Fatigue resistant rib-to-floor beam connections for orthotropic steel bridge decks with potential for reduced cost using automated fabrication
Richard SauseLehigh University, PA, USA
Orthotropic steel bridge decks (OSDs) have been utilized across the world in both new bridges, and as replacement decks for preserving existing bridges. An OSD consists of a continuous steel deck plate with longitudinal ribs that pass through transverse floor beams (or diaphragms). These components are joined using welded connections. The transverse floor beams (or diaphragms) are supported by primary longitudinal components of the bridge superstructure, including girders, girder webs, trusses, and/or cables. An OSD allows a bridge deck to be integral with this supporting bridge superstructure, resulting in increased rigidity and decreased material use. An OSD is lighter in weight, is easier to assemble due to its modular nature, and has potential to offer a longer service life than other bridge deck systems. One barrier to increased use of OSDs in the United States has been a relatively high initial cost of fabrication, resulting from specified details used to achieve the desired fatigue resistance of its welded connections.
Modern orthotropic decks are usually designed with relatively thin closed ribs (U-shaped or trapezoidal-shaped) and relatively thick deck plates. Each rib passes continuously through a matching cut-out in the floor beam. Fabrication of the connection of the rib to the floor beam, i.e., the rib-to-floor beam (RFB) connection, is often labor intensive, which adversely impacts the fabrication cost of OSDs. The RFB connection is also fatigue sensitive because it is subjected to complex in-plane and out-of-plane deformations and stresses from vehicular loads on the steel deck plate.
The presentation discusses: (1) the fabrication features of three types of RFB connections for OSDs and the potential for using automated fabrication processes for these RFB connections; (2) the potential fatigue performance of these RFB connections based on finite element analysis and fatigue design standards from the United States bridge design specifications; and (3) results from fabricating and testing full-scale laboratory OSD specimens with different RFB connections. Conclusions related to the applicability of these RFB connections in OSDs are given.