- #1
joemama69
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Homework Statement
A simple beam of length L = 5m carries a uniform load of intensity q = 5.8kN/m and a concentratexd load 22.5kN. Assuming stress allow = 110MPa, calculate the required section modulus S. Then select a 200mm wide flange beam (W shape) from the table. recalculate S taking into account the weight of the beam. select a new 200mm beam if neccessary.
Homework Equations
The Attempt at a Solution
Of first I was trying to calculate the Mmax and i made a boo boo somwhere.
First I found the Moment about A
0 = 5.8(5)(2.5) + 22.5(3.5) - 5RB... RB = 30.25kN
About B
0 = 22.5(1.5) + 5.8(5)(2.5) - 5RA... RA = 21.25kN
Then so determine the Maximum Moment I was preparing the Shear & moment graphs. I took x starting from the left where x = 0 @ A
0<x<3.5
Force sum in y = 0 = RA - qx - V... V = 21.25 - 5.8x
Sum of M = 0 = RAx - qx2/2 - M... M = 21.25x - 2.9x2
3.5<x<5
Force in y = 0 = RA - qx - P -V... V = -1.25 - 5.8x
Sum of M = 0 = RAx - qx2/2 - 22.5(x - 3.5) - M... M = 78.75 - 1.25x - 2.9x2
when I graph the V's, the lines do not intersect... did i do something wrong. Would it even matter as long as I did the M's correctly. Could someone just double check my work.