Analytical investigation of access holes in load-bearing diaphragms of steel box girders

This paper presents a series of parametric studies on the effect of access holes on the strength of the load-bearing diaphragms in steel box girder bridges. These parameters include the number of bearings, initial imperfections, the size and location of access holes, and the size of stiffeners around the openings. The load-bearing diaphragms were modeled using three-dimensional finite element analyses for material and geometric nonlinearities. It was found that the opening can be made large enough for practical purposes in order to provide convenient access to the inside of the box girder with no significant reduction in the ultimate strength of the load-bearing diaphragm. The location of the access hole has no detrimental effect on the diaphragm strength.