Sources, mitigation and implications of skew-related concrete deck cracks in girder bridges

Abstract

Characteristic cracks in skewed bridges, detrimental to service performance, form in deck acute corners and run diagonally across deck span. This paper presents the relationship between skew and deck cracks, investigates crack mitigation strategies and documents changes in live load distribution caused by cracks. Finite element analyses of in-service steel and concrete girder bridges were performed and qualitatively validated. The analyses were used to study the influence of skew angle, deck reinforcement amount and orientation, end diaphragm and girder restraint on deck strains and on live load distribution for shear (i.e., live load distribution to girders as vertical shear forces) from cracked decks to girders. The results showed that high skew induces stresses high enough to cause typical diagonal deck cracking on skewed bridges due to deck shrinkage. Restraint provided by end diaphragms, particularly by full depth concrete diaphragms and diaphragms connected to deck, magnify deck stresses. Orienting transverse deck reinforcement perpendicular to bridge centreline is more effective than parallel to substructure. Larger deck reinforcement cross-sectional areas increased deck restraint and likelihood of cracking. Shear live load reaction in exterior girders of the bridges studied increased by 35% due to deck cracks, although it remained smaller than interior girder reaction.