Study of Buckling Coefficient of Steel and Concrete Composite Beams with external tendons under Negative Bending

Abstract:

Abstract: In hogging moment regions, the cracking resistance of the beams can be effectively in creased on adding prestressing to the composite beams with external tendons,. The ultimate resistance of a composite beam prestressed with external tendon is governed by either distortional lateral buckling or local buckling, or an interactive mode composed of the two buckling which is sharply different from the lateral torsional buckling mode in a bare steel beam. Based on the proposed restrained torsional buckling model, inelastic finite element buckling analysis of composite beams in negative bending is investigated, considering the initial geometric imperfection and the residual stress patterns, and the FE results are found agree well with the test results. By varying cross-section parameters, 25 groups of composite beams under negative uniform bending with initial geometric imperfection and different patterns of residual stress in steel beams are studied by means of the FE method. The slenderness of the studied beam is defined and the calculated result is compared with the Chinese Codified steel column design curves. It is demonstrated that the Chinese Codified steel column design curves can be used in assessment of the buckling strength of composite beams with the slenderness defined.

Key words:external prestress; composite beams; distortional buckling; buckling coefficient; slenderness