The Design of a Full-scale Apparatus for Testing of Bridge Expansion Joints

Bridge expansion joints have become a subject of much concern in the United States and other countries. Failure of these joints has caused seri ous traffic problems. Joints are designed into most bridge structures to allow for normal expansion and contraction of pavement slabs. Presently, however, design is based on failure under a traffic loading which can only be assumed. A full-scale model study can simulate the performance of actual bridge joints under controlled representative loads. This type of model has recently been constructed by the Department of Civil and Environmental Engineering at the University of Central Florida under the sponsorship of Florida Department of Transportation. The model is a 50 foot diameter circular test track which is a 4-foot wide lane of concrete slab. Two bridge sections, 6 feet by 12 feet, with an expansion joint in each, are built into the track. The loading system consists of three 25 foot long W36 x 150 beams mounted at the center of the track. At the end of each beam assembly is a dual truck wheel modified from a truck driven axle. A 12 foot diameter by 8 foot high water tank centrally mounted on top of the beams is used to generate an additional weight load system. The total load varying between 30,000 and 75,000 pounds is evenly distributed to three dual wheels. The device is powered by a 220 horsepower diesel engine with a hydraulic transmission and is capable of speeds up to 30 miles per hour. A computerized data acquisition/control system has been assembled to monitor the performance and life expectancy of different expansion joints. Instrumentation from load cells, acoustic emission, strain gauges, and electromagnetic impulse is installed to monitor the system and collect test data. The design and construction of the model are described in detail in this paper