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Ultimate strength of composite beams
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Molenstra, Nadia Julia (1990) Ultimate strength of composite beams. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b1408194~S15
Abstract
The study of composite beams is characterised by the connection between
the two components: the concrete slab and the steel girder. In this thesis, two
different problems, related to this connection were studied: the problem of partial
interaction in composite beams of long spans with low degrees of shear connection,
and the problem of transverse flexibility of the stud connection 'joint' between
the concrete slab and the steel beam as part of a discrete inverted U-frame. This
thesis is therefore divided into two separate parts.
The study of beams with partial shear connection and solid slabs or slabs
with metal decking is considered in the first part. Such beams, with a uniform
stud spacing over each shear span, with spans longer than 10 m - generally
propped during construction, and with low degrees of shear connection, could fail
prematurely and suddenly in shear rather than gradually in bending, due to the
limited slip deformation capacity of the studs in shear. In order to investigate
the behaviour of simply supported and continuous composite beams with different
degrees of shear connection, different geometry and different shear spans under
design ultimate loading conditions, a numerical computer simulation program
was written. The program takes account of the relative displacement between
the slab and the beam and the non-linear behaviour of steel, concrete and stud
connectors. A data bank of maximum slip results for different beams is obtained
for ultimate beam loads designed to the interpolation method in Eurocode 4. The
computer simulation gives a conservative but safe assessment of the suitability
of the degree of interaction for a specific design ultimate load . The results were
used to formulate a tentative design method for composite beams with solid slabs
and partial shear connection.
Discrete inverted U-frame action exists between composite bridge beams with
intermittent vertical web stiffeners which provide lateral restraint to the bottom
flange in the hogging bending region near the internal supports. The design
method in BS 5400:Part 3 for discrete U-frame action gives values for the transverse
flexibility of a number of standard structural steel connections which are
used in the calculation of the effective buckling length and the lateral deflection
of the compression flange. To obtain similar values for steel-concrete joints, tests
were done to scale 1:1 on six flange-slab connections with different stud configurations,
but constant conservative dimensions for the steel flange and the concrete
slab. Their crack patterns can be predicted by using a truss analogy. All test
specimens either failed in shear or by puffing out of the studs, and shear cracking
and shear failure criteria for concrete beams can be used to predict the cracking
and failure loads. The transverse elastic flexibiities of the joints in these tests
only represent the behaviour of the same joints in a complete structure up to the
point where the shear cracks propagated over the full width of the specimens.
Based on these few test results, a limited tentative design equation is proposed
for the transverse flexibility of these type of stud connections, although further
research is required into the influence of the increased flexibility on the buckling
mode and the variation of the flexibility with variables other than the stud
configurations.
Item Type: | Thesis (PhD) | ||||
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Subjects: | T Technology > TA Engineering (General). Civil engineering (General) | ||||
Library of Congress Subject Headings (LCSH): | Composite construction, Shear (Mechanics), Joints (Engineering) | ||||
Official Date: | August 1990 | ||||
Dates: |
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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 ; Building Research Establishment ; Fonds national de la recherche scientifique (Belgium) | ||||
Extent: | xxxiv, 426 leaves | ||||
Language: | eng |
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