期比和抗震构造措施不满足现行规范要求,大震下结构会发生严重破坏甚至倒塌; 加固后结构构件承载力能满足7度小震(多遇地震提高1度)要求,小震下防屈曲支撑调整结构抗扭刚度,减小扭转效应,大震下防屈曲支撑屈服耗能,显著提高了结构的抗大震性能; 当结构的抗震性能明显提高时,抗震构造措施要求可适当降低。

Performance-based Seismic Design for Existing Building Reinforced with Bucking Restrained Braces

For the existing buildings in the original non seismic fortification area with low seismic capacity and seismic structural measures generally do not meet the current codes, the application of energy dissipation technology to strengthen the structure and the realization of seismic reinforcement targets through performance-based design method can solve the problems such as low efficiency and difficulty in implementation of traditional reinforcement methods. Taking the reinforcement project of an existing frame structure teaching building in the original non-seismic fortification area as an example, the method to improve the seismic performance by using bucking restrained braces and the design flow of performance-based seismic reinforcement for the existing building was introduced. The results show that the maximum torsion period ratio is 0.96 and the maximum displacement ratio is 1.38 before reinforcement, and the maximum torsion period ratio is 0.84 and the maximum displacement ratio is 1.20 after reinforcement. Before reinforcement, the bearing capacity of structural members under small earthquakes basically meets the requirements, but the torsional cycle ratio and seismic structural measures do not meet the requirements of current codes, and the structures under large earthquakes will be seriously damaged or even collapse. After reinforcement, the bearing capacity of the structural members can meet the requirement of 7 degrees small earthquake(increasing one degree in frequent earthquakes). The buckling restrained braces adjusts the torsional stiffness of the structure under small earthquake, which reduces the torsional effect. The yield energy dissipation of the buckling restrained braces under large earthquake significantly improves the anti-major earthquake performance of the structure. When the seismic performance of the structure is obviously improved, the requirements of seismic structural measures can be reduced appropriately.