Date of Graduation

5-2017

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

Gary Prinz

Committee Member

Micah Hale

Second Committee Member

Eric Fernstrom

Keywords

Applied sciences, Column axial load, Moment frame connections, Out-of-plane skew, Reduced beam section connections, Seismic design, Structural engineering

Abstract

Steel buildings in high seismic areas often require special structural systems to transfer large lateral forces induced by earthquake accelerations. The selection of an appropriate seismic steel system (braced frame, moment frame, shear wall, etc.) is often influenced by architectural considerations. Moment frame configurations offer the most architectural flexibility, but are limited by code prequalification requirements that limit the use of non-orthogonal (skewed) beam-column connection geometries. A recent study has investigated laterally skewed moment frame connections, indicating that skew increases the potential for column twist and column flange yielding; however, it is unclear how realistic column axial loads will affect the skewed connection performance.

This study investigates the effects of column axial loads on skewed special moment frame connections containing reduced beam sections (RBSs). Detailed finite element analyses are used for all investigations, and several beam-column connection configurations are considered, representing: 3 beam-column geometries (shallow, medium and deep columns); 4 levels of skew at the beam-to-column connection; and 4 levels of applied column axial load. Results indicate that combined beam skew, axial load, and applied connection rotations lead to local buckling issues within deep column moment frame configurations; however, increasing beam-skew and axial load has little effect on connection moment capacity prior to column local buckling initiation. Beam-skew angle is the dominate contributor to resulting column twist and increasing column axial load (up to 50% ΦPn) has a negligible effect on resulting column twist. Applied column axial loads have little effect on resulting column flange yielding within the skewed beam-to-column connections.

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