The question is stated below. I found out an answer but it doesn't seems to be correct to me. I made a few sketches to clear things up a bit, sorry for bad quality, too much compression.(adsbygoogle = window.adsbygoogle || []).push({});

The simple truss of Prob. 4/2 is modified as shown in the figure, in that the angle of the support surface at C can be varied from 0 (vertical) to 90◦ (horizontal).

(a) Plot the force in member BC as a function of ø over this range. Note any unusual conditions.

(b) For what value of ø, if any, is the force in member BC zero?

(c) If member BC is designed to fail at a load of 5 kN in either tension or compression, what is the allowable range for the angle ø?

Answers:

(a)

Fa = 500N

Fcx = Fbx + Fcx = 0

Fcx = -1200N

Fcy = tan(ø) = Fcy / Fcx

Fcy = -tan(ø) * -1200

Fbx = (Fa / 1,25) * 3 = 1200N

Fa + Fby + Fcy = 0

Fby = 500 – 1200 * tan(ø)

So if we want to plot this, x would be x = a vector from 0 to 90. And y would be y = –1200 * tan(ø).

If I plot this it shows some kind of weird looking tangens-function. Is this normal or did I make a miscalculation somewhere?

The function has a lot of 0-points so question (b) seems a bit strange too.

Maybe someone can help to clear things for me up a bit?

Thanks in advance :)

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# Homework Help: Statics truss problem

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