ABSTRACT
Many of the choices listed above offer options which involve fewer components of thicker material (1, 2, 6, 7 & 9). For shorter spans these options can produce competitive designs if the support sections can be kept compact. For longer spans compactness requires excessively heavy webs but the policy can still be economic for other reasons. Wide girder spacings are possible provided there are no vertical stiffeners which could cause fatigue problems under the resulting flexing of the concrete deck. The wide spacing puts greater loads onto the beams so the web must be less slender and the need for stiffness is reduced. Stiffeners are required at bracing positions but with a thick web there is significant bottom flange restraint from the out-of-plane stiffeners of the web, makinc it more likely that the bottom flange will require no intermediate bracing between supports. These mutually dependant factors make possible the 'clean beam' solution, with not intermediate stiffeners or bracing, adopted at Hyndford.
