Questions tagged [beam]

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

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2answers
350 views

Are linear beam element solutions ever exact and when are they used in practice?

In qualifying the results of a Finite Element (FE) beam model, I'm realizing that I dont understand FE beam elements as well as I should. Is there a procedure to determine what order beam element is ...
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2answers
9k 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
529 views

Maximum deflection of a beam, fixed in one end and concetrated load at free end [closed]

A 2 m long beam fixed in one side with a 2000 kg concentrated load at free end. Profile of the beam is HEB100 material S235. I would like to know if the beam will break under this load. If ...
4
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2answers
129 views

Undesired vibration of a beam under foot traffic

The other day I was in the waiting room of a doctor's office in a new building as part of UCLA medical complex. A new construction as part of multi million dollar extension of existing medical complex ...
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1answer
2k views

The boundary condition(s) for a continuous beam

I have a continuous beam across a center column (not sure whether I've draw it correctly or not) The Displacement and force diagram is as shown: The first diagram is the bending moment, second the ...
2
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1answer
9k views

How much weight can an aluminum tube beam support?

I'm building a set of monkey bars for my kids and want to use aluminum tubing (6061 T6) for the rungs. The tubes will be 3 feet long and 1 inch outside diameter. Supported on both ends with a circular ...
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1answer
271 views

Why do we need to take distance of center gravity of a distributed load to a point in order to calculate moment?

From the picture above, in order to calculate the moment of load acting on the beam we take moment $M=\frac{W}{L}×L×\frac{L}{2}$. Why can't we calculate the moment as $M=\frac{W}{L}×L×L$? Why do we ...
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1answer
98 views

IPE Beam weight

In civil engineering calculation I have seen weight of IPE 300 profile expressed in kN/m2 unit. IPE 300 0.42 kN/m2 I know IPE 300 is approximately 42.4 kg/m. How did they calculated that value ...
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2answers
400 views

Deflection of beam, according to thickness of top plate and bottom plate

When there is one rectangular beam like below image, I would like to know how the beam is deflected according to thicknesses of top plate and bottom plate. My concerning cross section patterns are ...
2
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2answers
451 views

Does a concrete slab (deck) cause compressive load in a wall beneath it?

Let's say you build a square reinforced concrete deck at height of, say, 3 meters, with the deck supported by its own steel reinforcement and by four reinforced concrete piers (call them, A, B,C, and ...
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2answers
426 views

Buckling of a cantilever with midway support

I'm trying to understand the implications for buckling and column sizing in the drawings below. A 3000mm 120x60 RHS steel column supports a 350mm horizontal steel beam. The column base and right side ...
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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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2answers
483 views

Solid mechanics: Deflection of a rectangular elastic membrane

I am trying to solve for the deflection $w$ of a rectangular membrane with tension $T$ acting on two opposite edges. These two edges are fixed i.e. $w = 0$. The other two opposite edges are free. The ...
5
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1answer
74 views

Can the thickness of a guard post be derived purely from energy principles?

Consider an ordinary staircase with a banister rail supported by a wall at one end and a steel post of constant profile at the other end. The base of the post is embedded rigidly in the fabric of ...
2
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1answer
787 views

Composite beam calculation

I'm building a shelf out of an Oriented Strand Board (OSB-3), reinforced with steel strip attached to it's bottom side. Please check my calculations for deflection. The OSB thickness is $h_{OSB}=18 \...
7
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1answer
598 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 ...
7
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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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0answers
49 views

Axially Distributed Load [closed]

Given a beam ($\rho, A, l$) rotating with angular velocity $\omega$, find the maximum stress in the beam and its location. I think the maximum stress occurs at the base, because the resultant force ...
2
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1answer
525 views

Problems with shear force diagram in beam model

I am starting to learn how to use ANSYS APDL. So I don't have much knowledge in the software. I have modelled a cantilever beam (with beam188 elements) and the only load that i have applied was the ...
4
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1answer
2k views

Deriving the deflection force equation for a beam that is fixed on both ends

I want to calculate the force-displacement equation for a beam that is fixed at both ends. I think I should use the superposition principle but I am not very sure how to get started. I know that for,...
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1answer
2k views

Strength of a Vertical Round Aluminum Tube with load cantilevered off it?

Can a vertical round tube safely support a cantilevered arm mounted near the top of the tube? ROUND VERTICAL TUBE: 6061 Aluminum 2 inch Outside diameter 0.25 inch wall thickness 3 feet height ...
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1answer
951 views

How determine the compression of a beam with a concentrated end load in the x axis?

I'm studying Electronics Engineering so I have almost no background in mechanics, just a little of statics and dynamics. I have recently started an internship in an investigation center where they ...
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3answers
3k views

Is it possible to convert uniform loads to point loads?

I want to perform a structural analysis on a portal frame using a finite element solver to get a displacements and reactions for a load. The software library only accepts loads applied to node, not to ...
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1answer
49 views

Evaluating replacement pulley axle strength

Repairs... My garage door has counterweights, and the weight of the door is connected to the counterweights with a steel cable which runs over two pulleys. The original (cast iron) pulleys had needle ...
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1answer
863 views

Maximum deflection of a beam with both ends fixed and distributed load

I'm designing a part, and I'm trying to figure out what distance a slot should be from the bottom of the part. For simplicity in analysis, I'm approximating the region between the bottom of the slot ...
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3answers
4k views

Why do we assume the moment is zero when analyzing a simply supported beam?

When calculating the reactions of a simply supported beam under any type of loading we assume that the moment about the reaction points is zero. What if our assumption is wrong and in actual practice ...
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1answer
303 views

Energy of a 3D Timoshenko beam

I am interested in the kinetic energy T and the potential energy U of a three dimensional Timoshenko beam. For a 2D Timoshenko beam the energies read: $$ T = \dfrac{1}{2} \int\limits_o^l \left( \rho ...
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1answer
142 views

Design a beam that is straightened with force on one end

From here, I read that if you have a straight beam, bend it with force at one end, and then create a beam with the resulting curvature, the equal and opposite force won't make a straight beam. What ...
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1answer
2k views

What is the mathematical derivation for shear center of a beam?

For me, it's a bit hard to imagine where shear center can be, and what purpose it serves. The definition I found online is very vague: Shear center is defined as the point on the beam section where ...
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1answer
2k views

Beam Reaction Problem With Hinged Joints

The problem was assigned in my Structural Analysis class, and I am having some difficulty with it. My professor said the problem is "very easy" if we just think about what the fixed end moment on a ...
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1answer
6k views

Can I remove one or both of these support posts in my basement? [closed]

Below is a picture of two supporting posts in my basement. The posts are directly underneath the kitchen/dining room. Would it be feasible to remove one or both of the posts? What would the cost ...
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1answer
1k views

Derivation of beam slope for a cantilever beam

I am trying to derive the maximum beam slope formula $\theta = \dfrac{wL^3}{24EI}$ for this cantilever beam: What method can I use for this derivation? So far I can only find simply supported beams ...
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1answer
146 views

Why is this box girder made of lattice on one side only?

Here's a zoomed piece of this image from Wikipedia That's a close-up of a tower holding a railroad bridge. A and B are two of the four columns in the tower's corners. I assume that they are placed ...
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2answers
3k views

Buckling: Do buckling mode shapes of n > 1 occur in reality?

In the buckling of columns we know that: $$P = \dfrac{n^2\pi^2EI}{L^2}$$ The smallest value of P occurs when $n=1$ which gives a simple buckling shape (one wave): $$P_{cr} = \dfrac{\pi^2EI}{L^2}$$ ...
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0answers
158 views

Finding My, Mz in Complex/Asymmetrical Beam Bending

So I have done a three point loading test on a piece of bone. I have been able to obtain the Second Moments of Area $I_{xx}$, $I_{yy}$, $I_{zz}$. As well as the centroid. I also have the data from ...
3
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3answers
961 views

How is shelf deflection determined?

Question: How is shelf deflection determined? More specifically, how is the deflection determined when one or more edges of the plate have reinforcing edging applied to them? I have been able to ...
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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 ...
3
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2answers
723 views

Why is there a moment at the cross section end when you cut a body?

I just started mechanics of materials, and it seems that my knowledge from statics has gotten rusty over the summer. But there was a new concept introduced in the first example problem today. There ...
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1answer
4k views

Is it acceptable, with reinforcement, to notch a floor joist more than 1/6 of the depth?

IBC 2308.8.2 states a rule of not notching more than 1/6 the depth of a wooden joist (emphasis added): Framing details. Joists shall be supported laterally at the ends and at each support by solid ...
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2answers
3k views

Unbraced Length for Lateral Torsional Buckling vs. Yield Strength

The AISC 360-10 Specification for Structural Steel Buildings gives provisions for calculating the maximum unbraced length of a compression flange that separates yielding moment from lateral torsional ...
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3answers
2k views

Strength of a welded steel gate with vertical bars vs. crossed diagonal bars

Looking for some hints on how to create a rough estimate for the following problem. Given two steel gates with the same dimensions, same material - e.g. everything is the same. The only difference ...
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2answers
27k 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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1answer
1k views

Large deflection of a cantilever beam with distributed normal load

I have a strip of stainless steel encastree'd at one end to which is applied a constant pressure on one side, and I need to know what the deflection equation y = f(x) is at equilibrium. If the ...
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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. ...
4
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1answer
142 views

Is the order of operations in jacking a cable relevant?

If you have a prestressed concrete beam or slab and are jacking a cable from both ends, does the order of operations alter the result? For a symmetric curve, the tension diagram along the cable's ...
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3answers
3k views

How do you select the correct area to consiser for first moment of area calculations?

I have just begun studying mechanics of materials and I am struggling to understand intuitively how to select the area in first moment of area calculations. I was hoping someone has a relatively easy ...
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2answers
224 views

Sum up the loads at same position on a deflected beam

I am computing the deflection of a beam. If the length of the beam is 10 m and I have load at the position 4 m from left with force 5 N. Now I add another load at the exact same position with force ...
5
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3answers
2k views

Does the length of a beam change upon deflection?

I have made a Python program in which I have computed the deflection of a beam. I am plotting the deflected beam and am now asked to show the length of the beam. If the beam is not deflected, it is ...
3
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1answer
3k views

Plotting deflection of a beam

I have a formula to compute the deflection of a beam. When I have computed the deflection I get a vector with non-negative elements representing the deflection in each position on the beam. When I ...
5
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1answer
146 views

Effects of constructed tubular/annular beam upon moment of inertia

I would like to construct a hollow beam using either 2"x4" or 2"x6" structural lumber.1 My thought is to take 4 boards and butt them against each other in order to form a square beam2 with a hollow ...