Proposed Specifications for Steel Box Girder Bridges

Proposed design specifications for steel box girder highway bridges are based on ultimate design approch. For design of unstiffened compression flanges a new strength curve is proposed considering the effects of residual stresses and geometric imperfections. Stiffened bottom compression flanges are designed by an interaction diagram giving the strength as a function of the column slenderness of the longitudinal stiffeners and the plate slenderness of the flange plate. Strength of webs is obtained as a sum of elastic buckling strength and a lower limit of tension field strength. Also given are design rules for other box girder members, fabrication tolerances and erection provisions. Attention is called to desirability of adjustment of load factors to be used with the new design rules.