Questions tagged [structural-analysis]

Structural analysis is the determination of the effects of loads on physical structures and their components. Structures subject to this type of analysis include all that must withstand loads, such as buildings, bridges, vehicles, furniture, soil strata, prostheses and biological tissue.

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13 views

Analysis of Machine Frames With Cut Outs

I have a structure that is used to support two shafts which are carrying relatively high loads. It is composed of two columns and a "shaft supporting block" in the centre (almost acting as a beam). ...
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23 views

Dependency between load capacity for reinforced concrete slab and thickness

How does the load capacity for a reinforced concrete slab depend on the thickness of the slab? Example: Let's suppose that we have the following constants: concrete quality (including the maximum ...
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2answers
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Parallel Axis Theorem for x and y Shift

I have a quick question about the parallel axis theorem. Let's say I have a box-like object rotated about the following pivot point I was wondering, by applying the parallel axis theorem, would the ...
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2answers
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Why not a reverse bending in the slab?

When I'm looking at images / videos about the load supported by reinforced concrete slabs, I always see a compression at the top of the slab in every point that varies from the center to the edges: ...
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Looking to design a cantilever support to hold up an 80kg projector

I need to make a support (preferably metal) for a projector to be fixed on the wall. The projector size is: Width: 0.7m Length: 1.1m Weight: 80kg If anyone knows how i can solve this please let me ...
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1answer
34 views

Can a horizontal foundation safeguard against earthquakes?

I have not taken any course in civil engineering. What I was taught was that a broad base would prevent something from toppling. So it makes me wondering instead of nailing the foundation of a ...
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Stopping Force of Irregularly Shaped Object

I have a quick question about the force needed to accelerate/decelerate an irregular object. Lets say I have a 3D object with the following general shape, This system is in general a gripper (gray) ...
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How to derive fixed-end moment of a beam?

Here is my attempt but I am not getting the right answer. Can someone tell me what I am doing wrong?
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Handling internal hinges (releases) in a FEA Buckling Analysis

Background I am running a FEA linear buckling analysis according to the equation $K_e x − \lambda K_g x = 0$ where $K_e$ is the global elastic stiffness matrix and $K_g$ is the global geometric ...
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Why is pure shear a “shear”?

If one looks up the meaning of shear strain, most sources talk about this situation: That is, a force acts along a surface of an element at it is elongated, turning a rectangle into a rhombus. ...
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1answer
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How is the stress concentration factor calculated in FEM?

I have written my own finite element code for a linear elastic (plane stress) problem consisting of a plate with a circular hole in the middle, fixed on one side, having a tensile force acting on the ...
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Machine Frame Design

How do I select the cross section for a machine frame? Do I need to refer to the AISC steel construction manual to find the capacity of beams, columns, etc?
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1answer
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Engine Combustion Cylinder Wall Thickness

Been referencing this website for some time but now need to seek specific help. I am not an engineering student but rather a DIY hack who loves engineering and machining neither of which I am ...
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Constrained optimization using Lagrangian

I'm trying to optimize the weight of a truss with the constraint that the trusses don't face more stress than the material resistance. Here is a sketch of my truss: I have a Python function that ...
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Structural analysis + thermal expansion using ANSYS static module

I am attempting to model a steel sample subjected to combined mechanical and thermal loading. The thermal loading can be quite elevated, where reduction in the elastic modulus will occur. Does anyone ...
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3answers
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How do I calculate the member forces of a truss when external force acts on the member (not joint)?

Given a three member truss structure shown here: How do I find the vertical and horizontal displacements at M? Assume all members are elastic and E,A, I and constant. I start with finding the ...
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Etabs Semi Rigid Diaphragms

In Etabs, if I model a building with semi-rigid diaphragms assigned to the floors, the floors will now transfer gravity loads when default meshing is assigned (as compared to rigid diaphragms ...
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1answer
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Selection of Aluminum (or steel) tubing dimension based on uniform load on supported beam

I am installing shades on a section of deck. The shade will be made of sections of fabric (which will let some wind through), but I assume a solid section. Dimensions are 3.5ft*4ft = 14ft^2 = 1.3m^2 ...
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1answer
25 views

2D Solid - Axisimmetric - Missing properties and material

Goodmorning, I'm trying to understand how 2D solid elements work. I want to study the local buckling of a simple aluminium pipe with thin walls. From what I understood, I can use 2D solid elements ...
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1answer
62 views

Maximum tensile and compressive stress in a T-beam

Where does the T-beam come from? There's just a straight beam resting on two supports. And where do 10 and 80 come from? I am so confused.
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1answer
43 views

Determining the direction of internal forces in a truss

I am learning the method of joints, but there's no explanation on how to figure out the direction of internal forces in my course. How do you know that BA is tension and BC is compression?
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How to state the PSD value (random vibration)

In random vibration analysis, the load is given as a PSD (power spectral density). The values are often $G^2/Hz$, but I have an example where the PSD is a pressure $Pa^2/Hz$. The value is written as $(...
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1answer
31 views

FEA: What is the difference between a spider of RBE2s and multiple SPCs

I am not sure what the difference is between using a spider of RBE2s. and multiple SPCs across a face. I've heard that the spider is the more accurate method as multiple SPCs make the model overly ...
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1answer
56 views

How to find the diameter of bolts in a flanged joint?

So I'm given this question with the following diagram: Two sections of a pipe are joined in a flanged joint as shown in the Figure below. The difference in pressure from interior to exterior is 2 MPa....
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What equation are we using to describe forces in FEA?

Engineers often use Finite Element Analysis software to solve for stresses inside complicated structures to generate pictures like the one above. I am familiar with FEA as a method to solve ...
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3answers
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What are the possible implications of the heating of the structural stonework of Notre-Dame cathedral during the fire?

Yesterday, Notre Dame cathedral caught fire. The roof and the central spire were destroyed and some of the stonework was subjected to high temperatures for an extended period. What are the likely ...
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1answer
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How to compute core stress in honeycomb structure?

Assume I have a honecomb(sandwich) panel under distributed normal load. Each edge of this panel is simply supported(pinned) as on the picture below: The problem is how to find the core stresses σ-z (...
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2answers
60 views

Influence of a diagonal fold on a web + double fold situation

I need to build a steel frame with a steel web in it, as illustrated below. Flanges of the frame will be welded, as well as the web, along its whole perimeter. Would adding a diagonal fold to the web ...
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Determination of Warping Function for Thin-walled Multi-cellular Beams

I am trying to find warping function $\mathcal{T}$ for a thin-walled multi-cellular beam. There are four rectangular cells. The governing differential equation for $\mathcal{T}$ is Eq. 8.98 as shown ...
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38 views

Traction Force or Reaction Force

I am doing an FEA of a link plate of a chain drive system. the plate is subjected to traction force at one pin joint this particular link is in contact with the sprocket. it is also in contact with ...
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1answer
47 views

Why/how normal shear stress is zero in thin-walled beams?

Please explain how the normal shear stress (shear stress normal to the cuve, C, defining the cross-section of a thin-walled beam) is zero. I have attached a screenshot from a book which says that the ...
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2answers
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Why not build container ships from plastic?

This may sound crazy but bear with me. I was thinking about why cargo ships are built from such heavy material as steel, while smaller boats are often made of plastics. I know cargo ships carry a lot ...
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Can I use fixed support for a frame?

Can we use fixed support at columns in a frame? Because If we do so , there will be 2 moments when we will cut the section.
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Need help with FEA bar analysis problem

I'm trying to solve this which is to find the total deformation of the bar. I'm trying to implement the finite element approach, but I am getting way too large of numbers. Here is what I did in ...
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1answer
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Should the corbel angle always be estimated as 60 degrees in masonry construction, or is there a formula to use instead?

In educational construction material as well as engineering publications, the corbel angle for significant excess loads, and also for substantial openings, in an ordinary brick wall is usually ...
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Why do stress concentrations really occur?

From doing some research I've learned that internal stresses inside an object can "concentrate" on sharp edges, as shown in the above picture. For that reason we often make fillets so that the change ...
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Why would a SMD (spring mass damper) model of steel break down?

Under what conditions would steel be able to be modelled as a 3D SMD model, and under what conditions would the model break down?
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2answers
57 views

Rotational and translation DoFs in structural mechanics

I'm a computational person, and I don't quite understand how rotational DoFs are manifested in the linear elasticity equations. I understand the translational DoFs are simply the displacement ...
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1answer
35 views

Member weight in a planar truss?

So I'm given a question in which a Truck drives over a pratt truss bridge. In the question the truss is in 3D. I'm given: 1)The loads from each axle of the truck 2)The weight of each member in the ...
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1answer
45 views

How to allow only one mode of resonance in a cantilever beam

So I am designing a MEMS structure consisting of cantilever arrays. For my problem, I want the cantilevers to vibrate only at their 1st mode of resonance and reject all the other modes of resonance ...
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49 views

Analytical calculation vs FEA

In terms of calculated stress, strain, displacement etc which method yields more conservative results. Analytical calculation or numeric calculation?
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2answers
51 views

Honeycomb structures vs shear stress

Honeycomb structures are made of top and bottom shells and honeycomb geometry at core. In terms of bending load, maximun normal strains take place on top and bottom hence, sheet parts can support them ...
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1answer
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Drucker-Prager Model Parameters, a Proper Choice

My task is to write a code from scratch for 3D elastoplasticity, namely a DP model (see for example DeSouza Neto, et al., 2008, Chapter 8) having yield surface $$ f(\mathbf{\sigma},c) = \sqrt{J_2(\...
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0answers
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Possible improved approaches to 6mx3m moment-resisting frame with eccentricity+torsion, in advance of detailed engineer discussion

I'm putting a steel frame in, to "open plan" the rear of a brick cavity-wall terrace house in the UK, which will then have a single storey extension added behind it. I have already retained a ...
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0answers
19 views

Displacement of Gaussian point after structure simulation

When we did the simulation, we would get deformation and got each nodes displacement. In physics, it shows the trajectory of a system of particles of the objects. Is it the same as the displacement ...
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1answer
51 views

defining the dimensions of a bucket elevator chain link

how to define the shape of a heavy duty chain link when the pitch of the chain and the traction load that the chain is subjected to is known? lets say i consider the traction load as the maximum load ...
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2answers
45 views

Material for car mounted fire extinguisher bracket

Don't try this at home. I am taking personal responsibility for what happens in my car. Hi all, I recently purchased a fire extinguisher for my car (it weighs 1.5 lbs or 0.68 kg). I browsed the ...
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1answer
43 views

Calculation of natural frequency in a hinged beam

What I tried: Using the conjugate beam method to find deflection and hence stiffness of the beam, but I am unable to find reactions in the conjugate beam.
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2answers
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Impact capacity of tension cables, columns and foundations

A rock is falling from an embankment of mass $m_a$ at a height of $h$. Below, a fall protection fence catches the rock, dissipating the energy through tension cables to steel posts and then into ...
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1answer
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Supporting flexible square plate of uniform density in equilibrium with only 4 rolling contacts placed along the square's diagonals

Consider a flexible square of uniform density with vertices (0,0), (0,1), (1,0), (1,1). I need the 4 coordinates for rolling contacts along the diagonals that will stably support it. Someone could ...