Prototype Testing of Intelligent Stiffener for Bridges at I-35 Walnut Creek Bridge

There is an evident need to develop technologies to extend the useful life of bridges. A recent report to the U.S. Congress indicates that approximately 25 percent of U.S. bridges are rated as deficient, with an estimated cost of $7 billion per year for the next 26 years to rebuild or replace those bridges. The Center for Structural Control at the University of Oklahoma has been engaged in a multiyear effort to develop smart technologies that extend the useful service life of bridges. The research effort has culminated in the development of an intelligent stiffener for bridges (ISB) that can be retrofitted to an existing bridge. Results indicate that the ISB system can add decades of service life to an existing bridge. The ISB consists of an otherwise generic stiffener retrofitted to a bridge. The stiffener is unique in that it is equipped with an adjustable hydraulic link that is used to regulate the amount of stiffness (and damping) provided by the stiffener as vehicles pass over the bridge, acting much like a muscle, sometimes flexed and other times relaxed. The ISB is referred to as a semiactive control system because it uses no line power and is energized by a 12-volt automobile battery. This paper reports the first successful demonstration of the ISB technology on an in-service bridge. Discussed are the ISB design features, the steps used to establish a reduced-order finite element model of the bridge, and a brief description of the procedures used to validate the bridge model.