Shock and Vibration Application Brief

Bridge Vibration

The Problem

A 100-foot section of a Connecticut Turnpike bridge collapsed and fell into the Mianus River, killing three people and critically injuring three more. Hundreds of thousands of drivers had to find alternate routes for almost three months while repairs were made. The repairs alone cost the state of Connecticut over $23 million after insurance. Additional funds were disbursed to investigate why the collapse had occurred in the first place, since the bridge had passed inspection only nine months earlier.

Structurally Deficient Bridges

It has been estimated that 35% of this country's 590,000 bridges were considered structurally deficient or functionally obsolete because of increased age and larger-than-expected service loads. Recent collapses or near-collapses have forced governments to develop extensive rehabilitation programs. Regulations require that bridges be inspected every two years, except old and high-risk bridges, which must be inspected more frequently. Current inspection techniques depend on human beings to recognize structural imperfections. A need to improve inspection techniques is evident.

Flexible and Powerful Analysis Software Required

Researchers at the University of Connecticut are studying the feasibility of assessing a bridge's structural integrity through vibrational monitoring. Structural imperfections in nuclear power plants and in offshore engineering structures are commonly detected using the evaluation of dynamic characteristics; since bridges have dynamic loads, it seems reasonable to evaluate them using these methods also. A full-scale prototype monitoring system developed at the University of Connecticut and at Vibra-Metrics, Inc. in Hamden, Connecticut provides a method of non-destructive evaluation for assessing a bridge's structural condition. It was initially tested on a laboratory bridge model and is currently being tested on a Connecticut bridge. This project requires that they use software sufficiently flexible and powerful to provide them with answers, yet easy enough to learn that it will not slow them down.