Steel Elements of Structural Wall Anchorage

[palves]

ASCE7 Section 12.11.2.2.2 say that the strength design forces of all steel elements in an achorage system need to be increased by 1.4. I'm working on a project with a wood roof and diaphragm and am using Simpson straps to satisfy the anchorage forces. It seems pretty clear to me that I need to increase these forcesd by 1.4, but I have had other people tell me that only counts for an anchorager system that is entirely made of steel. I'm a little dubious about that argument but thought I'd throw it out there and see what others thought.

 

[JAE]

The provision is to ensure that rigid, brittle steel connections and connectors don't fail first. I think it would apply at first glance - I probably would need to study 12.11.2.2.2 in context more but that is what I would say - yes, the Simpson straps would need the 1.4 factor.

 

[woodman88]

The Simpson 2011 catalog is based on the ASD. The catalog concerning the LSTHD/STHD holdowns, footnote 7 states "Multiply Seismic and Wind ASD loads values by 1.4 or 1.6 respectively to obtain LRFD capacities." You might want to talk to Simpson as the 1.4 factor may already be part of the catalog values.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[jdgengineer]

I agree with JAE, I think the Simpson straps should satisfy the 1.4 factor.

Woodman -- I believe the factors you are quoting are for the conversion from ASD to LRFD. For seismic it is 1/0.7 = 1.43 ~ 1.4, and for wind it is 1.6.

 

[woodman88]

jdgengineer - If that is the case, why is it only noted for the concrete embeded holdowns and not the other wind and seismic holdowns?

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.