Rubber Expansion Joint for Integral Abutment Bridges

Integral abutment bridges eliminate the traditional expansion joint at the abutment by making the deck and abutment monolithic. However, the thermal movement of the bridge deck must still be accommodated somewhere, and rubber expansion joints at the approach slab ends provide this function. The approach slab joint in an integral abutment bridge accommodates the full thermal movement of the bridge deck, which is transferred to the approach slab through the integral abutment. For a 60-meter integral bridge with a temperature range of 50 degrees C, the thermal movement at the approach slab joint is approximately 30 mm, similar to a conventional bridge of the same length. The approach slab joint is located at the transition between the approach slab and the road pavement, typically 5-10 meters from the abutment. This location is less critical than an abutment joint because it is not directly above the bridge bearings or the abutment foundation. However, the joint must still provide waterproofing to prevent water infiltration into the approach fill. Rubber compression seal joints are commonly used at approach slab locations due to their simplicity and low cost. The seal is compressed between the approach slab and the road pavement, accommodating movement through elastic compression and extension. The seal must be specified with a movement range equal to the full thermal movement of the bridge. Soil interaction at integral abutment bridges creates additional movement at the approach slab joint. As the bridge expands in summer, the abutment pushes against the soil, compressing it. As the bridge contracts in winter, the soil rebounds, pushing the abutment back. This soil-structure interaction can increase the movement at the approach slab joint by 10-20% compared to a simple thermal calculation. Maintenance of approach slab joints requires the same attention as abutment joints. Annual inspection should verify that the seal is intact, the joint gap is within the expected range, and the approach slab is level with the road pavement. Any differential settlement between the approach slab and the road pavement must be corrected to prevent a trip hazard.