chord (rebar) at slab ? 2

[DSAsteve]

Los Angeles, CA...
2001 CBC
8" and 12" CMU gymnasium, single story, 38'.

Plans callout for 'continuous' horiz rebar (some #5, some #6)at the Slab On Grade level (also in the code). Plans also specify additional increased lap at the chord steel (rebar).

Q)three part. Isn't the Slab On Grade considered a diaphragm? and aren't chord bars required at all diaphragms?
thus wouldn't increased lap splice be required at the S.O.G. level as well as the roof?

Thank you in advance
Inspector Steve

 

[msquared48]

Although a slab on grade is in the same plane of horzontal roof or floor diaphragm, it is not functioning as one really. It is generally not connected to the foundation, but floating. It mainly supports vertical loads and helps resist lateral loads from soil, mainly thru its dead load and soil-concrete frictional interaction.

Regarding the chord steel, it is placed in the walls supporting the roof and floor diaphragms, but not a slab on grade. Since the walls are connected to continuous strip footings, the footing steel could be considered as a possible form of chord steel, but not really needed as such.

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

 

[RHTPE]

Mike,

Never heard the term "chord steel" - care to enlighten me?


Ralph
Structures Consulting
Northeast USA

 

[slickdeals]

A diaphragm essentially behaves like a beam. The chord steel is placed at the extremities of the diaphragm (similar to tension steel in a beam) to counteract the tensile stresses induced in the diaphragm due to bending.

 

[hokie66]

Ralph,
The term chord is used in diaphragm design because of the analogy to truss chords. The edges of the diaphragm are like the top and bottom chords of trusses, and the part in the middle is analogous to truss web members.