Design resistance of helical seam pipe columns with limited tensile test data

This study conducts a capacity factor calibration for steel and steel-concrete composite columns with helical seam pipe (also known as spiral welded tube) sections considering the following three member types: (i) steel columns under axial compression, (ii) concrete-filled steel tubes (CFSTs) under axial compression, and (iii) CFSTs under combined axial compression and uniaxial bending due to load eccentricity. The calibration has been conducted for both forward and inverse reliability analyses. The forward analysis calibrates the capacity factor of steel contribution in the design models given in NZS 3404.1, AS 4100, AS/NZS 5100.6 and AS/NZS 2327 to meet the target reliability level provided in both ISO 2394 and AS 5104 when using API 5L products in non-composite and composite column applications. Whilst the inverse analysis estimates the required minimum number of steel tensile tests when the target reliability level and the capacity factors are all provided. In these analyses, a total of 68 experimental data collected from the literature are utilised to estimate the modelling uncertainty in terms of bias and scatter. For all member types, the design models achieve similar or higher reliability than the target reliability, and the corresponding required minimum amount of steel material tests are calculated and provided.