Non-linear Finite Element Analysis of Extended Shear Tab Connections PDF Download

Author: Mohamed Fawzi Suleiman
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ISBN:
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Languages : en
Pages : 149

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Book Description
The Manual of Steel Construction AISC 14th edition refers to an extended shear tab as a single plate shear connection. This method of providing simple connections has become quite popular with both fabricators and erectors. Extended shear tab connections were formally introduced in the 13th edition of AISC Steel Construction Manual. Using experimental data from extended shear tab connections, Sherman and Ghorbanpoor introduced a design methodology in 2002 for extended shear connections. Twisting of the shear tab controlled the capacity of the specimens tested by Sherman and Ghorbanpoor, which were not laterally braced. In the latest edition of AISC Steel Manual, design equations are provided to assess the need for stabilizer plates in the connection region of extended shear tabs. In an effort to understand whether twisting of the shear tab can be a controlling design limit state, three-dimensional nonlinear finite element analyses in conjunction with design case studies were conducted. The analyses included 364 connections with different configurations were studided with an "a" distance of (9, 11, and 16 inches). The finite element models were comprehensive in terms of simulating nonlinear material properties, boundary conditions, pretensioning in the bolts, geometric nonlinearity, etc. It was possible to accurately replicate the responses (shear force-connection vertical deflection and shear force-connection angle of twist) measured in a number of previous tests, and to fairly well predict the observed failure modes. Using a 3D nonlinear finite element analysis technique, the response of 16 selected connections, which had been designed to meet all the applicable limit states in AISC Steel Manual, were evaluated. The presence of floor slab, which braces the top flange of the beam, was simulated in the analyses. For a number of cases, the connection behavior at the ultimate limit state was dominated by twisting, i.e., the relationship between torsional moment and angle twist indicated a noticeable level of loss of stiffness in comparison to that from the shear-vertical displacement relationship. However, the level of lateral displacement of the shear tab was small, particularly for unfactored loads when control of deformations is an important design objective. According to AISC provisions (Eq.10-6), stabilizer plates would not be required for any of these 16 connections, which were evaluated by 3D nonlinear FEA. Therefore, current AISC provisions are a good predictor of the expected level of out-of-plane displacement of the shear tab due to twisting. It should be noted that large lateral displacements occurred at the ultimate state when the connection ductility is the main design consideration but not the magnitudes of deformations and distortions. Therfore, this equation can be used to determine whether stabilizer plates are needed or not; however, it does not predict whether the response at the ultimate limit state will be dominated by excessive loss of torsional stiffness of the shear tab. Instead of using stabilizer plates, a thicker plate can be used for the shear tab. This solution is considered to be more economical and easier than welding stabilizer plates in the connection region.