In-plane buckling strength of catenary CFST truss arches: Experimental and design formulas

This study performed an indoor experiment to examine the failure mechanism of a catenary CFST truss arch under a mid-span single-point load. A parametric analysis of a finite element model, validated with literature and experimental data, was conducted, taking into account material strength, rise-span ratio, arch axis coefficient, and steel ratio. A new buckling strength verification formula is proposed, which integrates stability coefficients for pre-buckling deformation and the rise-span ratio, as well as correction coefficients for varying bending moments and axial forces. The results indicate that in-plane failure modes in CFST truss arches typically initiate with the yielding of the web members before the chord tubes, contrasting with truss column failures. The buckling strength showed a direct correlation with material strength, rise-span ratio, and steel ratio, though with diminishing returns. The rise-span ratio and arch axial coefficient had minimal impact. The proposed verification formula, which includes pre-buckling deformation, arch axis coefficient, and the rise-span ratio, provides a precise and conservative method for evaluating the in-plane buckling strength of catenary CFST arches, enhancing engineering design practices.