R_Lefebvre
Expedition Leader
Just thought I'd open a thread to discus how the experts assess primitive backcountry bridges. Last weekend I was doing some exploring around Quebec, and my trip brought me upon several old bridges in various states of disrepair. The first one I came across was fairly decent looking, but had a fair drop underneath it and no weight markings. I'm wary whenever I come upon a bridge that appears to have been constructed by an ATV or snowmobile club, but this one looked solid enough. I was a little concerned because there was a sign far back on this road saying bridge closed ahead.
But I checked it out, steel girder construction, decking seemed decent. Crossed it no big deal.
Next, I came upon the bridge that was actually closed.
Looks great right? Well, it appears this bridge was recently replaced, and it must not have been the bridge guys responsibility to remove the signs, so they were waiting for the sign guy. I dunno, but the wood was already weathered, and the metal rusting. Anyway... Here's where it's interesting. It appeared like this bridge had been rebuilt once already. The original bridge had been redecked once, but now the pilings had started to collapse, and so they built a brand new bridge using much longer steel girders which spanned further than the old pilings.
But, let's say you came upon this bridge and it hadn't been rebuilt. Would you cross this? How would you determine if a bridge in such condition were suitable for crossing? What precautions to take?
Continuing on, the bridges got worse and worse. I came upon this one which was not "closed" but in worse condition than the others, AND it had a 2t weight limit, while my truck weighs 3t.
I checked under the bridge, it appeared to be constructed of two large logs, maybe 20" in diameter. Worst case if it failed, I figured the truck would flop over sideways into a shallow river. I instructed my passengers to unbuckle and be ready to get out. In hind sight, probably should have just had them exit? Anyway, made it across no problem. Of course, this begs the question about how to judge the weight ratings on bridges. How conservative are they? How would you then guess at the real rating now that it's weathered?
Finally, I came upon this mess.
It looked even worse in person. Most of the wood was just piled into holes. I was concerned about some large nails sticking out of the main logs. I restacked some of the wood, and since the consequences should it collapse seemed relatively minor, I went for it. Again, no problem. But, would you cross this if it were over a deeper river, or longer span?
But I checked it out, steel girder construction, decking seemed decent. Crossed it no big deal.
Next, I came upon the bridge that was actually closed.
Looks great right? Well, it appears this bridge was recently replaced, and it must not have been the bridge guys responsibility to remove the signs, so they were waiting for the sign guy. I dunno, but the wood was already weathered, and the metal rusting. Anyway... Here's where it's interesting. It appeared like this bridge had been rebuilt once already. The original bridge had been redecked once, but now the pilings had started to collapse, and so they built a brand new bridge using much longer steel girders which spanned further than the old pilings.
But, let's say you came upon this bridge and it hadn't been rebuilt. Would you cross this? How would you determine if a bridge in such condition were suitable for crossing? What precautions to take?
Continuing on, the bridges got worse and worse. I came upon this one which was not "closed" but in worse condition than the others, AND it had a 2t weight limit, while my truck weighs 3t.
I checked under the bridge, it appeared to be constructed of two large logs, maybe 20" in diameter. Worst case if it failed, I figured the truck would flop over sideways into a shallow river. I instructed my passengers to unbuckle and be ready to get out. In hind sight, probably should have just had them exit? Anyway, made it across no problem. Of course, this begs the question about how to judge the weight ratings on bridges. How conservative are they? How would you then guess at the real rating now that it's weathered?
Finally, I came upon this mess.
It looked even worse in person. Most of the wood was just piled into holes. I was concerned about some large nails sticking out of the main logs. I restacked some of the wood, and since the consequences should it collapse seemed relatively minor, I went for it. Again, no problem. But, would you cross this if it were over a deeper river, or longer span?
. Anyhow, my buddy who is our combat engineer planning officer (and Land Rover DI owner) would know this but he's in Kuwait, so I'll ask him when he gets back. Good news is most military manuals are available to the public, and this would be covered in a combat engineer skills manual. I'll report back at least a Field Manual reference on the subject soon. Good manual to have for expeditions, and great subject to bring up by the way.
