A beam is made from universal column with an “I� Section to BS4. The size of the beam is 356X127X39. The modulus of elasticity is 205 GPa. The maximum tensile stress in the beam must not exceed 350 Mpa and the elastic modulus z is 576 cm2. Calculate (a) the maximum allowable bending moment (b) The radius of curvature. Given y =176.7

To calculate the max moment the beam can withstand use the relationship

\sigma = \frac {Mc} I


You know c and I from the dimensions of the beam, and you are given a maximum value for \sigma, so you can find the maximum value for M.

For the second part of the question, the radius of curvature is found from:


EI \frac {d^2y} {dx^2} = M

Thanks for your help could you please explain what's what in both formulas I don't no what info to put were

First - please ask follow-up questions using the "answer" text box, not the "comments" box.

\sigma is stress.
M is the moment or torque being experienced by the beam
I is the moment of inertia - which is a measure of the beam's cross-section. Your text should explain how to calculate that for the shape in question.
c is the distance from the centroid of the beam to the top (or bottom) edge of the beam - this is where the stress is greatest.
E = Young's modulus, also called modulud of elasticity, and is a characteristic of the material the beam is made from.
\frac {d^2y}{dx^2} is the second derivatrive of displacement of the beam per unit length, and is equal to the curvature the bean experiences under load.

I suggest you review your mechanics text - this should all be covered in there.