Questions tagged [structures]

Questions relating to or the engineering application of a device that must withstand a loading via deflection, stresses, resistance to buckling, or natural frequencies.

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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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3 votes
0 answers
85 views

Normal stress - shear stress pairs not lying on Mohrs' Circles

The three Mohr's circles depict all the possible normal stress / shear stress combinations when material is taken and rotated along one of it's axes of principal stress. Nevertheless, it is clear that ...
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2 votes
0 answers
56 views

Hencky nets/slip-line fields on the the interior of a closed domain

This is a crossed post. The equations for Hencky nets are usually solved in the exterior of some domain; typical examples are the upper half plane or the exterior of a circle. I would like to know ...
2 votes
4 answers
192 views

Bending moment calculation

Considering all the variables are the same, how to rank these connections from highest to lowest bending moment?
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2 votes
0 answers
29 views

Help sizing of lug attachment flange/plate?

Apologies for the crude drawing attached, but here goes. Given Fx, Fy, and Fz loads applied at the lug hole, I've distributed the loading into each of the 6 fasteners to size them. I've also sized the ...
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1 vote
0 answers
37 views

Why are these food stretch films (LLDPE) holding one one-thousandth of the weight in reality than what is expected from the datasheet values?

I am trying to reproduce analytically the results found in this experiment where a weight of 3 x 5 lbs (6,8 kgs total) breaks the cling wrap (LLDPE) which is stretched over a medium size cooking pot. ...
1 vote
3 answers
555 views

Tension cable underneath rafter tie?

I just bought a new property with a large garage and I'm curious about the roof structure. The roof structure is supported entirely on the front/rear walls using rafter and collar ties. The rear wall ...
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1 vote
3 answers
105 views

How many support beams/rods needed for a firewood storage cabinet

I am building a firewood storage cabinet which should support around 100-150 kg of firewood. The cabinet is made out of wooden boards (...
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1 vote
0 answers
35 views

When settlement criteria of a foundation is satisfied, bearing criteria is also automatically satisfied?

We design the foundations to settlement criteria than bearing correct? Because settlement criteria is stricter? I mean, can there be an example where the settlement criteria is satisfied but bearing ...
1 vote
0 answers
23 views

Secure loads to gearbox shafts

I have a sculpture that is designed to rotate over 3 axes at max. 30RPM and is mounted on an aluminium disc. My plan is to use 3 of these geared steppers and secure the sculpture to the Z-axis shaft, ...
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1 vote
0 answers
281 views

Calculating diameter of steel rod required to not bend over a given length

I want to use steel (or other material) rods to support weight over a 900mm cavity. The weight that needs to be supported is technically unknown, but I'd specify some rough guidelines as: 100KG (max) ...
1 vote
0 answers
35 views

What does 'Analysis Model Value' in NASTRAN optimization mean?

I am new to MSC NASTRAN and PATRAN. I am running a simulation on composite laminate optimization. While creating the design variables for the study, I noticed that there is a parameter called '...
1 vote
0 answers
73 views

Calculating the Structural Forces Required to Support a Robot on an Overhanging Beam

this is my first time posting on here and I have a question regarding the structural properties a beam will need in order to fulfill some requirements we have for our robotics team. The scenario is as ...
1 vote
0 answers
474 views

Beam element stiffness matrix for variable area cross section with mass and shear center not coinciding

I would like to find the full (12 by 12) Timoshenko beam element stiffness matrix for a variable cross section with mass center axis and elastic center does not coincide. I have the full stiffness ...
1 vote
0 answers
37 views

How to support height extender on a rail?

I've got an 1/8" thick steel rail with 1.5" diameter and 15' in length sitting on two 5/32" thick steel rails with 2.5" diameter and 100" in length 14' apart: I want to add a diagonal support for a ...
1 vote
0 answers
44 views

Check of a nominaly pinned steel joint

I am interested how to check a nominally pined joint. Especially how to check its rotational capacity and whether i can define it as nominally pinned in structural fem model. I understand that there ...
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1 vote
0 answers
29 views

How to calculate a global strain from a field disitribution

For an arbitrary articulated structure subject to non-affine (non homogeneous) deformations, the components of the strain tensor are defined locally. Is there a way to calculate a numerical strain ...
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1 vote
0 answers
1k views

best way to reinforce existing structural header?

House remodeling. I need to enlarge (from 7 to 10-12 ft) and shift (about 5ft sideways) an existing header where one passes between rooms. On one side, the header has 2x8 ceiling joists nailed to ...
0 votes
2 answers
54 views

is a rebar arch structure a good idea?

I am thinking of building a simple shaded Arch for agriculture. I have an idea of building it with 30 ft sections of rebar that I will bend into a rough art shape. I would then weld rebar ...
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0 votes
0 answers
30 views

How to measure strength of stretch film on a mock up

Let's say I have an iron cube of 1 cubic meter and I want to make an aquarium out of it. To hold water I want to wind stretch plastic film around the walls of that experimental aquarium. Let's assume ...
0 votes
0 answers
26 views

Force that a surface made of stretch film can sustain

I need to estimate the static spread force (Newton) that a plastic wrap wound around a given square frame (1 sq meter) can sustain. The stretch film has a given thickness (eg 17 microns ~ 63 gauge) ...
0 votes
0 answers
10 views

Square box welding with T joint, welded with stick welding

When joining two square box beams in Tee, is it enough to weld them in only three sides or I have to weld the full perimeter of the square? If those 3 sided weld are suppose to bear weight, how much ...
0 votes
1 answer
42 views

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) ...
0 votes
0 answers
19 views

Spring loaded quad blade

I'm wanting to see if it is possible to create a functional prop that includes two blades that spring out creating a circular quad blade. 2 blades would be fixed at opposite ends of the circular ...
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0 votes
0 answers
20 views

Steel retaining wall

Hi im doing a DIY project which need to build 30cm height retaining wall to hold up some gravels for an above ground pool 5000liter size 2.3x4m And the foundation pad area is 3x4m Im thinking to use ...
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0 votes
1 answer
101 views

Is it possible to use Plain Cement Concrete post for fencing?

I am in need of around 700-800 posts to fence my farm in a semi-arid area in TN state, India. In my place granite posts mined from quarries are normally used. It costs around Rs 300-400 per post(6-7ft)...
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0 votes
0 answers
23 views

Wind behavior and pattern

From the 5 options, which one shows the worse wind effect? Is it (b) because wind speeds accelerate through a gap? But how about in comparison to (c)? Or (d) due to the height and sharp corners? If it'...
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0 votes
0 answers
447 views

Deflection Of Beam In Structural Rigid Jointed Frame

This is a recommended follow on to one of my previous questions. It was stated that I could find the deflections of a beam by idealising it as a simply supported beam and then calculating accordingly. ...
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0 votes
0 answers
77 views

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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0 votes
1 answer
106 views

Optimal method of attaching commercially-available heavy bag mount to finished ceiling with least risk of structural damage

Admittedly, this question is related to an earlier one on the same subject. I would like to mount a heavy bag using a system detailed in the attached picture (FirstLaw Fitness Shock Mount). The ...
0 votes
1 answer
104 views

A Steel post and base question

I make solid curved wood furniture and frequently need something like a metal plate (1/8") with a (3/4" about) supporting pipe attached at 90 degrees. Welding is a little too cumbersome but I was ...
0 votes
0 answers
34 views

Independent constraints - Procedure to verify it

I am wondering if there is a procedure to verify that the constraints of a system of rigid bodies are independent. Here there is an example of a system with dependent constraints: L beam - Strange ...
0 votes
1 answer
106 views

compression buckling under lateral load

I'm trying to figure out what size of round tube to use for a tensegrity structure that'll probably have people climbing on it. The rigid elements are 21' steel tubes, and in normal cases they ...
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-1 votes
2 answers
84 views

Beam/column sizing

If a load P is applied as shown to a fixed column-beam, pinned at the bottom, should the beam or column (or both) sizes be increased to resist the load?
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-1 votes
1 answer
38 views

Shear connections

Question: which of the three shear connections (beam/column) below will require diagonal bracing?
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-1 votes
1 answer
57 views

Method of joints not working on simple truss, supposed to be stable and determinant

In the process of editing the question to put better pictures of my dimensions in, I realized that how I calculated my angles was incorrect, and that is why my answers were yielding inconsistent ...
-1 votes
1 answer
320 views

What is the strongest structure?

I am not an engineer, but I thought maybe this could be a very old and classic problem in structural/mechanical engineering. I need to build a support structure to hold a uniformly-distributed load of ...
-1 votes
3 answers
57 views

How to solve a system of second order ODE from time t = T to t = 0

I have a system of second-order ODEs $$ \mathbf{M\ddot{x} + C\dot{x} + Kx = f} $$ I want to know some good numerical methods to solve this system of the equation given the initial conditions at time $...
-1 votes
1 answer
128 views

Flexure Deflection - Both ends fixed (one translation free)

I have a flexure problem. One of its ends is fixed to a frame (say F1) which is stationary (no rotation & no translation) and the other end is also fixed to another frame (say F2) which can move ...
-1 votes
1 answer
147 views

Wood Dimensional Stability

Between Glue Laminated and steel plate sandwiched between two wood beams, which one is more dimension-ally stable?
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