Research on Proper Diaphragm Layout of Long-span Continuous Steel-Box- Girder

Mechanical behaviors of the steel-box-girder(SBG) under eccentric load are analyzed. And then it is deduced that proper layout of diaphragms in SBG should be discussed from the point of view of controlling the distortional warping stress which is very complicated to calculate. Although several current standards already provide how to calculate the distortional warping stress, the long-span continuous SBG is beyond the application scope of these standards. Hence, here it is put forward that the distortion warping of the single-room rectangular-box-girder is regarded as the bending of the beam on elastic foundation (BEF) based on the similarity between the distortion warping control differential equation of the single-room rectangular-box-girder and the bending control differential equation of BEF. By this analogy method, the distortional warping stress of the single-room rectangular-box-beam can be solved more easily. Finally, the distortional warping stress of the Chongqi Main Bridge, whose SBG has the longest span and longest length in China, is calculated by this analogy method and thereby the reasonable rigidity, type and section area of its diaphragms are suggested. These suggestions are all adopted by the designer and used in the actual girder.