Hamilton Kent Blog

Building Bridges to Handle the Heat: On the Road with Randy Reimer

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Welcome to On the Road with Randy Reimer, a Q&A series featuring Hamilton Kent’s Director of Sales. Each month we’ll chat with Randy about current infrastructure news and how it affects our customers in the industry.

When Chicago’s DuSable Bridge overheated in early July, it had to be closed down and sprayed with cold water before it could be reopened for boats and two levels of road traffic. The double-decker steel bridge was apparently exposed to surface temperatures above 100°F that week, causing the bridge’s expansion joints to swell until they could no longer move.

At 98 years old, the bridge was evidently built for a different climate than the one Chicago experienced this summer. Issues like these are becoming increasingly common as bridges and other areas of infrastructure start to fail under more intense weather conditions brought on by climate change.

That’s what’s on Randy Reimer’s mind this month. We caught up with him to ask about bridges, expansion joints and steps builders can take to prepare bridges for extreme temperatures.

Hamilton Kent: What kinds of structural problems can you expect when bridges expand in hot weather?

Randy Reimer: Most of the severe problems around bridge expansion occur in bridges that require movement. Lift bridges are one example of that. If high temperatures cause the metal to expand more than what was anticipated during the design phase, it can expand to the point where interference keeps the bridge from functioning properly — like what happened in Chicago on the DuSable Bridge.

Even for stationary bridges or decks, if expansion occurs beyond the original allowances, the structures can experience tremendous forces over time and this can lead to premature failure.

HK: How do expansion joints alleviate the structural strain of thermal expansion?

RR: Expansion joints are built into the design of a bridge to allow for movement, contraction in colder periods, and expansion in warmer periods. The intention is to let the bridge decking expand or contract as needed without sacrificing structural integrity.

At their most complex, expansion joints consist of a number of different components: beams, sliding bearings, sliding springs, support boxes, anchors, and joint seals or membranes. All of these components are fitted into a structural box that tie the two decks together.

One feature of an expansion joint is the membrane or joint seal, which ensures nothing can fall through the gap between decks.

As an example, on a double-decker bridge, the seals or membranes keep debris from falling through the upper gap and injuring pedestrians or cyclists on the lower level. The seals also serve to keep debris from entering the expansion joint itself, which ultimately could lead to a failure of the moving or sliding components in the joint. If the expansion device seizes in place, a failure could be catastrophic.

That’s why the membrane or seal needs to perform well, last long and, of course, allow for movement.

expansion joint

HK: Should your expansion joints have certain attributes to properly absorb the impact of thermal expansion?

RR: Yes, but all of these attributes would be considered by the design engineer. The engineer considers climate, load, span and volume of traffic, along with local weather conditions, during the design phase.

Climate change is causing us to rethink all of our tolerances. Extreme temperature swings and weather events, including high and low temperatures, seem to be more frequent than in years past. As a result, the criteria for expansion joints need to be adjusted as well. More importantly, the criteria need to be considered during the initial design phase.

HK: Is there anything you need to watch out for when installing bridge expansion joints?

RR: Installation is almost always carried out by trained and certified bridge contractors. When it comes to the resilient part of the design — the membranes or joint seals — it’s important that the manufacturer use rubber materials that meet the specification. They must be able to withstand the oils or hydrocarbons, UV, and ozone in the environment. As is often the case, the most vulnerable of all parts is the rubber seal — it needs to fit perfectly and survive everything the elements throw at it.

HK: What kind of maintenance is needed?

RR: Preventative maintenance must be carried out as per the engineer or manufacturer’s requirements. If PMs are not done, eventually the expansion joint can fail, which can lead to many types of problems.

Also, the prospect of replacing an expansion joint is not easy or simple. Often the expansion joint is cast into a concrete bridge deck but in cases where it is not, it is still a complex connection. A premature failure can often lead to more extensive repair work.

HK: What are the roadblocks involved in bridge repairs? Why do governments let it fall by the wayside?

RR: This is a good question. Why is preventative maintenance sacrificed in any application? Often it comes down to dollars and a lack of public awareness.

Out of sight and out of mind, the general public has an expectation that bridges, like other large infrastructure, are built to last. When budgets are cut, it’s easy to say, “Let’s roll back the PM schedule.”

Invariably, reduced maintenance shortens life expectancy. It really boils down to a “Pay me now or pay me more later” scenario.

HK: What are the stakes if owners take too long or fail to address problems with their bridges?

RR: Obviously, the stakes are very high. Not only from the standpoint of safety, but also in terms of costs associated with delays due to repair work. Most municipalities use industry-adopted formulae to determine the type of maintenance program chosen related to the cost of the impact. These decisions are typically made based on a life cycle cost benefit (LCCB) analysis of bridges.

HK: Do you think changing weather patterns are having a different effect on bridge infrastructure today compared to many decades ago?

RR: There is no question that climate change is hastening the demise of many road bridges globally. According to the U.S. EPA website, “With the average US bridge now over 40 years old, more than 250 million vehicles cross deficient bridges every day.”

Of course, there are other major concerns for bridges when it comes to climate change — such as scouring from high water levels brought about by heavy rains — but expansion joints are still a big part of the issue, as mentioned earlier with the DuSable Bridge. Severe climate conditions age all infrastructure in a more aggressive way than what designers allowed for in their original plans.

HK: How can municipalities or bridge owners be proactive in the face of potential weather issues? How can they curb the need for emergency repairs?

RR: The most important things owners can do are to have all of their bridge evaluations up to date, keep up with their preventative maintenance schedule, and be prepared to shut down traffic over bridges that become so deficient they are dangerous to utilize.