earthquake seismic retrofit with bolted steel frame

[bdruehl]

am i to understand that if use a bolted omf "u" frame (for a all window front one (or two) story building) for lateral resistance retrofit (to take the front of the buildiung lateral because there are only windows) i need to use the "tested and accepted" bolt configurations as stated by Fema and other codes (CA)? if so, i cant find a detail for a "T" configuration (beam on TOP of column), attaching the roof (or second floor) to the beam? does this mean i have to use full height colum to roof with beam butting up against column? any ideas or even examples are appreciated. 16 foot high ceiling.. planning of plywood gusseting the webs of 3 trusses and and also a 4 ft wide plywood on the bottom of the trusses (with blocking if the beam doesnt line up with one of the trusses...) a total of 4 columns with 2x2x5 ft deep foundations (preliminary design)

 

[bdruehl]

i have perused some previous threads, specifically the base fixidity vs pinned including the the_design_manual_for_moment_and_stiff_of_column_plates.pdf

simple preliminary design with fixed base before the light reading mentioned above... 10k lateral applied by roof attachment to the (4) columns. no dead load or live load applied although failure of the front window as vertical support may need to be considered.

(4)16 ft high columns framed up to beam, about 8 feet from the windowed front of the building, beam and columns are w8x21 with 1" base plate 7"x14" with (4) 1" j-bolts (18" embed) into caged 2x2x5.5 ft footing with a 3.5 foot minimum soil embed for lateral resist. no drift analysis yet, no top connection yet.

 

[bdruehl]

------------------------------ <---- 10k
- - - -
- - - -
- - - -
- - - -16 ft high
- - - -
- - - -
- - - -

 

[msquared48]

Deflection will be critical here, not stresses or shears due to the windows, plus, since this is a window wall, you also need to consider wind and seismic loads perpendicular to the frame.

You really need to engage a structural engineer here. The 10K load seems a little high for a residence. What kind of structure is it?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[bdruehl]

it is not a residence, is a commercial storefront about 40 feet wide and 60 feet from the front glass wall to the interior shear wall. not replacing the front of the wall, frame set back in building about 8 feet. 10k is conservative prelim calc.

 

[bdruehl]

i believe that premanufactured steel frames such as simsson strong frames with such a load (using 2 frames maybe) would have a deflection themselves of less than 2 inches if memory serves me right.... although they are expensive , proabaly 5-6k a piece?... the load (after th3 6.5/3.5 conversion for OMF) would be more like 8k total lateral. anyhoo, i cant see any other retrofit other than a steel frame working or being cost effective(shear wall construction would close off the bulding front too much)... and arguably, using such a premanufactured product with the "structural engineering" inherent in the allowable loads would not necessitate a structural engineer;s expertise to design!?

 

[bdruehl]

possible job for bid:
rotted 16 foot!! cantilevered deck with 13 foot trib to cantilevered beams (originaly 7x20 glulams that extend maybe 15 feet to supports inside the house). cut rotted beam at exterior of house and scab another beam, probably steel... with the new requiremetn of 100 psf live load (for balcony over 100sf for residential), i figure i would run this by the forum for thoughts-especially if you have experience connecting this kind of loading. this is a big cantilever with large loads- and the devil being the details of the load transfer to the existing beam inside the house.