Questions tagged [beam]

Questions about the theory and applications of structural elements designed to resist bending.

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1answer
34 views

steel beam type and size for a clothesline

I have four posts in a square formation. Posts are also square. I want to bolt a beam between two posts on the left and a beam between two posts on the right, and than run some wire between the beams. ...
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1answer
44 views

What is the difference between W, S, I, H sections?

W and H sections look pretty much the same. S and I sections have their flanges rounded. What difference does this rounding make, why would an S-section be used instead of W-section for example?
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29 views

How to choose the dimensions for a prestressed I-beam?

I need to design a simply supported symmetric I-beam (for a school problem). However, I can't find much information about the selection of the section or if there exist any standards for that. the ...
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1answer
136 views

How to analyze a bent beam: Stress concentration?

I am analyzing a beam, that has a bend in it. Intuitively and inspecting FEA results using a linear solver, there is a stress concentration at the bend of this I-beam. The part was not a straight I-...
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1answer
51 views

Do the floorboards in timber beam floors have a structural function?

Timber beam floors with perpendicular timber floorboards as indicated in the drawing below are common throughout northern Europe. The floorboards are nailed onto the beams and are quite substantial ...
2
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1answer
58 views

Twist “buckling” critical load

I have a very long beam which is subjected to a torque (I have the moments and shear forces with respect to X along the beam). I can calculate the critical load when the beam would bend if it was ...
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1answer
46 views

Big Beam LVL or Glu Lam load capacity to support a gymnast

I need help knowing if I am selecting the correct wood beam. The load will be all near the center and a 250 pound man will be doing pull ups on it. I would estimate a 1,000 pound dynamic load to be ...
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1answer
237 views

Calculating area moment of inertia for a beam with underslung plate?

In a number of designs, a beam will have an underslung welded plate attached, as shown below: In this sketch, a symmetrical standard steel beam/column of dimensions H1 x B1, with web and flange ...
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1answer
67 views

Modification of Beam Equation for Thin Sheet

I am trying to determine the modulus of elasticity (Young's Modulus) for a rigid paper sheet. The issue I am having is that my results for the Young's Modulus change depending on what orientation (...
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1answer
92 views

simple supported Beam deflection question involving two point loads and a UDL

so i was given a problem by my mechanical principles teacher to work out the max vertical deflection of a simply supported beam with two point loads one a distance of 5.3 away from A and another 5.9 ...
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1answer
116 views

MSC Nastran - BAR3/4 elements - can't assign any properties

I'm modeling a pipe in Patran, and I'd like to try bar3 and bar4 elements. I assing the properties CBEAM to my geometry, but when I create the mesh, Patran tell me bar3 and bar4 don't support that ...
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2answers
101 views

Maximum induced bending stress within the beam

The Maximum induced bending stress within the beam. Given that: $$\frac{My}{I}$$ The beam depth is 300mm, the width is 150mm. The beam is an I section beam with a 5mm wall thickness. My ...
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22 views

Centroid of unsymetric bending in T-section

Can anyone please explain how this 24 is coming while calculating the x-cordinate of the centroid.
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1answer
42 views

RHS beam deflection with support on one end

A 1400 mm long galv steel beam, size 40x20x2. 80 mm of the beam on one end is welded in flat position to a platform. How much weight can I put safely on the other end? What if instead of being flat ...
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0answers
18 views

Pin connection on beam - FEA analysis

I am establishing a MatLab FEA code for determining the stiffness of a structure. Diagram of the structure is added below. I have established a code for determining the stiffness of the structure, but ...
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1answer
112 views

Beam stiffness matrix with sliding end release in arbitrary angle

I know how to get the stiffness matrix of a beam with any type of end releases (hinges and rollers) by applying Guyan reduction (static condensation) to the beam stiffness matrix in local axes. ...
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2answers
48 views

Boundary conditions for this beam deflection problem

consider the diagram above. I know that deflection is described by the equation $$EI\frac{d^4y}{dx^4}=p(x)$$ where $L$ is the length of the beam, $E$ is the Young's module, $I$ is the moment of ...
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2answers
66 views

Loadcell / strain gauge sizing for a joist

I am looking to use some load cells (foil based type) to detect presence for home automation within in a room. I was looking to mount some loadcells to the joists for the floor (UK Based house so ...
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2answers
296 views

Degrees of freedom of an internal hinge in plane beam?

What are the degrees of freedom of an internal hinge in a plane beam? I understand that the bending moment=0, does this mean there is no slope either? Or does it have both degrees of freedom of ...
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1answer
163 views

Should one use multiple elements through the thickness with multiple materials?

To get realistic results from a FEM calculation, it is common (or so I've been taught by someone who may not be up to date) to use at least four or five elements through the thickness of a beam or ...
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1answer
788 views

Design of transverse reinforcement in a wide beam

Besides satisfying nominal bar provision in the code, is there any special requirement in the provision of transverse reinforcement to ensure that the longitudinal reinforcement is fully effective in ...
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0answers
26 views

Sign convention for deflection and slope of beam?

What is the sign convention for deflection and slope of a beam as shown in the diagram below? When I derive the formula using Euler-Bernoulli for deflection and slope myself, I end up with - ...
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1answer
53 views

Why is there a row of circular holes in this concrete beam?

The reinforced concrete beam (approximate dimensions 36" x 18") shown in the image below has a row of circular holes at 3/5ths of the height of the cross-section at approximately 300 mm centres. My ...
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2answers
48 views

Bending moment in Euler-Bernoulli finite Element

I'm trying to calculate the bending moment distribution on a fixed-fixed Euler-Bernoulli beam. It is known that interelement nodes show different values for the bending moment. What is customary to do ...
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1answer
26 views

Shear flow for unequal leg channel

How does the sine part i.e. $\dfrac{\ell\sin(\theta)}{2}$ appear in the calculation of shear flow ($q$)? I mean, if I'm not mistaken, the sine part is the distance from the x-axis to point D, but how ...
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2answers
33 views

Dimensioning of beam pressed by screw in assembly

I need help dimensioning a screw-beam system of a press. I built one prototype but the beam is bending too much. Below is a sketch of my press. In the middle it has a fixing screw which presses ...
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3answers
699 views

Tolerance for Beam With Cope End

I need to have some beams fabricated with copes on the ends. They will be set on top of existing steel trusses, and used to replace undersized purlins to shore up existing rafters (hence the need ...
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2answers
10k views

Determining stiffness of a beam w/varying moment of inertia

I need to calculate $K$ or equivalent stiffness of a beam that has a varying $I$ across its length. $I$ has been given to me as a function of $x$, or length. I have been unable to find a proper ...
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2answers
56 views

What is the strongest way to fasten 8020 extrusions in this arrangement?

I am making a project using 10mm aluminum extrusions. I am trying to connect all three extrusions like the picture below shows and I am going to make my own bracket (in red) out of aluminum since the ...
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2answers
5k views

Multiple Varying cross section beam deflection

How do we calculate the deflection of a cantilever with two or three cross-sections, and different forces acting at the end of each section?
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2answers
43 views

Deflection and stress in a freely rotating beam

How do I calculate the deflection and stress of a beam that is rotating freely (for example in space) when a moment is being applied to it, for example by rocket motors at the ends of the beam?
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1answer
209 views

Problem while solving for the moment of a cantilever beam

As in the first image, Moment at any point between C and B should be 0. But when I try to solve it by substituting equal and opposite forces at end C so that anti-clockwise moment of $F(l-a)$ and ...
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2answers
3k views

Transfer of moments in beams with internal hinges

We have a beam with 1 internal hinge just like the picture. We know the internal hinge can not transfer moments between AB and BD. We know the 30 kN force makes some moments on BD & AB. If B (...
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140 views

Problem with cantilever beam and yield strength

Hey, I make a project in which I use a cantilever beam with distributed equal load across the whole beam and I'm using the formulas above to calculate the displacement, moment... My specifications ...
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1answer
62 views

Maximum I-beam girder S12x31.8 span

Does 200lb/in of load on a S12x31.8 over 15 feet seem reasonable? I'm having a tough time trusting the numbers. Two story house with an attic as below. Dotted lines show load bearing walls W1 and W2. ...
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1answer
1k views

How to rate a davit beam?

What forces are relevant when it comes to a davit lifting arm with a support? I'm not sure how to take the weight of the davit into account or how to calculate the max stress/strain on the system. ...
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2answers
29k views

How to deal with a point force acting right on the hinge of a beam?

I have been attempting to solve a question where there is a point force acting on the hinge of a beam. Here is the problem: I am not sure how to deal with the 2 kN point force at $C$ ($C$ and $E$ are ...
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3answers
4k views

Why does a continuous beam have less deflection than a pair of simply supported beams?

Inspired by this question, and also this answer to a separate question. I have two beam models, one with two independent spans (a full hinge), another is a continuous beam over both spans (only ...
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3answers
192 views

Buckling vs. Yielding Failure of Columns

As I have been working through examples of construction projects, I've noticed that in nearly every case of a structural column (sample size considers only homogeneous material columns, no composite ...
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1answer
41 views

What criteria must apply for torsional effects on this beam to be ignored in calcs?

I'm interested in how to work out whether torsional effects can be ignored or not, in calculating the adequacy of a given steel beam in the following idealised eccentric scenario. Or, equivalently, ...
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2answers
97 views

How to get the bending moment for tie member?

How to get the bending moment for tie member? For the tie member, there is no uniformly distributed load and concentrated load, right? How to get the bending moment? The tension force was found to be ...
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2answers
153 views

What is the name of this section?

I am trying to identify the section designation so I can determine it's properties. I have looked under "C 150 x 100 x 40" but I can't find its properties or what it's correct designation. What is ...
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2answers
73 views

Pin joint system displacement question

A pinned system comprising bars of the same material and cross-sectional area is subjected to a vertical load P. I am required to form a relationship between FAB and P. The first part of the ...
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2answers
325 views

What does it mean when actual member reaction is 100% of allowed?

I received construction documents for an extensive residential remodel and looking at the engineering there's a glulam drop beam with a calculated member reaction that is 100% of allowed (3965 lbs @ 5 ...
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1answer
61 views

Why are variations zero on the endpoints of a beam?

On Wikipedia derivation on Timoshenko beam equation we arrive at this: $$ \delta U = \int_L \left[-M_{xx}\frac{\partial (\delta\varphi)}{\partial x} + Q_{x}\left(-\delta\varphi + \frac{\partial (\...
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29 views

How to write the equilibrium stress equations for a hollow, rectangular beam?

I have a system consisting of a hollow, rectangular cantilever beam (pictured below). I'd like to write the equilibrium stress equations à la the Cauchy Stress notation. How do I account for the ...
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1answer
413 views

Torsional rigidity D vs torsional rigidity factor k vs torsion constant J

I have a physics background so apologize my ignorance. I'm confused by the constants $D$, $\kappa$, and $J$ when it comes to torsion of beams. From what I understand $\kappa$ and $J$ are the same ...
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54 views

Rotational bending in Timoshenko beam theory

The Wikipedia article on Timoshenko beam theory says: The model takes into account shear deformation and rotational bending effects, I am familiar with shear deformation, but what is meant by "...
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1answer
392 views

Along which direction is the area moment of inertia taken in bending moment equation?

Is it in the same direction of the applied load or in the co-planar perpendicular direction to the load applied?
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4answers
8k views

How do you calculate Mcr (critical buckling moment)

When designing a steel beam, the resistance to buckling is related to Mcr; the elastic critical moment for lateral-torsional buckling. However the Eurocodes give no advice about how to calculate this ...