IBC 2003 1605.4 Special Seismic Combinations
IBC 2003 1605.4 Special Seismic Combinations
(OP)
Paraphrase of IBC 2003 Section 1620.2.9:
Columns subject to vertical reactions from discontinuous walls or frames...shall resist special seismic combinations of 1605.4.
My question is:
Can someone show me a graphical representation (or a link to this subject) of which columns are subject to this requirement?
Here is an example of a bracing line:
http ://www1.sn apfish.com /slideshow /AlbumID=5 6268802/Pi ctureID=24 61920805/a =16364905_ 16364905/t _=16364905
There is a picture in the code (Figure 1620.2.9) that shows a couple of examples but I am dealing with an industrial structure that has vertical bracing in some bays and not others and where to apply these special combinations is not clear from the code.
Columns subject to vertical reactions from discontinuous walls or frames...shall resist special seismic combinations of 1605.4.
My question is:
Can someone show me a graphical representation (or a link to this subject) of which columns are subject to this requirement?
Here is an example of a bracing line:
http
There is a picture in the code (Figure 1620.2.9) that shows a couple of examples but I am dealing with an industrial structure that has vertical bracing in some bays and not others and where to apply these special combinations is not clear from the code.






RE: IBC 2003 1605.4 Special Seismic Combinations
RE: IBC 2003 1605.4 Special Seismic Combinations
RE: IBC 2003 1605.4 Special Seismic Combinations
2.8*1.4(strength)/1.7/1.33 = 1.73
RE: IBC 2003 1605.4 Special Seismic Combinations
The 1.7 factor you noted does not apply to this section of the IBC 2003. You might be considering the AISC Seismic Provisions.
Bagman
Yes, designing ALL the columns for this load is the easy way. But why take that route? We should have an understanding of why the code requires this increased load & how to apply it effectively. In a large braced frame like Dave shows in the link, the extra load could significantly increase the material costs.
Let me carry Dave's question one step farther...does anyone know of any papers or research that backs up the code requirements for using the seismic load Em (= omega*Qe + 0.2*Sds) rather than just E. I have not been able to find any even though it has been in the code a long time.
Thanks
RE: IBC 2003 1605.4 Special Seismic Combinations
If one of your vertical elements is not continuous then certainly omega comes into play. Your bracing is not continuous but that might be a good thing for seismic response.
If the columns in the frame line you posted get the overstrength factor then I have been misreading the code's intent!
RE: IBC 2003 1605.4 Special Seismic Combinations
IBC 2003 1620.2.9 states:
"Columns or other elements subject to vertical reactions from discontinuous walls or frames of structures having....vertical irregularity Type 4....shall have the design strength to resist special seismic load combinations of Section 1605.4"
RE: IBC 2003 1605.4 Special Seismic Combinations
I don't see why these columns would be crucial and need the overstrength factor; however, where your bracing jumps from one bay to another the collector elements between may require the additional strength.
RE: IBC 2003 1605.4 Special Seismic Combinations
RE: IBC 2003 1605.4 Special Seismic Combinations