Girder Bridge Case 12-11

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The results show that the bridge in Case 1 collapsed under 44% of the total applied load with 0.097 inches bending displacement and 0.45 inches buckling displacement, as shown in Figs 10 -11. The bridge collapsed due to the huge lateral movement at the top of the webs, which caused a loss of stability and ability of the webs to carry any load, Figs 12-13. The value of the bending displacement is small compared to the value of the buckling displacement because almost no bending moment was created under this situation, since the webs would not be able to carry the load and transfer it vertically to the bearing support. The failure mode in Case 2 is similar to that in Case 1, but the buckling load was increased in Case 2 to reach 51% of the total applied loads rather than 44% in the previous case. The end braces at the top of girder helped to resist and minimize the lateral moment of the webs, Figs 18-19. As a result, the load buckling increased (capacity) and the bending and buckling displacement decreased (0.021", 0.1"), as shown in Figs 16-17.…show more content…
Figs 21-22 in Case 3 and 25-26 in Case 4 show the normal bending behavior for the box girder under 100% of the total applied load. The load-displacement graphs in both cases clearly indicate the elastic behavior of the bridge, because the girder was able to carry all of the applied load with no failure, Fig 23 and 27. Since the truck loads in Case 4 are acting on one side of the bridge only, the stress concentration is high at that part as observed in Fig 25-26. The bending displacement in Case 3 is 0.024 inches, which is less than that in Case 4 (0.026 inches) because the bridge in Case 3 under the dead load only as mentioned
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