Probabilistic Analysis for Design Assessment of Composite Girders

摘要

Continuous steel-concrete composite girders are extensively used for the construction of short andrnmedium span bridges. In the sagging regions, where the compressed flange of the steel beam isrnconnected to the reinforced concrete slab, the cross sections generally belong to class 1 or class 2rn(compact sections) and plastic design is acceptable. In the hogging regions the cross sectionsrncommonly belong to class 3 or class 4 (slender sections), thus there is insufficient ductility forrnplastic design and elastic verification is required. However, in this combined design approach thatrnuses the cross section plastic resistance in the sagging regions and the elastic resistance in thernhogging regions, the design must satisfy the condition that the plastic moment in the sagging regionrncan develop while still leaving the bending moment resisted by the hogging regions sufficiently farrnfrom the elastic limit. The objective of this work is to assess this combined elastic-plastic designrnapproach for continuous composite girders by using probabilistic nonlinear finite element analysis.rnThe First-Order Second-Moment (FOSM) approximation is adopted to compute the first- andrnsecond-order statistical moments (means, variances and covariances) of structural responsernquantities. Deterministic and probabilistic results are illustrated and discussed by using a realisticrnthree-span continuous steel-concrete composite bridge as benchmark problem.