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RE: Load factor for Cooling Tower

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Our engineers at Black & Veatch use the standards per ACI 350 for cooling tower basins.

Regards,
Harold Sprague





From: "Ashraf, Mohammed (Qatar)" <mohammed.ashraf(--nospam--at)worleyparsons.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: Load factor for Cooling Tower
Date: Tue, 12 Sep 2006 07:34:32 +0300

Dear Harold,
Thanks a lot for your lengthy mail. The cooling tower which I am
designing is at an elevated level so sulphates are not a major issue
except for foundations.
As you suggested I will consider long term serviceability issues as per
ACI 350.
Regards
Ashraf

-----Original Message-----
From: Harold Sprague [mailto:spraguehope(--nospam--at)hotmail.com]
Sent: 11 September 2006 19:04
To: seaint(--nospam--at)seaint.org
Subject: RE: Load factor for Cooling Tower

Ashraf,
The only ignorance is to NOT ask the question.  And this is a good
question!

ACI 350 is specifically written for environmental structures.

From the Scope section of ACI  350:
"The code portion of this document covers the structural design,
materials
selection, and construction of environmental engineering concrete
structures. Such structures are used for conveying, storing, or treating

liquid, wastewater, or other materials, such as solid waste. They
include
ancillary structures for dams, spillways,and channels.

They are subject to uniquely different loadings, more severe exposure
conditions and more restrictive serviceability requirements than normal
building structures. Loadings include normal dead and live loads and
vibrating equipment or hydrodynamic forces. Exposures include
concentrated
chemicals, alternate wetting and drying, and freezing and thawing of
saturated concrete.

Serviceability requirements include liquid-tightness or gas-tightness.
Typical structures include conveyance, storage, and treatment
structures.
Proper design, materials, and construction of environmental engineering
concrete structures are required to produce serviceable concrete that is

dense, durable, nearly impermeable, resistant to chemicals, with limited

deflections and cracking. Leakage must be controlled to minimize
contamination of ground water or the environment, to minimize loss of
product or infiltration, and to promote durability.

This code presents new material as well as modified portions of the ACI
318-95 Building Code that are applicable to environmental engineering
concrete structures."

From the load factor section of ACI 350 the commentary reads:
"R.9.2.5 - This section addressees the need to consider loading due to
weight of fluid or fluid pressure. Although fluid densities and heights
are
usually well known, the load factor of 1.7 is used as a part of the
concept
of environmental durability and long-term serviceability of the
structure."

Obviously a cooling tower is NOT an environmental structure.  However,
if
you wish to consider long term serviceability, you should consider using
the
crack limits and load factors contained in ACI 350.  Until the cooling
tower
people develop a code of their own there is not much guidance.

In your area of the world, you have an issue with sulfates in the water
and
soil.  Sulfates are a major serviceability issue.

Regards,
Harold Sprague





>From: "Ashraf, Mohammed (Qatar)" <mohammed.ashraf(--nospam--at)worleyparsons.com>
>Reply-To: <seaint(--nospam--at)seaint.org>
>To: <seaint(--nospam--at)seaint.org>
>Subject: Load factor for Cooling Tower
>Date: Mon, 11 Sep 2006 09:23:16 +0300
>
>Dear fellow engineers,
>
>I am designing a cooling tower. I have some doubt regarding the load
>factors to be used.
>
>For  fluid load (F), ACI 350-01 says U=1.4D+1.7F. But ASCE-02, says
>1.4(D+F). Which load combination to used for cooling tower basin
>design?.
>
>Ignorance is regretted.
>
>Thanks in advance,
>
>Regards,
>
>Ashraf
>

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