Use of bolted shear connectors in composite construction

[EN] Composite beam incorporated steel profiled decking has been extensively used for multi-storey buildings and is now one of the most efficient and economic form of flooring systems. However, the current composite flooring system is not demountable and would require extensive cutting on site during demolition, and the opportunity to reuse the steel components is lost even though these components could be salvaged and recycled. This paper presents the use of high strength bolts as shear connectors in composite construction, the shear behaviour and failure modes were observed and analysed through a series of push-off tests and numerical simulation. The results highlighted the structural behaviour of three different demountable shear connection forms in which continuous slabs or un-continuous slabs were used. Numerical models were validated against experimental observation. Both experimental and numerical results support the high strength bolts used as demountable shear connectors and lead to a better understanding to the behaviour of this form of shear connectors.The research leading to these results is part of a joint project of the Steel Construction Institute, the University of Luxembourg, the University of Bradford, the Lindab SA, the Tata Steel Ijmuiden BV, the Stichting Bouwen Met Staal, the Technical University of Delft and the AEC3 Ltd. The funding was received from the European Commission: Research Fund for Coal and Steel (RFCS-2015, RPJ, 710040).Dai, X.; Lam, D.; Sheehan, T.; Yang, J.; Zhou, K. (2018). Use of bolted shear connectors in composite construction. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 475-482. https://doi.org/10.4995/ASCCS2018.2018.7039OCS47548

Flexural behaviour of composite slim floor beams

[EN] Composite slim floor beams comprise a steel section embedded in a concrete slab, offering the advantages of a steel-concrete composite structure combined with a reduced floor depth. Several mechanisms contribute to the shear connection in this type of beam, such as headed studs, friction and clamping effects and the using of reinforcement bars passing through holes in the steel beam web. However, to date, nobody has systematically identified these mechanisms and Eurocode 4 does not provide specific design guidance for slim floor beams. Hence, a series of shear beam tests and flexural beam tests were carried out in order to assess the degree of shear connection and connector capacity in these beams. The test set-up is described including different arrangements of shear connectors for each specimen. The paper presents the findings from the flexural beam tests. The results are compared with those from the previous shear beam tests. Numerical models will be developed in future to extend the data and include a wider range of parameters. The data will also be used to improve understanding of this type of beam and will lead to the provision of specific design guidelines for slim floor beams.The authors gratefully acknowledge the funding received from the European Community Research Fund for Coal and Steel under grant agreement number RFSR-CT-2015-00020.Sheehan, T.; Dai, X.; Yang, J.; Zhou, K.; Lam, D. (2018). Flexural behaviour of composite slim floor beams. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 137-144. https://doi.org/10.4995/ASCCS2018.2018.6963OCS13714

A No-Reference Quality Assessment Method for Digital Human Head

In recent years, digital humans have been widely applied in augmented/virtual reality (A/VR), where viewers are allowed to freely observe and interact with the volumetric content. However, the digital humans may be degraded with various distortions during the procedure of generation and transmission. Moreover, little effort has been put into the perceptual quality assessment of digital humans. Therefore, it is urgent to carry out objective quality assessment methods to tackle the challenge of digital human quality assessment (DHQA). In this paper, we develop a novel no-reference (NR) method based on Transformer to deal with DHQA in a multi-task manner. Specifically, the front 2D projections of the digital humans are rendered as inputs and the vision transformer (ViT) is employed for the feature extraction. Then we design a multi-task module to jointly classify the distortion types and predict the perceptual quality levels of digital humans. The experimental results show that the proposed method well correlates with the subjective ratings and outperforms the state-of-the-art quality assessment methods

Designing composite structures for reuse

YesSteel is a highly versatile and 100% recyclable material but is also carbon and energy intensive in production. Steel framed structures are inherently adaptable and potentially demountable. Reuse instead of the common practice of recycling steel by melting, makes good environmental sense, saving both on resources and carbon emissions. Reuse is commercially and technically viable, as demonstrated by isolated projects. Although steel reuse has been identified as an effective method to reduce the carbon and energy impact of construction, it is in effect only marginally used in practice. We found that although there is a sufficient spread between the price of steel scrap and new steel, this difference cannot be captured by the demolition contractors. In steel multi-storey high-rise building structures, composite construction is the most efficient and economic forms of construction. Composite beams incorporate composite floors with profiled steel sheeting are the most common structural system used in multi-storey high-rise buildings and is seen as one of the most important ways of expanding the use of steel buildings in Europe, i.e. increasing market share. However, in terms of reuse, current composite construction systems require extensive cutting on-site during the demolition process making reuse not viable. This paper presents an innovative composite system that is designed for deconstruction and reuse, its structural behaviour and failure modes were observed and analysed through a series of experimental studies and numerical simulation. The results showed that the structural behaviour of this new form of composite system not only allows for deconstruction and reuse, it has a similar structural performance to the traditional composite system with welded shear connectors

Dynamic variation of the dielectric permittivity of elastomers with mechanical constraints

Elastomers are commonly used as insulators or actuators in important fields such as robotics and electronics. The performance of elastomers is strongly influenced by their dielectric permittivity while determining the dielectric permittivity of elastomers appears to be rather challenging. With image processing techniques and a motor-driven biaxial test setup, the dynamic variation of the dielectric permittivity and dielectric loss of elastomers under dynamic mechanical constraints is first examined in this paper. Also, the mechanical rate-dependence and the cyclic behavior of the dielectric permittivity are investigated. At a given mechanical loading rate, the change in the dielectric permittivity is found to follow a cubic polynomial function. The variations of the stress and the dielectric permittivity indicate the mechanical constraints on the polarization of the material. Our experiment setup allows different mechanical loading paths to be applied to the elastomer when simultaneously measuring the dielectric permittivity and the dielectric loss

A Hybrid Genetic Algorithm for Bin Packing Problem Based on Item Sequencing

The bin packing problem based on item sequencing is defined as follows: given a set of sequenced items of different sizes, how should one pack them all into bins of different capacity, in order to make the utility ratio of bin capacity as higher as possible? In this paper, next fit algorithm, a heuristic method for bin packing problem, is introduced into simple genetic algorithm, and a hybrid genetic algorithm is proposed for solving bin-packing problem based on item sequencing. In the hybrid genetic algorithm, the idea of simple genetic algorithm is used to search the solution of the bins sequence, and the idea of next fit algorithm is used to pack the sequenced items into the bins sequence obtained. Finally, the effectiveness of the hybrid genetic algorithm is convinced through computational results of an example

Enzyme Stability and Activity in Non-Aqueous Reaction Systems: A Mini Review

Enormous interest in biocatalysis in non-aqueous phase has recently been triggered due to the merits of good enantioselectivity, reverse thermodynamic equilibrium, and no water-dependent side reactions. It has been demonstrated that enzyme has high activity and stability in non-aqueous media, and the variation of enzyme activity is attributed to its conformational modifications. This review comprehensively addresses the stability and activity of the intact enzymes in various non-aqueous systems, such as organic solvents, ionic liquids, sub-/super-critical fluids and their combined mixtures. It has been revealed that critical factors such as Log P, functional groups and the molecular structures of the solvents define the microenvironment surrounding the enzyme molecule and affect enzyme tertiary and secondary structure, influencing enzyme catalytic properties. Therefore, it is of high importance for biocatalysis in non-aqueous media to elucidate the links between the microenvironment surrounding enzyme surface and its stability and activity. In fact, a better understanding of the correlation between different non-aqueous environments and enzyme structure, stability and activity can contribute to identifying the most suitable reaction medium for a given biotransformation

New composite flooring system for the circular economy

NoCircular economy is an economic system aimed at minimizing wastes and making the most of the current resources. This regenerative approach contrasts with the traditional linear economy, which has been adopted by the construction industry. Developing new construction technologies for sustainable built environment is a top priority for the construction industry throughout the world. Much of the environmental impact from the construction industry is associated with the consumption of resources and generation of waste. The construction industry in Europe consumes over 70,000 million tonnes of materials each year and generates over 250 million tonnes of waste. Composite flooring formed by connecting the concrete slabs to the supporting steel beams has been widely used for many years and is well established as one of the most efficient floor systems in multi storey steel frame building structures. However, shear connectors are welded through the steel decking to the steel beams and cast into the concrete; this made deconstruction and reuse of these components almost impossible. A new composite flooring system which allows for the reuse of the steel beams and composite floor slabs is developed and tested to assess its potential and suitability for reuse. This paper presents the results of a series of full scale beam tests and demonstrates the reusability of this new form of composite flooring systems. Simplified hand calculations are also provided and compared against beam testsEPSRC, Structural Metal Deck Ltd