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One of the main reasons for the fatigue problems in Orthotropic steel decks is the low stiffness of the deck plate. In this study, By increase the deck plate stiffness with three methods of renovation, Reducing stress in the rib-to-deck connections is investigated. For this purpose, a orthotropic steel deck is modeled with ABAQUS finite element Software, and According to the AASHTO LRFD Bridge Design Specification is simulation of fatigue and Then with the help of three methods of Renovation Bonded steel plate, Sandwich steel plate and Reinforced High Performance Concrete ,This reduction of Stresses is studied. The analysis results indicate that at the rib-to-deck joints, Stresses on the deck plate can be reduced by 80% and on the rib web can be reduced by 70% using this renovation methods, As a result, fatigue life of the deck will increase significantly. Also, The comparison of the Renovation methods shows that among renovation methods, Reinforced High Performance Concrete method will give the best results. An orthotropic bridge deck (OBD) consists of a deck plate supported in two perpendicular directions by a system of longitudinal stiffeners and transverse crossbeams which are, in turn, spanned by main girders. All these elements are connected by welding. Fatigue is a well-known phenomenon in orthotropic bridge decks. Several welded details appeared to be extremely sensitive to fatigue loading and shortened drastically the life span of orthotropic bridge decks. One of the most threatening fatigue cracks concerning the traffic safety running on the bridge is the one at the longitudinal welds between the deck plate and trapezoidal stiffener. The main reason is the low stiffness of the deck plate, which is insufficient to deal with the wheel loads of heavy traffic. Moreover, the increase of heavy traffic in the last decades makes the fatigue phenomena an even greater concern. It became clear that existing orthotropic bridge decks needed to be stiffened in order to decrease the stresses at the welds and extend their fatigue life. In the past decades, this subject attracted international attention and several studies have been performed on the fatigue phenomena and on the possible reinforcement systems. The transverse distribution of wheel loads in orthotropic decks generates significant out-of-plane bending moments in the deck plate and rib wall at the rib-to-deck joint. Due to the relatively small thickness of both the deck plate and rib wall, the out-of-plane bending moments result in high local flexural stresses causing fatigue cracks to develop at the joint. in the rib-to-deck connections, Due to the geometry of the welding, there are four potential spots around the weld where the fatigue cracks may initiate, wherein: Crack 1 initiates in the weld root and propagates through the deck plate Crack 2 initiates in the weld toe in the deck plate and propagates through the deck plate Crack 3 initiates in the weld toe in the trough web and propagates through the trough web Crack 4 initiates in the weld root and propagates through the weld throat.

Keywords: Orthotropic steel deck, Rib-to-deck joints, points susceptible to fatigue damages, Renovation methods

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