Fracture Critical Bridge Test

Synopsis of Fracture Girder Testing: Click here for Slides

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On Saturday, October 21, 2006, the Ferguson Laboratory tested a full size bridge consisting to two 120 foot long trapezoidal box girder supporting a 23 foot wide roadway. The purpose of the test was to evaluate the ability of a bridge supported by steel box girders to remain intact if one of the girders suffers a brittle fracture. The fracture will be simulated by cutting the flange (bottom edge of a girder) using a small amount of a linear-shaped charge. Twin box girder bridges are often used in freeway interchanges when long curved spans are required. The I35 and Highway 290 interchange in Austin is an example of this type of bridge. The slender but very stiff and strong boxes provide an aesthetically pleasing and structural efficient solution.

The 120-foot-long steel girder is one of two girders that will support the roadbed and the weight equivalent to a fully-loaded truck (76,000 pounds). The explosion will mimic damage that can occur if a truck's weight fractures a steel girder. During the explosion and its aftermath, more than 120 gauges will capture the behavior of the bridge to provide data to calibrate the analytical and strength models the research team is developing for bridges. The Texas Department of Transportation and the Federal Highway Administration (FHWA) together provided more than $250,000 funding for the experiment to study the behavior of a bridge and develop methods of evaluating the performance of the thousands of bridges in the national inventory.

Texas and many other states have many miles of curved, steel-box-girder bridges. Since January 2005, the FHWA has required each girder to undergo detailed, close inspections annually by each state's transportation department. Texas spends an estimated $26 million annually on these inspections. The findings from this bridge study will guide decisions on modifying the inspection frequency based upon expected bridge performance, potentially reducing annual inspection costs.

For Press Release, visist the College of Engineering Website.