Further tests on thin steel and composite fabricated stubs

Results for tests conducted on thin cold fabricated steel–concrete stubs are presented. The studied sections were made of two cold formed U shaped steel plates welded to form a steel box or an I shaped steel section. The steel cross section dimensions were: 100 × 70 × 2 mm. The main studied parameters were: the stub height, the welding fillet nature and its location, the steel cross section shape, and the in filled concrete and its age. A total of 48 stubs were tested, 22 were empty and 26 were filled with concrete. The concrete was made of crushed slag from blast furnace as a natural gravel substitute. All failure loads were predicted numerically using Abacus program and by Euro-codes EC3 and EC4 for steel and composite stubs respectively. From the test results it was confirmed that the length and the discontinuous welding fillet for empty stubs had a drastic effect on the load carrying capacity and the failure mode was mainly a premature local buckling mode. Test results showed that I shaped steel stubs had a higher compression load carrying capacity with a lower load decrease rate compared to fabricated rectangular steel stubs with height over 200 mm. Providing rectangular steel stubs with continuous welding on mid-depth improved the load carrying capacity for both rectangular empty steel and composite stubs. Regarding the concrete age effect, test results obtained from testing composite stubs after 3 years of concrete casting date, showed enhanced performance. Both numerical and test results were in good agreement whereas EC3 and EC4 predictions were not conservative.

► Results on axially loaded steel and composite fabricated stubs are presented. ► Studied parameters were: welding route, shape of steel cross section. ► Continuous welding fillets improved the behavior. ► I shaped steel and composite stubs had ductile behavior. ► The in-filled slag concrete and its age improved the load bearing capacity.