Plastic design of composite bridges allowing for local buckling

This report is a documentation of the project "Plastic Design of Composite Bridges Allowing for Local Buckling" aiming at assessing the feasibility of using plastic design method for continuous steel-concrete composite bridges, in ultimate limit states. The method shall allow for local buckling in the steel girders at internal supports. In order to obtain the moment-rotation relationship for the steel girders at the internal supports, fifteen double-symmetric, welded, I-shaped steel girders were tested. Steel with a nominal yield strength of 700 MPa and 220 MPa was used. The 220 MPa steel was used in the web of two of the tested girders (hybrid girders), while flanges were made of 700 MPa. Flange and web slenderness ratios as well as the length of the girders were varied in the tests. The flange slenderness ratio (flange with over thickness) bfl/tf varied from 10 to 15, the web slenderness ration, hw/tw from 36 to 110 and the length of the girders from 2.66 to 6.0 m.The report shows that plastic design of composite bridges, taking into account local buckling in the girders, is feasible. An example using plastic design is outlined in the report. However more work has to be carried out with respect to the moment-rotation relationship and flange induced buckling.The plastic design method presented in this report saves approximately 10% of material in the steel girders compared to an elastic design.Godkänd; 1995; 20080820 (ysko