Fang Sheng-En, Wu Chen, Zhang Xiao-Hua, Zhang Li-Sen, Wang Zhi-Bin, Zeng Qing-Yi
School of Civil Engineering, Fuzhou University, Fuzhou 350108, China.
National & Local Joint Engineering Research Center for Seismic and Disaster Informatization of Civil Engineering, Fuzhou University, Fuzhou 350108, China.
Materials (Basel). 2021 Sep 7;14(18):5135. doi: 10.3390/ma14185135.
Theoretical or numerical progressive collapse analysis is necessary for important civil structures in case of unforeseen accidents. However, currently, most analytical research is carried out under the assumption of material elasticity for problem simplification, leading to the deviation of analysis results from actual situations. On this account, a progressive collapse analysis procedure for truss structures is proposed, based on the assumption of elastoplastic materials. A plastic importance coefficient was defined to express the importance of truss members in the entire system. The plastic deformations of members were involved in the construction of local and global stiffness matrices. The conceptual removal of a member was adopted, and the impact of the member loss on the truss system was quantified by bearing capacity coefficients, which were subsequently used to calculate the plastic importance coefficients. The member failure occurred when its bearing capacity arrived at the ultimate value, instead of the elastic limit. The extra bearing capacity was embodied by additional virtual loads. The progressive collapse analysis was performed by iterations until the truss became a geometrically unstable system. After that, the critical progressive collapse path inside the truss system was found according to the failure sequence of the members. Lastly, the proposed method was verified against both analytical and experimental truss structures. The critical progressive collapse path of the experimental truss was found by the failure sequence of damaged members. The experimental observation agreed well with the corresponding analytical scenario, proving the method feasibility.
对于重要的土木结构而言，在遭遇不可预见的事故时，进行理论或数值渐进式倒塌分析是很有必要的。然而，目前大多数分析研究都是在材料弹性假设下进行的，以便简化问题，这导致分析结果与实际情况存在偏差。基于此，本文提出了一种基于弹塑性材料假设的桁架结构渐进式倒塌分析程序。定义了一个塑性重要系数来表示桁架杆件在整个系统中的重要性。在局部和整体刚度矩阵的构建中考虑了杆件的塑性变形。采用了杆件概念性移除的方法，并通过承载力系数来量化杆件失效对桁架系统的影响，随后用这些系数来计算塑性重要系数。当杆件的承载力达到极限值而非弹性极限时，杆件发生失效。额外的承载力通过附加虚拟荷载来体现。通过迭代进行渐进式倒塌分析，直到桁架成为几何不稳定系统。之后，根据杆件的失效顺序找出桁架系统内部的关键渐进式倒塌路径。最后，针对解析和试验桁架结构对所提方法进行了验证。通过受损杆件的失效顺序找出试验桁架的关键渐进式倒塌路径。试验观测结果与相应的解析情况吻合良好，证明了该方法的可行性。
