框架-核心筒结构框架承担最小剪力比例限制的合理性

Rationality of Restriction of Minimum Proportion of Shear Force Born by Frame in Frame-tube Structure

规范《超限高层建筑工程抗震设防专项审查技术要点》规定框架-核心筒结构中框架部分按刚度计算承担的楼层地震剪力最大值不宜小于基底总剪力的10%,而实际工程受建筑布置等因素的限制有时难以满足,工程界对此颇有争议.为探讨其合理性,设计了5个钢筋混凝土框架-核心筒结构,主要的变化参数为框架刚度、框架强度和连梁的形式.利用PERFORM-3D软件进行了弹性反应谱分析和小震、中震和大震下的动力时程分析,考察了各个结构的响应规律.分析表明:当框架部分按刚度计算承担的剪力最大值小于基底总剪力的10%时,增大框架刚度的做法不经济,结构的抗震性能反而更差;增大框架强度的做法减小了框架梁的损伤,改善了结构的抗震性能,但没有形成有效的"强柱弱梁"机制;采用宽连梁和可更换连梁都可以使核心筒自身具有双重抗震体系特征,连梁耗能能力的提高有效地保护了墙肢和外框架,结构的抗震性能得到了显著改善.

It is specified that the maximum shear force born by the frame calculated according to the stiffness in the frame- tube structure should not be less than 10% of the total base shear in ＂Chinese National Specification Technical Points of the Special Review for Seismic Design of Super High Rise Buildings＂. However, due to some reasons, such as the building layout, this requirement sometimes is difficult to meet in engineering practice. This requirement is controversial. In order to investigate its rationality, five reinforced concrete （ RC ） flame-tube structures were designed, and the main variables were the stiffness of the frame, the strength of the frame and the type of coupling beams. Then the elastic response spectrum analysis and the time-history analysis under small, medium or strong earthquakes were carried out to assess the seismic responses of different structures. It is found that when the maximum shear force born by the flame calculated according to the stiffness is less than 10% of the total base shear, amplifying the stiffness of the frame is not economic but leads to worse seismic performance. Amplifying the strength of the flame can reduce the damage of frame beams and improve the seismic performance of structure, but it can not form the effective ＂strong column-weak beam＂ mechanism. Adopting coupling beams with large width and replaceable coupling beams can both lead to the dual system of core tube. The enhancement of energy dissipation capacity of coupling beams can protect the shear wall and outer frame effectively, and significantly improve the seismic performance of the structure.