Active control of extremely prestressed simple supported composite bridges

Abstract

More than 600,000 US bridges are considered to be in need of rehabilitation. More than 90 Billion US Dollars is the estimated amount of money required. According to the National Bridge Inventory, 18.5% of those bridges are structurally deficient. Many methods of rehabilitation have been sought out by engineers throughout the years. Perhaps the most interesting of all solutions is utilizing external post tensioning cables to add to the stiffness of the system. External post tensioning can be considered to be a cheap solution that is easy to install, and easy to fix in the future. What has not been discussed among engineers is the possibility of controlling the tendon force. Vertical deflections could be monitored and assessed, and a consequent axial prestressing force could be applied on the cables. This report investigates in detail the issues involved in the design of externally prestressed tendons on a simply supported composite bridge of specific properties, and touches on the reasoning behind active control and the limitations that the current technology has.