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I will expand on DKNguyen answer, because to my knowledge also the two reasons are: reduce contact/bearing stresses (having a significant effect on thin finishes live galvanisation) change the joint tightening characteristics (see joint diagram). reduce contact stresses on surfaces. The basic idea is that since contact stress is defined as: \sigma = \...

27

It is for spreading out the stress. But it is also for giving the bolt a bearing surface to turn on. The washer always goes on the side (nut or bolt) that is being turned. It prevents it from marring up the work surface and also changes the tightening characteristics. I don't know the specifics of that though but that's what I was told by a toolmaker. Always ...

26

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 subtle discomfort. Also, they have to be easy to scan by security cameras and not have hard-to-see corners easy to hide contraband material or even explosives! ...

16

Except for special applications, most washers are made of dead soft steel, which deforms under the compressive load imposed by a tightened bolt head. As the washer smooshes, it minimizes stress concentrations caused by bumps under the bolt head and surface flaws in the part the bolt is running through.

15

To visualize part of Nmech's answer: in the image, the washer actually greatly increases the contact area of the bolt head. The bolt head looks pretty big: But most of that is the shaft, which obviously does not spread out load on the material. So the actual contact area looks like this: Comparatively, the bolt head on the washer looks like this: That's a ...

14

Where concrete is exposed to water, the water is going to permeate concrete no matter what you do (for the most part). The voids introduced by air entrainment allow the water some place to expand into when it does eventually freeze, thereby reducing the pressure on the concrete to crack. Edit 2021/02/17 to add some supplementary information: ACI 201-16, &...

10

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 novel in some way (Even if that novelty feels stupid to you). Reason for this is that they are being selected that way from catalogs, trade magazines and display ...

10

One point of note is that the yield region is not as cleanly defined as BCD is in the image (although most books have it that way). In reality the yield region looks like The following image is one from many actual measurement that I took years ago (its Force Displacement). You can see the jagged yield region after the elastic region. The point is that the ...

9

You are worrying about the numbers and forgetting what the numbers mean. This is for the PE exam, so this is a very important topic to make clear in your mind. You solved the problem. You came up with an answer for what is required. You now have two options: Choose a small footing that your own solution just proved is too small for the requirements. Choose ...

8

The next time you see some kids playing jump rope, go out and ask them to hold the rope perfectly straight. If two kids hold the two ends of the rope with it dangling until it is almost on the ground, they have to hold the ends of the rope up but they don't have to pull much, end to end. The straighter the rope is, the more they will have to pull. If you ...

7

The air entrained in the concrete causes discontinuous voids, which will not cause water to penetrate the concrete. Water will permeate through the bleeding pores which are continuous cavities. The entrained air bubbles are small and will only allow space for the freezing water to expand.

6

The hyperbolic shape of cooling tower is preferred as this shape is stronger against wind pressure. Consequently, the concrete wall thickness can be reduced and optimised. from 1.5m at the base of the viel, the shell thickness rapidly fall to ~30cm. The venturi effect resulting in the usage of this shape is, contrary to popular belief, not improving the ...

6

Another important part of the answer is the symmetry of the stress pattern. The stress caused by a bolt head varies greatly between the points of the bolt head and the straight sides. As a result local stresses, which are what you really care about because those are what the materials have to withstand, can be much higher than the average stress. A washer's ...

5

Rod 38 is in tension, and therefore it stretches.

5

A Civil Engineer is a person trained on how to solve problems or put things together (build) using his/her brain and express his/her thoughts/ideas on the papers (reports, drawings) for the persons in trades to carry out (build), using their trained knowledge and skill for the specific trade, which usually requires physical strength. Actually, many engineers ...

5

The direction of Forces isn't necessarily along the connecting element. If that happens depends a lot on the constraints between the different elements. For example see the following image: In the left column is a "welded" structure, while on the right column is a pin jointed structure (a basic truss) if you like. On the top there are the shapes ...

5

Point "C" is the "offset yield point" or "proof stress" as described below. The yield strength or yield stress is a material property and is the stress corresponding to the yield point at which the material begins to deform plastically. The yield strength is often used to determine the maximum allowable load in a mechanical ...

4

In the bench that you show, the slats are supported and held in alignment by the end brackets. The armrests are supported by, and in line with, the legs. You could incorporate the end brackets into the leg structure but this would make for a more complicated moulding that either doesn't allow the same mixture of materials or has too many holes drilled in it ...

4

The short answer is: They are permitted/allowed to do work. Sometimes they can do (they have skills) at least some of the labor. Usually they don't get involved with the actual labor. The last part is the most important - IMHO- and there are many reasons for that: there is literally not enough time (usually engineers need to see the larger picture and ...

4

Yes; from B to C it is behaving elastically AND plastically. A small amount of plastic strain ( less than 0.2%) is mixed with elastic strain.

3

It’s total square footage not per floor square footage. Btw, the AIA has established EXACTLY how to calculate square footage of a building. That is to say, overhangs, canopies, balconies, pipe chases, open terrace, etc. is considered 1/2 square footage. So, if there is a 200 square foot entry canopy, it’s considered 100 square feet in the calculations. (You ...

3

A suspension bridge cable is the most effective use of material. Because it uses high tensile cables in a position where they are the most effective material: tension. The parabolic shape is the closest natural geometry a cable assumes under uniformly distributed horizontal load ( not the self-weight, that is a catenary curve). It has reduced the structure ...

3

I think the aim of this duet of exercises is to make you understand that you can break down problems and superimpose solutions. infinite stiffness In the first case what you do is you have a simply supported beam with moment in one support the beam BC. $\theta_1$ is the angle at the support. (note that Moment is negative and is equal to 40*1.5) Since you ...

3

It looks like a prestressed cable anchor.

3

What you are proposing is similar to the cone penetration test (CPT) used by geotechnical engineers to characterize the soil layers of a site before construction. The measured resistance to a continuously pushed tapered probe varies by soil type. By researching on the web the resistance by soil type values, (see Olsen Chart) you may get a feel for the ...

3

The answer is "Yes", and the direct source to find such relationship is from the technical publishing, that offer steel design tables/charts showing the most optimum beam/column sections for certain load with respect to the length of the beam column. The image below is an example of a chart comparing moment capacity (indicated on the left axis) of ...

3

I'm not doing notation for this, it's simple algebra. X = 1,000,000 = 5000 / .1 * ((1.1)^n - 1) 1,000,000 = 50,000(1.1)^n - 50,000 1,050,000 = 50,000(1.1^n) divide both sides by 50,000 21 = 1.1^n etc.

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The rebars just for the sake of being embedded in the concrete do not work! It has to be stretched to work. Hooks law, $\ F=Kdx, \quad K = E*A$ That's why we place the rebars on the bottom not near the center of the beam, to give them elongation. So a lot of good concrete that could be used for compression has to crack open stretching with rebar while ...

3

The stress is not uniform near the grip because there is a biaxial state of stress. There is the axial force the compression force from the grips. That is the reason that if the Cross-section was uniform the failure would start from the grip. the mental image is the following: If you have a ballon that you apply force from one end, and at the same time ...

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