Questions tagged [structures]

Questions relating to or the engineering application of a device that must withstand a loading via deflection, stresses, resistance to buckling, or natural frequencies.

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15
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1answer
1k views

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 ...
14
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8answers
7k views

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....
13
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1answer
366 views

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 ...
13
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1answer
995 views

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 ...
12
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2answers
1k views

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 ...
11
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3answers
555 views

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 ...
11
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3answers
2k views

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?
10
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3answers
1k views

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 ...
10
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1answer
2k views

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 ...
8
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2answers
2k views

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?...
8
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1answer
2k views

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 ...
8
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2answers
187 views

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 ...
7
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3answers
699 views

What concerns would I need to consider for building a swimming pool of gold coins?

If I wanted to build a gold coins swimming pool [as in DuckTales], what engineering (not security) concerns would I need to address to make such a pool feasible? For example, since gold is much ...
7
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5answers
372 views

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 ...
7
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2answers
1k views

How is biaxial bending considered for reinforced masonry design?

I am faced with a problem where I have to design a reinforced masonry beam for biaxial bending. The governing code is ACI 530-11. I cannot find a provision in this Code for biaxial bending. The only ...
7
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1answer
2k views

How do you check a weld for applied moment?

I have a single angle connected to a double angle via a 3/16" weld I know there is a factored, applied moment at that connection. I would like to ask how I can go about checking the capacity of this ...
6
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5answers
9k views

Is hydrostatic pressure a dead load or a live load?

I have a structural analysis question. I want to know if the hydrostatic pressure in a water tank is a live load or a dead load and why?
6
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3answers
508 views

Is a distributed load in two parts equal to a full distributed load?

I have a structure like such: Due to my lack of knowledge of ANSYS, I have made the singular distributed loading (GI) represented as two distributed loadings (GH and HI). Would this be an accurate ...
6
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3answers
1k views

Truss manufacturer drawings unclear

I am currently looking at a set of truss layouts produced by our truss manufacturing partner for a residential building project. I have reason to believe these layouts are generated using Alpine (...
6
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1answer
487 views

Dynamics of structures: combined plane stress and plane strain conditions

Problem statement For an engineering project in school, we are checking the stability in the longitudinal direction of an apartment building, taking into account the dynamic effect of earthquakes. ...
5
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3answers
3k views

Does the length of a beam change upon deflection?

I have made a Python program in which I have computed the deflection of a beam. I am plotting the deflected beam and am now asked to show the length of the beam. If the beam is not deflected, it is ...
5
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2answers
8k views

How to calculate deflection of a simple beam with a load in the center?

Given this type of arrangement: - image by Hermanoere Where the beam is of rectangular cross-section. I am specifically thinking of a wooden beam where I can look up some material characteristics (...
5
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2answers
467 views

Seeing through walls and noninvasive structural integrity metrics

Walking into a building, how does one find out where the pipes are, how strong the walls are (currently) and other key structural integrity measures? without breaking walls or utilising harmful-to-...
5
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2answers
147 views

Why do some guyed towers come to a point at the bottom?

Why do some guyed broadcast towers come to a point at the base. It seems that it would be more stable if each vertical bar was anchored separately rather than being balanced at one point.
5
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1answer
2k views

Logic behind location of shear centre

When we apply a vertical shear force Sy and the structure is symmetric about x axis, then why is it logical to have the position of shear center at the location of intersection of line of action of ...
5
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3answers
5k views

What are safe locations for openings in reinforced concrete beams?

I had an argument with a friend about the safe location for openings in reinforced concrete beams. I've chosen position 1, a little above reinforcement steel, as at this location, the beam is ...
5
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1answer
1k views

What kind of simplified structural system would a Leonardo bridge use?

What kind of simplified structural system would a Leonardo bridge use? I've tried approximating the system to a simple statically determined beam (see below) but our calculations did not give any ...
5
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0answers
293 views

How to account for pistons inside a free body diagram? [closed]

If you have taken basic statics classes you'll remember the free body diagrams used to calculate the forces inside a mechanical system; such as a beam structure consisting of pivots, rollers, fulcrums ...
4
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1answer
2k views

What is the advantage of statically indeterminate structures?

Most of the real life structures are statically indeterminate. What is the benefit of designing a statically indeterminate structure instead of a statically determinate one? I don't mean only beams ...
4
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2answers
1k views

Given the tensile strength of a rod, how do you calculate the max weight that can be hung from it?

Given a 3.25" long, 0.125" diameter rubber rod with tensile strength 1200 psi supported on both ends, how much weight can you hung from the middle of it without breaking it? (This is not homework I am ...
4
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3answers
578 views

Why would a column expand before accepting load through a narrow thunk?

Here's a column top which holds a driveway overbridge. The column is a reinforced concrete cylinder with an inverse truncated cone on top - so it expands sideways at its top. The column top holds ...
4
votes
2answers
452 views

Removing beam deflection through axial force

It's been a while since I've done any comprehensive work with structural dynamics, so let me know if I get anything wrong here. I have a horizontal beam that is clamped on one end and free on the ...
4
votes
1answer
17k views

What angle - for a strut - provides the greatest vertical strength/support for a cantilever?

I want to affix a cantilever to wall. I will support the other end of the cantilever with a strut made of wood, that attaches to some point on the wall below the cantilever, as shown in this sketch (...
4
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2answers
483 views

How to provide lateral support for adjacent masonry during installation of steel UC in an old cavity wall?

I've got a structural engineer ready to provide calcs on this job, but there is a specific aspect where I'd like a heads-up what the normal approach would be, before I raise it with him, in case he ...
4
votes
1answer
44 views

Why is a paraboloid hyperboloid shape preferred on some structures?

Why is preferred on the construction of big stadium roofs and of cooling towers, per example? What is the advantage of this geometric figure that makes it more economical?
4
votes
1answer
149 views

3D construction [closed]

Can someone please tell you what to start with to construct a Kids Bike Trailer as 3D. It should select material and geometry. I think I should start sketching with forces (children's weight) and ...
4
votes
3answers
687 views

How to calculate indeterminacy of pin-jointed frame?

I understand that to calculate the indeterminacy of a pin-jointed frame, the unknowns have to be considered i.e. the number of elements corresponding to the number of internal forces, plus the number ...
4
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1answer
235 views

What is the correct term for long cuts in a floor joist?

I would like to identify the correct term for a long, lateral cut within a floor joist. Based upon this guide and several other sources that I have come across, a ...
3
votes
1answer
458 views

Is there a theoretical bound to how tall a structure can be built?

Assuming that there are no constraints on cost, land to develop, or supply of materials, is there a theoretical limit on how tall a structure can be built? What are the main physical constraints that ...
3
votes
2answers
829 views

How do the columns in the 'magic mountains' sculpture stay up?

I am reading this story on artist Ugo Rondinone's sculpture in the Nevada desert (Building an Artist’s ‘Magic Mountains’ to Draw Visitors to the Desert) and simply wondering (as an artist myself): how ...
3
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2answers
4k views

Rectangular hollow section vs square hollow section [closed]

Which is better to use in contructing ceiling frame? RHS or SHS? And why?
3
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2answers
8k views

Steel Structure connection pin or fixed

For the connection above, I think that once the beam is loaded, their is no room for rotation of the beam. But as per British Standard this is a pinned connection. So I have been trying to determine ...
3
votes
1answer
1k views

How high can you stack mobile homes?

In Ernest Cline's novel Ready Player One, the main character lives in the "stacks" - a dystopian vision of what a trailer park may look like in the future. The "stacks" are primarily composed of ...
3
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2answers
178 views

How does one build a waterproof basement?

I have been doing a bunch of research online into how to build a basement that is below the water table. The common wisdom is to "not waste the money doing that" but as someone who doesn't like to be ...
3
votes
1answer
163 views

How to structurally bind bamboo stems for loads?

I would like to begin a case study in structural design using bamboo, which has currently become available to me. The design instance I would like to structurally copy is the Rogue RM-6 "Monster Rack" ...
3
votes
1answer
183 views

How can I absorb shock on an existing steel structure?

I'm currently trying to extend the shock-absorbing capabilities of a welded steel structure that is shown in the following image. It is a structure that supports a slat conveyor. A load is to fall ...
3
votes
1answer
370 views

How do I create a graph of the phase angle and response of a harmonic excitation in Matlab?

In my course of dynamics of structures, I am struggling with some basic principles. As a practice, I am plotting (or attempting to plot) the curves that are shown in the course book, with the help of ...
3
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1answer
285 views

Calculating stresses of section with varying depth

I'm trying to solve the question attached below (please note the handwritten values are ones that I calculated/not part of question) I am assuming that to find the load $q$ I need to get the bending ...
3
votes
1answer
95 views

Translating the name of a type of beam from Russian to English

I am trying to translate the name of a special kind of beam from a set of Russian-language drawings. The dictionary translates the name as simply supported beam, but it's not that simple. There is a ...
3
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3answers
113 views

Is there a specific name for diagonally braced truss members like those on the Queensboro Bridge?

I am wondering about this specific type of truss in particular, any links to further source information and images regarding this particular geometry would be much appreciated.