RAPID: Structural Damage Data Collection and Analysis of a Recently Damaged Bridge

University Of New Hampshire, Durham NH

Investigators

Abstract

It is proposed to collect structural data of a damaged bridge in the next 4-6 weeks before repair is completed. The Sarah Long Bridge, a 2804-foot double deck truss bridge, in Portsmouth, New Hampshire, was struck by a 473-foot cargo ship on April 1, 2013. After visual inspection and assessment, it was determined that the primary structural damage is the severely bending of two members of the 227-foot segment of the steel truss and they must be replaced. The bridge is closed to traffic till the repairs are completed. The New Hampshire Department of Transportation estimates the repair to cost $2.5 million and take 4-6 weeks. The proposed work fits RAPID's goal given that the collision is a rare, unanticipated event and the short time period available to collect perishable vibration data on the damaged bridge. The project team will deploy wireless sensors on the bridge and record ambient vibrations before and after the repairs. Additionally, the damaged structural members of the bridge will be documented and analyzed. The proposed measurements will provide rare data sets of a major structure at its damaged (pre-repair) and healthy (post-repair) states, which will help understand structural behavior of a damaged truss. The vibration data of the bridge at its healthy and damaged states will be analyzed and compared to identify changes in natural frequencies. In addition, the bridge data will also be used to develop a finite element analytical model of the bridge truss. The analytical model will be used to understand structural vibration characteristics of the truss and can postulate how frequencies of the truss will change with other damaged members. This exercise will answer the question of change in vibration frequencies with different levels of damage; and ultimately help in structural health monitoring field.