A novel advanced fiber beam-column element, which incorporates stability functions and the fiber distributed plasticity model to capture geometric and material nonlinearities, respectively, has been successfully developed to predict the nonlinear inelastic thermo-mechanical behaviors of steel frames subjected to aftershock after fires. To address the nonlinear dynamic problems resulting from aftershocks after fires, a sequential nonlinear thermal incremental-iterative solution scheme has been developed, which is based on the Newton-Raphson algorithm and Newmark-β method. In addition, a transcendental probability-based method is employed to express the statistical characteristics of aftershock intensity relative to the mainshock. The proposed method is applied to analyze three framed structures: a steel portal frame, a two-story plane steel frame, and a four-story asymmetric space steel frame. This analysis shows the accuracy, computational performance, and applicability of the proposed method. Remarkably, the results obtained from the code work, using just one or two elements per member, are in close agreement with all the results analyzed by Abaqus. This emphasizes that the proposed method effectively predicts the response of framed structures under aftershock after fires with excellent computational efficiency, significantly surpassing traditional finite element approaches in commercial software like Abaqus. The successful results of the dynamic analysis of the frames under aftershocks following fires underscore the importance of considering aftershocks after a fire incident. It is demonstrated that the occurrence of an aftershock accelerates the failure of the frame compared to the case when the frame is subjected to fire alone. This highlights the critical need to account for aftershocks when assessing the safety and structural integrity of framed structures after a fire event.

中文翻译：

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火灾后余震下钢框架的热机械响应


一种新型先进的纤维梁柱单元，结合了稳定性函数和纤维分布塑性模型，分别捕获几何和材料非线性，已成功开发用于预测钢框架在火灾后余震中的非线性非弹性热机械行为。针对火灾后余震引起的非线性动力问题，提出了基于Newton-Raphson算法和Newmark-β方法的顺序非线性热增量迭代求解方案。此外，采用基于超越概率的方法来表达余震强度相对于主震的统计特征。该方法应用于分析三种框架结构：钢门架、二层平面钢框架和四层非对称空间钢框架。该分析显示了所提出方法的准确性、计算性能和适用性。值得注意的是，每个成员仅使用一两个元素的代码工作所获得的结果与 Abaqus 分析的所有结果非常一致。这强调了该方法有效地预测了火灾后余震下框架结构的响应，具有出色的计算效率，显着超越了 Abaqus 等商业软件中的传统有限元方法。火灾后余震下框架动态分析的成功结果强调了考虑火灾后余震的重要性。结果表明，与框架单独遭受火灾的情况相比，余震的发生加速了框架的失效。 这凸显了在火灾事件后评估框架结构的安全性和结构完整性时考虑余震的迫切需要。