Experimental and numerical investigations on cold-formed titanium-clad bimetallic steel angle and channel section stub columns

Titanium-clad bimetallic steel (TCBS) exhibits outstanding corrosion resistance, and can be advantageously applied in corrosive environments. This study investigated an innovative application of TCBS in cold-formed stub columns. During the cold-forming process, TCBS demonstrated no discernible separation at the bonding interface of the Q235 substrate layer and TA1 cladding layer, indicating the maintenance of synergistic deformation between the cladding and substrate layers. The compressive behavior and ultimate resistance of cold-formed TCBS angle and channel section stub columns were investigated using both experimental and numerical methods. These tests included material tensile flat and corner coupon tests, initial local geometric imperfection measurements, and stub column tests. The stub column test comprised four cold-formed TCBS angle section stub columns and three cold-formed TCBS channel section stub columns covering the non-slender and slender cross-sections. The experimental results were utilized to validate the finite-element (FE) model, which was then used in a parametric study to obtain further numerical data at different cross-sections. A comparative analysis of the ultimate resistance from the tests and numerical analyses with the predicted results from design approaches in EN 1993-1-1, AISI S100, and the direct strength method (DSM) was revealed. The evaluation findings generally showed that the EN 1993-1-1 design method forecasts for cold-formed TCBS channel section stub columns were dangerous. The non-slender cross-section classification coefficient, which was inapplicable to cold-formed TCBS channel steel stub columns, was the primary cause of the above unsafe prediction. As for the design approaches in AISI S100 and DSM for cold-formed TCBS angle and channel section stub columns, as well as those in EN 1993-1-1 for cold-formed TCBS angle section stub columns, they were judged safe but conservative. The above prediction error was mainly caused by ignoring the enhancement in strength properties of the TCBS after the cold-forming process. The considerations mentioned above led to the proposal and demonstration of modifying recommendations that offered safe, accurate, and consistent design approaches to ultimate resistance for the cold-formed TCBS angle and channel section stub columns.