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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 ...
Forward Ed's user avatar
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3 votes
0 answers
107 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 ...
Bruno KM's user avatar
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2 votes
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Shape of a beam that is bowed under compression?

Suppose you have a uniform beam, such as a piece of plywood that is 4 feet long, six inches wide, and half an inch thick. Suppose you cause it to bend by attaching, for example, a string under ...
David Rose's user avatar
2 votes
0 answers
57 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 ...
Daniel Castro's user avatar
2 votes
4 answers
378 views

Bending moment calculation

Considering all the variables are the same, how to rank these connections from highest to lowest bending moment?
SSan's user avatar
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2 votes
0 answers
52 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 ...
Hunter's user avatar
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1 vote
2 answers
35 views

Structure's equlibrium state

The state problem of a structure at equilibrium is generally expressed as: $K(x) ~u = F(x)$ where $K$ is the stiffness matrix, $u$ is the displacement vector, $F$ is the force vector, and $x$ is the ...
user134613's user avatar
1 vote
0 answers
36 views

How did gothic church architects/builders properly scale up their models to full size churches?

In this video the author explains how ancient church builders used models to determine the proper shape and order of installation of architectural elements in gothic churches. From the little I know, ...
geeheeb's user avatar
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1 vote
0 answers
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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. ...
ChewingGumXpert's user avatar
1 vote
4 answers
3k 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 ...
ryan's user avatar
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1 vote
3 answers
137 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 (...
ddofborg's user avatar
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1 vote
1 answer
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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 ...
upstream's user avatar
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1 vote
0 answers
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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, ...
John M.'s user avatar
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1 vote
0 answers
341 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) ...
aaronrhodes's user avatar
1 vote
0 answers
37 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 '...
TV Raghav's user avatar
1 vote
0 answers
79 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 ...
Jonah Rolfness's user avatar
1 vote
0 answers
563 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 ...
Paul Thomas's user avatar
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 ...
This could be more creative's user avatar
1 vote
0 answers
46 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 ...
Tomas L's user avatar
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1 vote
0 answers
32 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 ...
GeoArt's user avatar
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1 vote
0 answers
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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 ...
RustyShackleford's user avatar
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0 answers
20 views

Techniques to make residential buildings more blast resistant

There are generally two approaches: First: use stronger materials (e.g. thicker RCC with fibres, go underground, etc). Second: for any given material, use a superior design. The First approach is ...
caveman's user avatar
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0 answers
24 views

I'm Missing Something on Problem 3 in Section A5.4 of Bruhn's Analysis and Design of Airplane Structures

I've been working through the 1943 edition of Bruhn's Analysis and Design of Airplane Structures. I found an archive.org pdf version of the 1948 edition that includes answers to select problems, as ...
brandonman's user avatar
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0 answers
60 views

Counterweight requirement and platform design for motorised speaker stand stability

I recently bought my dream speakers (Dutch & Dutch 8c), but at the cost of having to preserve a minimalist interior for the sake of household peace. To that effect, I plan to construct motorised ...
talalalal's user avatar
0 votes
0 answers
42 views

Should a house wall be perpendicular to the direction of a strong wind carrying rain water?

I am building a perfectly squared single-storey house (10m x 10m). To have the best output from the solar panels, which should face South as straight as possible, the external South facing wall of the ...
Alex Dumitrescu's user avatar
0 votes
1 answer
60 views

Beam deflection for FEA model validation

I'm trying to validate an FE model that I'm using by comparing to a simplified analytical solution to the problem. The part I'm analyzing is a lug that is constrained on one end and has a point load ...
Enzo 's user avatar
0 votes
1 answer
77 views

Does yield point of steel depend on thickness?

I have two different plates of different thickness and I need to calculate yield point. Does yield point of steel plate changes with changing of plate thickness?
Akshay Wagdole's user avatar
0 votes
1 answer
174 views

Calculating the plastic section modulus, Z, of an arc of a circle

I am trying to find a simplified formula for determining the plastic section modulus, Z, of an arc of a circle. In my case, I have a 20" diameter 0.375" thick pipe and I am cutting a 6" ...
TheSpareBoot's user avatar
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0 answers
20 views

How is a room structurally suspended above a garage cutout?

The garage of this cavity wall (outer brick layer wall, inner concrete load bearing wall) new build uk house is a cutout directly below a room. i'm confused because this obviously interrupts the ...
jg mr chapb's user avatar
0 votes
1 answer
121 views

Rectangular pressure vessel

I'm trying to find a theory reference for stress and deformation analysis of a closed rectangular pressure vessels with constant thickness subjected to pressure loads. By now, my test case would be ...
Enrico's user avatar
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0 votes
0 answers
41 views

Structure Grid for a building with irregular shape

I am making a building block with the shape as outlined in yellow in the attached capture, as for the structure I am not sure how to place the loadbearing poles and I could use some help
DADA's user avatar
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0 answers
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Looking to make a retractable disco ball

I am looking to make a disco ball that sits in its normal position, attached to a ceiling, but to be able to hit a switch and it track upwards at a 90° angle to be hidden horizontally in a case. I am ...
Mishmosh's user avatar
0 votes
0 answers
31 views

Displacement as a function of the force and the properties of the frame I and J

I was wondering how you would find the stiffness matrix of a triangular frame with unknown angles. A little context The pumpjack model involves a triangular frame on which the rocking beam is ...
samuel's user avatar
  • 1
0 votes
1 answer
63 views

Calculation of Drone Fuselage Natural Frequencies

I'm looking to do a frequency analysis of a fixed-wing drone. The goal is to calculate the first few natural frequencies of the fuselage to verify there is no resonance with the wing structural/...
Seth's user avatar
  • 1
0 votes
0 answers
31 views

Jibs fastening in a frame structure

I need to make a demountable frame for cycling trials: I want to make it based on steel profile square tubes: The design must have variable dimensions and slopes. I guess provide variable dimensions ...
Vladimir Bershov's user avatar
0 votes
1 answer
229 views

How to support the columns of a second level of an hypaethral building with reduction in space by height?

In this multi-leveled hypaethral building model there is a problem that the columns of the second floor aren't directly situated on the columns of the first floor. How to support the columns of the ...
somo's user avatar
  • 1
0 votes
0 answers
34 views

With respects to the North Channel (Irish Channel), has a causeway ever been proposed for a crossing?

Former UK Prime Minister, Boris Johnson raised the issue of a bridge between Scotland and Northern Ireland; his impromptu estimate of £15 billion was probably a little wide of the mark. The issues are ...
shackec's user avatar
0 votes
0 answers
33 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 ...
ChewingGumXpert's user avatar
0 votes
0 answers
52 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) ...
ChewingGumExpert's user avatar
0 votes
0 answers
23 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 ...
user586254's user avatar
0 votes
1 answer
568 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) ...
abouttostart's user avatar
0 votes
1 answer
226 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)...
Kumar's user avatar
  • 1
0 votes
0 answers
41 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'...
SSan's user avatar
  • 101
0 votes
0 answers
576 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. ...
Amit 's user avatar
  • 135
0 votes
0 answers
93 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 ...
Alex M's user avatar
  • 21
0 votes
1 answer
125 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 ...
Steve H's user avatar
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 ...
Gennaro Arguzzi's user avatar
0 votes
1 answer
128 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 ...
machinaut's user avatar
  • 101
-1 votes
2 answers
116 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?
San's user avatar
  • 1
-1 votes
1 answer
45 views

Shear connections

Question: which of the three shear connections (beam/column) below will require diagonal bracing?
San's user avatar
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