Low Incremental Collapse Capacity of Composite Beams

摘要

Incremental collapse is the aggregation of permanent deformation of a structure in the form of a collapse mechanism resulting from the repeated application of live loads of high magnitude. It can result in a structure becoming unserviceable through excessive deflections or in sudden collapse after ductility is exhausted. It is potentially significant for bridge decks. Good agreement between theory and tests was obtained for continuous beams in steel, reinforced and prestressed concrete, and for RC slabs with a moving patch load. However steel/concrete composite beams exhibited incremental collapse at loads as low as 53% of the static strength. The reduction in capacity is explained by the classical theory of incremental collapse on asymmetric cross-sections, exacerbated by a collapse mechanism involving slip of the shear connections, and further reduced by incremental slip of the shear connections at low shear forces.