Osman M. O. Ramadan

The use of appropriate reinforcement detailing in reinforced concrete coupling beams is crucial, particularly for those with a short span-to-depth ratio (ln/h < 2). These beams must be designed to exhibit ductile, inelastic behavior, thereby maintaining the stability of the coupled shear wall system. In practice, openings are often required in coupling beams to accommodate utility pipes for plumbing, electrical, and other building services. However, these openings can significantly alter the structural behavior and must be accounted for in the design. Since experimental investigation of various parameters is often expensive and time-consuming, this study employs computational modeling. A set of twelve reinforced concrete coupling beams, with and without openings, were analyzed using the non-linear finite element program ABAQUS to investigate their cyclic behavior. The beams featured different reinforcement details: conventional, diagonal confinement, and two configurations of rhombic details. All beams had identical dimensions of 200 mm in width and 400 mm in both depth and length (ln/h = 1). The primary variables were the presence, location, and reinforcement scheme around the openings. The results indicate that the solid coupling beam with diagonal reinforcement exhibited overall behavior superior to those with conventional or rhombic details. The introduction of an opening with relative dimensions of (lo/l = 0.125 and ho/t = 0.25) had a significant detrimental effect, especially when located at the mid-span. The behavior of beams with diagonal confinement was less affected by the presence of an opening than the other details, regardless of its location. Providing an opening 37.5 mm from the beam end reduced the shear capacity and maximum chord rotation by (10.2%, 30.4%), (5.5%, 15.6%), and (12.78%, 55.2%) for the conventional, diagonal confinement, and rhombic configuration 1 details, respectively, compared to their solid counterparts. Shifting the opening to the mid-span increased these reductions to (31.6%, 58.8%), (14.5%, 48.8%), (26.4%, 65.6%), and (19.2%, 50.2%) for the conventional, diagonal confinement, rhombic configuration 1, and rhombic configuration 2 details, respectively.

The effects of slab thickness and punching shear reinforcement ratio on the individual contributions of concrete and reinforcement on punching shear strength of interior slab-column connections are theoretically investigated. Numerical results of verified models are utilized to evaluate the effect of slab thickness, and the amount and detailing of punching shear reinforcement on punching shear capacity. Further, design code provisions are discussed in light of the obtained results. Extensive nonlinear FE models were developed and analyzed via ABAQUS software. Results of the developed FE models were first examined against Cairo University lab's 16 half-scale specimen tests. It is demonstrated that the developed FE model predicts the punching shear behavior of interior slab-column connections with practically adequate accuracy. Next, 65 full-scale FE models of slab-column connections were analyzed to study how slab thickness and punching shear reinforcement ratio affect concrete and reinforcement punching shear strength contributions. The analyzed cases included single, hat, multi, and closed stirrup. Results showed that slab thickness and the amount and detailing of shear reinforcement have important effects on the punching shear capacity of slab-column connections. The effectiveness of punching shear reinforcement is significantly influenced by both slab thickness and shear reinforcement ratio. Thicker slabs increase reinforcement strains with the same shear reinforcement. Besides, for thin slabs (ts = 160 mm), the concrete contribution decreases with the increase in shear reinforcement after cracking. Finally, the comparison between the FE results and the design codes (ACI, ECP, and EC2) showed that the ACI and ECP codes underestimate the punching strength of cracked concrete. To address this underestimation, a new formula was proposed and validated.

This research predicts the shear strength of reinforced concrete T-beams with flanges under compression stresses using nonlinear finite element (FE) analysis. A FE model is developed and verified against specially designed experiments (beams with varying flange width and depth). Results of the FE models were found to be in excellent agreement with their corresponding experimental results. The average load capacity and deflections (FE/experiments) ratios were 1.03 and 0.87, respectively. We then conducted an extensive parametric study to investigate the structural performance of flanged beams under the effect of two concentrated point loads. This parametric study examined four parameters: flange dimensions, longitudinal reinforcement in flange, concrete compressive strength, and shear span to depth ratio. Our findings indicated that the presence of compressed flanges in T-beams increases the shear strength by up to 260% of the shear strength of the web alone. The shear strength of flanged beams increases with the increase in flange dimensions, where the effect of flange thickness is more pronounced than that of flange width. Moreover, the presence of longitudinal reinforcement in the flange enhanced the beam's shear strength by up to 40%, compared to similar beams without flange reinforcement. Additionally, the shear strength increased up to three-fold for various beam conditions when the shear span to depth ratio was reduced from 2.0 to 0.5. These findings provide valuable insights for designing and constructing reinforced concrete T-beams with flanges under compression stresses.

This research addresses the nonlinear analysis of flat bottom clinker silos that are typically used to store granular materials. Most of silos’ failure is due to the inefficiency to resist seismic forces. One of the silo failure reasons is that filled granular material is usually treated as a water pressure which is not realistic. Water pressure is linearly distributed, while granular material has a nonlinear distribution along silo height. The main investigated variables were silo width, height, reinforcement ratio, and the existence of opening in the bottom part of the silo wall. Effects of these variables on silos’ dynamic properties - modal periods and mode shapes - as well as seismic response, base shear, base overturning moment, and the least number of modes needed to satisfy mass participation of 90%, were examined. Extensive numerical analyses were conducted to examine these parameters using different types of analyses such as free vibration, response spectrum, and pushover analysis. It was found that increasing height on time-period has a great effect when compared to the effect of diameter increase. Reinforcement ratio in silo without openings has a minor effect in small diameters while it has a major effect in case of silos with large diameters.

A 3D finite element model (FEM) for predicting the distribution of lateral pressure in a square flexible walled steel silo during the filling phase was analyzed in this study. The numerical approach, developed using Abaqus software, predicts the stress state in bulk solids, as well as the pressures exerted on the silo walls. An elasto-plastic model using the Drucker–Prager criterion was employed to simulate the behavior of the granular materials. The FEM simulates the behavior of the bulk solid and its interaction with the silo’s wall and base using a surface-to-surface discretization model. The model’s predictions were validated by previous experimental measurements. The results revealed good agreement between the FEM predictions and the experimental measurements. The research confirms that the lateral pressure distribution is not uniform at any silo level. This highlights the fact that many available theories and current design codes are not accurate for flexible steel walls. As a result of the wall’s deformability, pressure regimes on the silo wall change significantly in the horizontal direction at any level. The results showed that the horizontal variations of lateral pressure change drastically with regard to wall stiffness. The FEM has been used to investigate the effect of critical parameters on wall pressure distribution, such as properties of bulk solids, wall thickness, and silo type, whether deep or flat.

As is well known, in the current design codes, the shear strength of beams is calculated based on the modified truss theory, which does not consider the effects of the flange area of T-beams. The main objective of this paper was to gain a better understanding and enhance the experimental database of the shear behavior of RC T-beams and illustrate the contribution of the flange to the shear capacity of T-beams. To accomplish this aim, a specially designed experimental program was executed, and its test results were analyzed. The main investigated variables were flange dimensions (thickness and width) and its reinforcement (longitudinal and/or vertical). Nineteen simply supported beam specimens were tested to failure under a load configuration made of two concentrated loads. Eighteen specimens had T-shaped cross-sections, while one specimen had a rectangular cross-section for comparison purposes. The items monitored during testing included the development of diagonal cracks, concrete strains, reinforcement strains, maximum loads, and deflections. Test results showed a notable increase in the shear strength of T-beams compared to rectangular beams with the same web size. For the range of variables investigated, increasing the flange thickness-to-beam depth ratio (ρ_t) from 0.3 to 0.5 increased the shear capacity by up to 54%. In addition, increasing the flange width-to-web width ratio (ρ_b) from 3 to 5 increased the shear capacity by up to 19%. It was also shown that the results of three-dimensional finite element (FE) analyses using ANSYS compared reasonably well with the test results for all specimens. Finally, based on the test and FE results, a simplified method that accounts for the contribution of the flange to shear capacity was proposed.

A recently developed technique for the digital simulation of spatially incoherent seismic ground motions is extended to include two or three spatial coordinates. This extended approach allows for four situations: (1) Simulation in the far field; (2) simulation in the near field of a small source; (3) simulation in the near field of an extended source; and (4) simulation in the near field of a limited source. In each situation, both direction‐dependent (isotropic) and direction‐dependent (anisotropic) coherency structures are accounted for. The developments proposed may facilitate the seismic analysis of structures involving foundation coupling in two or three dimensions accounting for ground motion spatial incoherence, response nonstationarity, and system nonlinearities. They can also be useful in evaluating the response of structures to other spatially variable random fields such as those of wave forces and turbulent winds.