Published: Jan 1989
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Glass curtain walls consist of large glass panes typically supported by vertical and horizontal framing elements. Wind forces on the curtain walls are transmitted to the building frame at the floor levels, most often by the vertical framing. The glazing transmits the wind forces to the framing and also acts to restrain lateral-torsional motion of the framing. The horizontal members between mullions also may restrain lateral-torsional buckling of the mullions. This paper is concerned with the lateral buckling strength of the long slender framing elements and the design of such members. Since there is practically no literature on this subject, some designers make very conservative assumptions. For example, the paper illustrates that neglecting the bracing offered by structural glazing, even on the tension flange side of a member, can be very inefficient.
Analyses are given herein for several different supporting conditions that approximate minimum and maximum bracing and a realistic approximation to the restraint afforded by structurally glazed elements. For a typical application, comparisons are made of the allowable compressive stress given by current design procedures with corresponding values derived from different theoretical analyses. These comparisons show the great influence of the restraint that may be offered by the structurally glazed elements. Large increases in the allowable compressive stresses are possible. A method that experimentally provides verification of stability is presented, and several tests of such designs are discussed.
The significance of the conclusion generates a design/analysis method that more fully harnesses the multi-function capabilities of structurally glazed curtain wall framing. This will enable the designer, manufacturer, and contractor to provide a more efficient system that will thus have an edge in competition with other exterior wall products in the building construction industry.
lateral buckling, curtain wall mullion, slender beam, glazing, bracing, aluminum, design, elastic restraint, glass, structural silicone
Vice president, Curtain Wall Design and Consulting Inc., Dallas, TX