Tie, Collector, Diaphragm, Deformation compatibility[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: Tie, Collector, Diaphragm, Deformation compatibility
- From: "Stan Mulder" <seatown(--nospam--at)icon.co.za>
- Date: Sun, 16 May 1999 22:16:02 +0200
Could someone please explain the differences between "Tie, Collector, and Diaphragm" used in UBC ? The definitions given in the codes are very similar. "Diaphragm" is the horizontal floor bracing in a steel structure. I would generally consider a "tie" a beam connecting columns to the vertical bracing or portal bracing ? For some reason or other "collector elements" have larger seismic design loads than ties (in the CBC) but they have similar definitions.
What "structural framing elements" are being referred to by "Deformation Compatibility" in the UBC ? The calculated displacements have to be increased by 3Rw/8 times the lateral displacement and Pdelta affects must be taken into account. This seems to be referring to intermediate columns only.
Considering a Concentrically Braced Structure the bracing will resist the Pdelta effects from seismic drift. The columns would just lean over and only resist the effect of eccentricity of the beam reactions. If floor bracing is provided at each level there is also very little differential deflection at any level ? The intermediate columns can only deflect the same amount as the horizontal bracing, and all the floor elements are restrained by the bracing. However with floor bracing on every second level then unbraced columns span between the braced levels and can bend and deflect under lateral loads. Is this what this deformation compatibility clause is guarding against. By the way is it acceptable to only brace some floors levels of steel structures in seismic zones 3 and 4 ?
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