Shear lugs for column bases

Column base plates of steel structures in seismic zones have usually to transfer large shear forces to foundations, and, in some cases shear lugs have to be used. It is normally assumed that the controlling limits states are the bearing strength of concrete and the yielding of the steel lug working as a cantilever beam. In order to review the present design of shear lugs, an experimental program was conducted. This paper presents the results of the testing of shear lugs made of cross section steel shapes. It was found that the steel shear yielding mode becomes a more ductile and reliable failure than the concrete bearing failure mode, which, in some cases, exhibits an explosive failure. It is also demonstrated that the hypothesis of a cantilever beam behavior of the shear lug is not appropriate; so as a result, the analytical model should be modified.