The composite action between the layers of steel and concrete is governed by the shear connection. Because of the complicated interconnection behavior of these composite layers, it is difficult to detect damage in the composite structures, especially, the interfacial integrity of the two layers. In this paper, anovel method has been developed for structural damage identification of composite structures based on a steel-concrete composite beam element with bonding interface. In displacement-based finite element (FE) formulation, three damage indicators have been embedded into stiffness matrix of the composite beam that are defined as a stiffness reduction in the concrete, steel and interface layers. An algorithm-based on recursive quadratic programming has been proposed to identify structural damage in the composite beam from static measurements. The analytical FE model is validated by adapting its static responses in undamaged state with those obtained from an equal experimental model as well as a FE model developed in commercial software ABAQUS. A convergence study is conducted to determine the number of the composite beam FEs. To verify the proposed method, the static responses of the FE model with different damage cases at a given loading are calculated, and the measurements are simulated by adding different levels of white noise. Then, the proposed algorithm is applied to identify damage of the composite beam. The effects of measurement noise, loading location and amplitude, measurement numbers and the sizes of FE mesh on the identified results have been investigated. The numerical results show that this method is efficient and accurate to separately identify small damage in the concrete slab, and the steel girder and bonding interface of the composite beam.

中文翻译：

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一种用于结构损伤识别的钢-混凝土组合梁单元

钢筋和混凝土层之间的复合作用受剪力连接控制。由于这些复合层的复杂互连行为，很难检测复合结构中的损伤，尤其是两层的界面完整性。在本文中，基于具有粘合界面的钢-混凝土组合梁单元，开发了一种用于组合结构的结构损伤识别的新方法。在基于位移的有限元 (FE) 公式中，三个损伤指标已嵌入到复合梁的刚度矩阵中，它们被定义为混凝土、钢和界面层的刚度降低。已经提出了一种基于递归二次规划的算法来从静态测量中识别复合梁中的结构损伤。通过将其在未损坏状态下的静态响应与从相等的实验模型以及在商业软件 ABAQUS 中开发的有限元模型中获得的静态响应相适应来验证解析有限元模型。进行收敛性研究以确定复合梁有限元的数量。为了验证所提出的方法，计算了有限元模型在给定载荷下不同损伤情况下的静态响应，并通过添加不同级别的白噪声来模拟测量结果。然后，将所提出的算法应用于识别复合梁的损伤。研究了测量噪声、加载位置和幅度、测量次数和有限元网格尺寸对识别结果的影响。