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22 votes
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Why would a bearing plate that further concentrates load onto small surface be used?

Because bridges and other structures are not static objects. They must be allowed to flex under varying loads and also accommodate changes in length from thermal expansion. The hinge pin allows ...
Dave Tweed's user avatar
  • 6,884
20 votes

Is it structurally sound to cut an I beam to a T on one end?

While not an ideal situation, it is common enough that this type of cut/reduction of the beam as it comes to its support actually has a name. This is more often referred to as a coped or dapped steel ...
Forward Ed's user avatar
  • 1,211
20 votes

Aluminum weight saving

I believe it has less to do with strength and more to do with stiffness. A rod of aluminum of the same length and weight as a a steel rod will be just as strong (force required to break) but have ...
DKNguyen's user avatar
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17 votes

Why do we use multiple reinforcing bars instead of one bar with a big diameter in reinforced concrete?

There are a few reasons. I'm firstly going to assume you're talking about replacing a bunch of small rebars by a single reasonably-sized one: i.e. instead of $15\phi8$ (7.54 cm2), using $1\phi32$ (8....
Wasabi's user avatar
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17 votes

Is it structurally sound to cut an I beam to a T on one end?

This is a textbook example of what not to do. We don't get into stress concentration at the cut off of the corner of the beam, or the fact that the two very different stiffnesses of the beams are a ...
kamran's user avatar
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11 votes
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What happens from B to C in this stress strain diagram of mild steel?

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 ...
NMech's user avatar
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10 votes

Why would a bearing plate that further concentrates load onto small surface be used?

The reason is pretty simple. Steel is significantly stronger than concrete. Nowadays we have high-performance concretes with $f_c > 100~\text{MPa}$ (and ultra-high-performance, which is ...
Wasabi's user avatar
  • 13.1k
10 votes

Why do we use multiple reinforcing bars instead of one bar with a big diameter in reinforced concrete?

The main purpose of rebar is to improve the tensile strength of concrete and in practice most of these loads come from bending rather than pure tension. When a beam in subject to bending forces the ...
Chris Johns's user avatar
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10 votes
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How does the strength of a square tube depend on the side size?

Flexural capacity is based on the stress at the extreme fiber (the point farthest vertically from the neutral axis). $$\sigma = \frac{My}{I}$$ Or, rearranging $$M = \sigma \frac{I}{y} = \sigma S$$ ...
CableStay's user avatar
  • 2,760
9 votes

Steel vs Bamboo strength types/ weight and in various directions & orientations? Specific, Tensile, Compressive, Shear, Lateral etc?

Stating categorically that bamboo is stronger than steel is a bit like stating that automobiles are faster than planes. On its face, it is a bit shocking, and seems wrong. But a rocket-powered ...
do-the-thing-please's user avatar
9 votes

Aluminum weight saving

TL;DR: Materials perform differently under different loading conditions. Some applications are more suited for steel others for aluminium I will try to give another more general perspective/approach, ...
NMech's user avatar
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8 votes
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Do "non-iron steels" exist?

Iron and carbon have an interaction which make them different from most engineering alloys. This is to do with both the relative size of C and Fe atoms and their chemistry. Carbon atoms are just the ...
Chris Johns's user avatar
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8 votes
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How to strengthen an I beam

If your beam design is governed by yielding in bending (not lateral-torsional buckling/plate buckling, etc) then you need to increase the second moment of area (I) to increase the bending capacity. ...
atom44's user avatar
  • 2,641
8 votes

Is it structurally sound to cut an I beam to a T on one end?

If the white beam on the left is adequate, the one on the right is much bigger than it needs to be, so hacking a piece out of it might not matter. In general this idea is a horrible example of ...
alephzero's user avatar
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7 votes

Can I weaken a coil spring consisting of spring steel?

You could try a bath of concentrated acid. As long as you could maintain circulation so the concentration was fairly constant, a spring presents a very uniform cross-section and should be dissolved at ...
Gonzonator's user avatar
7 votes

Is it structurally sound to cut an I beam to a T on one end?

TL;DR: Since we can't see how the beam is supported on the other end, its not clear whether its structurally safe. Still, I don't believe this configuration can transfer safely any substantial ...
NMech's user avatar
  • 24.3k
7 votes

Is there a maximum life for things made out of stainless steel or cast iron?

Strictly speaking, very few metals are "stable" in terms of the laws of thermodynamics. True chemical stability is when the atoms are in their lowest energy state. For most metallic elements,...
Brian Ensign's user avatar
6 votes

What thickness of aluminium sheet do I need to achieve the same strength of a 1/8" steel sheet?

Using your plate as boat hull implies a complex load profile probably involving compression, shear and bending, possibly even torsion. In such cases, it is effectively impossible to give a simple ...
Wasabi's user avatar
  • 13.1k
6 votes

Aluminum weight saving

Sometimes the strength isn't required, so size for size, aluminium is lighter. e.g. bicycles often use aluminium screws to hold the bottle cage to the frame. The size of the screw is set to be ...
Jonathan R Swift's user avatar
5 votes
Accepted

How to calculate tensile strength of braided steel wire?

First off, the tensile strength is a property of the material, not the spring itself. Strength, often denoted as $\sigma = F/A$, can be considered how much force a material can withstand for a given ...
BarbalatsDilemma's user avatar
5 votes
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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 ...
minas lemonis's user avatar
5 votes
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Why are steel I-beams mostly symmetrical?

Academically, I believe you are correct in that you could potentially optimize an I-beam to have a higher failure-load to mass ratio. You would have to play with the area moment of inertia equations ...
ericnutsch's user avatar
  • 8,106
5 votes
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Spring degradation in hand grip trainer

for a properly-designed (right materials, right size, right manufacture) spring of that type, the applied stresses are far too small to cause any plastic deformation (permanent bending) at all. ...
niels nielsen's user avatar
5 votes

Which post would be stronger?

The incorrect posts are weaker as it is the dimension perpendicular to the fence which is critical. It sounds like you have a breach of contract here so you should ask them to replace with the ...
Jonathan R Swift's user avatar
5 votes

What happens from B to C in this stress strain diagram of mild steel?

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 ...
r13's user avatar
  • 8,174
4 votes
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How can I cut a thin (1mm) sheet of stainless steel with high precision?

Calling a small disc that is 9.5 mm DIA and 1.0 mm thick "a thin sheet of steel" is a bit of a stretch. Any machinist would simply clamp the disc in a suitable vise and mill away the unwanted part. ...
Dave Tweed's user avatar
  • 6,884
4 votes

How can the alloying materials of recycled steels be separated?

First the scrap is separated at the source ; for example cast iron generally only contains Si and Mn. High vapor pressure elements boil off or collected in the flux/slag : eg, Zn, Pb, Sn, Bi, An ,,,,...
blacksmith37's user avatar
  • 6,134
4 votes
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AISC Section Modulus numbers

To quote Wikipedia: The elastic section modulus is defined as $S = \dfrac{I}{y}$, where $I$ is the second moment of area (or moment of inertia) and $y$ is the distance from the neutral axis to any ...
Wasabi's user avatar
  • 13.1k
4 votes

Are British Universal Beams and Columns cut according to imperial or SI measurements?

There is a misnomer in the question in that the beams are not cut to section at all, and not measured with any sort of ruler during manufacture. The sections are rolled on a hot rolling mill where ...
achrn's user avatar
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4 votes
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Steel : is Damascus steel still relevant compared to modern alloys?

Damascus and Samari blades are artisan made , so have variations. They were a very clever way to make medium carbon steel before the science was understood. They are a combination for wrought iron ( ...
blacksmith37's user avatar
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