Research Team: Prof. Ahmed Elghazouli (Imperial College London, UK),Dr. Christian Málaga-Chuquitaype (Imperial College London, UK),Dr. Yanzhi Liu (Formerly at Imperial College London now at Hunan University, China)

Background

Whilst the moment-rotation behaviour of typical connection configurations has been extensively examined in previous studies, there is a relative lack of information on their performance under more generalised loading conditions, particularly in relation to semi-rigid connections to tubular columns.

To this end, this research aims to provide fundamental information that would enable an extension of the assessment and design of semi-rigid tubular column connections to loading scenarios involving significant axial or shear actions.

In particular, the research focuses on the behaviour of two cost effective semi-rigid open beam-to-tubular column alternatives: i) blind-bolted angle connections and ii) reverse channel connections with angles. The work involves experimental investigations, detailed numerical simulations and analytical studies, as well as application-oriented studies.

Fig 1: Top angle deformation at the end of shear tests in a combined channel/angle connection. Experiment (right) and FE model (left).
Fig 1: Top angle deformation at the end of shear tests in a combined channel/angle connection. Experiment (right) and FE model (left).

Outcomes

A series of experiments comprising a large number of axial, bending and shear tests on blind-bolted angle connections and combined channel/angle configurations have been carried out. The main behavioural patterns have been identified, and the key response characteristics such as stiffness, capacity and failure mechanism were studied. The experimental results provide crucial information for the validation and calibration of complementary finite element and simplified analytical models.

The inelastic mechanisms exhibited by Hollo-bolted connections under axial and shear forces have been investigated. These mechanisms primarily originate from the interaction between the angle components and Hollo-bolt/column face assemblage. It has been shown that the angle gauge distance, between column bolt centre and beam flange, has a significant effect on the initial stiffness and capacity of the connection.

Besides, the thickness of the column also has a notable influence on the connection capacity, in particular when thicker angles are employed. The experiments also showed that a reduction of the column thickness can lead to considerable reduction in the joint stiffness and to the accumulation of plastic deformations around the Hollo-bolts which should be limited in design in order to satisfy serviceability requirements. Similarly, the inelastic mechanisms exhibited by combined channel/angle connections in tension were identified. As with blind-bolted connections, these inelastic patterns stem directly from the interaction between different connection components.

For stiffer angles, the thickness of the reverse channel stands in direct relationship to the connection capacity and stiffness. Furthermore, the addition of web angles has been shown to significantly enhance the overall connection resistance.

Three-dimensional finite element models have been developed to simulate the response of bolted angle beam-to-tubular column connections subjected to direct tension/compression and shear actions. The results obtained by means of this FE representation have been compared with the experimental response in order to assess the accuracy of the numerical models. Finally, expressions for the estimation of connection stiffness and capacity under axial and shear actions have been proposed and validated and new component characterizations have been suggested.

References

  • Liu Y, Malaga-Chuquitaype C, Elghazouli AY, 2013, Behaviour of open beam-to-tubular column angle connections under combined loading, Steel and Composite Structures, In press.
  • Liu Y, Malaga-Chuquitaype C, Elghazouli AY, 2012, Behaviour of beam-to-tubular column angle connections under shear loads, Engineering Structures, Vol:42, 0141-0296, Pages:434-456
  • Liu Y, Malaga-Chuquitaype C, Elghazouli AY, 2012, Response and Component Characterisation of Semi-Rigid Connections to Tubular Columns under Axial Loads, Engineering Structures, Vol:41, 0141-0296, Pages:510-532
  • Malaga-Chuquitaype C, Liu Y, Elghazouli AY 2012, Response of beam-to-tubular column angle connections subjected to combined flexure and axial loads, 14th International Symposium on Tubular Structures, London, UK
  • Liu Y, Malaga-Chuquitaype C, Elghazouli AY 2012, Shear behaviour of open beam-to-tubular column angle connections, 14th International Symposium on Tubular Structures, London, UK
  • Liu Y 2011, Behaviour of beam-to-tubular column connections under extreme loading conditions, PhD Thesis, Imperial College London, UK
  • Liu Y, Malaga-Chuquitaype C, Elghazouli AY 2011, Shear behaviour of beam-to-Tubular Column Connections, Eurosteel 2011, ECCS European Convention for Constructional Steelwork, Pages:507-512
  • Liu Y, Malaga-Chuquitaype C, Elghazouli AY 2010, Numerical Modelling of Semi-Rigid Open Beam-to-Tubular Column Connections”, ICSCS10, Fourth International Conference on Steel and Composite Structures, ICSCS10, Pages:519-524