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# Re: ASCE 7-02 Time period in Metric

• To: seaint(--nospam--at)seaint.org
• Subject: Re: ASCE 7-02 Time period in Metric
• From: "Anantha Narayan C.K." <anant_27(--nospam--at)yahoo.com>
• Date: Thu, 28 Sep 2006 17:27:50 +0100 (BST)

Allen,

~Anantha

It appears that the reason for the discrepancy is that the factors for
metric are wrong in ASCE 7-02. Note that for ASCE 7-05 they have been
changed. For "All other structural systems" the metric equivalent is
0.0488 (instead of 0.055). It is also interesting to note that in ASCE
7-98 the metric equivalent was 0.0488, so for some reason they changed
the metric equivalent in ASCE 7-02 (erroneously), and then changed it
back for ASCE 7-05.

Using the correct coefficient:
Ta = 0.048 (14.6)^0.75 = 0.364 s
which is the same as is given using the US Imperial units coefficients
and values.
I recommend using the ASCE 7-05 value since it is consistent.
Allen

Chief Structural Engineer
RAM International
(800) 726-7789 x113

From: "Anantha Narayan C.K."
Subject: ASCE 7-02 Time period in Metric
To: seaint(--nospam--at)seaint.org

Greetings,

This might be the dumbest question on the forum, but could anyone
please let me know what I am doing incorrectly.

Reference : ASCE 7-02 Eq 9.5.5.3.2-1

Ta = Cu * hn ^ x

where for "All other structural systems" Cu = 0.02 (0.055 in metric)
and x = 0.75 [TABLE 9.5.5.3.2]

For a building that is 14.6 m high (= 47.88' )

Using English Units, Ta = 0.02 (47.88)^0.75 = 0.36 s

Using Metric Units, Ta = 0.055 (14.6)^0.75 = 0.41 s

Could anyone please tell me as to why there is a discrepancy between
the results?

Thanks
Anantha

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ANANTHA NARAYAN, E.I.
Structural Engineer
Bliss and Nyitray Inc.
Miami, FL - 33134

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ANANTHA NARAYAN, E.I.
Structural Engineer
Bliss and Nyitray Inc.
Miami, FL - 33134

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