Influence of patch load length on resistance of I-girders. Part-I: Experimental research

Abstract

Problem of behaviour and ultimate strength of the centrically patch-loaded steel I-girders without longitudinal stiffeners and with largely spaced transverse stiffeners is analysed. The research is focused on two parameters - load length and initial geometrical imperfections of a girder web. This paper presents the experimental research, while the companion paper includes a numerical analysis of the problem.The experimental campaign is described in detail. Results, comments and conclusions from seven tests are presented. The observed increase of the ultimate strength with the load length increase is not quantified due to the scatter of results which is typical for all previous experimental studies in this field. The scatter of results is a consequence of the intricate initial geometrical imperfections of the web which were measured on the most of the specimens. Following conclusions from the experimental research are used in the companion paper to develop reliable numerical models of the experimentally tested girders. It is necessary to model in detail the contact between load block and loaded flange, to account for the variation of contact pressure during the load application. The initial geometrical imperfections of the web in the load introduction zone have more significant influence on the development of lateral web deformation and thereof the ultimate strength, compared to the web imperfections adjacent to the unloaded flange.Finally, based on the performed experimental research, the companion paper presents a detailed parametric numerical analysis of the problem and proposes a correction factor for the load length.