Questions tagged [beam]

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

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1answer
36 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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1answer
78 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. When I was learning about ...
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32 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
84 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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52 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
51 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
57 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
85 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
150 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
58 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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1answer
102 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
56 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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1answer
107 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
685 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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2answers
271 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
58 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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26 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
199 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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47 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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2answers
3k 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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1answer
71 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
7k 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 ...
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3answers
65 views

Do internal / external stresses affect modal frequency?

Imagine a cantilevered beam, fixed on one end and with a tension line connecting the other end to ground (e.g. perpendicular to the length of the beam). If I increase the tension, does the modal ...
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3answers
91 views

Composite beam- increase in bending moment due to reinforced steel

While trying to solve this question and using the flexure formulas of bending for composite beams I obtained a lower value of moment for steel than for aluminum.How is that possible?
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88 views

Reaction Forces on a Beam

I'm new to beams and I'm struggling to find the correct vertical reactions forces at support C and E. The correct answer is 8.58 kN for $V_c$ and -3.58 kN for $V_e$ However, when I ...
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3answers
85 views

Why does concentrated shear force on a beam influence the whole beam?

This might be a silly question but can someone explain how this shear force on the right side of the beam causes Qy throught the whole beam? I understand it mathematically but not conceptually so I ...
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185 views

Simple beam deflection of cantilever beam

Recently I had need to prove the beam deflection equation for a simple cantilever beam with a point load at the end. The equation would be in reference to the Euler-Bernoulli theory taught in most ...
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2answers
199 views

Neutral axis in canteliver beam at support

First, I thought the neutral axis would just be the y bar which can be obtained from the centroid of the cross-section but is different. I have tried letting the net moment at the wall = 0 and the ...
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2answers
166 views

Statically indeterminate fixed-pinned beam problem

F=32KN; Mf1=60KN-m; Mf2=-58KN-m; g=30KN/m I need to solve this using Force method. Find the reaction at the pinned end.
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1answer
154 views

How to measure the unbraced length of lateral torsional buckling for negative moment in a W-shape steel beam?

I have a W-shape steel beam that is fixed-fixed and the top flange is fully braced for lateral torsional buckling. The negative moment at the end controls the design and there is no lateral bracing ...
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2answers
364 views

Simple beam with cantilever ends

I'm trying to find the maximum bending moment and deflection for this symmetrical simple beam. The formulae I can find, deal with either cantilever beams with one fixed end, or continuous beams ...
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2answers
722 views

Stiffness of a cantilever beam

I am working on calculating the stiffness of a cantilever beam by applying a distributed load. I wanted to ask if the distribution of the load on the beam effects its stiffness. For eg., if I apply a ...
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2answers
97 views

Indeterminate beam with a guide at each end

I've been battling with a statics question (as attached) and can't for the life of me figure it out. I've attempted removing the left side guide joint so then there are only 3 reactions and it should ...
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1answer
91 views

Shear forces along a beam using singularity functions

$\newcommand{\a}[1]{\langle#1\rangle}$ As you can see, the left end of the beam is fixed, and a distributed load is applied to the beam. I calculated the shear forces by conventional means, but when I ...
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1answer
207 views

Can bending moments for a combination of loads on a simple beam, be calculated by adding the individual B.M. of each load?

This problem is about bending moment of a simple beam subject to a mixture of 4 or 5 UDLs and point loads. The beam is assumed to be rigid enough that deflection of the combined load is "small". ...
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2answers
383 views

Shear force and bending moment for continuous span

It's given that L1 = 5m, L2 and L3= 7.5m, w = 8.9kN/m , I am asked to find the bending moment using these coefficient.. Prior to this , i need to have the value of shear force first.Shear force = ...
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37 views

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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1answer
299 views

Shape Functions of beam element with 3 nodes (quadratic element)

For a two node beam element there are four shape functions for four degree of freedom: For a straight three node beam element how shape functions are? Please note that beam is straight and not ...
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63 views

What is the optimal shape of a beam subject to three point bending?

Assume we have a beam with density $\rho$ that is subject to three-point bending according to the image above. The beam cross section is rectangular with the variable height $H(x)$ and constant width $...
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3answers
4k views

Are the points of inflection and contraflexure the same?

In theory of bending of beams, often these terms are used. There are no clear definition present. Most of them contradicting. Which of the property(bending moment and shear force) is zero in which ...
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1answer
76 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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282 views

Derivation of Bimetallic Strip Stress in Roark's Formulas

I am trying to understand some analytic expressions given in the handbook Roark's Formulas for Stress and Strain for bimetallic strip stresses. Namely, Roark's Formulas give the formulas $$\text{...
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1answer
18 views

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 ...
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4answers
886 views

How does stiffness/rigidity affect the bending moment of a beam

My question may sound silly as it’s mainly good sense but I may be mixing things up. Let’s consider a flexible cantilever beam of a given length and material is fixed at one end and free at the other ...
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1answer
67 views

Abaqus Failure for I-Beam Section in Major direction only

For my 4th year dissertation in Civil Engineering I've got to investigate the difference between BS5950, Eurocode 3 and ABAQUS failures. The only thing is, in the BS5950 and Eurocode 3 the failure can ...
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2answers
96 views

Why two identical beams without being pinned together will share half of the bending moments?

As shown above, two identical rectangular beams are placed and NO pinned together. I know each beam has its own neutral surface but why they carry half of the bending moments? I thought the bending ...
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1answer
37 views

What's the second moment of a T beam with a heel? [closed]

The second moment of area of a rectangle is $I_{yy} = \dfrac{bh^2}{12}$ b : base h : height What is the second moment of area of a T beam like this one?
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127 views

Longitudinal impact of steel rod on a steel plate to verify the contact duration

So I'm doing an experiment to verify the contact duration when a steel rod (Material: Mild Steel) is allowed to free fall longitudinally on a steel plate. The arrangement is real simple: The rod is ...
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0answers
55 views

How much (uniformly distributed) weight can this L beam support without bending? [closed]

As you can see in the picture, the L beam is 1in x 1/2in x 1/8in thick x 72in long and is made of ASTM A36 steel. It's bolted onto a vertical upright on both ends. What is the maximum uniformly ...
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2answers
122 views

Resulting torque on the cross section

I have trouble solving part A of the question. I thought the resulting torque would just be 10k * L of the beam.