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Project Title: Structural behaviour of beam to concrete-filled elliptical steel column connections

  • PhD Student: Jie Yang
  • Supervisors: Professor Dennis Lam, Dr Xianghe Dai & Dr Therese Sheehan

Background

Concrete-filled steel tubular columns have been widely used in the building industry owing to their superior structural performance. Recently, a new cross-sectional shape, the ellipse, has emerged in tubular construction. Complementary to existing circular, square and rectangular hollow sections, elliptical hollow sections (EHS) have additional visual appeal as well as structural efficiency due to the two principal axes. However, there is a lack of design rules to ensure safety and economy when using them in construction. Though effort has been taken to study the structural response of concrete-filled elliptical columns, behaviour of beam to column connections, the essential parts of framed structures, are unexplored and thus need to be investigated urgently.

Aims

  • To obtain the typical failure of simply bolted beam to elliptical column connections with various joint assemblies
  • To investigate the effect of in-filled concrete and stiffener plates on bending behaviour of these connections
  • To develop an acceptable finite element model
  • To predict the bending capacity of elliptical column to beam connections using a formula

Typical test setup. ‌Methodology

To achieve the first two objectives, connections were tested to failure under bending load. One 250 tonne hydraulic actuator was positioned above the column to exert a compressive force which was equal to 40% of columns compressive resistance. Upwards concentrated forces, representing the floor-slab load that would occur in a real structure, were then applied simultaneously at the beam ends using two 100 tonne actuators.

Subsequently, a finite element model (FEM) will be developed through ABAQUS software according to test details; material properties, loading and boundary conditions as well as possible imperfections will be taken into consideration.

After being verified by experimental results (e.g. failure modes, moment-rotation relationships, etc.), the FEM will then be employed to conduct a parametric study (parameters include EHS orientation, cross-sectional geometry, load ratio, concrete strength, etc.) and finally a predictive formula will be developed using the numerical data.

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