Problem statement: Rectangular steel plates are widely used in various steel structures and steel industries. For a proper design of steel plate structures and efficient use of material, the behavior, strength, buckling and post-buckling characteristics of plates should be accurately determined. Approach: Considering the significance of this matter, lateral vibration of thick rectangular plates was studied on the basis of mindlin plate theory. The exact characteristic equations for a plate which is single supported in two opposite edges are available in the literature. S-C-S-F boundary condition which covers all possible situations is selected in this study. Results: The plate frequencies were calculated for this boundary condition for a wide range of plate sizes and thicknesses. The plate mode shapes were obtained for different cases and the effect of changes in boundary conditions; size ratio and thickness on the vibration behavior of rectangular steel plates are studied. Conclusion/Recommendations: Since the results of this study is exact and without any approximation, the presented values can be used as a proper criteria to evaluate the error value of approximate methods which are used by engineers for design of steel plates. These results can provide a good gridline for efficient design and prevention of using high safety factors. Considering the wide range of steel rectangular plates, more sizes and thicknesses of plates can be studied. The behavior of plates with other boundary conditions can also be studied for future research.

Problem Statement: Since the time that steel was first used as a construction material, engineers have attempted to increase strength, reduce weight and produce more economical structures by using elegant member sections. However, the increase in steel strength and the decrease in cross section area are not always useful and in some cases it is necessary to reduce the strength to allow the structure to behave in a specific manner. This issue is seen in systems designed to withstand lateral loads, such as wind and earthquake loads. Approach: To improve the seismic behavior of braced frames, the V-EBF system with shear panels made of easy-going steel is presented. Using the finite element method, braced frames with shear panels made of easy-going steel were analyzed and compared to the behavior of the same frame with shear panels made of construction steel. The influence of shear panel systems made of easy-going steel is investigated by inserting this system in 4, 8 and 12-storey frames and analyzing them under earthquake loads. Results: The results indicate that contrary to shear panels made of construction steel no local buckling occurs in shear panels made of easy-going steel and the energy dissipation and ductility are increased considerably. Consequently, frames with shear panels made of easy-going steel exhibit better performance and energy absorption. Conclusion: In this research, it is attempted to improve the behavior of V-EBF frames by using a new type of steel, EGS, which has a lower yield stress than construction steel. The study shows that if EGS is used in a shear panel, seismic behavior of these frames improves noticeably.