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Simplified method to estimate damage of heavy vehicles on bridges

Simplified method to estimate damage of heavy vehicles on bridges

Simplified method to estimate damage of heavy vehicles on bridges

(OP)
I'm mostly involved in traffic and planning engineering. I'm doing some research on damage to bridges from freight moves to further my understanding on the topic.

What I'm looking to do is to estimate the damage on the different types of bridges (steel vs. concrete), (old vs. new), (long vs. short), etc.

This is not a very technical analysis as I'm looking at understanding the general idea of what is going on. I, however, would like to be able to quantify some of that damage or at least be able to compare it. or at least be able to quantify the damage from an overview planning perspective rather than from a bridge vs. bridge comparison.

I've done the same analysis to compare the damage on pavement by comparing the effective ESALs from one load to another.

The problem: Suppose you have to transport 40 Megatons of freight. Would you be better off transporting them with let's say 100 trucks @ 60 Tons per truck with configuration of single, tandem, quadrem axles where the steer has a max of 5,500, the tandem of 11,000, and the quad of 27,000 kg vs. 80 B-Train @ 80,000 per truck which has 9 axles in a single tandem tridem tridem configuration? These numbers don't add up but are just given to illustrate what I'm trying to do.

Bottom line question: You have to transfer x amount of material over a multiple kind of bridges, which truck configuration will cause you the lease amount of damage in terms of $ or bridge life.

To answer: What I have done so far, is developed a bridge matrix with the following parameters. They're also the ones, I have for my data set:
  • Span length : <2m, 2-5m, 5-15m, 15-40m, 50+m
  • bridge type: concrete, steel
  • road type: pavement, asphalt, gravel
  • number of lanes: #
  • year built: ####
  • design GVW, posted GVW
As I said before, I'm looking at doing a top-view analysis of what is going on and try to present at a preliminary state, or at a "CEO" state what is the damage potential between moving the same amount of freight over bridges.

Feel free to ask any questions, or suggest any methodologies. I would prefer to stick to any methods published in North America

Thanks,
D

RE: Simplified method to estimate damage of heavy vehicles on bridges

(OP)
Trying to bump my own question to see if it gets more traction hopefully

RE: Simplified method to estimate damage of heavy vehicles on bridges

??? Unclear what you think you're after, which is probably why no one is responding. So long as each truck is less than the rating of the weakest bridge, why do you care? The presumption would be if the rating of any bridge is not exceeded, there is no perceptible damage. Otherwise, we are grossly underpaying for tolls.

TTFN
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RE: Simplified method to estimate damage of heavy vehicles on bridges

For simple fatigue cases damage is proportional to the sum of N*W^5 for steel. The exponent is very much material dependent.

The UKs TRRL did some work on axle weight damage to roadways not bridges and came up with a similar model.

Sorry, no links.

Cheers

Greg Locock


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RE: Simplified method to estimate damage of heavy vehicles on bridges

Roughly, as the stress in a member goes down, the number of cycles before fatigue failure goes up, at an (approximately) exponential rate. Certain materials such as steel have an "infinite fatigue limit" - once you go below a certain stress, they will (theoretically) never fail due to fatigue.

That's a top-level view. For more, check out any AASHTO Bridge Design code, it will go into exhaustive detail about fatigue limit calculations.

Brian C Potter, PE
http://simplesupports.wordpress.com

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