he origin of the 2 bracing force

huangyhg

the origin of the 2% bracing force?
does anyone know the origin of this rule of thumb? where does it come from? it seems everyone knows the 2% rule but no one knows where it comes from! is it in any way related to the 2% that the code allows for out of plumbness? <scratch head>
clansman
if a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." code of hammurabi, c.2040 b.c.fff">
check out our whitepaper library.
salmon and johnson mention it in "steel structures--design and behavior", but they did not originate it.
daveatkins
no idea - but it seems to work.  also have heard 5%
err - error in the original post, meant to say 0.2% as opposed to 2% for out of plumbness.
clansman
if a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." code of hammurabi, c.2040 b.c.fff">
try this?
you might also read appendix 6 of the aisc specifications for structural steel buildings 2005 edition
clansman:
it may be related to the 2% minimum crown slope for highways.  anything is possible.   
mike mccann
mmc engineering
mike:
draw a smiley at the end, will you ! kind nice to find little tickling around on a friday afternoon. have a nice weekend.
he got me going, but only for a second! ;)
clansman
if a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." code of hammurabi, c.2040 b.c.fff">
i don't know, but it was 2%, 1% and 2% for the 1969, 1984 and 2001 editions of can/csa s16-01 respectively.  i don't think it has any sound theoretical basis.
best regards,
ba
winter's seminal papers in 1958 and 1960 on column bracing are the first widely known treatment of the subject that i am aware of.  the % force required for bracing in those was in the range of 1% - my guess is the "double that and you won't have to worry about it" effect came into play to arrive at the 2% "rule". on a side note, i've found very rarely in practice that the strength controls bracing though - almost always stiffness.