Hybrid welded T-section stub columns with Q690 flange and Q355 web: Testing, modelling and design

Comprehensive experimental and numerical investigations on hybrid T-section stub columns under compressive load were performed and are presented in this paper. The hybrid welded T-section stub columns comprise high strength steel Q690 flange and normal strength steel Q355 web. Material property studies were implemented through tensile coupon tests. Residual stress in membrane type was measured and recorded and its impact on structural performance was also assessed. Initial local geometric imperfection measurements were conducted for all the specimens. In conjunction with experimental studies, numerical investigation was performed to generate more test specimens extending the range of cross-section dimensions by which test data pool can be supplemented. The Eurocode of EN 1993-1-1, EN 1993-1-5 and EN 1993-1-12, the North American code of ANSI/AISC 360-16 and the Australian code of AS 4100 together with design approaches of Direct Strength Method and Continuous Strength Method were examined for its applicability for cross-section classification and compression resistance predictions of hybrid T-sections. Overall, the current specified limits were applicable for hybrid welded T-section and strength predictions from design codes were comparatively consistent and reliable. Strength predictions from Direct Strength Method and Continuous Strength Method were relatively appropriate though overly conservative predictions were provided for cross-section with large slenderness. In this study, modifications on the Direct Strength Method and Continuous Strength Method are proposed, which is shown to provide accurate predictions at cross-sectional level in a reliable manner.