Hot spot stress and fatigue behavior of bird-beak SHS X-joints subjected to brace in-plane bending

Bin Cheng, Fenghua Huang, Chen Li, Yinghao Duan, Xiao Ling Zhao

Research output: Journal article publicationJournal articleAcademic researchpeer-review

8 Citations (Scopus)


This paper deals with the stress concentrations and fatigue behaviour of X-shape bird-beak joints under brace in-plane bending. Static load was first implemented to record the strain distribution along the hot lines, and then stress concentration factors (SCFs) were obtained through quadratic extrapolation method. Numerical analysis was then developed to further determine key parameters affecting SCFs and to propose corresponding SCF design formulas. During the subsequent high-cycle fatigue test, the fatigue cracking process including crack initiation, crack propagation, and fatigue lives, as well as the rigidity degradation were captured. Results show that crack initiation always occurred at the crown area where the SCFs are proved to be the greatest. The through-thickness lives may be utilized to conservatively represent the fatigue design lives of SHS bird-beak X-joints. Bird-beak SHS X-joints demonstrated better fatigue behaviors than those for traditional joints if the same service load is applied.

Original languageEnglish
Article number106701
JournalThin-Walled Structures
Publication statusPublished - May 2020
Externally publishedYes


  • Bird-beak X-joint
  • Brace in-plane bending
  • Fatigue
  • Square hollow section (SHS)
  • Steel tubular structure
  • Stress concentration factors (SCFs)

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Mechanical Engineering


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