Expansion joints allow the bridge to expand and contract with temperature changes and to allow for rotation of the beam ends as the beams deflect under traffic loading. It is imperative that these joints be maintained with the proper opening to allow the bridge to function as it was designed. The most common type of expansion joint used when the Interstate was built is the steel sliding plate. These were designed to allow for at least 2" of movement, and 3" or more on the longer bridges. It is important that these openings be cleaned out periodically (at least once per year) so that incompressible material (such as gravel and asphalt)does not collect in the openings. If the road gets resurfaced, it is important that the paving does not extend across the joints without first vertically extending the joint with a small steel bar welded to each side of the joint and filling the opening between the bars with a rubberized asphaltic material (ASTM D3405).
Other types of expansion joints commonly used in Ohio include steel finger joints for movements greater than 4"; neoprene compression seals placed between vertical steel bars; and most commonly used now, strip seals. Strip seals are comprised of a neoprene gland anchored into special steel "jaw-like" bars. Other types of expansion joints occasionally used include a poured-in-place silicone and polymer modified asphalt "plug joints". The last several joints mentioned not only allow the bridge to expand and contract with temperature changes, but also seal the joint so as not to allow salt laden moisture to drip down onto the beams and substructure below.
Preventive Maintenance Recommendations:
- Remove dirt, stone, asphalt and other incompressibles from expansion joint openings at least once per year.
Closed or non-functioning sliding plate expansion joints, as shown above, can allow for transfer of pavement pressure to backwalls.
Typical sliding plate expansion joint
Asphalt plug joint
Strip seal detail
Asphalt plug joint
Cross-section of compression seal.
Example of strip-seal expansion joint.
Typical finger joint