Stress Analysis of Plate Girder Bridges as space structures

Abstract

This study includes the analysis of plate girder bridges as space structures under different cases of vertical and horizontal loading. It discusses the effect of the type ofhorizontal bracing (cross and warren) and the intermediate vertical bracing on the force and stress distribution for the different elements of the bridge. A comparison between the planar and space analysis of the bridge is also presented. simply supported and continuous bridges with two equal spans are studied in chapter IV.

The computer program GTSTRUDL was used to obtain the results of forces in members, stresses in the main girders and deflection shapes for the different bridges, under the various cases of loading.

The results of this study are smnmarized in :

• For cases of centric vertical loads, the space and planar analysis are similar in their results. The additional forces developed in the bracing members, due to the centric vertical loads, are considerably small, so that they can be neglected in the design of these members.

• The importance of space analysis shows in the case of eccentric vertical loading. The planar analysis leads to erroneous results, since it neglects the effect of torsional moment.

• For simply supported bridges, it was fow1d that the additional forces developed in . the bracing members due to the torsional moment in this case of loading are considerably •great, compared with the case of centric vertical load, which cannot be neglected. On the other hand, the forces developed in bracing members for continuous bridges were considerably small that they can be ignored.

• For the simply supported bridges, the m1loaded main girder is affected by nonnal stresses, which equal to a quarter of the normal stresses developed in the loaded main girder, although the reactions in the