A new 3D finite element model is presented to analyze creep in reinforced concrete (RC) and prestressed concrete (PC) bridges. The proposed hybrid model uses a 12-node solid element to simulate concrete and a 2-node truss element to simulate rebars, the volume occupied by rebars in concrete and ducts. Structures are meshed with a special meshing technique and truss element connects with solid element through non-nodal connection. In this study, an additional two-node spatial truss element with a negative area is introduced to consider the non-negligible influence of rebar ducts in concrete and obtain a more precise and efficient simulation of RC and PC bridges. Different uses of the truss element with a negative area in both RC and PC structures are also explained, and two drop-frame cases and associated construction stages are investigated to validate the applicability of this model. The construction process analysis of a simplified PC continuous rigid frame bridge is also conducted in this study to further demonstrate the ability of the newly developed program to capture shear lag effect. The results show that the proposed model with negative-area truss elements enables the long-term behavior of RC and PC structures to be effectively predicted.

提出了一种新的3D有限元模型，以分析钢筋混凝土（RC）和预应力混凝土（PC）桥梁中的蠕变。提出的混合模型使用一个12节点的实体单元来模拟混凝土，并使用一个2节点的桁架单元来模拟钢筋，钢筋在混凝土和管道中的体积。用特殊的网格技术对结构进行网格化，并且桁架单元通过非节点连接与实体单元连接。在这项研究中，引入了一个带有负面积的附加两节点空间桁架单元，以考虑钢筋混凝土中钢筋导管的不可忽略的影响，并获得更精确，更有效的RC和PC桥梁模拟。还说明了在RC和PC结构中具有负面积的桁架元件的不同用法，并研究了两个落架案例和相关的施工阶段，以验证该模型的适用性。这项研究还对简化的PC连续刚构桥进行了施工过程分析，以进一步证明新开发的程序能够捕获剪力滞效应。结果表明，所提出的带有负面积桁架单元的模型能够有效地预测RC和PC结构的长期行为。