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Controversy has risen about the suitability of small-scaled pushout tests to satisfactorily model the behavior of shear connections in composite beams. However, the determination of the strength of the shear connectors from full-scale composite beam tests is expensive, complicated, and subject to modeling inaccuracies. The results of several composite beam tests incorporating trapezoidal steel decking are presented along with the results of companion pushout tests. These were especially designed to deliver insight into the ductility of the shear connection when subject to the so-called 'brittle' failure modes of the concrete slab observed in small-scale pushout tests, and to examine the suitability of novel reinforcing measures such as waveform reinforcement components or stud performanceenhancing devices. The comparison of the shear connection performance in both the carefully conducted pushout tests where no additional lateral restraints were employed and the beam tests demonstrated that the failure modes experienced were identical, the load-slip behavior was also similar, and comparable connector strengths were achieved. The requirement of sufficiently ductile shear connection behavior in achieving a satisfactory composite beam performance was also established in these tests. DOI: 10.1061/(ASCE)0733-9445(2010)136:2(183) CE Database subject headings: Composite beams; Composite structures; Concrete slabs; Connections; Ductility; Studs; Decks; Tests. Author keywords: Pushout test; Composite beam test; Shear connection; Waveform reinforcement; Spiral stud device.

In this paper several design methods have been developed that can be used to conservatively estimate the strength of circular thin-walled concrete filled steel tubes under different loading conditions. The loading conditions examined include axial loading of the steel only, axial loading of the concrete only, and simultaneous loading of the concrete and steel both axially and at small eccentricities. Recent tests on circular concrete filled steel tubes have been used to calibrate and validate the proposed design methods. The test specimens were short with a length-to-diameter ratio of 3.5 and a diameter thickness ratio between 60 and 220. The internal concrete had nominal unconfined cylinder strengths of 50, 80, and 120 MPa. The bond (or lack of) between the steel and internal concrete was critical in determining the formation of a local buckle.

The tests described in this paper are the second in a program carried out to determine the effectiveness of intermediate stiffeners in controlling the buckling modes of profiled steel decks. A series of specimens with 'flat-hat' intermediate stiffeners were brake-pressed to designs that were chosen to ensure that the primary buckling mode took place in the elastic range and was not affected by plasticity. The specimens were loaded in pure bending, resulting in various buckling waveforms prior to ultimate failure through a plastic collapse mechanism. The experimentally determined buckling stresses are compared with studies performed using a computer analysis based on the finite-strip method. The existing design procedure for local buckling in Australian Standard AS1538-1988 and various methods involving distortional buckling are compared with the test results. A method of design accounting for the interaction of buckling modes and its effect on the ultimate moment capacity is proposed and compared with the test results.

The size and position of intermediate stiffeners in the compression flanges of thin-walled profiled steel decks exert a strong influence on the dominant buckling mode of the flange. The ability of the deck to provide both high load-carrying capacity before the onset of elastic buckling and a high ultimate-load capacity may therefore be affected. A program of tests to determine the effectiveness of intermediate stiffeners in controlling buckling modes is undertaken. A series of specimens are loaded in pure bending resulting in various buckling waveforms prior to ultimate failure through a plastic collapse mechanism. The experimentally determined buckling stresses are found to be comparable with studies performed using a finite-strip numerical analysis in which both local, and distortional buckling modes are predicted. A simplified design procedure for distortional buckling is proposed. The existing design procedure for local buckling in the Australian Standard AS1538-1988 is confirmed.

The strength of thin-walled cylindrical shell structures is highly dependent on the nature and magnitude of imperfections. Most importantly, circumferential imperfections have been reported to have an especially detrimental effect on the buckling resistance of these shells under axial load. Due to the manufacturing techniques commonly used during the erection of steel silos and tanks, specific types of imperfections are introduced into these structures, among them circumferential weld-induced imperfections between strakes of steel plates. A study on several factors influencing the buckling of silos and tanks was carried out using the finite-element method. The interaction between neighboring circumferential weld imperfections was investigated, and it was found that the influence on the buckling behavior depended on the strake height in relation to the linear meridional bending half-wavelength and the depth of the imperfection. The shape of localized circumferential weld imperfections was found to influence the buckling behavior of silos and tanks. The influence of a recently developed shape function on the buckling behavior has been examined. The strengthening effect of weld-induced residual stress fields was also studied, and the extent of the increase in buckling strength was derived for a large range of cylinder geometries.