UC San Diego

Many of today's low-rise building structures consist of thin-walled metal members that form Metal Building Frames (MBFs). Members associated with MBFs typically involve tapered webs. Although use of web-tapered members for MBFs are driven by economical efficiency, understanding on how these type of members respond under seismic loading is limited. Design of web-tapered members generally is governed by lateral-torsional buckling (LTB) and local buckling. To better understand the seismic response of MBFs that buckle, use of numerical methods that can simulate buckling and post-buckling behavior are desirable. Since it is not inefficient to use elements such as shells or solids for extensive seismic analyses, development of a one-dimensional beam-column element is researched and incorporated to the software OpenSees in order to capture warping and non-prismatic effects. In addition to monotonic correlations, six full-scale web- tapered members cyclically tested at UCSD were analyzed using this proposed beam-column element. Parametric studies associated with these analyses were also performed and included variation of axial loads, initial imperfections, and residual stresses. Based on the predicted analyses, events of initial LTB were captured reasonably well. However, it was observed that the proposed element is limited in its capabilities by events of local buckling. Because of local buckling limitation, attempt to expand the proposed element by introducing combined flange-web displacements was pursued. Although formulation of the updated element was successfully implemented, issues associated with initiating local buckling were observed during preliminary verification. Further development of incorporating initial displacements to the flanges is thus required