Slope and Deflection of a Simply Supported Beam

In summary, in order to find the Young's Modulus [E] and the second moment of inertia [I] for a beam, you need to know the geometry of the cross section and the material it is made of. These values can be found through measurement or by using tabulated values for common materials.
  • #1
MathsRetard09
22
0
The title is fairly misleading but is within the subject.

I have drawn up a beam of my own as part of my classwork because what bothers me is how you would find Young's Modulus [E] and the second moment of inertia without being given them.

Every question I have looked at has given me the two values combined hence, EI.

The beam I have drawn is 10m long. From the LHE going right, 2m in is a 90kN point load, 3.5m in from LHE is a 8kN point load, from 2m in from LHE across by 3m is a UDL 12kN/m, and 7.5m in from LHE is a final point load of 10kN.

RL = 103,1kN and RR = 40.9kN

In order for me to find ymax at the mid-point of the beam I require an EI value which because it's a beam I made myself, I do not have.

What I have available that I think was relevant:

a sheet that shows me data for different types of beams, with D x B, Ixx and Zxx values.
The bending equation: E/R=sigma/y=M/I
Ixx=bd^3/12

I had a go at this over 6 weeks ago and I got my E and I values, however I've lost the notes that have the calculations on them.

The values I got were, E = 200x10^9N/m and I = 2.9...x10^-3cm^4


All I am asking here for is the route / method taken to find the E and I - not EI, but the two individual values for the beam described above.

I would use symbols to draw the beam here but it would look a mess, but then again:



RL = 103.1kN |_2m_| 90kN_1.5m_| 8kN_3m_| 12kN/m[UDL] _2.5m_| 10kN_2.5m_| RR = 40.9kN

|____|[][][]|[][][]______|______| (Looks similar to this)


So if you know how to do all this just imagine your given this beam mainly to find the slope and deflection - which I know how to do.

Unfortunately you need an EI value, to find that you need both E and I.

If you know the method please share it here because my mind is blank haha.
 
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  • #2
MathsRetard09 said:
I have drawn up a beam of my own as part of my classwork because what bothers me is how you would find Young's Modulus [E] and the second moment of inertia without being given them.
...
Ixx=bd^3/12
...
The values I got were, E = 200x10^9N/m and I = 2.9...x10^-3cm^4


This is posted is in the wrong section, but anyway...

I depends on the geometry of the beam's cross section. Ixx=bd^3/12 is correct for a solid rectangular section.

E depends on the material. Basically you have to measure it, but the values for many materials have already been measured and tabulated. 200x10^9N/m^2 (note, m^2 not m) is a reasonable value for steel.

Google will find you tables of formulas for I for different shaped beams, and values of E for different materials.
 

1. What is the definition of slope and deflection of a simply supported beam?

Slope refers to the change in the angle of the beam at a specific point, while deflection is the vertical displacement of the beam at that same point.

2. How is the slope and deflection of a simply supported beam calculated?

The slope and deflection of a simply supported beam can be calculated using the equations derived from the Euler-Bernoulli beam theory, which takes into account the applied load, the beam's material properties, and its geometry.

3. What factors affect the slope and deflection of a simply supported beam?

The slope and deflection of a simply supported beam are affected by the magnitude and location of the applied load, the beam's length, material properties, and the support conditions at each end.

4. How does the slope and deflection change along the length of a simply supported beam?

The slope and deflection of a simply supported beam typically increase as you move away from the supports and towards the center of the beam, where the maximum values occur. This is known as the beam's point of maximum deflection.

5. What are some practical applications of understanding the slope and deflection of a simply supported beam?

Understanding the slope and deflection of a simply supported beam is important in structural engineering, as it allows for the design and analysis of various types of structures such as bridges, buildings, and other load-bearing structures. It can also help in predicting potential failures or deformations in a beam under specific loads.

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