One of the most important members of steel structure's connection region is beam-to-column connection. Rigid connection in steel moment frame has special role in the behavior of these structures and the fire resistance of these connections can be important. In this paper the behaviors of three common types of rigid connections in Iran under the effect of heat were studied by the use of numerical finite element methods through ABAQUS software. The models were verified by the use of an experimental model through elastic and plastic amplitudes up to collapse and during numerical results, and the effect of large deformation in the nonlinear region has also been considered. The results show that the connection with the end plate had a better performance against heat than other connections. Also reduced stiffness and lateral buckling in this connection were less than other connections.
The fresh and mechanical properties of self-compacting lightweight concrete (SCLWC) prepared by scoria and organic waste ash (OWA) were investigated, in which the OWA replaced limestone powder with different percentages. Besides, the effects of steel fiber on mechanical properties of mix designs containing 15% OWA replaced limestone powder were also investigated. To examine the fresh properties, slump flow, J-ring, and V-funnel tests were considered on fresh SCLWC, whereas compressive and splitting tensile strength were concerned for mechanical properties assessment. The results confirmed that the mix design containing 15% OWA replaced limestone powder achieved the lowest weight; however, its compressive and splitting tensile strength decreased by 28% and 20%, respectively, compared to the SCLWC made with limestone powder. Meanwhile, the inclusion of 1% steel fiber to this optimum mix design with 15% OWA replaced limestone powder increased the splitting tensile strength by 20%.
Progressive collapse is a relatively rare event which happens due to unusual loading on a structure that lacks adequate continuity, ductility and indeterminacy which causes local collapse in that structure and then extends it to other structural parts. In 2003, US defense department to published regulations UFC 4-023- 03 on the building design against progressive collapse and in 2009 submitted a revised version of the regulations. This regulation, based on the ASCE 7-05 standard, introduces two general approaches to building design against progressive collapse, including direct design and indirect design approaches. In this study, a variety of structural design methods for progressive collapse have been investigated. Moreover, their strengths and weaknesses have been mentioned. In general, the results of this study show that design based on AP is more economical than other methods. Also, using this method is much more commonly accepted by researchers and designers.
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