Chase Corporation Bridge & Highway

When designing and building a bridge, it's essential to consider how temperature changes will affect the joint movement—which is the opening or closing displacement of the joint. The difference between the region's maximum and minimum air temperatures, ∆T, is multiplied by the coefficient of thermal expansion, α, and the deck length to calculate how much the bridge deck will expand and contract.       

∆ = α L ∆T

The concrete and steel girder bridges demonstrate similar expansion and contraction movements. However, steel bridges tend to move faster with temperature changes. According to AASHTO standards, the recommended coefficient of thermal expansion for steel girder bridges is 6.5x10⁻6 per °F, while for concrete bridges, it is 6.0x10⁻6 per °F.

The type of joint system and material used depends on the maximum joint movement. During its service life, a bridge accommodates temperature changes through bearings, expansion joints, or deformation of piers and abutments. However, the wear and tear of the expansion joint material may require repair or replacement. The AASHTO Bridge Element Inspection Manual recognizes expansion joints as a crucial component of regular bridge inspections.         

Related Article: Answering the Most Common Expansion Joint Questions

Replacing or Repairing Bridge Deck Expansion Joints                

This section will discuss replacing or repairing expansion joints that can move within a 2-to-3-inch range. Two types of expansion joints are widely used: compression and bonded seal joints. Bridge construction drawings usually contain a table that lists the joint openings at different temperatures. This table provides guidance for the installation of bearings and expansion joints. When replacing a joint in cold weather conditions, the structure will be contracted, and the joint gap should be wider. A reasonable construction practice is measuring and comparing the joint opening with the design drawings before installing a new seal. If the design data is different from the actual measurements, all joints on the bridge should be measured, and the new seal material should be ordered based on the actual data.  

To determine the true thermal moving range at a location, the opening of the same joint should be measured at two completely different temperatures. Then, the joint opening can be calculated by interpolation corresponding to this region's maximum and minimum weather temperatures. Use this estimated range as a basis for determining the appropriate size of the material to be installed in the expansion joint. It should be noted that some expansion joints on the bridge structure do not move and are called "fixed joints." The opening of a fixed joint remains the same throughout the year.        

4 Tips for Repairing and Replacing Expansion Joints

If you want to repair or replace an expansion joint seal during cool weather, make sure to follow these steps for a successful outcome: 

1. Take multiple measurements of the gap width of the expansion joint using a reliable and accurate measuring tool, such as a digital caliper.
2. Record your measurements and any other relevant data, such as the temperature and weather conditions, to help ensure consistency and accuracy over time.
3. Calculate the average of your measurements by adding them together and dividing the result by the number of measurements taken.
4. Make sure to follow the manufacturer's guidelines for installation of the material, considering any specific requirements for cool weather conditions.

Follow these steps to accurately measure the bridge expansion joint opening during cool weather. This ensures proper fitting of the installed material, providing necessary performance and durability. 

If you have any questions or require information or assistance on your next expansion joint project, please visit the Chase website at  www.chasecorp.com.