Steel non-orthogonal reduced beam section moment connections—a case study

摘要

The architectural expressions for many modern buildings require creative and unconventional structuralnsolutions. Columns must be taller, beams must span further, the structure must be more slender, elementsnmust be curved, structural framing must be sloped and connections must deviate from conventional orthogonalnfit-up. Although the technology exists to analyze and design responsive structural systems, prescriptivencode requirements oftentimes hinder the implementation of those technologies. Although not a ‘tall building’nby traditional definition, the Tom Bradley International Terminal (TBIT) Modernization Program atnLos Angeles International Airport (LAX) provides an appropriate case study in the implementation of unconventionalnstructural geometry subject to code requirements that prescribe contrasting conventionalngeometry, which is a familiar challenge for many tall buildings.nThe architectural expression for the LAX TBIT Modernization Program required the use of long-spannsteel Special Moment Frames with non-orthogonal moment connections between the beams and columns.nThe beams were sloped, some were sloped and curved and some of the columns were sloped. The reducednbeam section (RBS) moment connection was selected for the project. ANSI/AISC 358, PrequalifiednConnections for Special and Intermediate Steel Moment Frames for Seismic Applications, provides prequalificationnlimits for using an RBS connection. Those limits do not address non-orthogonal moment connections.nANSI/AISC 358 implicitly limits connections to orthogonal geometry; hence, non-orthogonalnmoment connections are not prequalified for use in seismic applications. This paper describes the structurenand the cyclic testing program that was implemented to qualify the proposed non-orthogonal RBS connectionsnin accordance with ANSI/AISC 341, Seismic Provisions for Structural Steel Buildings, Appendix S fornuse on the LAX TBIT Modernization Project. Copyright © 2011 John Wiley & Sons, Ltd.