Modular Expansion Joint for Bridges with Integral Piers

Bridges with integral pier connections (frame bridges) have a different movement behavior than bridges with bearing-supported piers. The pier flexibility affects the distribution of thermal movement between the expansion joints and the piers, requiring careful analysis. Integral pier connections make the deck-pier joint monolithic, so the thermal movement of the deck is shared between the expansion joints and the pier bending. The stiffer the piers, the more movement is resisted by the piers and the less movement occurs at the expansion joints. The softer the piers, the more movement occurs at the expansion joints. Pier stiffness calculation requires knowledge of the pier cross-section, the pier height, and the material properties. Tall, slender piers are more flexible than short, stocky piers. The pier stiffness is used in the structural analysis to determine the distribution of thermal movement between the piers and the expansion joints. Movement range calculation for frame bridges requires a structural analysis that considers the pier flexibility. The analysis distributes the total thermal movement of the bridge between the expansion joints and the pier bending, based on the relative stiffness of each element. The expansion joint must be designed for the movement that it must accommodate, not the total thermal movement of the bridge. Pier design for frame bridges must consider the bending moments caused by the thermal movement. The piers must be designed to resist these bending moments without cracking or yielding. The pier reinforcement must be adequate for the combined effect of vertical load, thermal bending, and any other loads. Monitoring of frame bridge expansion joints is recommended to verify that the movement distribution matches the design prediction. Displacement sensors at the joint and strain gauges on the piers can measure the actual movement distribution. Any significant deviation from the design prediction should be investigated.