STRESS BEHAVIORS AND MECHANISM OF DETAILS OF ORTHOTROPIC STEEL DECK UNDER WHEEL LOADS

In order to clarify the stress local effects and stress behaviors at details of the orthotropic steel deck (OSD) under wheel loads, truck loading tests and finite element analysis were carried out at three typical transverse loading locations. Stress-time histories were recorded at the details of the OSD to investigate their stress behaviors and mechanism under the passage of a truck with a very low speed. The research finds that the details of the OSD impose significant stress local effects under wheel loads, which is limited to the range of one center-to-center rib space on both sides of wheel center in bridge transverse direction is limited in a zone of two center-to-center rib spaces in the transverse direction. Hence, the stress superimposition at the details, simultaneously produced by the left and right wheels of a truck or produced by trucks traveling side-by-side on adjacent lanes, can be ignored. For the area with significant stress local effects, one axle produces an individual stress cycle at the rib-to-deck (RD) detail. The riding-rib-wall loading is the most critical loading locations in bridge transverse direction for the RD, rib-to-floorbeam (RF) welds and cutout details. Under the wheel loads, the mechanism of stress at RD detail is that the deck plate acts as a continuous beam supported by the rib wall, and that the moment on the rib wall satisfies the moment equilibrium condition among both sides of deck plate and the rib wall. The mechanism of stress at the RF weld at the rib side (RF-R detail) is the negative moment acting on ribs at its supports provided by floorbeam. The mechanism of stress at the RF weld at the floorbeam side (RF-F detail) is due to its location at the upper portion of floorbeam web, while the mechanism of stress at cutout detail is the compressive force in the vertical element in the Vierendeel truss model. Understanding the stress local effects and their mechanism can simplify fatigue investigation of the OSD using the finite element analysis, which facilitates the design of the OSD against fatigue damage.