Three dimention beam or bending and buckling calc
Three dimention beam or bending and buckling calc
(OP)
Hi,
I have a three direction (bended and welded)beam that subjected to forces in two directions. these forces cause strains of bending and compression. can I add the bending strain to the compression strain and then to comer it to yield strain?
in other words, how can i calculate a cantilever that subjected to both bending moment and axial compression force at the end.
thanks!
Moran
I have a three direction (bended and welded)beam that subjected to forces in two directions. these forces cause strains of bending and compression. can I add the bending strain to the compression strain and then to comer it to yield strain?
in other words, how can i calculate a cantilever that subjected to both bending moment and axial compression force at the end.
thanks!
Moran





RE: Three dimention beam or bending and buckling calc
(Compressive stress/allowable comp. stress)+(bending stress/allowable bending stress)<= 1.0
RE: Three dimention beam or bending and buckling calc
can I add bending stress in one direction with a bending stress in other direction? meaning, if i have bending moments in two direction so sigma=sigma1+sigma2?
RE: Three dimention beam or bending and buckling calc
Yes, sigma1 and sigma2 are additive algebraically, but you have to know when it's (+s1) + (+s2) and when it's (+s1) + (-s2). But your questions and they way you have asked them, makes me wonder how you are going to arrive at your sigmas and other stresses. And, whether you have a handle on the difference between stresses and strains. How do you get from your loads, through a number of calculation steps, to the stresses.
RE: Three dimention beam or bending and buckling calc
supposed i have M1= bending moment in x direction and
M2= bending moment in y direction:
sigma= M1*c/I + M2*c/I
and then i comper sigma to sigma yield of the beam material.
do you think it is right?
RE: Three dimention beam or bending and buckling calc
calculate Pcr, then P/Pcr; < 0.10 ?
RE: Three dimention beam or bending and buckling calc
RE: Three dimention beam or bending and buckling calc
BUT, you may be asking "how do i know if the compression flange is stable ?" then i would combine the stresses as outlined above (!!) 'cause that'll tell you the stress in the compression flange (having already done the beam column analysis so you know the structure is good, if the flange is stable) and i'd compare this with the crippling allowable.
RE: Three dimention beam or bending and buckling calc
i will be very happy if you can look at the document attached and tell me what i did wrong.
i got very low "W" and it doesn't make sense to me.
RE: Three dimention beam or bending and buckling calc
RE: Three dimention beam or bending and buckling calc
RE: Three dimention beam or bending and buckling calc
RE: Three dimention beam or bending and buckling calc
M1 equation is wrong, integral should be (qx)*x/2 ... M1 = ql*l/2.
M2 equation is wrong 'cause you've omitted the moment at the plane of symmetry, and you haven't included the moment due to the shear q*l1.
you haven't analyzed the leg as a beam column. google "beam column" and you'll see it's quite a different analysis. how does the leg react the moment, M2 ? most likely as a reaction moment at the base ?? this is now a column with an off-set load ... google "secant formulae" or "column with offset load" or consult a text book.
thinking about it, maybe this is a better way to approach the loading ... make a free body of a 1/2 ... zero shear at the plane of symmetry, so the leg reacts all the load ... q*(l1+l2). the moment at the base is harder to calc ... the couple from the reaction and the applied load is conservative as there is some moment reacted at the plane of symmetry ...