Bridge Expansion Joint for Bridges with Expansion Joints at Intermediate Piers

Expansion joints at intermediate pier positions in multi-span bridges are more structurally complex than abutment joints because they must accommodate the movement of two adjacent spans while transferring vertical loads across the joint. The joint design must address this structural complexity. Structural continuity at intermediate pier joints requires that vertical loads can be transferred from one span to the adjacent span across the joint. This is typically achieved by using a joint with a structural edge beam that spans across the joint gap and transfers the vertical load. The edge beam must be designed for the combined effect of the vertical load and the thermal movement. Movement range at intermediate pier joints depends on the lengths of the two adjacent spans and the temperature range. For two 50-meter spans with a temperature range of 50 degrees C, the movement at the intermediate pier joint is the sum of the movements of both spans, approximately 60 mm. This is larger than the movement at an abutment joint for a single 50-meter span. Bearing design at intermediate pier joints must allow the deck to move freely while transferring vertical loads to the pier. Sliding bearings on the pier cap allow the deck to move longitudinally while the vertical load is transferred through the bearing. The bearing must be designed for the combined effect of the vertical load and the horizontal movement. Drainage at intermediate pier joints must collect water that infiltrates the joint and discharge it away from the pier cap. Water on the pier cap can cause corrosion of the pier reinforcement and deterioration of the pier concrete. The drainage system must be designed to prevent water accumulation on the pier cap. Inspection of intermediate pier joints requires access to both the top and the underside of the joint. The top of the joint is inspected from the road surface. The underside is inspected from a suspended platform or a snooper truck. The pier cap and bearings must also be inspected during the joint inspection.