ACI 350-20 - Ch. 9 vs App. D Comparison

[RattlinBog]

I'm fairly new to the design requirements of ACI 350-20. I wanted to compare the calculation of load factors and the environmental durability factor, Sd, using both Appendix D and Chapt. 9. App. D is straightforward, but Chapt. 9 is a bit tricky. It looks like Chapt. 9 can be more or less conservative than App. D depending on reinforcement spacing.

Would someone be willing to review my attached example calcs and confirm if I'm on the right track? I only checked flexural stress under fluid loads and normal environmental exposure for the example.

 

[aalmasri]

Hi RattlinBog
Your calculations seem valid.
appendix D is more used because of its simplicity,

 

[RattlinBog]

Thank you. I agree Appendix D is simpler, but I'm trying to optimize my design. If I'm allowed to use a smaller Sd value, I'd like to take advantage of it.

 

[strucbells]

Looks correct. There are some additional minimum Fs_max in 10.6.4.1 depending on 1-way/2-way behavior you might consider depending on the element you are looking at. ACI 350-20 rewards having tighter spacings with smaller bars because this has been proven to perform better for keeping cracks tight and limiting leaks, which is the whole point of the durability factor and modifications to typical ACI 318 design.

If you're new to ACI 350-20, pay special attention to the minimum reinforcing provisions, there are some significant changes to ACI 350-06 based on your restraint condition and your movement joint spacing (if you have any).