Bridge Expansion Joint for Bridges with Expansion Joints in Deck Slabs on Driven Piles

Bridge decks on driven piles require careful consideration of the effects of pile driving on adjacent expansion joints and structures. The vibration from pile driving can damage existing joints and structures, and the pile installation sequence must be planned to minimize these effects. Pile driving vibration can damage existing expansion joints by loosening the anchor bolts, cracking the concrete edge beams, and displacing the joint components. The vibration level at the joint location depends on the pile type, the pile size, the driving energy, and the distance from the pile to the joint. Ground vibration monitoring is recommended during pile driving near existing joints. Vibration limits for pile driving near existing expansion joints are typically specified in the project specification. The maximum allowable vibration level is typically 50 mm/s peak particle velocity (PPV) for reinforced concrete structures and 25 mm/s PPV for sensitive structures. The pile driving must be stopped if the vibration level exceeds the specified limit. Pile installation sequence must be planned to minimize the vibration effects on existing joints. Piles should be driven away from existing joints, starting at the farthest location and working toward the joint. This sequence allows the vibration to dissipate before reaching the joint. Pre-drilling of pilot holes reduces the vibration from pile driving by reducing the driving resistance. The pilot hole diameter is typically 50-75% of the pile diameter. Pre-drilling is particularly effective for reducing vibration in cohesive soils where the driving resistance is high. Post-driving inspection of existing expansion joints must verify that the pile driving has not caused any damage. The inspection should check the anchor bolt torque, the concrete edge beam condition, and the joint gap width. Any damage must be repaired before the bridge is opened to traffic.