Further tests on thin steel and composite fabricated stubs

Abstract

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: 100×70×2mm. 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 200mm. 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 3years of concrete casting date, showed enhanced performance. Both numerical and test results were in good agreement whereas EC3 and EC4 predictions were not conservative.