UHPC-based strengthening technique for orthotropic steel decks with significant fatigue cracking issues

Abstract

Fatigue cracking is a common drawback of orthotropic steel decks (OSDs), especially for long-span steel bridge decks, and it is difficult to repair such decks effectively. This paper proposes an ultrahigh performance concrete (UHPC)-based strengthening technique for OSDs with significant fatigue cracking issues. A multiscale finite element (FE) model based on the Wuhan Junshan Yangtze River Bridge is established. Analysis results show that the vehicle-induced stress values in the OSD are significantly reduced. However, the maximum tensile stress at the bottom of the UHPC layer is 12.9 MPa under the vehicle load, indicating that the UHPC layer is at risk of cracking. Two alternative retrofitting schemes for the UHPC layer are presented. One involves reinforcement by adding one-story transverse steel bars, and the other involves adding steel strips to strengthen the bottom of the UHPC layer. Transverse bending tests were conducted to compare these two schemes. The results show that the tensile strength of the UHPC layer strengthened with 80-mm-wide steel strips could reach 43.2 MPa, and that this was the superior scheme. A test involving 10 million fatigue-loading cycles was conducted to evaluate this steel strip strengthening scheme. The results indicate that the UHPC layer has a fatigue life of 8 million cycles. Thus, the fatigue life of OSDs with significant fatigue cracks can be improved using this strengthening technique.