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A Revolution in Bridge Repair

Today’s infrastructure is in disrepair, particularly our bridges. The issue, discussed in my previous post entitled The Age of Disrepair, has become a hot topic for discussion. As a result, research is being conducted across North America to develop new systems to find economical and environmentally friendly solutions.

Hannah Loring is a Civil Engineering graduate student at the University of Maine. Her research, under Professor Bill Davids, is focused on repairing the countries ageing bridge infrastructure. One of the major concerns with older bridges is weight capacity, as they were originally designed to withstand smaller, less frequent truck loads.

A proposed solution is posting weight limits on the bridges.  This will however cause traffic congestion. Alternatively, researchers at the University of Maine are developing a new product called a ‘polymer reinforced flexural retrofit system’.  This system uses strips of carbon and glass composites which are installed to the undersides of bridge decks using adhesive and concrete screws. The system increases the flexural capacity and lifespan of the bridge (Bangor News Report).

This product has the potential to revolutionize the way bridges are retrofitted. Professor Bill Davids suggests, “We’re giving a low-cost alternative for the short term that would increase the strength and durability of the bridge, prevent it from having weight [limits] posted, and allow the bridge to remain safe”. A typical deck replacement for a flat-slab bridge costs over $120,000. Using the composite strips, this can be reduced down to about $70,000. In addition, concrete beams reinforced with the polymer strips exhibit an increase in load carrying capacity from 15,000 lbs to 21,000 lbs (Bangor News Report). This research was presented at a recent press conference.

Press Conference Video

“Band-Aids” Aren’t Always The Right Solution

In some cases a full replacement of the bridge is required. Acrow Bridge, a company based out of the United States, specializes in prefabricated modular steel bridge solutions for permanent, temporary and emergency use. Acrow’s website claims that, “Through the simple addition of prefabricated modular steel bridge components, Acrow bridges are easily customized to the desired length, width and strength, allowing for diverse applications and uses”.

Acrow’s Temporary Bridge Being Used Adjacent to the Construction of a New Bridge. Photo Credit: Acrow Bridge

Acrow prefabricates the temporary bridge off-site, allowing for a quick assembly and minimal traffic disturbance. In addition, each section of these bridges can be re-used for different projects. Not only is this environmentally friendly, but it drastically reduces the overall cost. The product has been a huge success thus far. Bill Killeen, CEO of Acrow, said, “Consequently, more and more customers are expanding their inventory of modular steel bridges to deal with both emergency and scheduled repair work”.

There is no perfect solution for deteriorating bridges. However, with each passing day the process for repairing our bridges is being refined. If cities continue to take an active role in repairing bridge infrastructure using these technologies, bridge collapses may become a thing of the past.

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The Age of Disrepair: What Do We Do With All These Bridges?

The issue of ageing infrastructure has become a serious concern in countries throughout the world. Bridges built in the past century have begun to crumble causing serious  injuries, and in some cases death. In 2007, a bridge in Minnesota collapsed, killing 13 and injuring 145 people (I-35W Bridge Collapse) .Below is a video of the bridges collapse:

As a result, an investigation was conducted by the Federal Government of the United States to determine the cause of the collapse. In addition, the National Transit Safety Board was created to help improve the state of infrastructure and prevent future collapses. However, it seems that this issue has not been eradicated. During a speech in Galesburg, Illinois, President Obama stated, “We’ve got more than 100,000 bridges that are old enough to qualify for Medicare” (The Hill Report). According to a report released by Transportation for America, “11% of all bridges in the US are structurally deficient”. Considering that Americans make 260 million trips across bridges each day, this is a major issue (T4 America Report).

North of the border, Canadians are facing similar problems. A report released by Statistics Canada in 2007 stated that, “The average age of bridges went from 21.3 years in 1985 to 24.5 years in 2007, an increase of 3.2 years” (StatsCan Report). The province of Ontario has the third oldest bridge infrastructure in Canada (after Quebec and Nova Scotia) and its ailing bridge infrastructure has received a high degree of media attention. In Toronto, the capital of Ontario, the Gardiner Expressway has been identified as in need of serious repairs. The Gardiner is a major artery in Toronto’s downtown core, and a number of plans have been proposed to help rehabilitate it’s ageing bridges. However, the cost is quite steep. A current estimate puts the cost of repairing the bridge at $505 million (Globe and Mail Report).

Delamination on Gardiner Bridge Piers. Photo Credit: CBC News

It is well known that repairing older bridges drastically reduce maintenance costs. As a result, many engineers are starting to develop creative solutions to help restore these bridges. Innovation, unfortunately, comes with a price tag. As cities face more funding cuts, engineers are forced to use cheaper, less effective techniques to restore bridges. Professor Paul Gauvreau of the University of Toronto states, “When engineers are repeatedly requested to implement yesterday’s solutions – that is, not to innovate – engineering becomes a mere commodity that can be bought and sold at the lowest price” (Globe and Mail Report). As is often the case, these low-cost repairs are not very effective, and can lead to higher repair bills in the future.

A number of solutions have been proposed in the last few years that could potentially save cities millions of dollars on their repair bills. Some of these solutions include increasing the frequency of inspections, providing better drainage to current bridge decks, using domes to protect the bridge from rain and snow, and installing steel mesh beneath the bridges to catch any falling concrete (National Post Report).

Inspection of the Underside of a Bridge Deck in Missouri. Photo Credit: Missouri Department of Transportation

These solutions, however, are not always practical. More research needs to be done to find cost-effective repair techniques. Researchers all across the world are investing time and funding to help develop better, more efficient procedures for rehabilitating old bridges. As this research progresses, it will be interesting to see which solutions are adopted by the industry. In the meantime, cities will continue to pursue a ‘band-aid’ response to bridge deficiencies, leading to a higher potential for future accidents.