Deflection of Skid base Frame

[Hafiz_pipeco]

Hi all,

I just new in here and new in Structural engineering..
formula deflection is to calculate 1 nos of RHS, my case for 2m x 2m x 2m(H) using
3 Nos of RHS as a skid frame (refer photos)
could someone teach me how to calculate deflection for water tank details as per below.

Details:
tank size 2m x 2m x 2m(H) = 8000kg / 78.45kN of water
2nd moment : 1870000 mm4
length of RHS 125mm x 50mm x 3mm = 1700mm

photos no.1 is my calculation.

I hope you guys could help me on this,
young modulus = 210000 mpa

 

[BAretired]

Depends where the beams are located. With one in the middle and one at each end, the central beam takes more load than the two outside beams. You could move the exterior beams in so that the load is balanced, but as shown, the middle beam carries 5/8 of the load, or 5000kg. (more than half because of continuity)

If balanced, W = 8000/3 = 2667kg, or 26.2 kN (15.4 kN/m)

M = 26.2*1.7^2/8 = 9.46 kN-m
M_factored = 9.46*1.25 = 11.8

RHS 125 x 50 x 3 is not listed in my steel handbook, but strength should be checked.

Deflection = 5wL^4/384EI = 5*15.4*1700^4/384*1870000*210,000 = 4.265mm

Your calculation is incorrect for the balanced condition because you used the wrong value for W.
W = 26.2 kN or w = 15.4 kN/m

For the condition shown in the sketch, i.e. one beam in the middle and one at each end, deflection for the central beam will be nearly twice the value calculated above.

The symbol σ (sigma) normally represents stress and is defined by M/S where M is the unfactored moment and S is the section modulus . So you have sigma shown equal to the formula for deflection.

If I = 1870000 and d = 125, then S = 1870000*2/125 = 29,920mm^3 and σ = 9.46e6/29,920 = 316MPa for the balanced condition ( and 593MPa for the central beam in the sketch carrying 5000 kg).

Considering the possibility of misplacing the beams, it is recommended to design the central beam for 5000kg load.
Also, considering the likelihood of getting the beam turned the wrong way, I suggest using a square hollow section. There is only one way to place that on the skids. Also, it is less likely to get knocked over.

BA

 

[Hafiz_pipeco]

Dear Sir,

Thank you very much for your explanation, really appreciate this.
To be honest, I just newcomer in this job, and previously I am in Mechatronic background.
This project as a my kick start in my new field.