Recent research and development in semi-rigid composite joints with precast hollowcore slabs

Composite structure incorporating steel beams and precast hollowcore slabs is a recently developed composite floor system for building structures. This form of composite construction is so far limited to simple beam-column connections. Although the concept of semi-rigid composite joints has been widely research in the past, most of the researches have been carried out on composite joints with metal deck flooring and solid concrete slabs. Research on composite joints with precast hollowcore slabs is rather limited. As the construction industry demands for rapid construction with reduction in cost and environmental impacts, this form of composite floor system, which does not require major onsite concreting, has become very popular among the designers and engineers in the UK. In this paper, full-scale tests of beam-to-column semi-rigid composite joints with steel beam and precast hollowcore slabs are reported. Based on the tests data; the structural behaviour of these semi-rigid composite joints is discussed together with numerical and finite element modelling. Through parametric studies, an analytical model for the semirigid composite joints is proposed and is verified by both the experimental data and finite element model; and good agreement is obtained

Concrete - filled steel tube columns - tests compared with Eurocode 4

This paper summarises the data from 1819 tests on concrete-filled steel tube columns and compares their failure load with the prediction of Eurocode 4. The full data is given on the website http://web.ukonline.co.uk/asccs2 . The comparison with Eurocode 4 is discussed and shows that Eurocode 4 can be used with confidence and generally gives good agreement with test results, the average Test/EC4 ratio for all tests being 1.11. The Eurocode 4 limitations on concrete strength could be safely extended to concrete with a cylinder strength of 75 N/mm2 for circular sections and 60 N/mm2 for rectangular sections

Prediction of longitudinal shear resistance of composite slabs with profile sheeting to Eurocode 4

Composite slab incorporate profile sheeting is widely used for multi-storey buildings construction throughout the world. The profile sheeting not only providing the temporarily support to the wet concrete but also formed an integral part of the composite slabs, it provides the resistance to vertical separation and longitudinal slippage between the steel concrete interface. Longitudinal shear resistance of the composite slabs is difficult to predict theoretically and the Eurocode 4 method to predict the longitudinal resistance rely on experimental testing. The most common mode of failure of the composite slab is by longitudinal shear and loss of interlocking at the steel-concrete interface. This paper presents the testing of the composite slabs in accordance to the Eurocode 4

Structural design of concrete filled steel elliptical hollow sections

This paper presents the behaviour and design of axially loaded elliptical steel hollow sections filled with normal and high strength concrete. The experimental investigation was conducted with three nominal wall thickness (4mm, 5mm and 6.3mm) and different infill concrete cube strengths varied from 30 to 100 MPa. The effect of steel tube thickness, concrete strength, and confinement were discussed together with column strengths and load-axial shortening curves were evaluated. The study is limited to cross-section capacity and has not been validated at member level. Comparisons of the tests results together with other available results from the literature have been made with current design method used for the design of composite circular steel sections in Eurocode 4 and AISC codes. It was found that existing design guidance for concrete filled circular hollow sections may generally be safely applied to concrete filled elliptical steel tubes

Behaviour of concrete filled stainless steel elliptical hollow sections

This paper presents the behaviour and design of axially loaded concrete filled stainless steel elliptical hollow sections. The experimental investigation was conducted using normal and high strength concrete of 30 and 100 MPa. The current study is based on stub column tests and is therefore limited to cross-section capacity. Based on the existing design guidance in Eurocode 4 for composite columns, the proposed design equations use the continuous strength method to determine the strength of the stainless steel material. It is found to provide the most accurate and consistent prediction of the axial capacity of the composite concrete filled stainless steel elliptical hollow sections due largely to the more precise assessment of the contribution of the stainless steel tube to the composite resistance

Finite-horizon H∞ control for discrete time-varying systems with randomly occurring nonlinearities and fading measurements

This technical note deals with the H∞ control problem for a class of discrete time-varying nonlinear systems with both randomly occurring nonlinearities and fading measurements over a finite-horizon. The system measurements are transmitted through fading channels described by a modified stochastic Rice fading model. The purpose of the addressed problem is to design a set of time-varying controllers such that, in the presence of channel fading and randomly occurring nonlinearities, the H∞ performance is guaranteed over a given finite-horizon. The model transformation technique is first employed to simplify the addressed problem, and then the stochastic analysis in combination with the completing squares method are carried out to obtain necessary and sufficient conditions of an auxiliary index which is closely related to the finite-horizon H∞ performance. Moreover, the time-varying controller parameters are characterized via solving coupled backward recursive Riccati difference equations (RDEs). A simulation example is utilized to illustrate the usefulness of the proposed controller design scheme

Origin of Discrepancies in Inelastic Electron Tunneling Spectra of Molecular Junctions

We report inelastic electron tunneling spectroscopy (IETS) of multilayer molecular junctions with and without incorporated metal nano-particles. The incorporation of metal nanoparticles into our devices leads to enhanced IET intensity and a modified line-shape for some vibrational modes. The enhancement and line-shape modification are both the result of a low lying hybrid metal nanoparticle-molecule electronic level. These observations explain the apparent discrepancy between earlier IETS measurements of alkane thiolate junctions by Kushmerick \emph{et al.} [Nano Lett. \textbf{4}, 639 (2004)] and Wang \emph{et al.} [Nano Lett. \textbf{4}, 643 (2004)].Comment: 4 pages, 4 figures accepted for publication in Physical Review Letter