Steel and Composite Beams With Web Openings

Abstract

Three design methods, osiginally deveIoped by Donahey and Darwin (19861, for dewmining the maximum shear capacity of composite beams with unreinforced web openings are extended to include steel and composite beams with or without reinforcement at the opening. The three design methods incorporate sirnplirylng assumptions that pennit closed-form sofutions for maximum shear capacity. The first method assumes that the neutral axes for secondary knding lie in the flanges of the top and bottom tees and defines the interaction of shear and normal stresses by a linear approximation of the von Mises yield function. The second method ignores the contribution of the flanges to secondary bending moments and employs the von Mises yield function to define the interaction of shear and normal stresses. The third method ignores the contribution of the flanges to secondary bending moments and defines the interaction between shear and normal smsses with a linear approximation of the von Mises yield function. Simplified design expressions for the maximum moment capacity of steel and composite beams with web openings are presented. Six refinements of the design methods are investigated to determine their significance in predicting member strengths. Simplified design expressions developed by Darwin (1990) for determining the maximum moment capacity of steel and composite kams at web openings are surnmarjzed. The accuracy and ease of application of the design methods presented in this report (Methods I, TI, and JJI) and applicable procedures proposed by Redwood and Shrivastava (1980), Redwood and Poumboums (19841, and Redwood and Cho (1986) are compared with experimental results of fifty steel beams and thirty-five composite beams. Resistance factors are- calculated for use in LRFD of structural steel buiIdings. The simplest of the design methods presented in this coupled with moment-shear interaction procedures proposed by Donahey and Darwin (19861, provides excellent agreement with test results and a superior approach in terms of accuracy and ease of application. Resistance factors of 0.90 and 0.85, applied to both shear and bending, are suitable for steel and composite beams, respectively.