Several long-span bridges built in Thailand in the 1970s were designed using post-tensioned concrete, which allowed for a wide range of span lengths to accommodate wide rivers. But lengthier spans reduce bridge height. Using dapped-end connections accommodates the reduced bridge height and improves girders’ lateral stability. However, if improperly placed, these connections can become vulnerable and can crack. Often hard to detect, leading to delayed maintenance, these cracks multiply. Combined with material deterioration, this can lead to catastrophic bridge collapse.

Commonly found in the corner region, the cracks are not often visible during a visual inspection and pose safety concerns. Researchers Tidarut Jirawattanasomkul, Nuttapong Kongwang, Suched Likitlersuang, Wanchai Yodsudjai, Songpol Charuvisit, and Yasuhiko Sato wanted to identify the combined effect of the insufficient dapped-end reinforcement and prestress losses in the girders. They used two scenarios to investigate 13 cases of different bridge girder reinforcement layouts.

Their paper published in the Journal of Bridge Engineering, “Failure Analysis of Dapped-End Cracking in Posttensioned Bridge Girder” aims to identify the possible causes of existing damage and the potential modes of failure of the bridge's girder using nonlinear finite-element analysis. Read about their field observations to identify the main causes of crack initiation in PTC girders and their numerical simulations to investigate the problem of long-term failures in PTC bridge girders in the abstract below or by reading the full paper in the ASCE Library: https://doi.org/10.1061/(ASCE)BE.1943-5592.0001786

 

Abstract

This paper will examine in detail a post-tensioned concrete (PTC) girder bridge with dapped-end connections, with a re-entrant corner diagonal crack that is typical of these types of bridges. This paper aims to identify the possible causes of the existing damage and the potential modes of failure of the bridge's girder using nonlinear finite-element analysis (FEA). Failure analysis of the bridge girder will consider the effects of supplying the bridge with different dapped reinforcements and subjecting the bridge's prestressed tendons to losses in their prestressing forces. Various failure scenarios and cases will be simulated in numerical models. Numerical analysis results will be compared with design guidelines for bridge girders. Overall, the investigative results indicated that the combined impacts of insufficient hanger reinforcement and prestress losses in the girder's end-section were the probable cause of the bridge's re-entrant corner diagonal crack.

Read the full paper in the ASCE Library: https://doi.org/10.1061/(ASCE)BE.1943-5592.0001786

Author
Leslie Connelly
Leslie Connelly

Aff.M.ASCE