Experimental Study On Static And Fatigue Behaviors Of Orthotropic Steel Bridge Deck

The orthotropic steel bridge deck(OSD) has good mechanical performanceand is widely used in long-span bridges. Due to the complicated connection welds and the high degree of stress concentration at the connection details, the fatigue cracks are often detected in the OSD. The static and fatigue test of a full-scale OSD was conducted in this thesis, based on the structural form of one bulkhead installed in the U-rib. The improvement of the bulkhead for the mechanical performance and fatigue strength of the connection details of the OSD was also analyzed. Finite element model(FEM) was established to discuss the influences of mesh accuracy and the weld size on the calculated results of extrapolation points and hot-spot stresses. The FEM was calibrated by comparing the calculated results with the measured values derived from the static test. The influence of different forms and design parameters of bulkheads were analyzed based on the calibrated FEM. Reasonable forms and design dimensions of bulkhead were thus proposed. The main conclusions can be summarized as follows:1?The stress level at the rib-to-floorbeam(RF) connection detail is remarkablely reduced since the inner bulkhead was arranged; The peak stress of the cutout is also relieved to some extent. Thus the mechanical behavior of the of the floor beam(FB) can be significantly improved.2?The calculated results based on linear extrapolation recommend by DNV are less than the calculated results based on linear extrapolation recommend by IIW; When the element size equal to or less than 0.5t(t: thickness of U-rib web) is adopted for modeling, the hot-spot stress results recommended by the DNV and IIW are very close. When the FEM with element size equal to or less than 0.25 t is applied, the analytical results agree qualitatively with the measured values.3?The results of fatigue test show that the fatigue cracks easily occur below the weld toe of the RF connection detail. The decrease of the measured stress 10 mm away from the weld toe is taken as the criteria for the judgment of fatigue failure. The results show that the bulkhead can effectively delay the time of the occurrence and propagation of the fatigue cracks based on the analysis of the time,causes and forms of the crack occurrence.4?For the design of the bulkhead, it is better to set the bottom of the bulkhead terminated the tip of FB cutout 1.25 t. Regarding the shape of bulkhead, it is suitable to set the internal rib wall inside the U-rib as the unfavorable influence of the continuous bulkheads could be effectively prevented.