Dell
Dec26-09, 01:33 PM
h have a T shaped object (2-d) for which i need to find the moment of enertia,
i used a parallel axis theorem, then to check myself i found i site which had a direct equation for it
http://www.efunda.com/designstandards/beams/SquareTbeam.cfm
what i did
b1=100mm
h1=12mm
b2=12mm
h2=75mm
q=12.643mm(the distance from the joint of the 2 shapes to the centroid of the T)
>> ((b1*h1^3)/12)+((b1*h1)*(q+h1/2)^2)+((b2*h2^3)/12)+((b2*h2)*(h2/2-q)^2)
1.4094e-006 m4
using their equation
t=12mm
y=75-12.643=62.357mm
b=100mm
s=12mm
d=87mm
>> (t*y^3+b*(d-y)^3-(b-t)*(d-y-s)^3)/3
7.6247e-006m4
where have i gone wrong here?
i used a parallel axis theorem, then to check myself i found i site which had a direct equation for it
http://www.efunda.com/designstandards/beams/SquareTbeam.cfm
what i did
b1=100mm
h1=12mm
b2=12mm
h2=75mm
q=12.643mm(the distance from the joint of the 2 shapes to the centroid of the T)
>> ((b1*h1^3)/12)+((b1*h1)*(q+h1/2)^2)+((b2*h2^3)/12)+((b2*h2)*(h2/2-q)^2)
1.4094e-006 m4
using their equation
t=12mm
y=75-12.643=62.357mm
b=100mm
s=12mm
d=87mm
>> (t*y^3+b*(d-y)^3-(b-t)*(d-y-s)^3)/3
7.6247e-006m4
where have i gone wrong here?