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Rehabilitation Engineering Eventually structures will start to deteriorate under the forces of nature. Civil engineers are studying ways of economically rehabilitating and maintaining existing infrastructure rather than replacing it. Rehabilitation and maintenance of reinforced concrete bridges has become an important issue during the last few years. More than 40% of the bridges in Canada were built in the fifties and sixties, and most of these are in urgent need of rehabilitation (Neale, 1997). Frequently in winter, salt is spread on the bridge deck to melt snow. The salt solution formed attacks the steel reinforcement causing the bars to rust. The concrete cover in most of these beams was very small with respect to the amount of reinforcement. Thus, cracks appeared around the reinforcement, exposing most of the steel bars in the mid-span of the beams.
The girders shown above are 30 years old and had been repaired once (about 15 years ago) when loss of cover had exposed the reinforcing steel. Testing revealed that even in their current dilapidated state, the beams had more than adequate shear strength, but were low with respect to flexural strength. Rehabilitation techniques were therefore concentrated on improving flexural strength of the girders using methods that could be applied on site. Techniques assessed included patching and reinforcing with carbon fibre (CFRP) strips and sheets, or external post-tensioning. Fiber reinforced polymers are now being used to repair and strengthen bridges, overpasses, highways and other structures.
In England: Debut of prestressed carbon fibre as a beam strengthening technique. It increased the load carrying capacity of the ancient bridge by a factor of five without changing its appearance.
The deterioration of underground infrastructure such as sewer pipes is also a growing concern. To ensure continued service, municipalities check them on a regular basis in order to detect any defects. These checks are currently being done using CCTV camera which unfortunately is time consuming and expensive. A new automated inspection system has been developed by engineers which is able to detect the defects in the sewer pipes, analyze the findings and make recommendations for rehabilitation of the defect.
Rehabilitation is also discussed under Materials Engineering. |
Rehabilitation of the Centre Street Bridge in Calgary - 1999 - 2000
