Composite beams : reliability and longitudinal shear resistance with profiled sheeting
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Abstract
In this thesis, two problems have been studied: one is the reliability of design
resistances of composite beams in bending, the other is the longitudinal shear
resistances in concrete flanges of composite beams with profiled sheeting.
For the first problem, a general theory is developed based on the concepts of
safety-index and second-moment reliability, to analyse the reliability of a design
resistance for composite structures. This theory consists of two basic parts: one is
the determination of several distinct safety factors for a single resistance function,
with respect to the specified safety level; the other is the assessment of safety
level, corresponding to given safety factors. Application of this theory is related
to the relevant test results. In the scope of Eurocode 4, this theory is particularly
used to calibrate safety factors employed for design plastic bending resistances of
composite beams. From the calculation based on 122 test results, the reliability
of using the Eurocode provisions, including the recommended safety factors and
the theoretical models, is judged for bending resistances of beams with full and
partial shear connection.
In studying the longitudinal shear resistances in concrete flanges of composite
beams with and without profiled sheeting, a simple theory to determine the
resistances is established. This theory is based on the "friction-cohesion" and
"concrete strut" models for concrete in shear and takes the effect of profiled
sheeting into account. Associated with the theoretical work, seven tests on three
specimens for investigating the longitudinal shear resistances are reported. From
both experimental results and theoretical calculation, the behaviour of the test
specimens is studied, and, finally, new design recommendations are made to predict
the longitudinal shear resistances of the composite beams