EXPANSION JOINTS - AN OVERVIEW OF TRL RESEARCH

Any type of joint is a potential source of weakness. Modern concrete and steel bridges have joints to accommodate the movements of the bridge deck relative to the adjacent pavement. Most of these joints leak, allowing water and chlorides to penetrate deck ends, abutments, piers and crossheads and cause corrosion of the reinforcing steel. The performance of current joints is very variable. Some are satisfactory, but many have service lives of only a few years and are expensive to maintain. Joint performance is determined by a complex combination of factors. Some of the main factors are: the movements at the joint resulting from thermal variations and traffic loading, the installation conditions and standard of workmanship, the choice of materials, and the 'liveliness' of the structure. This paper describes planned TRL research to develop a performance based specification based on approval testing. Laboratory test rigs are used to simulate movements and wheel loading on joints and a range of material tests are assessed for use in quality control. Methods of eliminating joints are also being studied. Continuous spans rather than a series of simply supported spans reduce the number of deck joints. More recently bridges have been designed to be fully integral by building-in to the abutments, eliminating deck joints altogether. The performance of various designs, in the UK and other countries has been studied. (A) For the covering abstract see IRRD 860342.