Questions tagged [structural-engineering]

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

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What really is the difference between allowable stress design and ultimate limit state design?

I'm trying to understand this difference. From what I've read, ASD basically deals with making sure the stress in a structure does not exceed a certain limit, the yield stress of the material. It ...
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2answers
22 views

Meaning of this sentence in lecture notes about buckling of nonlinear column

Above picture is from my lecture notes. It deals with a column subject to axial load, which follows Euler buckling theory. The material is nonlinear, approximated by two lines as seen in the stress-...
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Statically determinate system

he exercise is taken from linear algebra and its applications, prof. G.strang exercise 2.4.8 truss I have already found that: m=n=8 → system is statically determinate, therefore solvable by ...
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45 views

What thickness do I need for a 30x30 (cm) aluminium plate to hold 350Kg on three points?

I want to make a strong connected weight-scale Arduino project, for which I already own 3×350Kg sensors (red). I plan to make the plate (green) around 30cm×30cm in 99.5 Brut aluminum, with my three ...
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11 views

Steel floor for a paint booth

I am attempting to cover an old half pit in a service station and convert the space into a paint booth. If i put a grid of 2ft x 4ft under the steel, how thick of sheet steel would I need to support ...
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25 views

deformable object squeezing

I have the problem following. There is a deformable sphere with radius r. It goes inside a constriction channel with d*d cross section. Assuming that the sphere volume is constant and the sphere shape ...
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34 views

Why loads in serviceability limit states usually don't include factors of safety?

For example, characteristic combination found here: It can be seen that the dead loads $G_k$ are taken as the characteristic values instead of multiplying them by some factors of safety as in the ...
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1answer
31 views

How to design two reinforced concrete beams crossing each other at the same level?

If I have two beams of same stiffness and present at same level, how can i decide which beam is supporting the other beam? What would the moment diagram look like? How to design both the beams? How to ...
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3answers
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Why doesn't prestressed concrete crack at the top before the load is applied?

In prestressed concrete, we add a tensioned steel cable at the bottom half of the beam to balance out the tensile forces resulting from the applied load. But before the load is added, doesn't the beam ...
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double integration of continues beam to find the deflection at mid span [duplicate]

does any one know how to derive the deflection equation of a continues beam of three span of equal length and equal UDL load some of the steps of this explanation I didn't understand it Here's a link ...
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27 views

Continues beam deflection

does any one know how to derive the deflection equation of a continues beam of three span of equal length and equal UDL load Here's a link these two pictures shows my tries to solve the question
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1answer
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how can i find Spectral Acceleration (Sa(T1; 5%))?

I want to do incremental dynamic analysis (IDA) for my project and for hunt and fill algorithm i need the 5% damped Spectral Acceleration at the structure’s first-mode period (Sa(T1; 5%)) . Can i find ...
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1answer
23 views

Derivaiton of maximum deflection of a cantilever beam with intermediate load

I am trying to derive the maximum deflection of a cantilever beam. L is the length of the beam and a is the where force is applied. For the case 0<x<a, I use the method below and it gives me the ...
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correcting mode shape for modal damping

I have mode shapes and eigen frequencies from FE simulation. I have modal matrix and eigen frequencies corresponding to each mode. The mode shape is mass normalized. I am required to correct each ...
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3answers
82 views

How can deflection and spring constant of cantilever beam stack be calculated?

How can I calculate some properties of a stack of 2 bonded cantilever beams like in the image? Especially I am interested in the spring constant and deflection with force on random locations. However, ...
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22 views

Design of T-Beam

Please design a T-beam section size such that hf ≥ 125 mm, bw ≥ 200 mm, be ≥ 500 mm, d ≥ 300 mm, the concrete f'c strength is 25 MPa; the calculated concrete shear strength Vc that can be provided is ...
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1answer
26 views

How do hooks/bends cause bearing stresses in reinforced concrete?

Can someone please explain the exact mechanics of development of bearing stresses in concrete on account of bending of steel reinforcement and/or providing of hooks at the beam-column junction for ...
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1answer
23 views

Can anyone help me with the concept of bearing stresses in steel reinforcement in Reinforced Concrete?

When there is tension reinforcement(steel) embedded in concrete, does it not also undergo bearing stresses on account of the weight of the concrete and other forces which are acting above the steel? ...
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1answer
35 views

How do you account for buckling in a brick and mortar structure?

I was thinking about this question from quite a while back about height limits of a brick and mortar tower. One answer pointed out that, due to the high compressive strength of brick, one could build ...
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1answer
23 views

How to determine the fixed end moment?

I was trying to compute the fixed end moment for the beam (given below) using equilibrium equation for x, y displacement and moment but there are 4 unknown variables reaction and moment at both ends ...
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31 views

Program name of this buckling modeling

My instructor sent this solving with program that I don’t know the name , does anyone know the name of the program ?
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5answers
500 views

How does the parabolic curve help in the integrity of a suspension bridge?

Why do suspension bridges need to be parabolic? Why can't they connect the towers directly? Would it not use less material and cost less?
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40 views

Do any roller coasters actually use the brachistochrone curve?

Not sure if this is the right place to ask this. But I'm assuming roller coasters are related to engineering. I know that in theory, the brachistochrone curve is the fastest way from point A to point ...
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1answer
36 views

What is the best way to fasten securely a load onto a hollow brick?

Due to the ongoing COVID pandemic, I decided to put a basketball hoop on one of our outside walls, so that me and my son can stretch a bit. The problem is that the wall I plan to put the basketball is ...
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1answer
33 views

What's the best FEA software if you want reliable data [closed]

What's the best FEA software if you want reliable data and are a beginner? So, I've never used FEA software before so I want to learn one that is powerful and relatively approachable. I am most ...
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2answers
28 views

Modelling an annular ring

I am trying to model the shear failure of an annular ring with a uniformly distributed pressure, the ring is hashed out. I am not sure how the problem would be modelled as part of the ring is ...
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1answer
31 views

3D printer printing out cotton-candy like material after repeated use

I recently purchased a JGMaker Magic 3D printer. It worked well for about 3 months [first picture], but now it is having a lot of trouble. As you can see in the images below, when printing new pieces, ...
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2answers
32 views

How effective are screen protectors?

Screen protectors are supposed to protect your devices from nicks and scratches, as well as the stress of impacts which might otherwise lead to cracks or shattering. The fundamental principle behind ...
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31 views

Main Beam Cut and Settled at Some Point What Are The Options?

It looks like someone cut the main beam and there was settling at some point in the past. There is a noticeable dip and cupping in the floor near the main beam in the floors above. Why might someone ...
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2answers
34 views

Why is there tension in outstand flanges of compressed elements?

Above table is from Eurocode. According to the table, the stress distribution in a flange of a beam can be negative in part of the flange when the part is subject to bending and compression. Why is ...
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21 views

Using a thermos flask as a vacuum chamber

I want to create a vacuum chamber (-900 mbar) that can withstand heat (120°C). I thought about using a pressure cooker similar to most DIY vacuum chambers, but then thought about using a large food ...
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1answer
22 views

Meaning of $\lambda_1$ factor in Eurocodes

I'm reading here on buckling resistance of members according to Eurocode. Non-dimensional slenderness is defined as: $$\bar{\lambda}=\frac{\lambda}{\lambda_1}$$ where $$\lambda_1=\pi \sqrt{\frac{E}{...
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1answer
50 views

$\lambda_1$ factor in context of buckling

I'm studying this text about buckling. There a factor called $\lambda_1$ is defined: $$\lambda_1=\pi \sqrt{\frac{E}{f_y}}=93.9\sqrt{\frac{235}{f_y}}$$ But how was that last step made? Where did that ...
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1answer
19 views

Where does the equation for shear stress of a rectangular beam (3/2 V/A) come from?

I am writing a report and need to reference every equation used. I am using the equation for shear stress in a rectangular beam of tau = 3/2 * V/A but am not sure where it came from or what textbook ...
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22 views

Elasticity values in stiffness matrix?

Stiffness, k, is defined by $$k=\frac{Force}{deformation}$$ if you insert this into formula $deformation = \frac{\text{Force}\times\text{ Length}}{AE}$ you get $$k=\frac{A.E}{L}$$ where E is ...
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Why can we assume the stress distribution under a pad footing to be linear?

In structural engineering, a pad footing under a normal load N and a moment M is assumed to have a linear distribution of stress under it. Is there any intuition why we can make this assumption?
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38 views

What is the difference between plastic and compact cross sections?

I'm studying beam cross section classifications here. It is explained that the difference between plastic and compact cross sections is that while both do develop their plastic moments, only plastic ...
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5k views

Why are engine blocks so robust apart from containing high pressure?

Lately, I've been pondering why some engine blocks are so bulky, I always thought intuitively it was because they had to last a long time whilst containing thousands of combustion cycles but the more, ...
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1answer
36 views

Help needed: dimensions and weight of concrete base required

We have an art project that involves a steel structure. The structure weighs around 200KG; it is 3 meters tall and 1 meter wide. It will be exposed to wind outdoors of around 38m/s. What are the ...
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1answer
55 views

What is meant by the rotation capacity of a cross section?

I'm reading about classification of beam cross sections here. It is said: The ratio of the ultimate rotation to the yield rotation is called the rotation capacity of the section. The yield and the ...
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57 views

Choice for HEAVY blacksmith table

I have an old 7,000 lb. blacksmith table (I had it weighed at truck stop). Similar to the one this man has: Sorry for the size of the pic. I need to lift one end the way he is doing and I have a farm ...
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1answer
41 views

Which is stronger, a round sign post or a square-cross-section sign post?

Which is stronger, a round sign post or a square-cross-section sign post? I will be using one or the other to hold the top corner of a shade sail. I tried an aluminum pipe but a strong wind on the ...
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1answer
44 views

Stress Concentration Factor – Why a Specific Range?

I was trying to find the stress concentration factor for a specific situation and I found two different resources for it. Ref: Shigley's mechanical engineering design Ref: Roark's Formulas for ...
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1answer
67 views

Is using a 4x4 bolted to the face of 2x12 enough?

I am working on a project that has three 2x12’s supporting a load of 12,000 lbs. similar, but not exactly, to how joists support a house. The 2x12’s are supporting about 6,000 lbs. on each end. The ...
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39 views

Sunlight-powered device set to change world: will it work? [closed]

Vast areas of desert sand are being shone on upon by the sun. Now that's some ENERGY! Using this proposed apparatus: Sunlight over large area is concentrated on steam chamber, where water turns into ...
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1answer
32 views

unbraced length of the compression portion of a long member

I am designing a truss. the bottom chord in the first two panels at each end or at the supports are in compression and the rest of the bottom chord is in tension. there is no lateral bracing along the ...
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1answer
48 views

What are the disadvantages of cylindrical residential buildings? [closed]

I've been spending an hour finding references for my research, but unfortunately I can't see useful information. So, I would really appreciate it if you could give me some references about the ...
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100 views

Shear force and bending moment

Today I came across this question and I can't sleep thinking about how to solve it. How do I find the principal values and sketch a shear force and bending please see my attempt as I'm not sure if ...
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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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1answer
40 views

Steel beam size

I'm a customer not an engineer! I had 2 sets of drawings for a project to put in bi fold doors. The original drawing had a beam of 230mm and then the engineer sent a revision with a beam 260mm. The ...

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