Shear Capacity of RC Elements With Transverse Reinforcement Through a Variable-Angle Truss Model With Machine-Learning-Calibrated Coefficients

Shear Capacity of RC Elements With Transverse Reinforcement Through a Variable-Angle Truss Model With Machine-Learning-Calibrated Coefficients

Dario De Domenico, Giuseppe Quaranta, Qingcong Zeng, Giorgio Monti
Copyright: © 2023 |Pages: 18
DOI: 10.4018/978-1-6684-5643-9.ch007
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Abstract

This chapter addresses the shear capacity prediction of reinforced concrete elements with transverse reinforcement through a hybrid approach in which a mechanical model (i.e., the variable-angle truss model incorporated in the Eurocode 2) is enhanced with two machine-learning-calibrated corrective coefficients aimed at improving the accuracy of the numerical predictions. Genetic programming is adopted to derive closed-form expressions of the corrective coefficients, thus making the proposed formulation suitable for design purposes and usable by practitioners. The model predictive performance and the improvements over alternative code-based formulations is demonstrated through a wide database of experimental results of reinforced concrete beams and columns with plain and hollow sections failing in shear under both monotonic and cyclic loading conditions. The proposed approach leads to numerical-to-experimental shear capacity ratios having mean value close to one and coefficients of variation equal to 32%, 28% and 24% for beams, columns with plain and hollow sections, respectively.
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A Short Review About Some Code-Conforming Shear Capacity Equations For Rc Beams And Columns

Starting from the truss resisting mechanism postulated by Ritter and Mörsch in the early 1900s, two approaches were developed to reduce the conservativeness of the original truss model: 1) the additive approach, in which an additional concrete contribution (generally having empirical nature) is considered along with the truss contribution with compression struts inclined at 45° (e.g., ACI 318 Building Code (2019) and the pre-standard version of the Eurocode 2 (1991)); 2) the variable-angle truss model with compression diagonals inclined of angles generally less than 45° (e.g., Model Code 90 (1993), the Eurocode 2 (2004) and other national building codes in Germany and Italy). The reason for such “variable” inclination is related to the observation of some physical phenomena occurring during shear failure of RC members with stirrups, such as aggregate interlock, dowel forces and residual tensile stress, that induce a strut rotation mechanism to cross adjacent cracks (Walraven et al. 2013).

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