"Torsional stability and lap eccentricity in extended shear tabs "
The presentation will be based on an AISC Engineering Journal paper published in the Second Quarter of 2011. The design procedure for extended single-plate connections will be presented. This procedure will include a check of lateral-torsional stability of the extended single plate, which resembles a double-coped beam. Research has shown that coping of beams can reduce the lateral-torsional buckling strength of beams. This paper presents a proposal to use the double-coped-beam concept to ensure the lateral-torsional stability of the extended plate. The question of stiffeners and the effect of the small eccentricity due to the lapping of the plate with the beam web will also be addressed. This research is incorporated in the AISC Manual, 14th Edition. Additional information on this topic can be found in these reference papers by Fortney and Thornton, http://www.cives.com/Cives-Engineering-Corporation-Publications.
"Shear lag factors for longitudinally welded tension members "
The presentation will be based on an AISC Engineering Journal paper published in the First Quarter of 2012. This paper gives recommendations for a generalized design procedure for welded connections of plate, angle, channel and tee tension members. The theory does not limit the minimum weld length to be at least the distance between the welds. Longitudinal welds of unequal lengths are treated. A summary of the treatment of various current building codes/specifications (AISC and CSA) on this topic is presented along with the results of several published experimental research projects that evaluated the behavior of these types of connections. Two analytical models are presented, and recommendations for changes to the current AISC Specification are made, followed by an example problem illustrating the practical application of the recommendations. This research has been approved by the AISC Specification Task Committee TC6 for a full committee ballot, for possible incorporation in the next AISC Specification. A vertical brace connection is a highly indeterminate system. In designing these connections, it is not known what the distribution of the forces is, mainly due to the routinely made assumptions during the analysis process. However, as long as the design has a force distribution that satisfies equilibrium, does not exceed any limit state and measures are taken to ensure ductility, the design is acceptable. The Uniform Force Method represents one statically admissible force distribution in which no moments exist at the connection interfaces. While there are several available analysis methods that will provide safe designs of diagonal bracing connections, the Uniform Force Method will yield not only a safe design, but an economical one. This seminar will discuss the history of the Uniform Force Method, highlight the Uniform Force Method procedure as detailed in the 14th Edition of the AISC Steel Construction Manual, and demonstrate the versatility of the Uniform force Method through a bracing connection example.