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# Re: UBC shearwall reinf.

• To: seaint(--nospam--at)seaint.org
• Subject: Re: UBC shearwall reinf.
• From: "Michael Valley" <mtv(--nospam--at)skilling.com>
• Date: Mon, 18 Oct 1999 11:31:52 -0700
• Comments: Authenticated sender is <mtv(--nospam--at)linux.skilling.com>
• Priority: normal

```The definitions of rho(v) and rho(n) have been unnecessarily
confusing for a number of years.  The problem arose when the
codewriters tried to generalize the definitions to cover
reinforcement that was placed at an angle (not vertical or
horizontal).  The resulting definitions are very difficult to
interpret at they confuse what is perpendicular (the reinforcement or
the plane).

The definitions in ACI 318-99 are finally clear.  Here they are:

rho(n): ratio of area of distributed reinforcement parallel to the
plane of Acv to gross concrete area perpendicular to that
reinforcement.

rho(v): ratio of area of distributed reinforcement perpendicular to
the plane of Acv to gross concrete area Acv.

-Mike

> Date:          Mon, 18 Oct 1999 08:23:30 -0700
> From:          Panos Trochalakis <panost(--nospam--at)ckcps.com>
> Subject:       UBC shearwall reinf.
> In UBC 1921.6.5.2 the shear capacity of a wall is based on rho(n). In
> the beginning of section 1921, rho(n) is defined as the shear
> reinforcement PERPENDICULAR to plane of Acv. In this same section Acv is
> defined as the net area bounded by the web thickness and length of
> section in direction of shear force considered. I would interpret Acv as
> a section through the wall in plan. Therefore, rho(n) would be defined
> as the vertical reinforcement? (perpendicular to Acv plane) The
> horizontal reinforcement is typically designed as the shear
> reinforcement and this is specifically called out in numerous texts
> including PCA's seismic design book. Am I reading the UBC definition of
> rho(n) incorrectly?
>
> thank you,
> Panos

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Michael Valley                                   E-mail: mtv(--nospam--at)skilling.com
Skilling Ward Magnusson Barkshire Inc.                  Tel:(206)292-1200
1301 Fifth Ave, #3200,  Seattle  WA 98101-2699          Fax:        -1201

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