Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

re: Modeling Rubber in SAP2000

[Subject Prev][Subject Next][Thread Prev][Thread Next]



Young's modulus and poisson's ratio are not really the right material
properties for a detailed analysis. PR = 0.5 will always blow up the kernel
matrix because of the divisor term (1-2*PR). Thats why SAP won't let you do
it. <snip>

This is also why it is a good idea not to use .499999999 as v. The matrix inversion won't fail, but you'll have a very large stiffness on your K matrix diagonal, relative to the rest of your structure. The roundoff errors, even using double precision, can cause inaccuracies in your model. Not being a user of the popular SE analysis packages, I don't know what kind of checking results you get (NASTRAN will output a value of the largest/smallest eigenvalue ratio. The "old" standard was 1000:1 - anything higher and your model was generally poor wrt element uniformity and you should consider a better model technique)



Jordan Truesdell, PE



******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
* Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********