• Axial Capacity of Circular Concrete¿filled Tube Columns.

      Giakoumelis, G.; Lam, Dennis (2004)
      The behaviour of circular concrete-filled steel tubes (CFT) with various concrete strengths under axial load is presented. The effects of steel tube thickness, the bond strength between the concrete and the steel tube, and the confinement of concrete are examined. Measured column strengths are compared with the values predicted by Eurocode 4, Australian Standards and American Codes. 15 specimens were tested with 30, 60 and 100 N/mm2 concrete strength, with a D/t ratio from 22.9 to 30.5. All the columns were 114 mm in diameter and 300 mm in length. The effect due to concrete shrinkage is critical for high-strength concrete and negligible for normal strength concrete. All three codes predicted lower values than that measured during the experiments. Eurocode 4 gives the best estimation for both CFT with normal and high-strength concrete.
    • Axial Capacity of Concrete Filled Stainless Steel Columns

      Lam, Dennis; Wong, K.K.Y. (2005)
      Concrete filled steel columns have been used widely in structures throughout the world in recent years especially in Australia and the Far East. This increase in use is due to the significant advantages that concrete filled steel columns offer in comparison to more traditional construction methods. Composite columns consist of a combination of concrete and steel and make use of these constituent material's best properties. The use of composite columns can result in significant savings in column size, which ultimately can lead to significant economic savings. This reduction in column size can provide substantial benefits where floor space is at a premium such as in car parks and office blocks. The use of stainless steel column filled with concrete is new and innovative, not only provides the advantage mentioned above, but also durability associated with the stainless steel material. This paper concentrates on the axial capacity of the concrete filled stainless steel columns. A series of tests was performed to consider the behaviour of short composite stainless steel columns under axial compressive loading, covering austenitic stainless steels square hollow sections filled with normal and high strength concrete. Comparisons between Eurocode 4, ACI-318 and the Australian Standards with the findings of this research were made and comment.
    • Axial Capacity of Concrete-Filled Steel Elliptical Hollow Sections

      Lam, Dennis; Testo, N. (2007)
      Concrete filled steel tube (CFST) columns are becoming increasingly popular due to the advantages they offered. They are not only considered aesthetically pleasing but can also offer significant improvement in axial capacity without increases in crosssectional area being required. Elliptical steel hollow sections represent a recent and rare addition to the range of cross-sections available to structural engineers, however, despite widespread interest in their application, a lack of verified design guidance is inhibiting uptake. The use of elliptical steel hollow section with concrete infill is new and innovative, not only provides the advantage mentioned above, but also on the basis of both architectural appeal and structural efficiency. The aim of this paper is to investigate the behaviour of the elliptical CFSTs under axial loading. A total of 12 specimens were tested with wall thicknesses of 4 mm, 5 mm, 6.3 mm and concrete core strength of 30 MPa. This paper reported on the behaviour of concrete filled elliptical hollow sections under axial load. The effect of the wall thickness of the steel section, the bond between steel and concrete and the concrete confinement are presented.
    • Axial compressive behaviour of stub concrete-filled columns with elliptical stainless steel hollow sections.

      Dai, Xianghe; Lam, Dennis (2010)
      This paper presents the axial compressive behaviour of stub concrete-filled columns with elliptical stainless steel and carbon steel hollow sections. The finite element method developed via ABAQUS/Standard solver was used to carry out the simulations. The accuracy of the FE modelling and the proposed confined concrete stress-strain model were verified against experimental results. A parametric study on stub concrete-filled columns with various elliptical hollow sections made with stainless steel and carbon steel was conducted. The comparisons and analyses presented in this paper outline the effect of hollow sectional configurations to the axial compressive behaviour of elliptical concrete-filled steel tubular columns, especially the merits of using stainless steel hollow sections is highlighted.
    • Behaviour of Axially Loaded Concrete Filled Stainless Steel Elliptical Stub Columns.

      Lam, Dennis; Gardner, L.; Burdett, M. (2010)
      This paper presents the details of an experimental investigation on the behaviour 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 equations proposed by the authors on concrete-filled stainless steel circular columns, a new set of equations for the stainless steel concrete-filled elliptical hollow sections were proposed. From the limited data currently available, the equation provides an accurate and consistent prediction of the axial capacity of the composite concrete-filled stainless steel elliptical hollow sections.
    • Behaviour of composite steel beams with precast hollow core slabs in hogging moment regions

      Lam, Dennis; Fu, F. (2005)
      The chapter discusses the behavior of composite steel beams with precast hollow core slabs in hogging moment regions. Full-scale composite beams to column semi-rigid connections with precast hollow core slabs are tested in the chapter. The chapter presents a steelwork connection consists of a flush end plate bolted to column flanges. The main variables studied are shear stud's spacing and degree of shear connection. Comprehensive instrumentations are used for all the tests, based on the experimental data, and equations to predict the rotation and the moment capacity for this type of composite connection are proposed in the chapter. A precast composite hollow core floor is a newly developed composite system for building that use precast hollow core slabs as the structural flooring. However, research on composite construction incorporating steel beams with precast hollow core slabs is still relatively new in comparison to the more traditional composite metal deck flooring.
    • Behaviour of Headed Shear Connectors in Composite Beams with Metal Deck Profile

      Qureshi, J.; Lam, Dennis (2009)
      This paper presents a numerical investigation into the behaviour of headed shear stud in composite beams with profiled metal decking. A three-dimensional finite element model was developed using general purpose finite element program ABAQUS to study the behaviour of through-deck welded shear stud in the composite slabs with trapezoidal deck ribs oriented perpendicular to the beam. Both static and dynamic procedures were investigated using Drucker Prager model and Concrete Damaged Plasticity model respectively. In the dynamic procedure using ABAQUS/Explicit, the push test specimens were loaded slowly to eliminate significant inertia effects to obtain a static solution. The capacity of shear connector, load-slip behaviour and failure modes were predicted and validated against experimental results. The delamination of the profiled decking from concrete slab was captured in the numerical analysis which was observed in the experiments. ABAQUS/Explicit was found to be particularly suitable for modelling post-failure behaviour and the contact interaction between profiled decking and concrete slabs. It is concluded that this model represents the true behaviour of the headed shear stud in composite beams with profiled decking in terms of the shear connection capacity, load-slip behaviour and failure modes.
    • Behaviour of Headed Shear Stud in Composite Beams with Profiled Metal Decking

      Qureshi, J.; Lam, Dennis (2009)
      This paper presents a numerical investigation into the behaviour of headed shear stud in composite beams with profiled metal decking. A three-dimensional finite element model was developed using general purpose finite element program ABAQUS to study the behaviour of through-deck welded shear stud in the composite slabs with trapezoidal deck ribs oriented perpendicular to the beam. Both static and dynamic procedures were investigated using Drucker Prager model and Concrete Damaged Plasticity model respectively. In the dynamic procedure using ABAQUS/Explicit, the push test specimens were loaded slowly to eliminate significant inertia effects to obtain a static solution. The capacity of shear connector, load-slip behaviour and failure modes were predicted and validated against experimental results. The delamination of the profiled decking from concrete slab was captured in the numerical analysis which was observed in the experiments. ABAQUS/Explicit was found to be particularly suitable for modelling post-failure behaviour and the contact interaction between profiled decking and concrete slabs. It is concluded that this model represents the true behaviour of the headed shear stud in composite beams with profiled decking in terms of the shear connection capacity, load-slip behaviour and failure modes.
    • Behaviour of Headed Shear Stud in Composite Beams with Profiled Metal Decking

      Qureshi, J.; Lam, Dennis (2012)
      This paper presents a numerical investigation into the behaviour of headed shear stud in composite beams with profiled metal decking. A three-dimensional finite element model was developed using general purpose finite element program ABAQUS to study the behaviour of through-deck welded shear stud in the composite slabs with trapezoidal deck ribs oriented perpendicular to the beam. Both static and dynamic procedures were investigated using Drucker Prager model and Concrete Damaged Plasticity model respectively. In the dynamic procedure using ABAQUS/Explicit, the push test specimens were loaded slowly to eliminate significant inertia effects to obtain a static solution. The capacity of shear connector, load-slip behaviour and failure modes were predicted and validated against experimental results. The delamination of the profiled decking from concrete slab was captured in the numerical analysis which was observed in the experiments. ABAQUS/Explicit was found to be particularly suitable for modelling post-failure behaviour and the contact interaction between profiled decking and concrete slabs. It is concluded that this model represents the true behaviour of the headed shear stud in composite beams with profiled decking in terms of the shear connection capacity, load-slip behaviour and failure modes.
    • Behaviour of Headed Stud Shear Connectors in Composite Beam.

      Lam, Dennis; El-Lobody, E. (2005)
      In composite beam design, headed stud shear connectors are commonly used to transfer longitudinal shear forces across the steel¿concrete interface. Present knowledge of the load¿slip behavior and the shear capacity of the shear stud in composite beam are limited to data obtained from the experimental push-off tests. For this purpose, an effective numerical model using the finite element method to simulate the push-off test was proposed. The model has been validated against test results and compared with data given in the current Code of Practices, i.e., BS5950, EC4, and AISC. Parametric studies using this model were preformed to investigate variations in concrete strength and shear stud diameter. The finite element model provided a better understanding to the different modes of failure observed during experimental testing and hence shear capacity of headed shear studs in solid concrete slabs
    • Behaviour of inclined, tapered and STS square CFST stub columns subjected to axial load

      Lam, Dennis; Dai, Xianghe; Han, L-H.; Ren, Q-X.; Li, W. (2012)
      This paper describes the finite element method using ABAQUS to model the axial compressive behaviour of inclined, tapered and straight-tapered-straight (STS) concrete filled steel tubular stub (CFST) columns with square hollow sections. The accuracy of the numerical model was verified by comparing the numerical predictions with experimental study of the 200×200×3.75 RHS filled with C60 concrete with inclined angle of 0-9° and tapered angle of 0-4°. The results show that the compressive behaviours, load vs. strain relationship and failure mode predicted by the numerical simulations were agreeable with experimental results. After the validation, a parametric study was performed with 3 typical steel hollow sections (200×200×3.75 RHS, 300×300×6.3 RHS and 400×400×8.0 RHS) and extended the inclined angle and tapered angle to 0-15° and 0-12° respectively. The parametric study highlights some of the behaviour observed in test and extends the application range. In addition, reduction factor for calculating the axial capacity of this form of CFST columns are proposed.
    • Behaviour of normal and high strength concrete-filled compact steel tube circular stub columns.

      El-Lobody, E.; Young, B.; Lam, Dennis (2006)
      This paper presents the behaviour and design of axially loaded concrete-filled steel tube circular stub columns. The study was conducted over a wide range of concrete cube strengths ranging from 30 to 110 MPa. The external diameter of the steel tube-to-plate thickness (D/t) ratio ranged from 15 to 80 covering compact steel tube sections. An accurate finite element model was developed to carry out the analysis. Accurate nonlinear material models for confined concrete and steel tubes were used. The column strengths and load¿axial shortening curves were evaluated. The results obtained from the finite element analysis were verified against experimental results. An extensive parametric study was conducted to investigate the effects of different concrete strengths and cross-section geometries on the strength and behaviour of concrete-filled compact steel tube circular stub columns. The column strengths predicted from the finite element analysis were compared with the design strengths calculated using the American, Australian and European specifications. Based on the results of the parametric study, it is found that the design strengths given by the American Specifications and Australian Standards are conservative, while those of the European Code are generally unconservative. Reliability analysis was performed to evaluate the current composite column design rules.
    • ¿Behaviour of semi-rigid composite beam ¿ column connections with steel beams and precast hollow core slabs.

      Lam, Dennis; Fu, F. (2006)
      This paper is concerned with the behaviour of beam ¿ column connections of steel ¿ concrete composite beams with precast hollow core slabs. Experiments were carried out to investigate the joint rotation characteristics and ultimate moment capacity of these connections. Details of the test specimens, instrumentation, test set-up and test procedures are described. Results obtained for the connection moment capacity, rotation capacity and failure modes are presented. It is found that through proper design and detailing, these simple steel connections display the characteristics of a semi-rigid connection with very little extra cost.
    • Behaviours of circular CFDST with stainless steel external tube: Slender columns and beams

      Zhao, H.; Wang, R.; Lam, Dennis; Hou, C-C; Zhang, R. (Elsevier, 2021-01)
      In this work, experimental and numerical investigations were performed on the behaviours of circular concrete filled double steel tubular (CFDST) slender columns and beams, in which the external tube employed stainless steel tube. Eighteen specimens, 12 slender columns and 6 beams, were tested to obtain the failure patterns, load versus deflection relationships and strain developments of stainless steel tube. A finite element (FE) model was developed and verified by experimental results. The validated FE model was then employed to investigate the effects of key parameters, including hollow ratio, eccentric ratio and material strength, on the load-carrying capacity. The load distribution among the components and contact stress between steel tube and sandwiched concrete were also analyzed. Finally, the design methods for CFDST, hollow CFST and solid CFST members with carbon steel external tube respectively suggested by Han et al. (2018), Chinese GB 50936-2014 (2014) and AISC 360-16 (2016) were employed to evaluate their applicability for the circular CFDST slender columns and beams with stainless steel outer tube.