38
votes
What are those large poles for that are always in front of US stand-alone store buildings?
They are called bollards.
Their function is to provide safety for pedestrians from traffic, distracted drivers who may encroach into the sidewalk, or runaway cars e.g a driver who inadvertently ...
- 22.6k
29
votes
What are those large poles for that are always in front of US stand-alone store buildings?
They are called Bollards. But these aren't defensive as suggested.
Look closer. There's no curb.
This is a new style of store (from the architecture) and curbs have been eliminated for ADA reasons ...
25
votes
Why are some public benches made with arm rests that waste so much space?
I am not sure about this particular design. But in public places, the benches are designed to provide temporary comfort but discourage using them as a vagrant or homeless hang out, hence designed ...
- 22.6k
23
votes
Accepted
Why does a gear have extra holes?
Different gears have different drivers for having holes.
One way you can categorize gears is by whether they are used primarily for transferring:
motion: transferring angular position and angular ...
- 24.2k
17
votes
Accepted
Why does a jumping rope have no bending stiffness and compression stiffness?
TL;DR: The bending and compression (buckling) stiffness is so small because the second moment of area of the fibres is small.
Bending stiffness
It does have a bending stiffness however it is really ...
- 24.2k
11
votes
Accepted
What is the advantage of statically indeterminate structures?
For example, take a look at the following static systems.
Assume they have the same length and the same (constant) cross-section. Thus an equal allowed bending moment $M_u$.
The first system is ...
- 1,186
10
votes
Why are some public benches made with arm rests that waste so much space?
Benches are not usually engineered as such. They are being made by furniture designers, (landscape/interior) architects etc.
Now generally these professions put a lot of work into making their items ...
- 3,675
10
votes
How did this building's windows get like this?
OP states that the staining is not always present. here is a possible reason for it:
If the building is air-conditioned and has single-glazed windows, then the outside of the window glass might be ...
- 15.1k
9
votes
What are those large poles for that are always in front of US stand-alone store buildings?
Bollards and other defensive oriented structures significantly predate the 2016 Nice attacks. They have been in place at the construction of many buildings in the US and across the world for decades ...
- 191
8
votes
Accepted
Why do some guyed towers come to a point at the bottom?
If the base of the tower is "rigidly" fixed to the ground, the foundations have to withstand the bending moments from the side loads (e.g. wind) on the tower. Otherwise, the foundations will work ...
- 12.5k
8
votes
Why does a gear have extra holes?
In addition to the other answers such as weight reduction and inertia, there are other possibilities:
Often there can be a precision machined hole for timing purposes. A common solution for some / ...
- 15.9k
8
votes
How did this building's windows get like this?
To add to the other answer:
When ledges protrude out from the wall then the water, and dirt, falls away from the wall surface. Also, the underside of the ledge usually has a drip channel or groove to ...
- 15.9k
7
votes
Accepted
Given the tensile strength of a rod, how do you calculate the max weight that can be hung from it?
You're hanging it from a rod supported by both ends - and need to use the bending equations. For this case (case 7 in the link), the max weight is:
$$W_{max} = \frac{\pi d^3 \sigma}{8L}$$
$\sigma$ ...
- 5,333
7
votes
Why does a gear have extra holes?
It could be for combination of reasons.
lubrication: the holes will both pump and let the lubricant pass through.
Reduced angular momentum reduces backlash and adds to gearbox responsiveness.
...
- 22.6k
6
votes
Rectangular hollow section vs square hollow section
Use an RHS over an SHS when you want significantly more bending/shear capacity about/in one axis than the other.
The additional depth that an RHS has in one axis gives it greater shear capacity in ...
- 3,133
6
votes
Accepted
Calculate whether a polycarbonate plate can withstand a certain force
For impact force calculations you need some more information such as the shear modules and the material properties like toughness and tensile yield and shear yield.
Also you need to define a physical ...
- 22.6k
6
votes
Accepted
Is it practical to use tensile cables in a composite beam?
Steel beams and columns can and have been prestressed by steel tendons in major buildings.
Because steel tendons can be applied post-construction many times they are employed in refurbishing bridges ...
- 22.6k
6
votes
Why does a gear have extra holes?
Also someone may have to pick the machine up and carry it.
Reducing weight is not just related to the intrinsic function of the machine, its shafts and so on.
5
votes
Accepted
Steel Structure connection pin or fixed
Pinned connection in structural context doesn't mean free rotation/zero moment. Pinned connection means much bigger rotations and much lower strength compared to the connected members. According to ...
- 347
5
votes
Accepted
How do I build a miniature concrete house?
Concrete isn't a good material for such a small model. I would suggest foamboard. You can get it at craft stores. If you can't find half inch thick material, laminate two layers of quarter inch board. ...
- 915
5
votes
Accepted
Rectangular hollow section vs square hollow section
Obviously this depends on the relative size of the sections.
Assuming that the rectangular section's smallest dimension is equal to (or greater than) the square section's side and their thicknesses ...
- 13.1k
5
votes
Accepted
Trying to shed some weight on my design, any thoughts?
Your equation for bending is wrong. Force x distance is appropriate for a cantilever. For a point load applied to a "table" you are either talking simply supported (in which case Mmax = Force x span / ...
- 3,133
5
votes
Accepted
Pin support, why is there no horizontal reaction force?
Assuming I'm understanding the problem statement correctly and we have a vertical load transferred to a beam via a sort of angled frame, then here's how I'd think about the beam reactions.
The Quick ...
- 2,760
5
votes
Why does a gear have extra holes?
Depends on the application, but generally there are two reasons why: reduced weight lowers inertia loads (opposite of a flywheel), but more often less material = lower costs if these are high volume ...
- 2,347
5
votes
Do windows add to strength or rigidity?
Well, "adds strength" relative to what? A single-piece continuous hull is the strongest & most reliable but you can't see through it. Adding a windshield to the windshield frame of a ...
- 4,249
4
votes
Accepted
How can I absorb shock on an existing steel structure?
Large displacement shock absorbers used to dampen the effects of seismic events may be suitable for this application. These could be used to isolate the part of the structure that is grounded and the ...
- 1,078
4
votes
How to structurally bind bamboo stems for loads?
Bamboo in its natural shape is very prone to splitting. Having any kind of hole will reduce its high bending strength resistance significantly.
In addition, bamboo culm does not have a constant ...
- 41
4
votes
Accepted
Deflections Of Statically Indeterminate Structures
To rigorously solve for deflections of indeterminate structures, the most feasible method is the Direct Stiffness Method (aka matrix methods). This is generally the approach finite element method ...
- 2,760
Only top scored, non community-wiki answers of a minimum length are eligible