ASME AG-1:2003 pdf download ARTICLE AA-D-3000 RECTANGULAR DUCTWORK
AA-D-3100INTRODUCTION
The methods presented in this article are suggestedmeans of approach for analysis of rectangular ductwork.The presence of compressive loads due to pressureor external forces requires that the ductwork and supports be designed properly for these loads. Bucklingis the major concern in the design of rectangulatductwork and is the governing failure mode to beconsidered in design.
The methods contained in this article, or other sourcesmay be used.However, the requirements of ArticleSA-4000 must be met.
AA-D-3200RECTANGULAR DUCTANALYSIS
Properties of sections (cross-sectional area.momentof inertia. section modulus, radius of gyration, etc.)shall be determined in accordance with conventionalmmethods of structural design, Properties shall be basedon the full cross section of the members (or net sectionswhere applicable) except where the use of a reducedcross section, or effective design width, is required bythe provisions of the American Iron and Steel Institute’s(AISI) Specification for the Design of Cold-FormedSteel Structural Members [see Article AA-D-5000Specifications for the Design of Cold-Formed SteelStructural Members)l.
Use of AISI Specification provisions, however, withthe specified maximum effective design widths andheights (w/t and h/t ratios where w and h are thewidth and height of the duct respectively), may resultin duct thicknesses in excess of those commonly usedfor ductwork constructed to.or similar to.SMACNAspecifications，Tests performed have demonstrated that ducts constructed to SMACNA specifications can adequately withstand specified dynamic loads. In effectthe following options may be utilized to calculateproperties of ductwork sections.
(a) AISI specifications
(b) Testing as permitted by the ASI specification(c) Finite element models using large displacementcriteria
Option (c) can be used to extend the range ofapplicablility of the AISI equations and/or arrive atother suitable provisions in place of the AlSI provisionsIn addition these models can be used to develop valuesfor pressure-induced stresses not readily covered bythe AISI provisions.
AA-D-3300
ALLOWABLEDESIGN STRESSES: SERVICELEVEL A
The maximum normal allowable stresses to be usedin design for Service Level A load combinations given inTable SA-4212 shall not exceed the following equations.
AA-D-3310 AXIALLY LOADED COMPRESSIONMEMBERS
The average axial stress,P/A, in compression mem-bers shall not exceed the following values of oal [seeArticle AA-D-5000 (Specifications for the Design ofColf-Formed Steel Members and Yu 1985)l: