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Journal of Zhejiang University SCIENCE A
ISSN 1673-565X(Print), 1862-1775(Online), Monthly
2017 Vol.18 No.11 P.910-926
Damage behavior of steel beam-to-column connections under inelastic cyclic loading
Abstract: Brittle cracks were observed in the welded beam-to-column connections of steel frames during an earthquake. The crack propagation and accumulated damage to the connections can lead to fractures at much lower ductility ratios. Understanding the connections’ damage behavior during an earthquake is crucial for the design of steel moment frames in seismic areas. Nine full scale beam-to-column connections were tested under constant amplitude and variable amplitude cyclic loading. The effects of loading amplitude, loading history, and peak load on the connection damage were analyzed. The damage characters were studied and three damage evolution models were calibrated and validated based on test results. The damage mechanism was investigated and an effective plastic strain index was developed to evaluate connection damage based on a ductile fracture mechanism. A fatigue fracture mechanics-based model, for evaluating the damage process of beam-to-column connections under cyclic loading, was proposed.
Key words: Beam-to-column connection; Cyclic loading; Connection test; Damage mechanism; Ductile fracture
创新点:1. 通过足尺节点试验,分析加载幅值、加载历程和荷载峰值对节点损伤性能的影响;2. 基于试验结果,标定并验证3种经验损伤演化模型,提出基于疲劳断裂力学的节点损伤评估模型。
方法:1. 通过对9个足尺梁柱节点试件开展往复加载试验,包括5种变幅加载制度及4种常幅加载制度,分析加载幅值、加载历程和荷载峰值对节点损伤性能的影响;2. 基于试验结果,根据节点损伤特点,在能量模型基础上,推导并拟合适用于节点循环加载的双参数损伤演化方程,并与其他模型进行比较,以验证其准确性;3. 结合疲劳和延性断裂理论,依据损伤机理,定义"有效塑性应变"量化损伤过程,并以疲劳裂纹发展公式为基础,推导适用于计算在极低周循环荷载下节点损伤过程的损伤演化方程。
结论:1. 加载跨幅对节点性能影响较小;加载历程的影响与历程中峰值位移循环次数密切相关;突发性的强峰值对节点造成的损伤最大。2. 节点损伤过程为幂函数形式;通过比较表明,在能量模型基础上推导出的适用于节点循环加载的双参数损伤演化方程,相对于单参数线性模型,能够更准确模拟节点在极低周循环下的损伤过程。3. 基于疲劳断裂力学理论的损伤演化方程物理意义明确,能够描述节点循环损伤试验中所表现出的加速损伤及"损伤拐点"特征。
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DOI:
10.1631/jzus.A1600520
CLC number:
TH161.12
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On-line Access:
2024-08-27
Received:
2023-10-17
Revision Accepted:
2024-05-08
Crosschecked:
2017-10-12