Ultimate limit state of slender steel webs subject to (i) constant and (ii) repeated partial edge loading

The objective of the contribution is to describe the main results and conclusions of a several years' experimental investigation into the ultimate limit state of steel plate girders whose thin webs were loaded by a partial edge load. The first stage of the research dealt with the performance of steel webs under the action of constant patch loading. Altogether 184 experimental girders were tested, with the following geometrical characteristics of the test girders being varied from girder to girder: (i) the depth-to-thickness ratio of the web, (ii) the flange size, (iii) the position of the longitudinal rib, (iv) its dimensions and (v) the length of load. In conclusion, the authors established formulae for (i) the optimum rigidity of the longitudinal rib and (ii) the predicted ultimate loads of webs subject to partial edge loading and stiffened by a longitudinal rib. The aim of the other part of the Prague experimental research was to look into the effect of the repeated character of patch loading on the ultimate limit state of steel plate girder webs fitted with longitudinal ribs. Eighty experimental panels were tested, the flange size, and the position and dimensions of the longitudinal ribs being varied. During the tests, the ‘breathing’ of the girder webs under the action of a cyclic patch load, the initiation and propagation of cracks in the most heavily stressed areas of the webs, and their influence on the ‘erosion’ of the plastic failure mechanisms of the test girders were carefully studied. Final analysis of the data obtained made it possible for the authors to establish the limit fatigue loads, P fat, of longitudinally stiffened steel plate girders whose thin webs are subject to a repeated partial edge load.