By Cl 8.2 of AS4100 or Cl 8.2.2 of NZS3404, when checking member capacity of combined actions, N*, Mx*, My* use the maximum values even if they might be at different stations.
When checking double bending by Cl 8.4.5.1 of NZS3404 for example,
Given data for example: a taper rafter of portal frame. Maximum x-axis bending moment, Mx_max * is at knee point – the first segment. Maximum y-axis bending moment, My_max * is at the fourth segment.
(1) After checking ‘critical section’ for x-axis, the first segment is the critical section. When calculating Mcx, the section properties of the first segment are used in calculation.
(2) When calculating Miy, since the applied bending moment is at the fourth segment, which segment’s section properties – the first or the fourth segment are used for the Miy calculation?
(3) Why Code defines all maximum forces at the same time to check member capacity? For example, Mcx uses the first segment's section properties and Miy uses the fourth segment's properties. Is it too conservative? Or is it just what Code wants?
Can we design by one case of Mx_max* plus the My* and N* at the same station of Mx_max and another case of My_max* plus the Mx* and N* at the same station of My_max, even if it breaks the Clause? By this way, we can avoid using the mixed section properties of different segment.
Any thoughts? Thanks.
When checking double bending by Cl 8.4.5.1 of NZS3404 for example,
Given data for example: a taper rafter of portal frame. Maximum x-axis bending moment, Mx_max * is at knee point – the first segment. Maximum y-axis bending moment, My_max * is at the fourth segment.
(1) After checking ‘critical section’ for x-axis, the first segment is the critical section. When calculating Mcx, the section properties of the first segment are used in calculation.
(2) When calculating Miy, since the applied bending moment is at the fourth segment, which segment’s section properties – the first or the fourth segment are used for the Miy calculation?
(3) Why Code defines all maximum forces at the same time to check member capacity? For example, Mcx uses the first segment's section properties and Miy uses the fourth segment's properties. Is it too conservative? Or is it just what Code wants?
Can we design by one case of Mx_max* plus the My* and N* at the same station of Mx_max and another case of My_max* plus the Mx* and N* at the same station of My_max, even if it breaks the Clause? By this way, we can avoid using the mixed section properties of different segment.
Any thoughts? Thanks.
