This computational investigation focused on numerical modeling of the shear behavior of ultra-high-performance concrete (UHPC) beams reinforced longitudinally with high-strength rebars and ordinary-strength steel (stirrups). Nonlinear three-dimensional finite element model, using the concrete damaged plasticity model and material properties obtained from uniaxial compressive and tensile laboratory tests, was conducted to simulate UHPC concrete beams within a commercial finite element software package ABAQUS 6.13. This investigation included the effects of various parameters; shear span-to-effective depth ratio (a/d), volume fraction of steel fibers, V f , longitudinal reinforcement ratio, ρ, and stirrups spacing, s, on shear behavior of UHPC beams. Numerical results compared with previously obtained experimental results in terms of shear force-midspan deflection and cracking-propagation behaviors. The results showed that finite element analysis predicted the shear behavior of UHPC beams in good agreement with the experimental data and predicted the response of the beam with variation in various parameters with a good accuracy. K E Y W O R D S ABAQUS, concrete damaged plasticity (CDP) model, high-strength rebars, numerical modeling, shear behavior, ultra-high-performance concrete (UHPC) beams 1 | INTRODUCTION New construction methods and technologies are growing to extend the lifespan of existing and new structures. As part of the new technologies, new developments in concrete are gradually changing the design and construction worlds. 1Invented about two decades ago, ultra-high-performance concrete (UHPC) is characterized by steel fibers, cement, silica fume, fine sand, superplasticizer, and very low watercement ratio. 2 This new-generation concrete material possesses high tensile and compressive strengths, high ductility, low permeability, and good durability because of its dense microstructure. The use of UHPC allows designers to select lighter sections and longer spans for structural members. 3,4 The inclusion of steel fibers in UHPC improves its mechanical properties, reduces its brittleness, and alters the crackpropagation behaviors. 5 The shear behavior of concrete is one of the very important, but complex, topics in concrete structures, which has been investigated by many researchers. The brittle shear behavior of concrete in structural elements makes experimental investigations difficult to conduct, time consuming, expensive, and need more human resources to accomplish, as compared to finite element model (FEM). 6 Although many aspects of structural behavior of reinforced UHPC beams have been studied experimentally (e.g., in References 7 and 8), a limited number of numerical studies have been reported in the literature on the shear behavior of UHPC beams. Schramm and Fischer 9
