How can we improve the structure of bridges to make sure it wont collapse?

Question

How can make sure bridges will not collapse like the I-35 bridge over the Mississippi River?

Answer 1

Such structure designs are already in use in newer bridges. The I-35 bridge was built 40 years ago. Before such improvements existed. Todays bridges are constructed so that in case a particular section of the bridge happens to fail, the adjoining sections remain intact. In the case of the I-35 bridge, a major weakness in one of the sections would cause a domino effect and the entire bridge collapses.

Answer 2

How to improve the performance of structures is a full life cycle question.

In the 40 years since the structure that collapsed was designed and constructed, there have been many improvements in the design and details used on structures. If at all possible, designers will avoid structures that are Fracture Critical. These structures have members that are called fracture critical meaning that if they fail there are no other members to carry that load path. In other words, there is a lack of redunant load paths in the structure. With the lost of a fracture critical member, the structure will have catstrophic failure which we saw in this case. Over the last twenty to thirty years, there has been extensive research in the area of metal fatigue, particularlly , in bridge metal fatigue. Dr. John Fisher at Purdue University is the best expert in this field. We now know that certain details on structures perform better than others that have been used on older structures.

To keep our structures safe, In 1979, the FHWA instituted the Federal Bridge Re-Inspection Program. Every structure in this country that carries public traffic,or crosses public traffic, that is over 20 feet in length is inspected every 2 years for condition and structural integrity.

So the question is: With safeguards in place, why did this structure fail? The simple answer is: money. Most Departments of Transportation (DOT) lack the necessary funds to address infrastructure issues adequately. Often maintenance or replacement is deferred and the result can be that structures can be extended beyond their practical service life. They tried to strech the life of this structure too far. Unfortunately, it often takes and event such as this one to get our government focused on transportation.

The answer is: (1) fund the departments transportation to repair or replace structures on a more realistic schedule, (2) design structures to latest design standards, and (3) fund the routine or rehablitation repairs recommended by the engineers responsible for maintenance.

Answer 3

Good Question. I'm sure that "Terrorism" was looked at already. The investigation will show two things. Design flaw, no redundant supports in case of a problem, and Lack of maintenance. The Bridge was being re-habed at the time it collapsed, and that may have been part of the problem. The bridge was built in 67, the traffic flow then and today, and the weight of the traffic flow might be vastly different. It was the right design and bridge in 67, but not in 07.

Answer 4

If it is a new one it can be designed to the more modern standards that guarantee that the failure of one support will not bring the whole thing down. The one that just collapsed predated those better standards.

The biggest problem we face with bridges is that no one has spent to maintain them for decades. If someone said to a politician you need to raise taxes to keep that bridge from getting weaker and weaker the typical answer would be "I can't get re-elected if I raise taxes."

Most states are facing hundreds of millions in deferred maintenance. Bridge collapses will get to be common unless that money is spent.

Answer 5

We can't - because all materials will eventually fail due to weathering and stress. They KNEW that bridge was dangerous, but politicians didn't want to spend money on it. It's another example of the sort of thing that happened with Hurricane Katrina - they knew those flood control dikes were unstable and unsafe, but did nothing. And now, all these months later, they've STILL done nothing - so I'd suggest taking George Bush's promise regarding rebuilding with a couple grains of salt...

Answer 6

If we spent all the money we spend on Iraq in one year on all our bridges, then we would not have this problem.