Abstract
Analyses of catastrophic collapse of some adjacent precast concrete box beam bridges reveal the fact that the hinge joints between the adjacent beams were not sufficiently designed. The joint failure caused by deterioration is the result of system reliability deficiency of this type of bridges. To understand the system performance of the bridges, the redundancy and robustness of a bridge model with a scale of 1 ∶ 2, based on the prototype design drawings for 10-meter adjacent box beam bridges in China, were assessed through a system safety evaluation procedure. The result confirmed the assumption that the redundancy and robustness of certain adjacent precast concrete beam bridges did not meet the pertinent requirements proposed in National Cooperative Highway Research Program (NCHRP) reports 406, 458, and 776 as a result of hinge joint failure. To address the current design deficiencies, a system factor is recommended in this paper to calculate the nominal resistance that reflects the level of redundancy of this type of bridges. In addition, a new framework is proposed to address the particular structural feature and topology of adjacent precast concrete beam bridges for the assessment of structural redundancy and robustness, which can reduce the computation complexity compared to existing approaches. The full-range load test performed in this research verified the previous research results on bridge system safety that were mainly based on theoretical analysis and simulations.
Highlights
Adjacent precast concrete box beam bridges are widely used worldwide because of their unique advantages including the simple structural design, quick installation, and high cost effectiveness. e first bridge of this type was built in the United States in the 1950s; at present, about two-thirds of states in the United States have built precast adjacent box beam bridges, which account for nearly one-sixth of the bridges built annually on public roads [1]
E bridges are built by placing precast concrete box beams side by side in parallel. e beams are connected using hinge joints longitudinally grouted in between and covered with a concrete pavement deck. e hinge joints and the concrete deck provide the transverse connection between concrete box beams
Most adjacent box beam bridges have been in service for many years and generally performed well
Summary
Adjacent precast concrete box beam bridges are widely used worldwide because of their unique advantages including the simple structural design, quick installation, and high cost effectiveness. e first bridge of this type was built in the United States in the 1950s; at present, about two-thirds of states in the United States have built precast adjacent box beam bridges, which account for nearly one-sixth of the bridges built annually on public roads [1]. The function loss of the edge hinge joint was the main cause of the collapse of the exterior beam of the approach bridge of the 3rd Hangzhou Qiantang Bridge. E damage of the edge hinge joint resulted in the formation of the “Single Plate Load Effect”; as a result, no load was transferred between the adjacent beams. E load carrying capacity evaluation of adjacent precast concrete box beam bridges is presently based on elastic analysis. Hinge joints are relatively weak compared to the beams; the cracking and deterioration of hinge joints would significantly change the load distribution among beams and change the system behavior of the bridge. Is paper presents a system performance evaluation approach for the precast adjacent concrete box beam bridges. A destructive test on a model bridge was conducted, and complementary 3D nonlinear finite element models were developed to demonstrate the performance change of the bridge over the complete loading cycle. e system performance analysis provides a basis for optimal new designs and rehabilitation strategies of this type of bridges
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