Economical Design of Presstressed Plate Girder

The limit states design concept is employed. Relations expressing statical properties of the cross section; geometry of the system; and equilibrium, continuity, and strength-conditions are respected, goverened by a properly selected decision function; four decision functions are observed. These relations are expressed in terms of three parameters: web-slenderness, section-asymmetry, and a chord-parameter. Web-slenderness being selected, the latter two parameters represent the only unknowns. Their values follow from solving two rather involved analytical expressions, to which the mentioned numerous relations can be reduced. They are handled numerically by the use of Fibonacci's search and an iterative method. An appropriate organization of results enables the setting up of simple design formulas, with coefficients expressed through the aforementioned three parameters. A table with these sizing coefficients is prepared for a representative scope of characteristic cases.