Retrofitting of Existing Bridge Using Externally Bonded FRP Composite–Applications and Challenges
S. V. Chandramouli, Manager (Technical); Sindhu S Saraswathi, Manager (Technical Services), M N Ramesh, Director, BBR (India) Pvt. Ltd., and N. Munirudrappa, Professor of Civil Engineering, Dayananda Sagar College of Engineering, Bangalore.
The increase in deterioration of bridge infrastructure is a large-scale national problem. Maintaining the existing bridge infrastructure network and adapting it to new capacity requirements has become one of the most challenging tasks for today's engineers. Bridges designed and built only a few years ago are now subjected to traffic loads well above the design ones. At the same time, it has become evident that the durability of bridges is not always guaranteed, even for relatively recent constructions. For bridges in urban areas, the space concerns are predominant and building a new bridge alongside an existing one is not a viable option. It is therefore necessary to intervene on the structure with most feasible, economical and efficient methods to upgrade, repair or strengthen the existing bridges while preserving, at least partially, its traffic bearing capacity. These challenges are greater than the ones required to design and build a new bridge. Fiber Reinforced Polymer (FRP) composites represent a new and promising solution to the shortcomings of several traditional materials and upgrading techniques and has a great potential to integrate into the bridge infrastructure. In the recent years several, researchers have investigated the performance of external bonded FRP composites and found to be a successful effective technique for upgrading structural element. This paper highlights the applications of external bonded FRP composites overlay for bridge infrastructure, the challenges involved and path to implementation.
Introduction and Background
The bridge infrastructure has been deteriorating for many years, a result of sometimes like harsh environmental conditions, heavy loads, insufficient maintenance, and, frequently, unintentionally damaging maintenance practices and it has be come a large-scale national problem. It has been widely reported that approximately 40% of India's bridges are either structurally deficient or functionally obsolete. Structural "deficiency" does not imply that a bridge is unsafe or likely to collapse. With proper weight restrictions and enforcement, most deficient bridges can continue serving traffic safely when limited to posted maximum loads. The main reasons for classifying a bridge as structurally deficient are low load ratings (or weight restrictions), deteriorated decks or deteriorated substructures. Maintaining the existing infrastructure network and adapting it to new capacity requirements has become one of the most challenging tasks for today's structural engineers. Bridges designed and built only a few tens of years ago are now have to carry traffic loads well above the design ones. At the same time, it has become evident that the durability of bridges is not always guaranteed, even for relatively recent constructions. In this context, the engineer is often asked to design refurbishments, enlargements and repairs on structures that are under heavy usage. This presents challenges that are even greater than the ones required to design and build a new bridge. For bridges in urban areas the space concern are predominant and building a new bridge alongside an existing one is not a viable option. It is therefore necessary to intervene on the structure while preserving, at least partially, its traffic bearing capacity. Due to budget constraints, many authorities are forced not to proceed with strengthening but to post load restrictions on their bridges as a temporary measure. A significant number of bridges all over the world need rehabilitation and strengthening.
