Satisfactory margin of safety against shear failure of lightweight reinforced concrete beams: 3D finite element modeling

Abstract

In concrete structures a satisfactory margin of safety should be ensured against shear failure that might occur under the forces that act upon the structure during its lifetime. Therefore, knowledge of the design and construction guidelines for shear of normal and high strength Lightweight Concrete (LWC) beams is desirable to better understand the structural design and performance of LWC beams. Thus, research is required to address and investigate the contribution of concrete compressive strength, shear span to depth ratio, tensile reinforcement ratio, and shear stirrups spacing as well as the failure mechanisms in situation of using LWC beams. As a result, this paper presents Nonlinear Finite Element Analysis (NLFEA) results of reinforced LWC beams because of the main benefits of NLFEA by providing substantial savings in the cost, time, and effort compared with the fabrication and experimental testing of structure elements as well as the ability to change any parameter of interest and the capability of demonstrating any interesting behavior at any load value and at any location in the system. After reasonable validation of NLFEA with the experimental test results, the NLFEA was expanded to provide a parametric study of fourteen hundred LWC beams that correlates the ultimate shear stress to studied parameters. Results indicated that the lower bound was for the beams with shear span to depth ratio, concrete compressive strength, and tensile reinforcement ratio of 5, 27.5 MPa, and 0.71%, respectively, and the upper bound was for the beams with shear span to depth ratio, concrete compressive strength, and tensile reinforcement ratio of 1, 68.8 MPa, and 2.21%, respectively. In addition, the performance of simulated models was investigated in terms of ultimate load capacity, ductility and energy absorption. Finally, a new parametric model is introduced in this paper to compute the shear strength of reinforced LWC beams without stirrups. The proposed equation was compared with numerous previous analytical models and founded that some models to be in a good agreement.