Rehabilitation and condition assessment of a centenary steel truss bridge

Abstract

The maintenance and rehabilitation of old steel bridges are fields of growing relevance in terms of economic impact. In this context, the state-of-the-art and state-of-the-practice in non-destructive testing and evaluation are crucial for an accurate condition assessment of the bridges, which in turn provides reliable data to assist the decision making process in their management, to identify the actual impact of the modifications introduced in the bridge behaviour as a result of rehabilitation programmes, as well as to improve these projects at the design stage.This paper presents the experimental and numerical study of a centenary steel bridge, the Pinhão Bridge, which underwent an extensive rehabilitation and strengthening process. The scope and objectives of the project are outlined. The field tests carried out before and after the construction works are described and the collected measurements are analysed. In order to discuss the test results and to perform the safety assessment of the new bridge condition, 3D numerical models were developed and duly validated.The results show a significant increase of the flexural stiffness of the bridge spans due to the strengthening of the deck floor system. In addition, the effectiveness of the adopted solutions was, in general, evidenced. However, the structural analysis revealed that the strengthening design of the girders' chords was unbalanced, which has led to an inadequate safety level for the upper members. On the contrary, the strengthening of the steel members pertaining to the floor system was overdesigned, thus resulting in a costly outcome.