Experimental study of innovative steel beam-to-column joint under impact loading to mitigate progressive collapse

The structural response of two steel substructures in a beam-column-beam arrangement under accidental loads was studied in the experimental impact tests. Both versions of the bolted joint, the classic flush end-plate and the innovative one were tested with the same impact energy level applied by dropping the free-falling steel-concrete package. Special measuring equipment dedicated to dynamic investigations was used. The main aim of the tests was to examine the strains and deformations in order to determine dynamic parameters in steel members and bolts. The strain rate and the dynamic impact factor (DIF) were calculated based on the experimental test results. Johnson-Cook, Cowper-Symonds and Malvar-Crawford models were used to determine the DIF. The comparison and discussion of results for both specimens are presented in the paper. The results show that steel bolted flush end-plate joints and innovative joints exhibit high structural ductility under impact loads. The resistance of the flush end-plate joint is limited by the fracture of the bolts. In comparison, the resistance of the innovative joint was not reached during the tests, which indicates significant reserves of the load capacity in this type of joint.