Effects of Member Size, Shear Span-to-Depth Ratio, and Longitudinal Reinforcement Type on the Shear Behavior of Lightweight Concrete Beams: A Numerical Study

The shear response of lightweight concrete beams depends on the member size, shear span-to-depth ratio, and longitudinal reinforcement type. Based on checks against two previously reported LC60 beam tests and three-dimensional nonlinear finite element analysis, this study evaluated these parameters within the investigated model series. Increasing the effective depth from 85 to 340 mm substantially increased the absolute shear capacity, while the nominal ultimate shear strengths remained approximately 0.895, 0.951, and 0.937 MPa and showed no pronounced classical monotonic decrease. Increasing the shear span-to-depth ratio from 1.5 to 5.0 shifted the computed response from arch action toward beam action and reduced the nominal ultimate shear strength by up to 75.9%. Replacing steel reinforcement with lower-modulus GFRP reinforcement reduced the stiffness and ultimate shear strength, although the difference between the two reinforcement types decreased with the member size. These results provide a numerical basis for understanding the effects of the member size, shear span-to-depth ratio, and longitudinal reinforcement type on the shear response of LC60 lightweight concrete beams.