America’s infrastructure has recently been put in the spotlight. New plans and bills have been put in place to fund work on infrastructure. Experts assert that this increased focus and effort is vital to the health of our nation.
Our Crumbling Infrastructure
When discussing the state of the United States infrastructure, experts tend to use phrases like: “dangerously overstretched” and “lagging behind competitors”. Civil engineers warn that many bridges and drinking/wastewater systems are antiquated and risky to public health.
This puts us at a disadvantage when compared with our economic competitors like China, who have put more funding into developing their infrastructure. A failing infrastructure comes at a cost to the local economy – from catastrophic failures of bridges to a loss of economic productivity due to poorly maintained roads, trains, and waterways.
Changing Climate, Changing Priorities
A new study done at Colorado State University (CSU), suggests that this new spotlight is very timely.
The United States currently has over 600,000 bridges. Of these, around 80,000 are simply supported steel girder bridges. These types of bridges have expansion joints that help the bridge naturally expand and contract during hot and cold weather.
Typically, these expansion joints clog with debris. This restricts the bridge’s ability to freely expand and contract, which places extra stress on the joints. This is even more of an issue in hot weather with more expansion. While the short-term solution has been to regularly clean these joints, the researchers at CSU felt it was important to look at the impact climate change could have on our bridges.
If future changes cause the temperature to rise higher than temperatures that the bridge was designed to handle, then the bridge, the expansion joints in particular, could deteriorate quicker.
The study looked at four different bridges built during different seasons and different temperatures. It studied the rate of deterioration based on projected temperatures for 2040, 2060, 2080, and 2100.
They found that the bridges in the Southeast and Northeast are the least susceptible to damage from increasing temperatures. Bridges in the North – the Northern Rockies and Plains, Norwest and Upper Midwest are the most likely to be damaged. With this information government officials can rank bridges in a way that accounts for possible future climate changes.
A New Approach: Maintenance Over Replacement
Researchers at the University of Georgia propose a way for states to save money and get more life out of bridges. Currently there is a fairly simple depreciation formula engineers use to determine a bridge’s health and when they should be replaced. Many think this formula gives a too conservative estimate. Since current bridge upkeep relies on replacement over maintenance, this results in bridges being replaced before they need replacing.
The researchers proposed a new approach that flips the old approach on its head. Called the “bridge coactive model”, it views and considers the way the 60 to 80 components that make up a bridge interact. It also assumes that regular maintenance will allow the bridges a much longer life than previously assumed.
Going back to the expansion joints we discussed previously, they are relatively inexpensive to replace. In the short term, replacing them doesn’t make a big difference to the performance of the bridge. De-icing salt or water can seep through the damaged expansion joint and damage more valuable parts of the bridge below the joint. By replacing the joints, we can prevent that damage.
By focusing on regularly maintaining and replacing damaged parts, the study found that we can extend the life of a bridge from 75 years to more than 100 years. The next phase of the study is to develop a tool to assess the bridge life cycle to be used by across the state of Georgia.