Fatigue Performance of a Lightweight Composite Bridge Deck with Open Ribs

An innovative lightweight composite deck (LWCD) is proposed for steel bridges to avoid premature fatigue cracking. The composite deck is composed of an open-ribbed orthotropic steel deck (OSD) and a thin ultrahigh-performance concrete (UHPC) layer. This study is based on a suspension steel bridge in China, namely, the Second Dongting Lake Bridge. The following investigations were performed: (1) preliminary finite-element analysis (FEA) was carried out to evaluate the vehicle-induced stress ranges (i.e., Δσ = σmax − σmin) of six typical fatigue-prone details; (2) parameter analyses were performed to investigate the effects of the shape of cutouts and the thickness of the floor beams; and (3) two fatigue tests, one that used a full-scale LWCD panel and another that used a LWCD beam specimen, were conducted to reveal fatigue performance of the OSD and the stud shear connectors, respectively. Results of the preliminary FEA show that, with the contribution of the UHPC layer, the vehicle-induced stress ranges at some fatigue details of the LWCD, such as the rib–deck plate welded joints and the splice welds of the longitudinal ribs, were reduced to be less than their constant-amplitude fatigue limits, which indicates theoretically infinite fatigue lives of these details. The parameter analyses reveal that the apple-shaped cutout had relative good fatigue properties among the four cutout schemes and that the thickness of the floor beams is recommended to be 14–18 mm. According to the fatigue tests on the composite panel specimen and on the composite beam specimen, both the open-ribbed OSD and the stud shear connectors exhibited satisfactory fatigue endurances, which were much greater than 2 million cycles. The current theoretical and experimental investigations reveal that the proposed open-ribbed LWCD has favorable fatigue performances.