• Designing composite structures for reuse

      Lam, Dennis; Yang, Jie; Dai, Xianghe; Sheehan, Therese; Zhou, Kan (2018)
      Steel 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.
    • Experimental study of beam to concrete-filled elliptical steel tubular column connections

      Yang, Jie; Sheehan, Therese; Dai, Xianghe; Lam, Dennis (2015-10)
      This paper investigated the rotation behaviour of simply bolted I-beam to concrete-filled elliptical steel tubular (CFEST) column connections experimentally. Ten different joint assemblies were tested to failure, with a constant axial compressive load applied to the column and upwards concentrated loads at the beam ends. All of the steel tubes were hot-finished and had a cross-sectional aspect ratio of 2. The orientation of the column and the arrangement of the stiffening plates were taken into consideration. Moment versus rotation relationships and failure modes were compared for each joint, highlighting the benefits of using core concrete and stiffeners in these connections.
    • Finite element analysis of concrete filled lean duplex stainless steel columns

      Lam, Dennis; Yang, Jie; Dai, Xianghe (2019-10)
      In recent years, a new low nickel content stainless steel (EN 1.4162) commonly referred as ‘lean duplex stainless steel’ has been developed, which has over two times the tensile strength of the more familiar austenitic stainless steel but at approximately half the cost. This paper presents the finite element analysis of concrete filled lean duplex stainless steel columns subjected to concentric axial compression. To predict the performance of this form of concrete filled composite columns, a finite element model was developed and finite element analyses were conducted. The finite element model was validated through comparisons of the results obtained from the experimental study. A parametric study was conducted to examine the effect of various parameters such as section size, wall thickness, infill concrete strength, etc. on the overall behaviour and compressive resistance of this form of composite columns. Through both experimental and numerical studies, the merits of using lean duplex stainless steel hollow sections in concrete filled composite columns were highlighted. In addition, a new formula based on the Eurocode 4 was proposed to predict the cross-section capacity of the concrete filled lean duplex stainless steel composite columns subjected to axial compression.
    • New composite flooring system for the circular economy

      Lam, Dennis; Yang, Jie; Wang, Yong; Dai, Xianghe; Sheehan, Therese; Zhou, Kan (Techno-Press, 2021-09-10)
      Circular 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 tests
    • Structural behaviour of beam to concrete-filled elliptical steel tubular column connections

      Yang, Jie; Sheehan, Therese; Dai, Xianghe; Lam, Dennis (2017-02)
      Elliptical Hollow Sections (EHSs) have been utilized in construction recently because of their visual appearance as well as the potential structural efficiency owing to the presence of the two principle axes. However, little information currently exists for the design of beam to elliptical column connections, which is an essential part of a building structure. Thus, to ensure the safe and economic application of EHSs, a new research project has been initiated. Rotation behaviour of simply bolted beam to concrete-filled elliptical steel column connections was investigated experimentally. Various joint types were considered and the benefits of adopting core concrete and stiffeners were highlighted. This paper covers the experimental studies and simulation of the connections using the ABAQUS standard solver. Comparisons of failure modes and moment vs. rotation relationships of the connections between numerical and experimental results were given. Good agreement has been obtained and the developed finite element model was therefore adopted to conduct a preliminary parametric study to explore the effect of critical parameters on the structural behaviour of beam to concrete-filled elliptical column connections.