Salter, John Barry (1976) Column behaviour and deflection control in steel frames. PhD thesis, University of Warwick.

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Abstract

The work described in this thesis is concerned with the behaviour of steel building frames.

Two computer programs have been developed, based on the formation of stiffness matrices for the frame under analysis, which give ultimate load assessments of uniaxial and biaxial frames respectively. The uniaxial analysis estimates the reduction in stiffness due to specified regions of plasticity forming within the frame. Analysis is then continued until the combined effects of plasticity and elastic frame instability are sufficient to cause collapse of the frame.

The biaxial analysis extends the uniaxial stiffness matrix to allow for the extra minor axis, torsional and warping degrees of freedom which can give rise to out-of-plane buckling failures. In addition, a more general method of calculating reduced flexural and axial stiffnesses due to plasticity is used. The method, based on moment-curvature techniques, is also used to calculate corresponding torsional, warping, and cross product of inertia values. The latter rigidity is then introduced into the overall stiffness matrix to account for the shift in shear centre resulting from non-symmetric formation of plastic regions. Both computer programs are generally found to give good agreement with a variety of previously cited theoretical and experimental analyses.
A series of experimental tests on pin-ended tapered steel columns have been performed to investigate the ultimate behaviour of these columns as part of a portal frame structure. The columns were subject to a combination of axial load and major axis bending moments, the latter being incremented to cause failure. In general, the columns fail predominantly due to elastic instability rather than excessive plasticity. The tests also serve as a useful check on the validity of the biaxial computer analysis in assessing the ultimate failure loads of the columns.

Finally, a simple linear method of proportioning the members of steel frames to satisfy deflection requirements in an efficient manner is presented. The method, which requires a computer program for a solution, is found to give a design which is usually as good, and sometimes better, than previous optimisation methods based on more rigorous non-linear programming techniques.

Item Type:	Thesis (PhD)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Library of Congress Subject Headings (LCSH):	Building, Iron and steel, Steel framing (Building), Structural frames
Official Date:	August 1976
Dates:	Date Event August 1976 Submitted
Institution:	University of Warwick
Theses Department:	Department of Engineering
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Anderson, D.
Sponsors:	Science Research Council (Great Britain)
Extent:	viii, 265 leaves : illustrations, charts
Language:	eng

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