The Breakroom > The Water Cooler
Building a Bridge
vtsteam:
Bill the trucker decided he trusted the bridge, and again we had a first slow crossing with my eyes glued to the Bridge-O-Meter. He said his truck weighed about 77,000 lbs with a full load of gravel, as he had here.
About 2/3 of his truck weight is on the back axles, and here they are mid-span.
vtsteam:
Again, the Bridge-O-Meter showed only a deflection of tiny 1/8". And because the tires did a smoother job of crossing than the steel tracks of the excavator, there was no bounce at all.
Dumping made no difference in deflection either..
vtsteam:
Dave and I were super happy with the bridge's performance at this point. :ddb: :ddb:
A calculated point load at center of 88,000 lbs would theoretically give a 1/2" deflection for those beams alone, and represent 66% of yield strength. We didn't even come close to that deflection with a real life 77,000 lb load, and proved that for any use I'm likely to need, the bridge will handle it.
The only conventional vehicle likely to exceed what we've already tried would be a fully loaded concrete mixer with three back axles. I think they're around 80,000 lbs Of course that would be a more spread out three axle load as well, and not a point load. So fairly likely to be another small fraction of max permissible deflection.
I have no plans to ever pour concrete again however! Two weeks of that was enough! :doh:
vtsteam:
The end of a long, but exciting day:
PeterE:
Wow, that is one hefty bridge! Well done :clap: :clap: :clap:
One question though; Will you also build retaining walls to protect the backfill for the abutments? I can imagine a good spring flow wanting to eat into the backfill if it gets the chance. Perhaps a good use for the discarded blocks?
/Peter
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