Usability Evaluation and Life Extension Criteria for Expressway Bridge Reconstruction and Expansion
Aiming at the problem of whether existing bridges in expressway reconstruction and expansion projects can remain in service,the evaluation method was established with the appearance durability of bridge components as the first-level indicator,and the remaining durability as the second-level indicator.The method took the overall technical condition,bearing capacity and remaining durability life status into consideration.The life coefficient and available life coefficient were proposed,which represented the remaining durable life of components.The life extension criteria and strategies for existing bridges were established.The relation among available life coefficient,target service life,effective protection life of single life extension and number of maintenance measures was discussed.Taking Beijing-Shanghai expressway reconstruction and expansion project as the study background,there were 9 existing bridges selected as the typical bridges.The remaining durability life of main reinforcement and stirrup was calculated according to the target service life of 100 years,and the remaining durability life of typical bridge was got.According to the available evaluation method,the life extension,life extension cost and available life coefficient with different life extension measures were calculated.There were 5 life extension methods from class A to class E put forward according to the economic optimization principle.The result indicates that the durability life according to stirrup is lower than that of main reinforcement,so it is recommended to use the life according to stirrup.When the target service life is 100 year,the serviceable ratio of main beam members is 94%.The serviceable ratios of pier column unit,cover beam unit and abutment unit are 67%,11%,44%respectively.The actual project shows that the evaluation result of the propsed method is basically consistent with the actual state of structure.It is basically equivalent to the actual disposal measures taken by the project,which verifies the method rationality.
bridge engineeringlife extension criteriaevaluation methodmain componentdurabilityreconstruction and expansion
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