耗能伸臂桁架抗震性能的试验研究

该文以某8度区超高层框架-核心筒-伸臂桁架结构为工程背景，采用1：3比例缩尺，对三个不同构造形式的伸臂桁架抗震性能进行了拟静力试验研究。试验表明普通伸臂桁架由于腹杆整体屈曲，以及弦杆受弯屈服后翼缘局部失稳等原因，存在承载力退化速度快、延性差和耗能能力不足等缺点。将腹杆改为防屈曲支撑（BRB）可有效提高腹杆的耗能能力。采用截面削弱（RBS）构造形式可以有效提高弦杆的变形能力，防止受弯屈服截面翼缘发生局部失稳。而腹板焊接构造形式则在焊接处易发生低周疲劳破坏，不能充分发挥BRB的耗能作用。试验结果表明该研究提出的RBS与BRB相结合的伸臂桁架变形性能良好，滞回曲线饱满且承载力保持稳定，取得了良好的抗震设计效果。研究结果可以为伸臂桁架结构抗震设计提供参考。

EXPERIMENTAL STUDY ON THE SEISMIC PERFORMANCE OF ENERGY DISSIPATION OUTRIGGERS

Based on an actual building project (i.e., a super-tall frame-core-outrigger building located in zone of 8° seismic intensity), the seismic performances of three types of 1:3 scaled outriggers with different construction details are investigated through pseudo-static experiments. The experiments highlight three drawbacks of the regular outrigger, i.e., rapid degradation of bearing capacity, poor ductility and energy dissipation capacity, which are attributed to the overall buckling of web members and flexural yielding induced local buckling of flanges on the chords. Hence, web members are being replaced by buckling restrained braces (BRB) to improve the corresponding energy dissipation capacity. In addition, the reduced beam section (RBS) connection is adopted for the chords to improve the deformation capacity and prevent the flanges of chords from flexural yielding induced local buckling. The test results indicate that low-cycle fatigue damage often occurs at weld connections on the webs of chords, which hinders the fully development of the energy dissipation capacity of BRB. In contrast, the proposed outrigger with a combination of BRBs for the web members and RBS for the chords shows good seismic performance, including good deformation capacity, stable bearing capacity and sound energy dissipation capacity. The outcomes of this work will provide a useful reference for the seismic design of outriggers.