屈曲约束支撑框架的支撑布置原则研究

屈曲约束支撑框架的支撑布置原则对其减震效果和结构的抗震性能影响显著。建立检验减震效果的6层和16层钢框架基准模型，分别以位移和层间位移不均匀系数为衡量结构地震损伤程度和损伤集中效应的指标，分析了支撑和框架间以及楼层间支撑较优且经济适用的布置原则。结果表明：减震效果随支撑面积的增加而减弱，建议主体框架加入支撑后结构的基本周期降低不宜超过1.5倍~2.0倍；支撑面积在楼层方向线性分布的比例系数为0.5~1.0时，结构的损伤集中效应较小。以“上层BRB屈服应发生在下层框架屈服之前”为性能目标，推导了楼层间支撑面积比上限值的理论公式，并用一个算例验证了公式的正确性。公式表明：当框架刚度较低或者屈服位移较小时，需严格限制支撑面积比，以防出现仅有某层或者较少层BRB屈服的集中损伤模式的不利现象。基于上述布置原则，给出了屈曲约束支撑框架设计流程。

RESEARCH ON LAYOUT PRINCIPLE OF BRACES FOR BUCKLING-RESTRAINED BRACED FRAMES

The layout principle of the buckling-restrained braces (BRBs) for buckling-restrained braced frames (BRBFs) significantly affects the mitigating effect and the structural aseismic performance. To test the mitigating effect, 6-story and 16-story steel moment resisting frames are built as benchmark models. Taking the displacement and the drift concentration factor (DCF) respectively as the indices to measure the structural seismic damage degree and the damage concentration effect, the optimal, economic and practical brace layout principle are studied between the braces and the frames as well as those among different stories. The ruselts show that the mitigating effect is weakened with the increase of the BRB area, and the fundamental period of structures shoud reduce no more than 1.5~2.0 times after installing the BRBs to the main frames. When the linear distribution proportional coefficient of the BRB area among different stories is 0.5~1.0, the DCF of the BRBF is insignificant. Using the performance target that the yielding of the upper BRBs should occur before the adjacent lower frame yielding, a theoretical formula determining the upper limit value of the BRB-area-ratio among different stories is deduced. A numerical example is used to verify the formula, showing that when the stiffness or the yield displacement of the main frames is small, the BRB-area-ratio should be limited rigorously to prevent the serious phenomenon of damage concentration that the BRBs yield only at one or a few stories. Based on the above layout principle, the design process of the BRBF is obtained.