Diane Purdy is a senior project manager in Urban’s State College, Pennsylvania, office with more than 25 years of experience managing and designing transportation projects, bridges, transit facilities, and building structures. We spoke to the Harrisburg native to get her take on the state of our country’s infrastructure and the role engineering plays in it moving forward.
A: As a transportation advocate, it concerns me. We have an aging bridge inventory across the country and that’s why we’re seeing over 54,000 bridges rated as “structurally deficient.” As an engineer, our first concern is to ensure public safety. We travel on highways and bridges; trains and planes; and ports and waterways, on a daily basis. People need to be able to get from Point A to Point B in a safe, reliable manner. We shouldn’t have to worry about bridge collapses or rail crashes as we use these modes of transportation. It’s important we reinvest in the infrastructure to ensure future economic development and avoid catastrophic failures.
A: Poorly maintained roads, bridges, railways, and waterways cost the U.S. billions of dollars in lost revenue. Our economy depends on a reliable infrastructure to efficiently move goods, provide services, connect people to their jobs, and create opportunities for our local communities. Infrastructure also creates demand for materials such as concrete and steel. An unreliable infrastructure will not stimulate growth and imposes hardships on our economy.
A: Simply put, the U.S. has not spent enough to maintain the infrastructure over the past few decades. Some comparisons show we spend about 2.5 percent of the economy – or GDP – as compared to about 3.9 percent spent in Canada, Australia, and South Korea, 5 percent for Europe, and 10 percent in China.
Our primary means to fund transportation projects is the Highway Trust Fund, which generates funds primarily through a gas tax. We spend these funds on our roads and bridges. However, we haven’t raised the federal gas tax since 1993 and the fund is in jeopardy.
One of the challenges is that no one wants to raise the federal gas tax. Two options to pay for this investment are user fees or taxes. The longer we wait, the more it will cost. We’re in a reactive mode trying to fix crumbling bridges or perform road repairs before they fail or collapse. We fix one, and four more come on the inventory that need attention.
A: We have over 600,000 bridges in the U.S., almost four in 10 are over 50 years old, according to ASCE Infrastructure Report Card mentioned earlier. As engineers, we face the challenge of designing safe, durable structures that will last up to 100 years and offer low-maintenance over their shelf life. Corrosion is a leading factor in the deterioration of bridges. For bridges made of structural steel, we apply protective coatings to the steel elements to prevent them from rusting. The coating acts as a barrier between the steel and the corrosive environment, such as salt spray. For reinforced concrete bridges, we use epoxy coated or stainless steel reinforcement to prevent the corrosion of reinforcement bars in concrete bridge decks.
Many older bridges have failed deck joints that leak water containing road salts. This contributes to the corrosion of the bridge. Proper maintenance can help to prevent the premature failure of these joints, but we’re also evaluating other ways to address the problem such as elimination of the joint with closure pours, or extending the deck at supports. From a design and maintenance perspective, we’re minimizing or eliminating joints, using corrosion resistance reinforcement bars and expanding applications of ultra-high performance concrete to increase the life expectancy of bridges.