Questions tagged [structural-engineering]

Questions related to the integrity, design requirements, or analysis of structures.

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Relation between welding bead and outer diameter of a pipe?

How can we find a relation between welding bead and outer diameter of a pipe? Welding bead is inside of the pipe and I am using M.S. pipe. Dimensions are listed below: Pipe OD=25.4mm Thickness=2mm ...
23 views

how to determine the direction of support reactions in a truss?

Hi, I am not sure how to determine the direction of support reactions at point A and K. I know point A has a pin support, therefore, it can take in horizontal and vertical loads and point K has a ...
21 views

Timber strength in tangential and radial directions

Normally for structural timber, two values for compressive and tension strength are given. One value is given for timber in direction of the grain, and other is given at 90 degrees (perpendicular) to ...
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I am designing a simple structure using PROKON. The structure is a full 3D space frame. When I run the analysis I get an error called the Paradiso Error. This error only occurs when the structure is ...
1 vote
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Beam load - bending design value of southern GC yellow pine for treehouse beam span

I'm looking to build a treehouse and wanting to ensure the support beams can carry a sufficient load over an 11-ft span. Based on page 78 (aka 83) of https://awc.org/wp-content/uploads/2021/12/AWC-...
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Pull out force for a 5/8" tapped bolt

I am looking for the pull out force on a 5/8" bolt tapped into 1/4" thick tube steel. Does the thickness of the steel need to match or be greater then the bolt diameter?
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Rafters in loft

I have two which I believe to be tie rafters in my loft. They are 1.2 meters from the boarded floor. They both are wobbly. My question is can I remove them and replace them with vertical timbers to ...
29 views

How to find the tension in wires before a column buckles

I already have the solution for this problem, I just need some explanation about a certain part. Can someone please explain the highlighted section, how do I obtain the tension formula used here?
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Aeroelastic flutter results (NASTRAN) extraction : v-g and v-f plots

for those that have worked on nastran to obtain aeroelastic flutter (sol 145) results with MSC Flightloads: what are the different ways to generate velocity-damping and velocity-frequency plots from ...
43 views

Why isn't lateral torsional buckling of rectangular timber members dependent on torsional stiffness?

I'm reading about buckling of timber members from Eurocode 5: Design of timber structures part 1. Section 6.3.3 gives instructions to check the stability of beams subject to compression, bending or ...
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Why is this bridge thickest above the support pillars instead of the mid-span where the bending stress is highest?

Why is a bridge designed like this? The depth of the section at pillars is more than the depth at middle. If I model this as a simply supported beam having load at mid span then the bending moment ...
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What are design considerations for an RCS test range be relocated fully underground?

Sites like the Lockheed Helendale RCS or the Tonopah test range are only known to have an underground pit to support raising or lowering of test articles. But is it technically possible to have a ...
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Calculations of a sphere

I apologize if the question is very basic, I admit I'm not the best at math and physics. I am doing an experiment with a sphere, the measurements are as follows: The sphere has a diameter of 330 mm (...
1 vote
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TMT Steel in layers

The Site Engineer and I were arguing about the placement of the reinforcement bars in layers. The Steel technician (TMT) placed the third layer of reinforcement in the 2nd layer. I said it didn't ...
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How to design the thickness and diameter of a cantilever beam in bending for both composites and metals?

The goal is to find the optimum values of the diameter and the thickness of the circular cross-section of a cantilevered beam in bending, with the lowest weight (cross-sectional area). The main ...
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Ideal design for a long fruit plucking pole

I need to design a long (6-7m) pole for plucking fruits from tall trees. The following are the requirements: The pole material needs to be as light as possible. The pole should not be flexible ...
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I applied acceleration at the base of model in Abaqus. I ran the model and got the output, the acceleration at the base doesn't match the input. Why?

I am modeling an earthquake in Abaqus. I applied acceleration in the horizontal direction at the base of my model. I plotted the input acceleration. I ran the model and got the acceleration at the ...
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Strain energy, Conservative force and Potential energy

What I know: In general, the work done by a conservative force $F$ is equal to the negative change in a potential energy. $$\int_1 ^2F.ds = - (U_2 - U_1)$$ A potential energy is always associated ...
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How did horizontal progressive collapse occur in 7 World Trade Center?

Please try to avoid associating this question with baseless controlled demolition theories I suppose the former 7 World Trade Center and it's fate does not need an introduction. The progressive ...
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Best way to deploy a projector screen from the bottom?

I want to design a system for an electronically deployable projector screen, where when not in use the screen is stored at the bottom and there are no structural elements sticking up significantly, ...
17 views

3D printed titanium durability/material quality concerns

What is the material strength of titanium 3D printed parts....compared to cast or machined parts? also how do they bond the individual pieces?
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1 vote
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Influence line question for calculating maximum bending moment

I have the following question: I have no trouble drawing the influence line but I have problems with finding the magnitude. Can someone please explain how to get $\frac{8}{3}$? How should I use the ...
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1 vote
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Natural Frequency of a Shear Frame

Hi I've been stuck on a problem for one of my exam revisions, we were asked to identify the natural frequency of the following structures I know that the equation for the stiffness is as follows Left ...
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Mechanism and static determinacy

I was doing exam question and am confused as to how to determine if the structure is a mechanism or not. Say that j = number of joints, r = total number of reactions, b = number of bars. For both (a) ...
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Solving an indeterminant truss with static redundancy of 2 confusion

I have the following truss and I want to calculate the reactions using the flexibility method. Using this method means that I need to break this indeterminant system into a determinant system and two ...
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Justification of static equilibrium for a cut structure/frame

Axial deformations are ignored. This structure is under the specified force: Is the internal shear force in column BC equal to that of column DE? If we cut the structure at middle of BC and DE ...
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Why do wooden gate designs recommend a brace under compression instead of tension?

Looking at guides for building wooden frame gates I almost always find the following design recommendation: The idea is that the cross brace will distribute load from the top outside corner into the ...
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Transforming the Area of a Hollow Square Section filled with concrete into the equivalent area of just steel

I need to complete the 3D stiffness matrix of steel concrete composite columns under all kinds of stresses (axial and rotational as shown in the image below). So because the section is a Square Hollow ...
6k views

Why are two wires used in railway overhead equipment?

While watching the train videos, I came across these overhead wires. After searching on the internet, I found that both catenary and contact wires carry the same voltage and are connected by vertical ...
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1 vote
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Symmetry to determine the support reactions of a statically indeterminate frame

The following is an indeterminate frame consisting of two beams that are rigidly connected to each other at the corner support. I want to find the support reactions. As far as I can see, this is a ...
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What is the cause of this cracking pattern in a simply supported beam?

Background On May 5th 2022, a bridge was struck in Brantford, Ontario, Canada by a commercial vehicle. This vehicle struck a reinforced concrete protection beam placed on the on-coming side for the ...
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Any way to approximate effect of two point loads with just one?

Imagine a 3D problem where the goal is to calculate the max. cantilever beam deflection. There are 4 equal point loads A, B,C,D separated equally from the beam's major axis. Is there a way to ...
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Work done by a force in a deformable body

Consider a deformable body that is acted upon by several forces at different points of application. Under these forces, the body remains at rest but deforms and the particles have some displacement. ...
1 vote
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Direction confusion for shear and moment when sectioning a beam

I have been practising the superposition method lately and I am confused in terms of drawing the directions when sectioning. Here is the problem: Heres is the process of converting a indeterminate ...
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Max bending moment estimate

Context: I study aerodynamics and want to design and build an RC wing to put the theory I learned into practice. The essence of the theory I learned is: Given some mass of wing building material, how ...
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Can/should you support a sagging ceiling from above?

1) How long of a span is too long for rough cut 2x4 inch (45x100) ceiling joists? Pending what those more knowledgable say, my guess is this room at 5.3m is OK, but not great. It has sagged up to 50mm....
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ISO-Strain/Stress Misunderstandings

I've conducted a 3-point beam bending test on two unidirectional composite samples of different orientation to find their Youngs' modulus. I believe I understand the basic premise behind the Iso-...
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Degree of Kinematic Indeterminacy

Is the degree of indeterminacy 3 in this structure? How to clearly determine DOKI of a structure? I am confused to determine whether hinge D can allow rotation to occur in this diagram. Rotation: at B/...
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Calculations of Retaining Wall

If I have to find the maximum bending moment of this retaining wall, is the maximum bending moment located at the toe? If not, where is the location of the maximum bending? In order to find the ...
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Is it valid to solve for the young's modulus required for a given critical load with Euler Columns?

I am working on a problem for research that is about material choices. I was wondering if the following rearrangement of Euler columns would be a valid way to check to see if a material exists for a ...
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Is half of depletion region a part of N region or P region?

Is it correct to say that if the P-N junction is in the middle of the depletion region, half of the depletion region is for the P region and the other half is for the N region?
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Effects of straightening a bent rod of iron with and without heat

I've been told that straightening a bent rod of steel (e.g., rebar) without heating it first will actually weaken it as microfibers (i.e., molecular structures) are being broken as opposed to first ...
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1 vote
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Method of Joints confusion

Say we have the following truss, with $1$ kN load pointing upwards at node 5. The goal is the calculate all the reactions and the internal forces within the members using the method of joints. I used ...
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How to know whether a vertical truss displacement is upwards or downwards (using virtual work)?

Say I want to determine the vertical displacement of the truss at Node B How do I tell whether the vertical displacement is upwards or downwards just by looking the real forces? Where do I draw the ...
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Calculating the reactions and using method of joints

Determine the vertical displacement of joint C of the steel truss. The cross-sectional area of each member is A = 400 mm2 and Est = 200 GPa. I think I know how to calculate the displacement using the ...
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1 vote
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Is structural strength the only reason for the hyperboloid shape of natural draft cooling towers?

I have read that the main reason for the hyperboloid shape of cooling towers you find next to thermal power plants is because it allows more structural strength with less material. According to some ...
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Question on plastic limit theorems and reinforced concrete

The lower plastic limit theorem is stated in Wikipedia as follows: If an equilibrium distribution of stress can be found which balances the applied load and nowhere violates the yield criterion, the ...
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How to derive the equation for fixed-pinned beam?

I have a problem in finding the reaction force of the pinned-fixed structure. If I take moment at both ends, the reaction forces at A and B should be the same and the answer is wrong. How to derive ...
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Consider that at a particular point of the body the state of stress was that of a pure shear one, with $\tau_{xy}$ and $\gamma_{xy}$ as the shear stress and strain. I read two statements in two ...