Questions relating to or the engineering application of a device that must withstand a loading via deflection, stresses, resistance to buckling, or natural frequencies.
Questions tagged [structures]
282 questions
15
votes
1 answer
Why are hyperboloid towers not popular anymore?
Hyperboloid towers were very popular in the end of 19th and the first half of 20th centuries - water towers, powerline anchor towers, sometimes tall radio towers were built using this design. The claimed advantage is using less steel compared to…
sharptooth
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14
votes
8 answers
What are those large poles for that are always in front of US stand-alone store buildings?
Screenshot of a video where they are featured in the background:
They appear to have no electronics built in, such as an electric charge station, or a parking ticket dispenser or something like that.
They appear to just be large, solid metal poles…
Elijames Gosha
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14
votes
1 answer
Why does prestressing in trees make them stronger?
In "Structures: or Why Things Don't Fall Down" James Gordon talks about trees being prestressed with the outside in tension and the inside in compression. Why does it make a tree stronger to have it in tension on the surface and compression at the…
Voltron
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13
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1 answer
Additional jacking force to overcome stiction/dry friction
It is common to lift bridges to replace bearings, etc.
In an ideal world the lifting capacity required of the jacks would be the self-weight of the bridge divided by the number of jacks (+ allowances for wind/snow, etc.).
From my (limited)…
thomasmichaelwallace
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12
votes
7 answers
Why does a gear have extra holes?
In a gear you normally have a center hole for the shaft to be put into. Why do some gears have holes surrounding that center hole?
Is it for weight reasons? Does it add stability? Is it so you can add special parts?
Mat NX
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11
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3 answers
How different is using styrofoam rather than empty cans when pouring concrete?
In the recent 6.4 earthquake that hit Taiwan, it was seen in a newswire photograph of rubble that metal cans were embedded in the concrete.
The quote from an official regarding this practice:
For such purposes in construction, it was not illegal…
user348
11
votes
2 answers
Why are three way bridges rare?
It's true that most bridges are "two directional."
But three way bridges are pretty rare, globally. I can understand why there wouldn't be many for rivers, but if bridges are designed based on the lie of the surrounding ground, why wouldn't there be…
Tom Au
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11
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3 answers
What kind of protection should I give structural steel in a natatorium (swiming pool) environment?
What would be the best type of steel to specify? Would a heavy galvanization suffice?
Are there specialty paints/coatings available for this particular application? If so, how long do they last?
cKrug
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10
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1 answer
Where did I go wrong conceptually when attempting to calculate the maximum force on a truss at a given joint?
In the problem statement below, the question states to find the maximum load $\vec{P}$ that the truss can support. My method of approach was:
Draw a FBD for the entire structure.
Generally I would identify all external forces, however for this…
Hunter
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10
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5 answers
Why are some public benches made with arm rests that waste so much space?
While watching a YouTube video today, I noticed this public/park bench somewhere in the USA:
It looks strange to me the way the arm rests on each side are so far into the bench, wasting a rather large combined space if you count both sides.
Why…
B Burnie
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10
votes
3 answers
Is a permanent platform that is hanging and moving a dead load or a live load?
If a permanent room or platform is suspended from a larger structure (say, on a cable that is attached to a hook on a track in a ceiling) and designed to be in constant but not necessarily repetitive motion, does the load that the room/platform…
Matt
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9
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2 answers
What is the practical limit on the number of storeys in residential buildings built with monolithic reinforced concrete?
I have recently bought a flat in a 25-storey building. I wonder what is the practical limit for the number of storeys in a mass-produced residential buildings built from monolithic reinforced concrete?
Can we expect the number of storeys in typical…
Anixx
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8
votes
2 answers
Vertical wave action on bridge
Rio de Janeiro, Brazil is currently stunned by the fact that yesterday a span of a brand new (innaugurated in January) bicycle bridge along the coast collapsed when struck by a wave, killing some people that were on it at the time.
A few videos have…
Wasabi
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8
votes
1 answer
Why build a cell lattice tower with square cross-section instead of triangular cross-section?
First, a neat image from Wikipedia
Here the cell tower has three vertical (or maybe slightly inclined to the inside) thicker pipes which are located at angles of a triangle and those three thicker pipes are interconnected with numerous thinner…
sharptooth
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7
votes
5 answers
How can we prevent/detect hydrogen embrittlement?
There has recently been a series of high profile bolt failures on 'The Cheesegrater' in London, which have been attributed to hydrogen embrittlement.
What can engineers do to ensure that hydrogen embrittlement doesn't effect their structures?
thomasmichaelwallace
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