The average New York Times reader might have found the September 4th article “Climate change can cause bridges to ‘fall apart like tinkertoys’, experts say” deeply disturbing--after all, the assertions within it are genuinely alarming.
The good news for readers and the traveling public is that that article is largely inaccurate and grossly oversimplifies and overstates the impact that climate can have on steel bridges.
To say that “extreme temperatures resulting from climate change could cause one in four steel bridges in the United States to collapse by 2050” is not only flat-out wrong but also irresponsible.
Bridges will not be falling down en masse anytime soon simply because the bridges Americans drive on today are already designed for extreme temperatures. In fact, some engineers will check a bridge’s performance up to an ambient temperature of 140 degrees Fahrenheit.
Explaining why and how requires a bit of technical detail. Bridge materials, steel or otherwise, expand when they heat up. They contract when the weather cools down. They do this thanks to design elements called “expansion joints,” which must remain free to move, unclogged by dirt and debris, to work effectively. In fact, a 100-ft-long simple bridge span will expand by roughly 1/16” for every 10-degree increase in temperature--well within the bounds of current expansion joint designs and applications.
Despite this author’s attempts to undermine public trust, it is important to remember that a bridge owner’s number one priority is public safety. Regularly cleaning expansion joints that may become clogged with debris is typically part of normal maintenance.
A clogged expansion joint is just one of the worst-case-scenario assumptions required for the article’s questionable math. The National Bridge Inventory is a natural place to start an analysis, but the database doesn’t include crucial design, inspection, and maintenance information about each bridge. The author would have to track down that information individually for all 80,000 steel bridges considered in the research for it to be accurate--a Herculean undertaking.
There is one real climate-change-related danger, which is already being addressed by the bridge design and construction industries: water. Flooding and “scour” (erosion around a bridge’s foundation caused by fast-moving water) are generally the top causes of bridge failure. Bridge owners and designers consider flooding and scour every single day. Over the last two decades, the design community has developed improved hydraulic modeling and water-flow considerations that allow for more detailed scour investigation.
In summary: No, one in four bridges will not collapse in the next 26 years. To say so is both incorrect and alarmist. The proof is right in front of us--or rather, it’s beneath our feet. Thousands of steel bridges across the country are still in service after more than a century, and Americans cross them safely every day, rain or shine.