ML20138M308

Responds to Re Application of Combined Stress Equations in Spec for Design Fabrication & Erection of Structural Steel for Bldgs

ML20138M308
Person / Time
Site:	LaSalle
Issue date:	07/25/1985
From:	Haaijer G AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC.
To:	Ashar H NRC
Shared Package
ML20138M288	List: ML20138M284 ML20138M290 ML20138M298 ML20138M304 ML20138M308
References
NUDOCS 8511010085
Download: ML20138M308 (2)

Text

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AMERICAN INSTITUTE OF STEEL CONSTRUCilON. INC.

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GttRHARD HAAUIR PhD.

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• 3 July 25, 1985 Mr. Hans Ashar U.S. Nuclear Regulatory Commission 5650 Nicholson Lane Washington, DC 20555 Re: Application of Combined Stress Equations

in Section 1.6 of the AISC Specification to Single Angles subjected to combined Axial Load and Biaxial Moments

Dear Hans,

This is in answer to your letter of June 13, 1985 regard-ing the subject application of the AISC Specification for

• the Design, Fabrication and Erection of Structural Steel for Buildings, November 1, 1978.

As indicated in the Preface, the intention of the Speci-fication is to cover the many everyday design criteria in routine design office usage. It is not intended to cover the infrequently encountered problems within the full range of structural design practice. Thus, the Specifi-cation does not cover axially loaded members that fail by torsional or flexural-torsional buckling. Because the strength of single-angle struts may be governed by flex-ural-torsional buckling, the applicability of Section 1.6.1 4

should be established by the responsible design profes-sional. ,

Although not part of the Specification, the application of Section 1.6.1 to single-angle struts is discussed on pg. 3-4P of the AISC Manual of Steel Construction, Eighth  !

Edicior,s 1980. The discussion refers to the technical lit-erature tor the anali :Ts of flexural-torsional buckling of single angles. You may with to consider the follcwing re-ferences:

1) Alexander Chajes and George Winter, " Torsional-Flex-ural Buckling of Thin-Walled Members", J. of the Struct. Div.,'AFCE Vol. 91 No. ST 4 August 1965.

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l Mr. Hans Ashar July 25, 1985 Page 2.

2) Tsutomu Usami and Theodore V. Galambos, "Eccen-trically Loaded Single Angle Columns" IABSE Pub-lications Vol. 31-II, 1971.

3) " Electrical Transmission Line and Tower Design -

Guide", J. of the Struct. Div., ASCE, Vol. 93, No. ST 4, August 1967.

Regarding the specific questions raised by Dr. Mark Galambos, we Hartzman in his letter to Prof. T.V.

offer the following comments:

1) The x- and y- axis are defined on pg. 5-12 as the subscripts referring to strong-axis and weak-axis bending, respectively. These are the prin- .

cipal axes.

2) Equations 1.6-la and 1.6-2 should be evaluated at a given " point under consideration", which re-fers to the section location along the member axis. The points in the cross section where the stresses are calculated may be different for bend-ing about the two principal axes.

3) Similar to item 2, the maximum moments about the two axes may occur at different points along the member.

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In considering the above points, it should be remembered j

that the interaction equations are approximations intend-i ed to give correct answers in the limits when only the respective load effect is present, and to give conserva-c tive results for combined effects.

I believe that the Specification and Commentary are clear regarding the above matters. We have, therefore, not pro-cessed a formal inquiry with our Committee on Specifica-tions. However, we would be pleased to do so if you have further questions.

incerely yours, deerha Haaijer GH/cd raa.rhGt - %% @alambos ._.