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Steel plate shear walls are very effective lateral load resisting systems which have high lateral stiffness and high ductility capacity at the same time. Although there are valuable experimental data available for such systems, most of the current seismic codes (including Iran’s Standard NO. 2800) provide none or limited design provisions for such structural systems. One of the important seismic performance parameters of the structures is “over-strength factor” which is implicitly or explicitly part of seismic design base shear formulation. Most of the available data on this factor are obtained from experimental research and therefore results are limited to low-rise structures and/or with reduced scaled structures/specimens. The main objective in this research is to assess the over-strength factor for the steel plate shear walls. A closed-form-solution is proposed for obtaining this factor based on a plate-frame interaction. This formulation is on the basis of the assumption that steel plate yields first and then the frame undergoes into the inelastic range. Therefore, an important factor that controls the amount of overstrength in an steel plate shear wall panel is the ratio of the steel plate yield displacement to the that of the steel frame. The lower this ratio is the higher the overstrength factor would be. The results of four experiments from four different universities accross the world were considered. The results also include the geometric and material properties of the specimens as well as their hystresis behaviors under cyclic loading. From the hystresis loops one can obtain experimental overstrength factors. It was found that the over-strength factors obtained by this proposed method are in line with available experimental results obtained from these four tests. It was also found that as the steel plate thickness decreases, the overstrength factor increases. Also, as yield stress of the steel plare decreases, the overstrength factor increases. In other words, the softer the steel plate /panel becomes, the better the chance of the redistribuition of internal forces would be and therefore the higher the overstrength factor would become. Two sets of results and/or comparisons are made in this study. First for the purpose of vrification of the proposed closed form solution, one of the test specimens were extended and it was shown that for the certain condition of that the test the proposed formulation matched the experimental results however if the plate thickness were to increase the overstrength factor would drastically decreases. The second set of results were for steel plate/panels with real sizes and not small lab sizes. It was shown that for such moderate and realistic steel panel sizes and thicknesses the overstrength factor comes out to be about 1.3. In addition, an square like panel has the highest overstrength factor compared to a rectangle ones.

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Steel plate shear walls are very effective lateral load resisting systems with high lateral stiffness and ductility capacity. Although there are valuable experimental data available for such systems, most of the current seismic codes (including Iran’s Std. 2800) provide none or limited design provisions for such structural systems. One of the important seismic performance parameters of the structures is “over-strength factor” which is implicitly or explicitly part of seismic design base shear formulation. Most of the available data on this factor are obtained from experimental research and therefore results are limited to low-rise structures and/or with reduced scaled structures. The main objective in this research is to assess the over-strength factor for the steel shear walls. A closed-form-solution is proposed for obtaining this factor based on plate-frame interaction. It was found that the over-strength factors obtained by this method are in line with available experimental data and analytical results obtained in this study. In derivation of this closed form solution the following assumptions are made: 1) beam-to-column connection is rigid, 2) SPSW behaviour is affected by the interaction of the steel plate and its surrounding frame members, 3) the first storey, usually the soft storey, controls ductility and strength of the structure in general, 4) the beam remains rigid and the plastic hinges only form in the columns, 5) stresses due to the bending action in the plate do not interfere with the stresses due to buckling in the plate, 6) stress-strain relationship of the steel plate and the steel frame members are elastic-perfectly plastic. The experiments on SPSWs used in this study were conducted in four major universities three of which in Canada and USA. The analytical model used in this study for finite element verification of the results is a three storey building that is adopted from a previous study on SPSW structures which was based on SAC buildings. It was found that the overstrength factor of a multistorey SPSW structure can be estimated by that of only the first storey of that. Also the results for the overstrength factor are not that sensitive to the angle of tension field in the plate. Moreover, it was found that this factor decreases with a decrease of plate thickness and the yield stress of the plate.

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This research investigates notch effect on fatigue life of HSLA100 steel which is widely applicable in the marine industry. Experimental tensile tests and rotating bending fatigue tests were performed on both smooth and notched cylindrical specimens and the corresponding mechanical properties and S-N curves were obtained. To better investigate the notch and also size effect on fatigue life of the specimens, two different notch geometries and specimen dimensions were used. To calculate the fatigue strength factor, stress distribution under bending load is simulated for smooth and notched specimens. Then, the stress distribution under bending load is converted to stress distribution under rotating bending load using an in-house developed code. Finally, using an in-house developed code, the fatigue strength factor of the specimens is calculated by weakest link theory. In order to better investigate the weakest-link theory, in calculating the fatigue strength factor, this factor is calculated from the classical methods and compared with experimental results. Finally, Comparison of theoretical with experimental results shows that the weakest-link theory gives better predictions than other classical methods and the results are closer to experimental ones. Also, Weakest-link theory uses the finite element results to predict notch effect. This facilitates the use of this theory in fatigue design of complicated specimens.