The orthotropic steel deck (OSD) has been used in bridges with varying spans and different structural forms owing to their excellent properties, howeverit is susceptible to fatigue failures due to overweighed trucks, poor design and fabrication [1,2]. Fatigue cracks occur at the fatigue-prone locations like the rib-to-deck joint, rib-to-floor beam joint and the rib splice leading to development of several types of crack patterns. Regarding the effects of fatigue cracking, several studies have been conducted in an attempt to prevent premature fatigue cracking, with emphasis on improved structural detail and parameters. Recently, increasing the bridge deck stiffness by increasing the load sharing has been identified as a promising solution. Specifically, a cement-based overlay cast on the deck has been used in addition to sandwich steel plates reinforcement systems to improve the performance of the orthotropic steel deck bridges.
Professor Zhiwen Zhu of Shantou University and Dr. Ze Xiang of Hunan University, together with Dr. Edward Zhou from Bridge Instrumentation and Evaluation Center of AECOM analyzed the stress behavior and fatigue performance of an orthotropic steel deck bridge stiffened with the ultra-high-performance concrete (UHPC) layer using finite element method. The main objective was to develop an orthotropic steel deck structure with infinite fatigue life for bridges subjected to high traffic volumes. The work is published in Journal of Constructional Steel Research.
Briefly, the research team started by exploring the features and performance of the ultra-high-performance concrete when used in reinforcing steel bridge decks. This included determining the stress responses under wheel loads. The stress behaviors observed by the finite element models were compared to the stress response measurements data available in the literature. Finally, the results on the causes of stress at fatigue prone areas were used to conduct a parametric study to determine and investigate the effects of critical parameters on the stress range.
The authors observed that the stress range at the deck side of the rib-to-deck joint could be reduced by 70.9% by using a 45 mm thick the ultra-high-performance concrete layer. This could lead to the realization of the infinite fatigue life. However, for the three remaining details: the rib side rib-to-deck joint, rib wall at the rib-to-floor beam joint and the side of the rib-to-floor beam joint remained of great significance due to several factors. This included rotational and poisons effects as well as the impact of both in-plane and out-of-plane stress components.
Taking into consideration the critical parameters affecting the stress range, it was noted that the ultra-high-performance concrete layer did not exhibit a serious impact on the mechanical properties of the bridge. Additionally, increasing the thickness of the ultra-high-performance concrete layer and rib wall decreased the stress ranges near the deck plate and at the rib side respectively. The same was observed at the floor beam side of the rib-to-floor beam joint by increasing the cutout clearance. Based on the results of the new model parameters by Professor Zhiwen Zhu and his colleagues, the bridge design criteria for achieving infinite fatigue life under high traffic volume have been proposed.
 Zhu Zhiwen, Huang Yan, Xiang Ze. Fatigue Performance of Floorbeam Cutout Detail of Orthotropic Steel Bridge on Heavy Freight Transportation Highway. China Journal of Highway and Transport,2017(3):104-112. (In Chinese).
 Zhiwen Zhu, Ze Xiang. Fatigue cracking investigation on diaphragm cutout in a self-anchored suspension bridge with orthotropic steel deck. Structure and Infrastructure Engineering, 2019, 15(10):1279-1291.
 ZhiwenZhu, Ze Xiang, Jianpeng Li, YanHuang, Shipeng Ruan, Fatigue behavior of orthotropic bridge decks with two types of cutout geometry based on field monitoring and FEM analysis, Engineering Structures, 2019,12. https://doi.org/10.1016/j.engstruct.2019.109926.
 Zhiwen Zhu, Tao Yuan, Ze Xiang, et al. Stress behaviors and fatigue performance of details in orthotropic steel bridges with UHPC-deck plate composite system under in-service traffic flows. ASCE, Journal of Bridge Engineering, 2018, 23(3): 04017142-1~21.
 Zhu, Z., Xiang, Z., & Zhou, Y. (2019). Fatigue behavior of orthotropic steel bridge stiffened with ultra-high performance concrete layer. Journal of Constructional Steel Research, 157, 132-142.