Khaled M. El-Sawy

Effect of aspect ratio on the elastic buckling of uniaxially loaded plates with eccentric holes

The Finite Element Method (FEM) has been employed to determine the elastic buckling load of uniaxially loaded rectangular perforated plates with length a and width b. Plates with simply supported edges in the out-of-plane direction and subjected to uniaxial end compression in their longitudinal direction are considered. Integer plate aspect ratios, a/b=1, 2, 3 and 4, have been chosen to assess the effect of aspect ratio on the plate buckling load. Two perforation shapes of different sizes are considered; circular, and rectangular with curved corners. The rectangular perforation is oriented such that either its long or its short side is parallel to the longitudinal direction of the plate. The center of perforation was chosen at different locations of the plate. The study shows that the buckling load of a rectangular perforated plate that could be divided into equal square panels is not the same as that of the square panel that contains the perforation when treated as a separate square plate. For rectangular plates, the study recommends not to have the center of a circular hole placed in a critical zone defined by the end half of the outer square panel, to try always to put the hole in an interior panel of the plate, and to have the distance between the edge of a circular hole and the nearest unloaded edge of the plate not less than 0.1b. The study concludes also that the use of a rectangular hole, with curved corners, with its short dimension positioned along the longitudinal direction of the plate is a better option than using a circular hole, from the plate stability point of view.

Three-dimensional modeling of soil-steel culverts under the effect of truckloads

Soil-steel culverts have been successfully used as a cheap alternative to the conventional steel or reinforced/pre-stressed concrete bridges. Current design codes and researchers usually approximate the effect of live loads on such soil-steel culverts. In this study, three-dimensional (3D) finite element (FE) analyses of two existing soil-steel culverts are performed and compared to the published theoretical and experimental results. The study shows that the results of the 3D FE analyses for the thrusts compare well with the experimentally measured ones with differences less than 30%. On the other hand, the FE results for bending moments show less agreement which may be due to the sensitivity of the bending moments to the accurate modeling of the properties of the soil material. The study also shows that the effect of the live loads extends for a very limited longitudinal length of the examined corrugated steel culverts and validates the use long prismatic longitudinal geometry in performing their 3D FE analysis.

Stability of biaxially loaded square plates with single central holes

The stability of a biaxially loaded perforated square plate has been studied using the finite element method. The parameters considered in the study are the plates slenderness ratio, diameter of the circular hole, the materials yield stress, and the ratio of biaxial loads. The study shows that the bigger the hole diameter, the less the plate strength and stability. Specific plate slenderness ratios, at which the plate buckling changes from elastic to elasto-plastic, are identified. Families of curves suitable for design purposes are also generated to define both of the elastic and elasto-plastic buckling stresses for the different plate hole sizes as functions of the plates slenderness ratio, loading ratio, and yield stress.

Neural network for the estimation of the inelastic buckling pressure of loosely fitted liners used for rigid pipe rehabilitation

Abstract One of the structural design aspects of most of the liners is to check their stability under external uniform pressures. This requires the definition of the critical pressure at which the liner destabilizes. A neural network based on the results of a previous parametric study using the Finite Element Method (FEM) is developed. The neural network provides an estimate for the critical pressure of an elasto-plastic loosely fitted liner. The inputs for the network are the liner’s thickness-to-radius, gap-to-radius, and the equivalent yield stress-to-Young’s modulus ratios. The network results are checked against the FE results and compared to Jacobsen solution. The results of the neural network show excellent agreement with the FE results and Jacobsen solution for thick liners. This network provides a new tool that can be used in the structural design of loosely fitted liners.

Assessment of Material Strength Implications on Seismic Design of Tall Buildings through Collapse Analysis

High-strength materials are widely utilized in multi-story buildings with shear walls to effectively utilize floor areas and control lateral drifts. To investigate the impacts of high-strength concrete on the seismic design coefficients of shear wall-supported structures, five different designs of 60-story buildings with varying concrete strength are considered. The reference structures are designed and detailed such that they have very close periods of vibration. The large number of inelastic analyses performed at different intensity levels using twenty earthquake records and detailed fiber-based simulation models enabled the effective verification of the seismic design coefficients. The results reflect the enhanced profits and safety margins of shear wall-supported structures with increasing concrete strength. There is a possibility for increasing the design coefficients, which has several economic advantages. This systematic study provides practical insights into the seismic response of high-strength shear wall-supported tall buildings at different performance limit states and enables the verification of essential coefficients used in seismic design.