Maher A. Adam

The evaluation of torsion investigations is based on the increasing demand for the creative design of curved structural members; yet, they are limited concerning lightweight concrete beams. Lightweight concrete has many and diverse utilizations, including multistory building frames and floors, curtain walls and bridges. This paper investigated the effect of fiber on torsional behavior of lightweight concrete beam. Many variables were studied such as compressive strength of lightweight concrete, fiber type, fiber volume ratio, spacing between stirrups, diameter of stirrups and CFRP reinforcement. The numerical results showed that the increment in fiber content resulted in better mechanical properties and torsional resistance of lightweight concrete beams. The effect of carbon fiber and steel fiber is evident from the volume ratio 2%, which produced the highest ultimate torque enhancement to 77.64% and 76 % respectively. In addition, a rational approach is proposed to predict ultimate torque to develop the torsion design of lightweight concrete beams.

The flexural behavior of concrete beams reinforced with hybrid reinforcing schemes is investigated experimentally in this work. The effects of steel fibers inclusion on the flexural behavior of concrete beams reinforced using hybrid schemes were investigated using four half-scale beams. The steel fibers content (0.00%, 0.50%, and 1.00%) was the most important parameter. The experimental results demonstrated that steel fibers inclusion significantly improved the ultimate load, stiffness, and toughness of concrete beams. Load capacity was enhanced by around 13% and 21% for steel fibers volume ratios of 0.50% and 1.00%, respectively. Toughness improvements were around 97.7% and 161% for steel fibers volume ratios of 0.50% and 1.00%, respectively. A non-linear finite element analysis (NLFEA) was performed to simulate the flexural behavior of RC beams reinforced with hybrid schemes. The load-deflection responses and crack patterns of experimental specimens and numerical models were compared. The comparison showed a good agreement between the experimental and numerical results. The overall average value of the ratio between the experimental flexural capacities to the predicted capacities is about 0.94 and the standard deviation was of 0.028.

In this manuscript, structural testing was conducted on high-strength concrete slab specimens to investigate the behavior of such specimens when reinforced with a locally produced GFRP reinforcement. Subsequently, a finite element model (FEM) was constructed and validated against the experimental results. In the experimental phase, a total of eleven specimens (nine were reinforced with GFRP, while two were reinforced with conventional steel) were constructed and tested. The slabs dimensions are 700 mm × 1750 mm with variable thickness from 100 mm to 150 mm and different reinforcement ratios using different diameters. The structural behavior of the tested slabs was investigated in terms of ultimate load, ultimate deflection, load–deflection relationship, and crack pattern. Additionally, a nonlinear finite element model using the software ANSYS 2019-R1 was constructed to simulate the structural behavior of slabs reinforced with GFRP bars. The results obtained from the finite element analysis are compared with experimental results. The outcomes showed that the contribution of GFRP rebars in concrete slabs improved slab ductility and exhibited higher deflection when compared with traditional steel rebars. Good agreement between experimental and nonlinear analysis was obtained.

Cairo Metro Network is one of the major national projects in Egypt. It aimed at developing underground transportation system to solve the severe traffic problems in Greater Cairo which includes 3 crowded governorates; Cairo, Giza and Qalyubia. The project started in the last decades of the twentieth century where 2 lines were executed. In this century, the project is expanding and more lines are constructed. The tunnel constructed for Cairo Metro Line 3 has a circular cross section that consists of a precast segmental lining thickness of 0.40 m. This paper presents a parametric study on the effects of seismic waves on the tunnel structure through numerous simulations employing the finite-element analysis. Full dynamic analyses were performed employing three different earthquake motions as well as the effect of train-induced dynamic load. Also, the induced tunnel straining actions were studied. The analysis of soil-structure interaction was done using the commercial software PLAXIS. The results proved that the 0.40 m thick circular cross section can safely sustain the expected static, dynamic and seismic stresses.