Finite Element Analysis of Post-Tensioned Concrete Trough Bridges

The demands on civil structures have increased during recent years.Many structures are required to carry higher loads and larger trafficflows than what they originally were designed for. Also many structureshave grown old and have suffered deterioration, so that they do not any longer fulfill the safety requirements. If a structure is no longer able to satisfy the safety level, that structure should be replaced, repaired or strengthened.The purpose of this thesis is to investigate a suitable strengthening method for railway concrete trough bridges - a bridge type quite common in Sweden. The goal is study the benefits of the method and to discuss when it is preferable to strengthen a bridge instead of replacing it.There are a few strengthening methods, which can be used. In our case the method studied is internal unbonded post-tensioning. This seems to be a very promising strengthening method. Internal unbonded post-tensioning may be defined as a prestress introduced by tendons located inside the deck of a bridge.The main advantages using this technique are (1) the method is economic; (2) both flexural and shear strength can be increased without the penalty of increased dead load; (3) the tendons can be made fully replaceable; (4) no traffic restrictions are required on the bridge being strengthened; and (5) the method can be applied to both new and existing structures.In order to study this strengthening method a finite element study wasperformed. The results were discussed and compared with the results of a laboratory and a field study performed by Jonny Nilimaa.The studies were successful and proved that internal unbonded post- tensioning increases the flexural and the shear capacity, improves the cracking performance and decreases the internal strains of the structure.Validerat; 20150629 (global_studentproject_submitter