PEMB Uplift
PEMB Uplift
(OP)
I know there are several threads referring to this topic, but, i haven't seen any addressing the 0.75 i am about to inquire about.
I know i can only use 0.6D to resist. BUT... does IBC EQ 16-13 allow me to reduce the reported PEMB uplift by 0.75?
In my office, we've pondered how PEMB engineers design buildings with (seemingly) virtually no safety factor. Are there other factors i am not aware of to apply to the PEMB reported uplift reaction?
Thank you!
I know i can only use 0.6D to resist. BUT... does IBC EQ 16-13 allow me to reduce the reported PEMB uplift by 0.75?
In my office, we've pondered how PEMB engineers design buildings with (seemingly) virtually no safety factor. Are there other factors i am not aware of to apply to the PEMB reported uplift reaction?
Thank you!






RE: PEMB Uplift
RE: PEMB Uplift
RE: PEMB Uplift
RE: PEMB Uplift
RE: PEMB Uplift
This is becoming more problematic as their use in office/church/retail/finished space is growing, since these structures utilize conventional finishes, often without deflection accommodation.
For foundation design, usually metal building guys will report all their load cases (20+ of them). Sometimes they will envelope these with max and min values, but rarely do I find their application of load combinations to be well clarified/accurate. Identify the controlling wind/seismic uplift load CASE as well as the dead+collateral cases (0.6dead+wind). Check if they are using ultimate or service wind (believe most still use ASCE 7-05 service). Then apply your IBC equations (0.75 won't apply to governing uplift). Whether to include collateral load (extra dead) in uplift resistance is engineering judgment. In my opinion the 0.6 factor is there to cover "artificial" dead load values such as this. Interior column footings will nearly always be controlled by uplift, same as Walmarts and other single-story warehouses. Use soil and SOG weight above to resist, and consider lowering your footing and increasing pedestal height to minimize concrete volume.
Metal Building anchor bolt design is another can of worms.