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# Re: UBC 1997 - Rebar development length & Splice length

• To: seaint(--nospam--at)seaint.org
• Subject: Re: UBC 1997 - Rebar development length & Splice length
• From: C Chan <seaint_list(--nospam--at)yahoo.com>
• Date: Thu, 31 Oct 2002 15:34:47 -0800 (PST)

I believe UBC 1921.5.4 pertains to development length of rebars terminating at joints only when designing for high seismic zones. Chapter 1912.15 should still apply for lap splices. Hoop reinforcement per 1921.3.2.3 is required over the lap length.

"Vasu, Ravi" <Ravi.Vasu(--nospam--at)jacobs.com> wrote:

Pl. refer to UBC 1997 section 1921.5.4, development length for rebar in tension.
In this section, it is not given to calculate splice length for class A & B splices.

For example, development length for a # 10 straight bar is 64.9(=3.5*18.54) inch per above section.(60 ksi rebar &
4000 psi concrete).
When it comes to Splicing of rebar in tension for Class B, do we have to multiply the ld (=64.9 in.) by 1.3??
In section 1912.15.1 for splice length(=1.3*ld), it is said to refer ld from section 1912.2. & not ld from section 1921.5.4.

The splice length for #10 class B top bar is 73.6 inches.(per UBC 1912.15.1, with clear cover = 2", beta = 1 & lambda = 1)
The ld = 64.9" (from section 1921.5.4) is about 9 inch less than 73.6" . If you multiply 64.9" by 1.3, it comes to 84.4"
(now it is 11" more than 73.6". Which one should we consider???

Section 1912.2 is given clear to calculate ld(same as ACI section 12.2 per ACI 318-99), with factors to adjust for.
The ld (for a straight bar)from section 1921.5.4 does not need any adjustment factors??

Ravi Vasu, P.E.

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