ARCHIVED - Research and Graduate Studies in Civil Engineering
CFRP Sheet Strengthening of Damaged Full-Scale Double-T Prestressed Concrete Beams
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By: Capt U.V. Honorio
Supervisor: Major R.G. Wight
Abstract
Military engineers are often tasked to assess the integrity and sometimes repair war-damaged or heavily deteriorated bridges in theatres of operation to restore and maintain freedom of movement. Common methods used to resolve such issues may include detours, over-bridging and/or reconstruction. These approaches are usually time-consuming, labour and maintenance intensive, and very costly. Therefore, an alternative rehabilitation technique is required that is robust, expedient, cost-effective and non-restrictive to traffic flow during application. Externally bonded carbon fibre reinforced polymer (CFRP) sheets is a suitable repair and strengthening method that is becoming an accepted practice for rehabilitating existing structures in the civilian sector. CFRP’s durability, high strength-to-weight ratio, light-weight and minimal requirement of resources during installation, makes it a very attractive repair method for military applications in theatres of operation.
The experimental program reported herein investigated the effectiveness of externally applied, non-prestressed and prestressed CFRP sheets for flexural post-strengthening damaged full-scale double-T prestressed concrete girders. For this investigation, two full-size commercial girders (17m and 18m) acting as two independent double-girder simply supported bridges, were erected on the grounds of Canadian Forces Base Kingston. Each girder was load tested with a tandem-axle dump truck under undamaged, damaged and repaired conditions. For the damaged state, one of the webs was successively damaged at mid-span by severing the first (bottom) and second steel reinforcing strands. The damages were repaired, where one girder was strengthened with non-prestressed and the other with prestressed CFRP sheets. The flexural behaviour of the girders was predicted numerically using a non-linear predictive model, supplemented by a commercial finite element software. Lateral re-distribution of load between the undamaged and the damaged/repaired webs was also investigated. Finally, the installation of CFRP sheets in a field environment was evaluated to determine its viability as a practical rehabilitation technique that could be adapted by the Canadian Forces.
Experimental load-deflection results correlated well with the theoretical predictions. The progressive decrease in stiffness due to incremental web damage led to increased member deformation. The application of CFRP laminate, non-prestressed and prestressed, restored, and, even exceeded, the stiffness of the previously damaged web, improving the load bearing capacity and serviceability of the girders. It was demonstrated in this investigation that repair and strengthening of a damaged or deteriorated bridge with externally bonded CFRP laminates can be carried out with minimal requirements in a reasonably short period of time.
