Análise numérica do comportamento estrutural de vigas em concreto de ultra-alto desempenho com aberturas na alma pelo modelo concrete damaged plasticity

Abstract

The execution of openings in reinforced concrete beams is a common practice in structural design; however, it alters the stress flow and can compromise the overall performance of the element. Considering the growing use of ultra-high-performance concretes, this study aimed to numerically analyze, through the Finite Element Method (FEM) and the Concrete Damage Plasticity (CDP) constitutive model implemented in ABAQUS, the structural behavior of concrete beams with web openings, comparing conventional concrete and Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC). The numerical model was calibrated using experimental results from the literature and subsequently extended to UHPFRC, with adjustments to constitutive properties and CDP parameters in order to properly represent the nonlinear behavior of the material. A comprehensive parametric study was conducted, varying the opening position (none, near the support, and at mid-span) and the presence of stirrups, to understand stress redistribution mechanisms and the influence of geometry and transverse reinforcement on the overall beam performance. The results showed that UHPFRC beams reached ultimate strength about 1.8 times that of conventional concrete and toughness approximately three times that of conventional concrete, as well as a better capacity for stress redistribution and energy dissipation. The numerical model accurately reproduced the failure modes and critical stress concentration zones, confirming the applicability of the CDP model in the analysis of brittle and semi-brittle materials. It is concluded that UHPFRC provides significantly superior structural performance when subjected to discontinuities caused by openings, ensuring greater stiffness, ductility, and overall safety of the system. The most critical case occurred in beams with openings near the support, which exhibited the greatest reductions in strength and stiffness, highlighting the need for special attention to this configuration in structural design. The study contributes a robust and replicable modeling methodology that can support future experimental calibrations and the development of normative guidelines for the design of structural elements made of ultra-high-performance concrete.