Lateral Buckling in Curtain Wall Systems

Recent demand for increasingly complex exterior facades of commercial buildings has driven a need for more efficient high‐performance curtain wall designs. Current codes can be improved by formulations that more closely parallel required criteria. In this paper, formulas for the elastic lateral buckling strength of slender monosymmetrical beams that represent curtain wall mullions with practical loading and supporting conditions have been derived by approximate energy procedures for four different assumptions of possible glazing restraint. The equations have been constructed in a general manner so that a large variety of glazing (bracing) positions is accommodated. Analysis of a typical design situation indicates that the currently used allowable compressive stresses of the Aluminum Association Specifications for buildings are extremely conservative for this application. Also, a method to experimentally verify the assumed glazing restraint is presented via the Southwell plot method. Use of the more accurate analyses herein will result in significant design efficiencies on many curtain wall systems.