CHARLESTON, WV – West Virginia Division of Highways bridge maintenance workers are cutting, hammering and clearing debris on a bridge in northern Kanawha County as cars and tractor-trailers whiz by at 55 mph. They’re in the process of replacing expansion joints on the McQuain Brothers Bridge.
Expansion joints are an important part of bridge construction, and maintaining them is a key part of keeping our bridges safe, said WVDOH State Bridge Engineer Tracy Brown, P.E. That’s because bridges don’t just sit there – they breathe.
“A bridge is going to move,” said Brown. “You can’t stop it. It’s going to move the way it wants to move, and all you can do is accommodate that movement.”
A steel and concrete bridge expands as it warms up and contracts as it cools, a factor bridge designers must take into account. Brown said a 100-foot bridge will be about a quarter of an inch longer at 120 degrees Fahrenheit than it is at 68 degrees, and it will be about three quarters of an inch shorter if it’s 30 below zero.
An expansion joint at each end of the bridge allows the span to stretch and shrink without damaging the bridge or the roadway.
There are different kinds of expansion joints, but all are designed to expand and contract with the bridge while keeping debris and water from getting to the bridge superstructure underneath.
A properly installed expansion joint should last for 15 or 20 years, but sometimes they get damaged or wear out sooner. Brown said there are WVDOH bridge crews who routinely travel the state looking for bad expansion joints.
To replace the expansion joint on the McQuain Brothers Bridge, repair crews first cut out the old expansion joint and removed it. Then they cleaned out all the debris from the hole. A foam spacer the width of the joint will then be placed in the hole and concrete will be poured on either side of the spacer. The work is being done on one lane of the bridge at a time to allow traffic to continue using the bridge.
Once the concrete sets up, the foam spacer will be removed, and a new expansion joint made of compressible material will be installed.