Chen, Shiming (1992) Instability of composite beams in hogging bending. PhD thesis, University of Warwick.

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Abstract

This work is concerned with local buckling and lateral distortional buckling, two
aspects of instability that govern the design of composite beams in hogging regions.
Local buckling in hogging regions of a continuous composite beam was modelled
by moment curvature characteristics of a cantilever, modified by two curvature
ratios, K1 and K2. Test based expressions for K1 and K2,
in terms of a combined
slenderness λc, were developed, and subsequently used in numerical analyses
of 50 two-span composite beams to assess moment redistribution allowed for Class
2 beams by draft Eurocode 4. The analyses include effects of non-linear material
properties, residual stresses and local buckling. The parametrical studies include
adverse values, in relation to practice, of relative length of adjacent spans, span-to-depth
ratio, and ratio of hogging to sagging moment of resistances. It is concluded
that the redistribution of elastic bending moments allowed by the draft Eurocode 4
is safe and economical.
Distortional lateral buckling of composite beams with both continuous and discrete
U-frame actions was studied experimentally. Distortional lateral buckling was
found in the tests of two composite beams with inverted U-frame actions. Web
distortion was effectively reduced by vertical web stiffeners, which form a part of
discrete U-frames together with the slab and the connection of U-frame. The work
provides background to assess lateral buckling strength for composite beams with
both continuous and discrete U-frame actions. A further theoretical approach on
the topic of discrete inverted U-frame action was presented.
Strength and stiffness of discrete U-frame connections were also studied. The
strength of a discrete U-frame connection was found to be influenced by both the
shear failure of concrete, and the yielding of steel top flange in the connection. A
simple rule to assure strength of U-frame connections is proposed by checking these
two failures separately. The prediction of shear failure of a U-frame connection is
based on a truss model, and the prediction of failure in the steel top flange is based
on a rigid plastic mechanism. A semi-empirical formula for flexibility of a U-frame
connection was derived. They were all checked against test results. Interactive U-frame
force and U-frame stiffness were also studied. A tentative design method for
discrete U-frame composite beams was proposed.

Item Type:	Thesis (PhD)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Library of Congress Subject Headings (LCSH):	Composite construction, Buckling (Mechanics)
Official Date:	July 1992
Dates:	Date Event July 1992 Submitted
Institution:	University of Warwick
Theses Department:	School of Engineering
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Johnson, R. P. (Roger Paul)
Sponsors:	University of Warwick ; Overseas Research Students Awards Scheme (ORSAS) ; Chinese Educational Commission
Extent:	ix, 240 p.
Language:	eng

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