Bridge#2

[whitedogone]

LOL

1/8" is like L/2400.............that's nothing

 

[buggyman1]

OK Buggy,....better document the "fort" too,...should be interesting for a whole lot of us. But I'm looking forward to the kitchen project when you get to it. By the way,...you (and the bricklayer) do some pretty nice work !!

CHEERS!
. . tug

Thanks...I will document the fort, and the kitchen.

 

[buggyman1]

LOL

1/8" is like L/2400.............that's nothing

What does L/2400 mean?

 

[whitedogone]

What does L/2400 mean?

That your deflection expressed as a fraction of the span e.g. 1/400 or 1/600. Either the strength limit state (allowable stress) or the serviceability limit state (deflection considerations amongst others) may govern the minimum dimensions of the member required. The deflection must be considered for the purpose of the structure. I'd bet that the static (dead load) deflection excedes the (live load) deflection.

 

[whitedogone]

If you want to check Total deflection, pull a dry line VERY tight along the bottom web with the bridge empty. You'll have to block it down 3/4" on the ends. Then measure the gap at midspan and subtract that from the 3/4" blocks. Paint that number down under the bridge somewhere along with the date. That will give you a base line for checking for future inspections. Add your 1/8" and that will give you total deflection.

 

[JohnDeere4300]

The bridge looks great.. and you did an excellent job!

 

[Transit]

1/8"!!! Transit would mark that as a failure!



(just kidding Transit)

The 1/8 inch deflection is not what I was concerned about. Remember the Oakland Bridge in California that was closed this weekend? Did you see the Dog Bone Link that cracked at the Eye? That crack was the result of stress-concentration as opposed to average stress. That type of crack starts at the inside of the hole [a point of discontinuity] that the link-pin secures and works its way outward.[ first discussed in 1864 by Barre de Saint-Venant] Now that bridge and its components are many times stronger than it has to be [safety factor] and that link could have completely failed, other links in the catenaries would have safely taken up the extra load. Drill holes in the wrong place and you setup a very local overload that will fail some day. I could bore you for hours with the details of Mores Circle, Dynamic and repeated loading, etc.
Bottom line is, Buggyman ends up in the ditch crushed with the tractor on him.

PS, not kidding.

 

[wedge40]

wow, guess you should have had the Amish come in and built you a nice covered bridge.. Some of the those things are still holding up well after 100 plus years. The again I'm guessing that bridge will still be around for quite awhile with a little maintenance. I'm still impressed. You can build one for me any day.
Remember at some point you need to just shoot the engineers and get some real work done.

Wedge
PS BS/EE from MTU.

 

[whitedogone]

The 1/8 inch deflection is not what I was concerned about. Remember the Oakland Bridge in California that was closed this weekend? Did you see the Dog Bone Link that cracked at the Eye? That crack was the result of stress-concentration as opposed to average stress. That type of crack starts at the inside of the hole [a point of discontinuity] that the link-pin secures and works its way outward.[ first discussed in 1864 by Barre de Saint-Venant] Now that bridge and its components are many times stronger than it has to be [safety factor] and that link could have completely failed, other links in the catenaries would have safely taken up the extra load. Drill holes in the wrong place and you setup a very local overload that will fail some day. I could bore you for hours with the details of Mores Circle, Dynamic and repeated loading, etc.
Bottom line is, Buggyman ends up in the ditch crushed with the tractor on him.

PS, not kidding.

Geeee....... I wonder why that failed? Oh, wait ...I think I might have an Idea. The bridge opened in 1936 and has appox 270,000 cycles per day. That would be 719,415,000 cycles before stress failure.

 

[wedge40]

Geeee....... I wonder why that failed? Oh, wait ...I think I might have an Idea. The bridge opened in 1936 and has appox 270,000 cycles per day. That would be 719,415,000 cycles before stress failure.

Ya think buggyman can make that many trips over the bridge in the next 50 years? Guess he'd better quit his day job.

Very good point.. Nice way to put it into perspective.

Wedge