Effects of joint geometry on response of asphaltic plug joints

The asphaltic plug joint (APJ) is commonly used to accommodate structural movement in motorway bridges. Despite its widespread popularity, the performance of this jointing system is unpredictable, and premature failure is common. A brief description of the standard APJ system currently employed is given, together with proposed alternative joint geometries to improve the in-service performance of APJs. The finite element (FE) code ANSYS v5.1 was used to complete a pilot study of the performance of the APJ system, where models of the standard and of two geometrically altered designs of joint plug (trapezoidal and sinusoidal) were examined. A compression test conforming to ASTM D1074-96 of an APJ sample ensured that measured values of the stress-strain curve were used in numerical analysis. Different structural loading conditions were simulated, and a simplified method to model the interaction between a moving truck wheel and the plug was used to approximate vehicle loading. The results, presented in the form of plots of the distribution and magnitudes of internal stresses, and graphs of maximum stresses at key locations, provide a basis for the study of joint response as a function of plug geometry.