rscassar
Structural
- Jul 29, 2010
- 631
Hi, I just want to have another run at this code provision relating to column design & earthquake design (thread744-468892).
AS3600 Cl 10.7.4.3.iii Says that a column where Lu<5*D then the column must be detailed to Section 14.5. Cl.14.5 is a provision for IMRF (mu=3.0). From experience, most carpark columns are blades with minimum D=1000 and floor to floor 3.0m & this is similar for residential buildings. Retail and Office columns might not fall within this provision as floor to floors are 3.7m to 5.0m with square or circular columns are preferred. So many columns will have this EQ detailing for mu=3.0 imposed onto them even if a mu=1.0 is adopted. And once this provision is required, it does not distinguish between long or short dimension, it's just concerned about minimum dimensions, so the tie spacing for blade columns get's very close when the maximum spacing of 0.5*B is required.
I understand the more onerous detail requirements for a mu=3.0 structure, also the shear design of columns is an item that wrongly does get overlooked by engineers in the industry. But why wouldn't a column designed in a building where a mu=1.0 is adopted, designed in accordance with the column provisions of section 10 and the provisions of Cl.8.2 where shear reinforcement would be required when V*>0.5*phi*Vuc and detailed with maximum spacing accordingly.
The analysis and design is very onerous particularly when cracking and load reversal of 8.2.4.5 is considered. But it does allow the column to be designed and detailed in accordance with design actions. Blade columns where the 0.5*B tie requirements imposed on them irrespective of the design shear force in the weak-axis dimension seems unnecessary. I'm running thru a design of blade columns now (adopting mu=1.0) where the shear and moments in these columns about there weak axis are 10kN and +/-15kN-m.
AS3600 Cl 10.7.4.3.iii Says that a column where Lu<5*D then the column must be detailed to Section 14.5. Cl.14.5 is a provision for IMRF (mu=3.0). From experience, most carpark columns are blades with minimum D=1000 and floor to floor 3.0m & this is similar for residential buildings. Retail and Office columns might not fall within this provision as floor to floors are 3.7m to 5.0m with square or circular columns are preferred. So many columns will have this EQ detailing for mu=3.0 imposed onto them even if a mu=1.0 is adopted. And once this provision is required, it does not distinguish between long or short dimension, it's just concerned about minimum dimensions, so the tie spacing for blade columns get's very close when the maximum spacing of 0.5*B is required.
I understand the more onerous detail requirements for a mu=3.0 structure, also the shear design of columns is an item that wrongly does get overlooked by engineers in the industry. But why wouldn't a column designed in a building where a mu=1.0 is adopted, designed in accordance with the column provisions of section 10 and the provisions of Cl.8.2 where shear reinforcement would be required when V*>0.5*phi*Vuc and detailed with maximum spacing accordingly.
The analysis and design is very onerous particularly when cracking and load reversal of 8.2.4.5 is considered. But it does allow the column to be designed and detailed in accordance with design actions. Blade columns where the 0.5*B tie requirements imposed on them irrespective of the design shear force in the weak-axis dimension seems unnecessary. I'm running thru a design of blade columns now (adopting mu=1.0) where the shear and moments in these columns about there weak axis are 10kN and +/-15kN-m.