The nonlinear analysis of large complex reinforced concrete (RC) frame structures with shear-critical members requires numerical approaches that combine high accuracy and computational efficiency. At the same time, existing modeling approaches either involve detailed and costly discretization of the deformations in the frame members (displacement-based approaches), or compromise on accuracy by greatly simplifying (or even neglecting) shear effects. This paper presents a novel nonlinear force-based fiber beam-column element that addresses both these challenges. The element is capable of capturing the complex moment-axial-shear interaction response of planar RC frames and walls, while at the same time requiring minimum discretization. The proposed formulation consists of two nested iterative procedures at the structure and sectional levels. The introduction of the sectional level procedure explicitly satisfies sectional equilibrium, which is not achieved in either existing displacement or force-based line element formulations. As a result, a stable convergence of all average strain, local crack strain, and slip strain components of the constitutive relationship is ensured. The efficiency and accuracy of the proposed element formulation is illustrated with the help of beam and frame tests from the literature.

中文翻译：

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基于力的纤维梁柱单元预测钢筋混凝土框架的弯矩-轴剪相互作用

具有剪切临界构件的大型复杂钢筋混凝土 (RC) 框架结构的非线性分析需要结合高精度和计算效率的数值方法。同时，现有的建模方法要么涉及框架构件中变形的详细且昂贵的离散化（基于位移的方法），要么通过大大简化（甚至忽略）剪切效应来降低准确性。本文提出了一种新颖的基于非线性力的纤维梁柱单元，可以解决这两个挑战。该单元能够捕捉平面 RC 框架和墙的复杂力矩-轴向-剪切相互作用响应，同时需要最小的离散化。提议的公式由结构和截面级别的两个嵌套迭代程序组成。截面水平程序的引入明确满足截面平衡，这在现有的位移或基于力的线单元公式中都无法实现。结果，确保了本构关系的所有平均应变、局部裂纹应变和滑移应变分量的稳定收敛。在文献中的梁和框架测试的帮助下，说明了所提出的单元公式的效率和准确性。