Skip to main content
6 votes

Why does a simple pin-ended triangular (arched/curved) beam deflect more due to secondary effects (non-linear analysis)?

Play around with a simple version of this structure, made from a sheet of paper fixed in a slight curve, and see what happens when you apply a load to the mid point. If the first example, any ...
alephzero's user avatar
  • 12.6k
6 votes
Accepted

Deflection of a cantilever beam composed of separate (not bonded) planks

in a cantilever beam the deflection is $$\delta_{max} = \frac {PL^3}{3EI} $$ In this case assuming free sliding between the planks the load P is going to be supported equally between the 3 planks. ...
kamran's user avatar
  • 22.6k
5 votes
Accepted

Where is the axis of bending for a box lifted by a crane?

If by axis of bending you mean box functioning as a beam and also the top and walls and bottom of the box are integrated and work like a hollow rectangular beam, then the neutral axis is at the mid ...
kamran's user avatar
  • 22.6k
5 votes
Accepted

Why does rebar in reinforced pre-stressed conrete reduce in deflection if compressive stress is applied to member?

Prestress creates an upward deflection on the beam due to the combination of elastic strain, creep and shrinkage in the unloaded beam. This negative deflection will bend back to a straight stance or ...
kamran's user avatar
  • 22.6k
4 votes
Accepted

Structural Frame Real World Deflection

Yes the left column would deflect in the real world. The reasons are: 1) Eccentricity of the connection / column: In reality the load will not be transferred perfectly to the center of the column ...
atom44's user avatar
  • 2,651
4 votes
Accepted

Round beam deflection under its own weight

No, as the Wikipedia article states, a uniform load's unit is in "force per unit length" ($F/L$), which means it is a load applied along a given distance. So, if you have a 102 g beam, it weighs ...
Wasabi's user avatar
  • 13.1k
3 votes

Why does rebar in reinforced pre-stressed conrete reduce in deflection if compressive stress is applied to member?

Concrete is strong in compression but weak in tension. In tension, it will crack at a much lower stress than the allowable compression stress. A reinforced concrete beam without any prestressing will ...
ingenørd's user avatar
  • 1,288
3 votes

Deflection of a cantilever beam composed of separate (not bonded) planks

Thanks to @kamran for his answer. I simulated the problem in ANSYS student v19 to verify his approach. In the pictures below, the upper beam is solid, the middle one is split into two segments and ...
Yaniv Ben David's user avatar
3 votes

Why does a simple pin-ended triangular (arched/curved) beam deflect more due to secondary effects (non-linear analysis)?

The answer of alephzero is spot on. I just want to mention that the arch structure is particularly sensitive to 2nd order effects when it is shallow (say depth to span ratio ~0.1) . It's not ...
minas lemonis's user avatar
3 votes
Accepted

Deflection of thin plate with 1 free edge and deflection > thickness

You are correct that this problem falls within the category of 'large-deflection' problems since the deflection is larger then about $\frac{t}{2}$. To correctly analyse a plate under large-deflections ...
atom44's user avatar
  • 2,651
3 votes
Accepted

How to calculate deflection of a cantilever beam subject to point loading

Both answers are incorrect. Your answer to (a) would imply that the bending moment is equal to zero at $x=0$ and increases linearly until $x=L$. This is only true if you put $x=0$ at the free end of ...
Wasabi's user avatar
  • 13.1k
3 votes

What plastic material is best for a snap-fit design?

I have designed parts which are snap-fit using Polypropylene. They work well, but the best advice I can give make one (or a few) in one or more material and do some life testing to figure out which ...
am304's user avatar
  • 1,841
2 votes
Accepted

Undesired vibration of a beam under foot traffic

An exact theoretical analysis of this is rather involved so I will take an approximate approach. We can idealise the beam as a single degree of freedom (SDOF) dynamic system. The theory behind this ...
atom44's user avatar
  • 2,651
2 votes
Accepted

What is the formula for deflection of an end-loaded cantilever rod beam?

For a cantilever with a point load at the free end, the deflection at that free end is: $$\dfrac{WL^3}{3EI}$$ Handbook of Structural Steelwork - 3rd edition where $W$ = point load $L$ = beam ...
AndyT's user avatar
  • 3,143
2 votes

Deflection of a stack of disks under applied force/pressure

Between disc 1 & 2, there is a reaction force on disc 1 which is not going to act on the edge rather at the distance of 2nd disc edges. This means you need to have the model of 1st disc bending ...
Nagarajan's user avatar
2 votes
Accepted

Why do we increase the minimum beam/slab depth if we increase the grade of the reinforcement to control the deflection

The principle behind that table is that you will be doing a strength calculation in any case and need the table for a guideline of whether deflections or bending strength will be the design driver. ...
ingenørd's user avatar
  • 1,288
2 votes

Deflection of a cantilever beam composed of separate (not bonded) planks

Although I agree with @kamran, I have another way of thinking about it The deflection of the structure is $$\delta=\frac{P\cdot L}{3\cdot E\cdot I}$$ The only difference in this problem between then ...
NMech's user avatar
  • 24.4k
2 votes

FEA: What is the difference between a spider of RBE2s and multiple SPCs

... the spider is the more accurate method as multiple SPCs make the model overly stiff ... That depends what you are trying to do. Remember that (1) the RBE2 does not have to connect to all 6 DOFs ...
alephzero's user avatar
  • 12.6k
2 votes

Deflection In Multistory Structure

In US, The American Society of Civil Engineers (ASCE) Structural Engineering Institute (SEI) publishes Minimum Design Loads for Buildings and Other Structures (ASCE/SEIĀ 7-10). Section 12.8.3 Vertical ...
kamran's user avatar
  • 22.6k
2 votes

How can I find deflection in a member that doesn't have a constant area moment of inertia?

There are two aspects to this problem that are each significantly more complicated than what you seem to have tried so far: The angle of 45 degrees by which the cross section is changing dimension is ...
ingenørd's user avatar
  • 1,288
2 votes

How much deflection can/should I accept with Aluminum Extrusions?

In general the acceptable deflection has to do with perception. What I mean by that is, if it is possible to perceive the deflection of the structure. Therefore it is usually presented in building ...
NMech's user avatar
  • 24.4k
2 votes

Castigliano's theorem for deflection

It is because of the boundary condition - point B is fixed against deformation, so if you apply the load at point B, it results in zero strain, thus zero energy.
r13's user avatar
  • 8,237
2 votes

Need to find beam deflection of a steel tube

The formula is shown below. For load in the mid-span, set a = b. You need to figure out E, I yourself.
r13's user avatar
  • 8,237
2 votes

Which beam deflects and twists more, open section or closed section?

For a transverse force on the tip of the beam the deflection will be the same because M/I=E/R. For a torque on the end of the beam about the long axis (call it the X axis) of the beam the I beam will ...
Greg Locock's user avatar
1 vote
Accepted

Pin joint system displacement question

This is not a statically determinate system. To find how the load splits between the members, start by finding their stiffness. Since the materials and cross-section areas are the same, the stiffness ...
alephzero's user avatar
  • 12.6k
1 vote

Where is the axis of bending for a box lifted by a crane?

As implicitly mentioned in @kamran's answer, the neutral axis (which is what I understand by 'axis of bending') is constant regardless of the applied load. That's because the neutral axis is a ...
Wasabi's user avatar
  • 13.1k
1 vote

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

I calculated the same but I got a different value from yours. The maximum deflection that I got is .31818 mm at x = 3.25 m The constant from the double integration method is -23.189. I checked it with ...
Nelson Raj's user avatar
1 vote

Deflection of Rectangular Plate with 2 Simply Supported Edges

This Plate is simply supported. You may find the deflection of the plate by using simple beam theory in this particular case. If this doesn't work for you, you may also check Timoshenko theory of ...
Sergey Dukman's user avatar
1 vote
Accepted

Bending equation and max deflection of UDL and multiple point loads

Note: I'll be using the following notation: $q_1, q_2$ are the distributed loads (where you use $w$, which I reserve for deflections) $L = c + 2(a+b)$, the total length of the span $\ell = a + b$ I'...
Wasabi's user avatar
  • 13.1k
1 vote

Deflection of a stack of disks under applied force/pressure

The Radius of curvature on a beam bent under moment is $1/r = m/EI $ If we use this just as a rough model the m affecting each disk gradually becomes smaller as we go up and radius of curvature ...
kamran's user avatar
  • 22.6k

Only top scored, non community-wiki answers of a minimum length are eligible