Wasabi
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slope and deflection of beam engineering
4 votes

You messed up your integration from $EI\dfrac{dy}{dx}$ to $EIy$. It should be $$EIy = \dfrac{75x^3}{6} - \dfrac{15x^4}{24} + c_1x + c_2$$ but your denominator for the first term is $3$, not $6$. (In ...

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Help an electrical engineering student with a beam deflection question
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4 votes

Yes. The first derivative of the deflection is equal to the tangent of the deflection, which for small deflections can be approximated as equal to the angle of rotation of the beam at each point. ...

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Fragmentation of a curved cantilever beam under compression
4 votes

Your assumptions are incorrect. The breaking point will almost always be at the fixed point. Here are the internal forces in your structure with loading at two different positions: Axial force is ...

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What is the splice length for two reinforcement bars in tension of different diameter?
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4 votes

The use of the smaller diameter is theoretically correct. What is a splice? It is when tension force in a rebar is transferred to the concrete via adhesion and then to another rebar. Since concrete ...

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Why the design of continuous beam is always more economical than beam with supports?
4 votes

The reality is a bit more complicated, and depends greatly on the materials being used. Let's take the following structure as our example, where the middle support may or may not be hinged (creating ...

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Heuristics for Efficient Structure (Shed) Design
4 votes

Reading your question, my understanding is that you trust your engineer to have done at least a reasonable job designing the structure. You aren't worried the structure might collapse, that the ...

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Center of Gravity of Precast Concrete Steps
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4 votes

The equation to find the center of gravity of an object which can be subdivided into smaller parts is the following: $$\text{CG} = \dfrac{\sum \overline{y}_iA_i\rho_i}{\sum A_i\rho_i}$$ where $\...

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How to construct a very large circular wall made of concrete?
4 votes

You can build this wall as you would any other. Given its size, the fact that it's a ring becomes irrelevant, which means that for all intents and purposes, it can be designed and constructed with the ...

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AISC Section Modulus numbers
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4 votes

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 ...

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Where do the tributary angles/ratios for tributary areas come from?
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4 votes

I wouldn't be surprised if these tributary angles are merely a rule-of-thumb obtained over time. (Correct me if I'm wrong!). While it makes obvious sense that, in a slab with neighboring fixed and ...

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How can I prove the location of centre of gravity of centroid?
4 votes

For a planar surface, the centroid is defined by the equation $$\overline{y} =\dfrac{\int y\ \text{d}A}{\int\ \text{d}A} = \dfrac{\int y\ \text{d}A}{A}$$ where $y$ is the distance of each point from ...

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How to model elastic support in FEM?
4 votes

What you need is the modulus of subgrade reaction (MSR) of the soil. This is a measure of soil deflection under a given pressure, so the unit is in (for example) kPa/m, or equivalently, as I'm more ...

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Calculating stresses of section with varying depth
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4 votes

As always, the first thing you need to do is calculate your properties. \begin{align} A_A &= 150\cdot10 + 6\cdot(200-10) = 2640\text{ mm}^2 \\ \overline{y}_A &= \dfrac{150\cdot10\cdot195 + 6\...

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Standard specification for direction of lateral load for beams
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4 votes

The nomenclature adopted by the authors is unusual, yes. Usually that load $Q$ would be called a transverse load, as you've mentioned. That being said, there is nothing that distinguishes a lateral ...

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How can double I-section walers be spliced to ensure effective moment transfer?
4 votes

Double-I beams cannot be spliced like single-I beams for the reasons you mentioned. Indeed, they must be spliced like box beams, which suffer from the same problems (lack of access to internal face). ...

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Is bending moment along a beam independent of the cross sectional area of the beam?
3 votes

You seem to be mixing up a few concepts. As others have mentioned, bending moment is independent of a structure's cross-sectional dimensions. After all, bending moment is simply the sum of $F_i\ell_i$,...

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a model of a solid using trusses to approximate internal stresses?
3 votes

Not only can this be done, but it also is done for concrete structures all the time. The shear reinforcement in concrete beams is calculated using Mörsch's truss analogy model: Source The concrete ...

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Confused about internal hinges for calcualting reactions
3 votes

An extended discussion on internal vs. external forces We usually like to describe hinges as "places where the moment is always zero." But, wait a minute, the moment is always zero anywhere ...

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A statics problem containing a distributed triangular load and a linear load
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3 votes

When you've done an exercise and got the wrong answer, it's always useful to check to see if your result ever passed the "smell test". That is, does your result make much sense. Now, we can see a few ...

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What is the meaning of these two inverted triangle water table symbols in a borehole record?
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3 votes

The water table in some locations may vary during the day or over time. For this reason, the borehole drilling process includes waiting periods to see if there are any changes to the water table. The ...

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Rayleigh-Ritz method, calculating slope of beam?
3 votes

The Euler-Bernoulli beam equation is as follows: $$q = \dfrac{\partial^2}{\partial x^2}\left(EI\dfrac{\partial^2 \delta}{\partial x^2}\right)$$ where $q$ is the distributed load along the beam, $\...

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Analysis Of Statically Indeterminate Structures By Hand
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3 votes

In my professional experience, I've found few opportunities to perform literal "by hand" verification. Unless you're dealing with simple structures (or structures which can be simplified as such), it ...

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Definition of buckling as a sudden deformation
3 votes

Real structures do suffer from buckling. Yes, real structures are never perfect. Columns aren't perfectly vertical, cross-sections aren't perfectly consistent throughout the span, the material isn't ...

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Derivation of the stiffness of a uniformly loaded cantilever beam
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3 votes

You came so close to the answer, you ran right past it! As you've said, the stiffness coefficient is defined as force over distance: how much force you need to apply to deflect an object (a beam or a ...

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Determining stiffness of a beam w/varying moment of inertia
3 votes

The short answer is you can't. The slightly longer answer is you can, but the solution is specific to the adopted cross-section. The much longer answer will now demonstrate why this is the case by ...

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Resolving forces in a simple truss
3 votes

As @mg4w already mentioned in a comment, this is a statically indeterminate structure. This means that the structure can't be trivially solved as you have tried (unless you use a simplifying ...

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Bending moment diagram from shear force diagram
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3 votes

Your shear diagram is correct. Bending moment is equal to the integral of shear. Therefore, the point of maximum bending moment is the point of zero shear. I can see you calculated that point as 4.38,...

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Simple Free Body Diagram
3 votes

Your result is correct: member 4 is what's known as a zero-force member. This result is inescapable given it's definition as a rod which can only take in axial loads. Since it's on a diagonal, any ...

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What are these "water fountains" in the middle of a river in North Korea? (Probably also found elsewhere.)
3 votes

They are merely ornamental. Near the top of the image you can see the base of Juche Tower (Google Maps), a monument in Pyongyang on the bank of the Taedong river. (the two large fountains are ...

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Design a part to straighten moment and reduce torsion
3 votes

First a review of how to determine the direction of the supports In these cases, it's always useful to imagine what would happen if there were no supports. In this case, what would happen if there ...

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