耗能型屈曲约束支撑在结构设计中的合理应用与参数控制

Application and parameter controlling for dissipative BRB in structural design

针对耗能型屈曲约束支撑(BRB)在结构设计中遇到的突出问题开展理论和案例研究,讨论并整理了耗能型BRB在结构方案选型时主要考虑的因素和技术参数,对BRB屈服荷载与轴向刚度的合理匹配以及屈服变形与支撑长度的合理匹配进行分析,定义了两组参数匹配系数,并分别建议了合适的取值区间。通过案例分析了BRB屈服耗能可能对结构整体指标产生的不利影响,提出应在设计中评估设防地震及罕遇地震作用下结构可能产生的性能突变,不宜同时考虑BRB调整结构刚度和耗能双重作用的发挥,建议限制BRB在超过设防烈度地震作用以后再进入耗能阶段。通过附加阻尼比计算式的推导和参数分析,明确了BRB耗能效果的基本规律特征:附加阻尼比大小受结构自身和BRB参数双重影响,BRB分担的楼层地震剪力比例是主要影响参数,且随着地震作用的增大附加阻尼比并非一直增大,而是对应某一地震作用水平具有最大值。分析了BRB多遇地震耗能与大震变形控制问题,给出不同结构体系中保证支撑罕遇地震作用下使用安全的变形要求,并提出采用改进型BRB构造形式的建议,以满足在多遇地震耗能的同时保证罕遇地震作用下使用安全的特殊需求。研究结论为耗能型屈曲约束支撑在工程中的合理、高效应用提供理论参考。

Theoretical and case studies were carried out for several outstanding issues in the engineering application of dissipative BRB. The main factors and technical parameters were discussed for the technology selection of this kind of BRB. The reasonable matching relationship between the yield capacity and axial rigidity of BRB, as well as the matching relationship between yield deformation and BRB＇ s length were analyzed. The effective range of the two types of defined matching coefficients were given. The impact of BRB＇ s yielding on the whole structural response index was analyzed. It was suggested that the possible structural performance degradation under rare earthquake be evaluated in the schematic design, and avoid considering the BRB＇ s dual role of stiffness adjustment and energy consuming at the same time, or make the BRB reach yielding stage under design level earthquake. Through the calculation formula derivation of the additional damping ratio and the parametric analysis, the basic rule of the BRB＇ s energy dissipation effect is clarified： the additional damping ratio is affected by both the structure itself and the BRB＇ s parameters and the BRB ＇ s story shear ratio is the main controlling parameter. The additional damping ratio does not always increase with the increase of earthquake action, which has the maximum value corresponding to a seismic action. The problem about how to ensure the structure and BRB＇ s safety in rare earthquake if the BRB reachs yielding stage from frequent earthquake is discussed, the deformation requirements in different systems and suggestions for devices improvement are given. The study results can provide theoretical reference for dissipative BRB＇ s reasonable and efficient application in engineering.