考虑支撑断裂及节点板作用的中心支撑框架抗震性能研究

中心支撑框架(CBFs)具有良好的抗震性能和经济性，是常见的抗震结构体系。CBFs通常利用支撑受拉屈服和受压屈曲行为满足延性变形需求。在以往的地震中，CBFs结构的极限破坏模式均为支撑断裂。然而，在框架分析或设计时，CBFs通常被理想化为桁架结构，即将支撑构件两端考虑为铰接或固接连接并且忽略支撑断裂行为。该文提出能考虑支撑断裂行为和节点板作用的OpenSees数值模型。通过对单支撑构件、一层、三层中心支撑框架进行建模分析，模拟结果与试验结果吻合较好，验证了数值模型的有效性。采用验证后的三层框架模型进行动力增量时程分析表明，不考虑支撑断裂时，框架的倒塌储备系数偏大。建议对CBFs结构进行设计和分析时，应考虑支撑断裂和节点板作用，以合理评估其抗震性能。

SEISMIC PERFORMANCE OF CONCENTRICALLY BRACED FRAMES CONSIDERING THE BRACE FRACTURE AND GUSSET PLATE EFFECT

The concentrically braced frame (CBF), which shows good seismic performance with a low cost, is a popular seismic resistant structural system. Generally, CBFs are designed to meet the ductility requirement to ensure that the braces buckle in compression or yield in tension. As observed in previous major earthquakes, the ultimate failure mode of CBFs is the fracture of the braces. However, CBFs are often idealized as trusses in a frame analysis or design, considering the boundary of braces as pinned or fixed connections and ignoring the fracture behavior of the braces. In this paper, a numerical model using OpenSees considering the brace fracture and gusset plate effect was proposed. A single-brace model, a one-story frame model and a three-story frame model were simulated to verify the reliability of the numerical model. The simulated results showed good agreements with the corresponding experimental results. The calibrated three-story frame model was then adopted for an incremental dynamic analysis. The results indicated that the collapse margin ratio of the frame was overestimated if the brace fracture was not considered. It is strongly recommended that the brace fracture and gusset plate effect should be considered for the design and detailing of CBFs to reasonably evaluate the seismic performance.