框架-核心筒结构连梁抗弯刚度折减系数取值方法研究

Study on determination of flexural stiffness reduction factor of coupling beams in frame-core structures

对于框架-核心筒结构,连梁抗弯刚度折减系数取值的大小会影响结构的抗侧刚度与地震响应,从而影响到地震作用在核心筒与框架之间的分配比例,最终将影响连梁的设计内力和配筋。首先改进了预设屈服模式设计方法,在一次设计后,通过设防烈度作用下的弹塑性分析,计算各连梁的实际抗弯刚度折减系数,并利用该系数对结构进行二次设计。通过对比罕遇地震下结构弹塑性性能,发现二次设计后,结构的最大基底剪力和最大层间位移角均有所减小,且剪力墙的损伤程度得到改善,而二次设计对结构的配筋量无显著影响。其次,探究连梁抗弯刚度折减系数初始值对设计结果的影响。计算表明,当连梁抗弯刚度折减系数初始值分别为0. 7、0. 6和0. 5时,经过设防烈度地震作用下的弹塑性分析,各连梁抗弯刚度折减系数的计算值相差较小,二次设计后的配筋量亦较为接近,说明该设计方法受连梁抗弯刚度折减系数初始值的影响较小。最后,研究了改进的预设屈服模式设计方法的迭代收敛性,结果表明,连梁抗弯刚度折减系数的计算值随着迭代设计次数的增加而逐渐收敛于一系列稳定的值,并且该值与连梁抗弯刚度折减系数的初始值无关。通过计算发现,迭代设计的收敛性较快,一般进行两次迭代即可使连梁抗弯刚度折减系数的取值趋于稳定。

In frame-core structures, lateral stiffness and seismic response the flexural stiffness reduction factor of the structure, thus influencing the （FSRF） of coupling beams influences the distribution of seismic-induced forces within the core tube and the frame, and this can further influence the design internal forces and reinforcement of the coupling beams. Firstly, this paper improves the pre-determined yield mode （PdYM） design method. After the first design has been completed, actual FSRFs of each coupling beam are calculated based on inelastic analysis under fortification earthquakes, and are then used to run the second design. By examining the seismic performance under rare earthquakes, it is revealed that the maximum base shear and inter-story drift are reduced and the damage of shear walls is mitigated by using PdYM design method. The volume of reinforcement almost remains the same. Secondly, the influence of the initial FSRF of coupling beams is studied. When the initial FSRF of coupling beams is taken as O. 7, 0.6, or 0.5, the actual FSRFs and necessary reinforcement of the considered structures are very close to each other after an inelastic analysis under fortification earthquake. This suggests that the PdYM design method is not sensitive to initial FSRF of the coupling beam. Finally, convergence of the PdYM design method is investigated. Results reveal that the FSRF of the coupling beam converges to stable values as the time of iteration increases, and these values are also insensitive to the initial FSRF of coupling beam. It is found that the speed of convergence is fast, and a stable value of FSRF of the coupling beam can be achieved within two design iterations in most of the cases.