Subject: RE: Rebar in members resisting earthquake force
From: "Sprague, Harold O." <SpragueHO(--nospam--at)bv.com>
Date: Wed, 22 Mar 2000 13:02:02 -0600
Without seeing the model, I can't say whether or not you have the potential
to develop inelastic rotations in the column to foundation interface. The
best way to evaluate the potential for inelastic rotations is to do a
non-linear (pushover) analysis.
The only way you can make an assessment with the R values is to reduce them
to 1.25, which would assume linear performance.
> -----Original Message-----
> From: Soojin Hur [SMTP:sjhur(--nospam--at)hec.co.kr]
> Sent: Wednesday, March 22, 2000 2:11 AM
> To: SEAOC
> Subject: Rebar in members resisting earthquake force
> I designed a R.C building in Zone 4, which building is dual structure
> (moment resisting frame + shear wall) with reinforcement of ASTM A615
> Grade 60.
> According to 21.2.5 in ACI 318, there are two additional requirement for
> reinforcement resisting earthquake-induced force, one of which is as
> '(b) actual ultimate tensile strength / actual tensile yield strength
> > 1.25'
> However, construction team at site have already finished concrete work
> for foundation and part of column and shear wall by reinforcement with
> the ratio = 1.17.
> With this condition, how can I approach to check the acceptability of
> the existing structure? Is the following approach reasonable?
> - Since the ratio is related with inelastic rotation capacity, and
> plastic hinge is not likely to occur at joints between foundation and
> column, column and wall, so 'No Problem'.
> - Since the ratio is also related with response modification factor (R),
> check the existing structure with reduced R-value. If this is correct,
> how to quantify it?
> Any input from anybody would be appreciated.
> Thanks in advance.
> Soojin Hur
> HDEC, Korea
> e-mail : sjhur(--nospam--at)hec.co.kr