How to force forces of the floors

  • Thread starter Thread starter texasfight
  • Start date Start date
  • Tags Tags
    Force Forces
AI Thread Summary
The discussion focuses on calculating the forces acting on a steel column supporting two floors in a building, given the downward movements of points A and B. The initial calculations for the forces resulted in incorrect values, with the correct forces identified as P1 = -90 kip and P2 = -130 kip. A key error noted was not accounting for the symmetrical nature of the problem, which affects the force distribution. Additionally, the importance of considering the displacement and separation between the floors was emphasized for accurate calculations. Understanding these factors is crucial for resolving the discrepancies in the force calculations.
texasfight
Messages
2
Reaction score
0

Homework Statement


The steel column is used to support the symmetric loads from two floors of an officer building. Determine the loads P1 and P2 if A moves downward 0.12 in and B moves downward 0.09 in under the applied loading. The steel column has a cross-sectional area of 23.4 in2.
Length of A from the ground = 22ft
Length of B from the ground = 12 ft


Homework Equations


δ=(Force*Length)/(Area*Modulus of Elasticity)
Force = (δ*Area*Modulus of Elasticity)/(Length)


The Attempt at a Solution


Force of A = (-0.12in*23.4in2*30000Kpsi)/(264in) = -319Kip
Force of B = (-0.09in*23.4in2*30000KPsi)/(144in) = -438.75 Kip
The correct answer is Force of A = -90 kip and Force of B = -130 Kip
What did I do wrong?
 
Physics news on Phys.org
The correct answer is Force of A = -90 kip and Force of B = -130 Kip

Well that is not written correctly.
It should be P1 = -90 kip and P2 = -130 Kip ( or vice versa )

You should home in on two things.
Force of B = (-0.09in*23.4in2*30000KPsi)/(144in) = -438.75 Kip
which surprisingly is twice of P1+P2 so you have a factor of 2 that you are not taking into account. You should read every word of the problem. ( symmetrical )

and the displacement.
If I move 10 inches to the right and you move 4 inches to the right we are now separated by 6 inches. Take separation and/or movement of the floors into account, And maybe the distance between the floors would be helpful in one of your calculations.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top