Abstract This paper deals with the development of a non-linear finite element model for reinforced concrete members under torsion. Using multi-fiber approach and displacement-based formulation, an enhanced multi-fiber 3D beam is proposed for predicting the behavior of reinforced concrete elements under torsion. The sectional analysis under elastic torsion is considered following Saint-Venant torsional theory for beam in order to take into account the effect of warping phenomenon. Elastic behavior under large displacements is also investigated in this model using a second-order approximation of the Green-Lagrange strains. In the inelastic domain, after cracking, following the space truss theory, the whole element is assumed to act as a tube, meaning the applied torsional moment is resisted only by the shear flow in the wall of the tube. Then, the effective wall thickness of the member after cracking is determined by an empirical formulation developed by the authors. Moreover, the section is discretized into different regions following its material response. In each region, depending on its characteristics, an appropriate constitutive material model is applied. For the concrete, the proposed behavior models are based on the Modified of Compression Field Theory and its extension. In order to correctly predict the torsional response, the authors proposed some modifications in the tensile behavior of concrete, based on experimental tests in torsion. In the elastic domain, the model is validated by comparing to the analytical solution and some results from other researches. In the inelastic field, a good agreement is obtained between a series of experimental tests and numerical results.

中文翻译：

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具有一致材料参数的受扭钢筋混凝土构件的增强有限元模型

摘要 本文讨论了受扭钢筋混凝土构件非线性有限元模型的开发。使用多纤维方法和基于位移的公式，提出了一种增强型多纤维 3D 梁，用于预测受扭钢筋混凝土元件的行为。为了考虑翘曲现象的影响，弹性扭转下的截面分析考虑遵循梁的圣维南扭转理论。该模型还使用格林-拉格朗日应变的二阶近似来研究大位移下的弹性行为。在非弹性域中，开裂后，根据空间桁架理论，假设整个单元充当管子，这意味着施加的扭矩仅由管壁中的剪切流抵抗。然后，开裂后构件的有效壁厚由作者开发的经验公式确定。此外，该部分根据其材料响应被离散化为不同的区域。在每个区域，根据其特性，应用适当的本构材料模型。具体而言，所提出的行为模型基于压缩场理论的修正及其扩展。为了正确预测扭转响应，作者根据扭转实验测试对混凝土的拉伸行为进行了一些修改。在弹性域中，通过与解析解和其他研究的一些结果进行比较来验证模型。在非弹性领域，一系列的实验测试和数值结果之间取得了很好的一致性。