Detailing of I-beam-to-CHS column joints with external diaphragm plates for seismic actions

Alireza Bagheri Sabbagh, Tak Ming Chan, James Toby Mottram

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49 Citations (Scopus)


In this paper monotonic and cyclic finite element (FE) analyses are presented for the development of an I-beam-to-CHS column steel moment joint for seismic actions. The development process for the final joint details includes: (1) eliminating two identified structural deficiencies of distortion in column web panel and strain concentrations in the external diaphragms; (2) creating a multi-fuse energy dissipation mechanism; (3) devising a joint to delay onset of beam yielding. Two external diaphragm collar plates are welded to the circumference of the CHS column for connection to beam flanges. Various collar ring widths are examined for these horizontal diaphragms and a width (based on achieving full strength of the beam flanges) is found to produce an acceptable web panel performance. Different types of stiffener geometries in the connection region are then trialed to eliminate strain concentrations in the diaphragms. Two pairs of triangular diaphragm stiffeners are found to provide the desired performance. In order to produce a multi-fuse energy dissipation mechanism, tapered cover plates (TCPs) equipped with vertical stiffeners (VSs) are integrated into the joint. Oversized web holes of 4–10 mm are required to enable inelastic deformation for an overall joint rotation of 60–100 mrad, without undesirable web distortion. Further FE analyses are used to design the TCPs and VSs so they can be replaceable link post-seismic actions. For the final joint detailing it is shown that 6 mm oversized holes for the TCPs will delay the occurrence of yielding in the beam until the joint rotation is 70 mrad.
Original languageEnglish
Pages (from-to)21-33
Number of pages13
JournalJournal of Constructional Steel Research
Early online date28 May 2013
Publication statusPublished - Sept 2013

Bibliographical note

The authors are grateful to the Engineering and Physical Science Research Council (EP/1020489/1) for the project funding and Emeritus Professor David Anderson (University of Warwick), Dr David Brown (Steel Construction Institute), Dr José Miguel Castro (University of Porto), Mr Ken Hudson (Cleveland Bridge UK Ltd.), Professor John Miles (Ove Arup and Partners and University of Cambridge) and Mr Trevor Mustard (TATA) for their generous technical and scientific support.


  • Moment–rotation behavior
  • Seismic performance
  • External diaphragm plates
  • Strain concentration


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