(02-25-2009, 10:13 AM)concreteok Wrote: yasir,
Never really into composite or steel design but i have seen demo of csc fastrak. Its seems to me, giving much better control on the designing part. Since its shared here, maybe u can try it out.
Secondly, i am much of a manual designer. For concrete design, why should we use multiplier to the reinforced concrete frames' stiffnesses when we carry out elastic analysis? Unless we are performing non linear analysis. Pls advise.
concreteok, the modifier is required to estimate the effective stiffness of your frames at ultimate limit state--drifts are checked at ULS in accordance to code (drift at ULS ~ disp. ductility * drift from linear analysis). The preceding approximation of drift at ULS is based on equal displacement hypothesis--may not be actually true but still acceptable within the present codes' concept of force-based design methodology.
regards,
juice