Design investigations on some welded mild steel plate girders

Abstract

The thesis gives details of a series of design investigations carried out on mild steel, welded, plate girders, having a constant I section and supported laterally and torsionally only at the ends of the span. The main aim is to establish a General Method for expediting the design calculations for obtaining the optimum cross sectional dimensions of such a girder, essentially in accordance with the regulations as laid down in the British Standard Specification (B.S.449, while observing some rules for efficient or economical design. Here Minimum Weight Design has been chosen as the criterion of efficiency, though the methods devised can readily be extended or adapted to deal with other criteria. The moment of resistance, as reduced by lateral buckling, is deemed to be the significant factor in each design, though the various other effects are considered as well. A review of the problem is given, and an empirical investigation is then carried out to obtain the sectional dimensions of girders at Minimum Weight, spanning 100 feet, and resisting various moments. This work is then extended to a wider application by means of a theoretical analysis, and a General Method is obtained. Suggestions are made as to how this Method may be applied, viz: by the construction of charts and tables or by the writing of an all embracing computer programme to give automatic design. Various additional effects are described and finally an outline is given as to how this work can be extended to deal with more complicated practical girders.