seyed bahram beheshti

In the present study, a novel hybrid damper is introduced based on the combination of steel and glass-fibers reinforced-polymer (GFRP) rods. Sharing effort of the appropriate energy absorption properties of steel subjected to hysteretic loads and the GFRP rod reversibility due to their elastic behavior create a unique energy-absorbing system that, in addition to being economical, has a good efficiency during seismic excitations. In this research, at the first stage the materials have been tested to better understand their behaviors used in the fabrication and analytical modeling of proposed hybrid dampers and employed in numerical modeling to acquire more accurate results. Then several analytical models of damper were prepared and analyzed according to the various compositions of the materials. In the following, hybrid damper specimen has been fabricated and tested to obtain a good comparison of actual damper behavior and the results of numerical models. The results showed that the innovative hybrid dampers achieved good performance for their assigned tasks The ease of fabrication, availability of materials, and cost-effectiveness of the damper construction have distinguished the features of an economical and high-performance hybrid damper. The damper can be used as a convenient, reversible and economical energy absorbing system for the seismic control of structures in high risk earthquake prone areas.

This paper numerically studies the effect of the width-to-thickness ratio of inclined strips on the behavior of a novel slotted steel plate shear wall (SPSW). The slotted SPSW consists of horizontal and vertical boundary elements (BEs) and two inclined-slotted plates (ISPs) connected by high-strength steel bolts. The directions of the slots in each infill plate are opposite. Steel bolts are used to connect the two infill plates through the created holes at the intersection of each inclined slot. This paper numerically examined four slotted steel shear walls with different width-to-thickness ratios of strips. The research showed that when the slotted steel shear walls were put under cycling loading, the inclined steel strips on one side of the wall were placed in tension; however, the strips on the other side undoubtedly were in compression. Additionally, the study showed that when the width-to-thickness ratio of strips was properly used, the strength, stiffness, and energy absorption capabilities of slotted SPSWs were significantly increased, whereas the out-of-plane displacement was minimized by 40.00 %.

A comparison between design codes i.e. ACI and AISC-LRFD in evaluation of flexural strength of concrete filled steel tubular columns (CFTs) is examined. For this purpose an analytical study on the response of CFTs under axial-flexural loading is carried using three-dimensional finite elements with elasto-plastic model for concrete with cracking and crushing capability and elasto-plastic kinematic hardening model for steel. The accuracy of the model is verified against previous test results. The nonlinear modeling of CFT columns shows that the minimum thickness that recommended by ACI and AISC-LRFD to prevent local buckling before the steel shell yielding for CFT columns could be increased. The comparison of analytical results and codes indicates that the accuracy of ACI in estimation of lateral strength of CFT columns is more appropriate than AISC-LRFD. The ACI lateral strength of CFTs is located on upper bond of the AISC-LRFD’s provisions. AISC-LRFD estimates the lateral strength conservatively but ACI in some ranges such as in short columns or under high axial load levels computes lateral strength in non-conservative manner. Supplementary provisions for post local buckling strength of CFT columns should be incorporated in high seismic region. This effect would be pronounced for column with high aspect ratio and short columns.