huangyhg

building with expansion joints
if we have a 800' long box warehouse with 2 expansion joints(8" wide)along the width, then do we treat it as a cont. beam with internal hinge at exp. joint points( to represent expansion joint) and supoorted on 4 supports (representing lateral bracing system)?
thanks
if you mean the diaphragm, you can treat it as a hinge as long as you provide details such that all of the shear can be transferred across the diaphragm. the alternative is to provide support on each side of the joint independent of what's on the opposite of the joint.
the analysis approach would depend upon what you are trying to achieve. obviously, the detailing has to be representative of the analysis and vice versa.
if there is no shear transfer across these joints, then i would suggest that you treat them all as completely separate units. if you want shear transfer across the joints, then your approach sounds like that is the way it should be modeled.
there will be separate roof aangle at the expansion joint. this means there will not be any shear transfer across the expansion joint.
so when transfering the wind force normal to 800' wall, will this wind be treated basically as acting on 3 separate buildings and the the interior vxb at the expansion joints will get double the load as compared to end vxb( assuming flexible diaphragm and equal stiffness for all vxb)?
if that is the case, then what will be the chord
if you have one common brace between two buildings, then obviously it will need to resist load from each half.
the shear will need to be transfered thru the slide bearing into the single column and then into the common collector/drag/chord and into the vertical brace.
if the single column and single bracing, the shear transfered thru the slide bearing will put a torque on the column which you may want to account for.
obviously, another option is to use double columns and double bracing.
"so when transfering the wind force normal to 800' wall, will this wind be treated basically as acting on 3 separate buildings and the the interior vxb at the expansion joints will get double the load as compared to end vxb( assuming flexible diaphragm and equal stiffness for all vxb)?" yes, i agree
"if that is the case, then what will be the chord members at the expansion grid, assuming one column at expansion grid and sliding connection at one side of column?"
i always refere to chords as the tension and compression members in the diaphragm equivalent to the top and bottom flanges of a beam, to avoid confusion. if you have 2 separate diaphragm angles with a common support beam at the expansion joint, then your chord for each building segment will respectively be each angle. the drag strut will be the common beam, which will be receiving forces from each building segment as you said.

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