NBCC Seismic connection force

[palk7 EIT]

Hi,

In Canada, for seismic connection force, according to clause 4.1.8.18. " connections to structure shall be designed to accommodate building deflections" and the building deflections are amplified by multiplying Rd*Ro to get the realistic displacements, so that implies that the connection forces should also be that of the amplified displacements? (Simple terms the members to be checked for Base shear / (Divided) Rd*Ro and the displacements & connections will be for Base shear* (multiplied) Rd*Ro?)

Thank you!

 

[TLHS]

No. That's the section for components and non structural elements. What it's saying is that the connections of such elements have to accommodate building deflection. This means that you have to properly account for building deflection in connections for things like glazing, separation walls and things like that.

Design things to allow for story drift, don't install equipment so it crosses movement joints, don't fasten your steel stairs so they act as a lateral load path unless you meant to, etc.

 

[TLHS]

Also, most of the clauses in the seismic section of the code are further explained in the structural commentaries

https://nrc-publications.canada.ca/eng/view/object/?id=a23153d5-ad9d-46f9-9a29-3f76aa09dd7c

 

[palk7 EIT]

So in ASCE the connection design forces to be designed for an over strength factor, so similar to over strength factor what would be the amplification factor for connection forces for Canadian seismic? Appreciate it!

 

[skeletron]

Read Article 4.1.8.18(7) (a) through (f).
You design the OFC for the force in Article 4.1.8.18. Then you design the connection by removing the Rp value. I believe this is more-or-less what you are asking with comparisons to ASCE

 

[palk7 EIT]

Thank you Skeletron, If we are looking for the actual frame itself, like let's say a portal frame with 5 kips as the horizontal seismic force, calculated according to 4.1.8.11 V= S*(Ta)Mv*Ie*W/ (Rd*Ro) Rd=1.5&Ro=1.3 for conventional moment resisting frames.....Now when checking for the connection at beam-column, should the Rd&R0 be taken as 1 (Meaning the V force will be 1.95 times more for the connection design?, or 4.1.8.15(8), the Rd&Ro need not exceed 1.3 ( which kind of becomes, 1.5 times more for the connection)

Thank you!

 

[TLHS]

This section does not apply to the overall structural system. This clause relates to non-structural components and building components only. The main force resisting system is basically every other clause in the seismic section of the building code.

The requirements for connections are mostly in the material codes. For steel that would be CSA S16.

In S16 you'd want to go to the seismic section of the code, read the general requirements and then also read the requirements for the type of lateral force resisting system you're using.

Also, skeletron, I don't agree with your interpretation of the non-structural component requirements. You use the Rp of the component except in a couple of exception cases:

1. If you are using fully non-ductile connectors like power actuated connections or adhesives then you use Rp=1
2. If you are using most types of concrete anchors and they have a depth to diameter ratio of less than 8 you use Rp=1.5
3. If you are specifically looking at a wall, parapet, or exterior ornament that is on the building exterior and overhead then you either have to design the fastening system to be ductile or use Rp=1 and Cp=2

 

[skeletron]

@TLHS:
Misworded my response, thanks for bringing it to my attention.
Yes, don't simply "remove" the Rp but "replace" it with the Rp in Sentence (7) (a) to (f). It needs to conform to Sentence (1) and Sentence (7). Sometimes the net change is zero, but often it's a larger force on the connection vs. the actual component.