07-01-2010, 05:56 PM
I don't agree with the fact that for gravity loads we should use 100% of I because the design of RC elements is made for behavior stage II (cracked section). If the concrete were in stage I (uncracked) the reinforcement stress would be very small (30-40 N/mm2). The reduction of I is clearly visible on the relation M-phi (curvature) for a section in bending.