Structural Exam Problem
Structural Exam Problem
(OP)
Not really, but interesting none the less.
We all have extended metal tape measures to see how far we could make the cantilever before it failed.
Considering the degree of concave arcing of the tape, the materials, and the angle of inclination to the horizontal to the tape, what is the equation to determine how far the tape can be pulled from the holder before snap-thru occurs, causing a hinge to form and the tape to drop?
We all have extended metal tape measures to see how far we could make the cantilever before it failed.
Considering the degree of concave arcing of the tape, the materials, and the angle of inclination to the horizontal to the tape, what is the equation to determine how far the tape can be pulled from the holder before snap-thru occurs, causing a hinge to form and the tape to drop?
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask






RE: Structural Exam Problem
I do not think it is an easy question. The tape fails by buckling, does it not?
RE: Structural Exam Problem
RE: Structural Exam Problem
Regardless, my little experiment with different angles on a 12' stanley leverlock tape , 44" is the longest that it would go before it snap-buckled.
Starting off at a angle of 0 or 90 gave better results than any other angle. It seems like sway and the clip at the ends had some effect as well. Steady hands would be needed:)
RE: Structural Exam Problem
As for loads, you'd have to eliminate air movement, vibration, etc.
You might be able to approximate it empirically, but the theory and math would get dirty, really fast.
RE: Structural Exam Problem
Last year I spent some time looking at pedestrian bridges that were bottom chord suspended from arch / vierendeel trusses on either side of the deck. The trusses were splayed outwards 15 degrees or so. The question of interest was LTB of the trusses and whether or not they would prefer to buckle inwards or outwards.
For shits & giggles, we made some models using bent up cardboard (U shaped). We'd cantilever them off the end of a desk, load the ends, and observe the buckling patterns. They always buckled such that the side walls would tend towards the horizontal. Ditto for the walls sloping inwards.
All this, it seems to me, bears some similarity to your tape measure problem. As for the equation... beats me. Time to call on Teddy G.
RE: Structural Exam Problem
Build on this example, but with a uniform dead load and a cantilever instead of the point load and two-hinged arch.
http://www
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_docanchor=&view=c&_searchStrId=1235364331&_rerunOrigin=google&
_acct=C000050221&_version=1&_urlVersion=0&_userid=10&
md5=fbad658f9eb8c50204475f4baf75cc04
WOW! I didn't think the link was that long... Oh well...
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Structural Exam Problem
Suppose you have a thin dome. Cut one pie-shaped section out of that dome. Can you support it at the center and the outside without it collapsing?
RE: Structural Exam Problem
RE: Structural Exam Problem
RE: Structural Exam Problem
There must be a bigger FatMax now than the one I have becasue it is a bona fide fact that one cannot be extended more than 11' when horizontal.
I am the all-time King of tape extending.I will challenge any one on earth to a tape-off.
I was the unrivaled king of tape extension for nearly ten years in my state during my construction years.
I once extended a regular 1" Stanley Powerlock tape the full 25 feet (albeit nearly vertically) in order to measure a wall in the 2 story open foyer. People still ask me about it when I go out for coffee at the local Dunkin Donuts and that was nearly 10 years ago now.