Abstract:

In this paper,the ultimate bearing capacities of steel tube-gusset plate connections with a tube size of 219×6 and with 1/4 annular ribbed plate subjected to negative eccentric force are analyzed.The investigation is performed for the connections with constant diameter-thickness ratio but variable length-diameter ratio and negative eccentricity,and for the connections with constant length-diameter but variable tube diameter,tube thickness and joint plate length.Then,a formula to calculate the ultimate bearing capacity is proposed.The results indicate that the negative eccentricity is unfavorable to the bearing capacity of steel tube with a length-diameter ratio higher than 30 because the entirety stability of steel tube is the main effect factor.However,the negative eccentricity is favorable when the length-diameter ratio is less than 30 because the local bucking is prior in this situation.It is also indicated that the tube diameter,the tube thickness and the joint plate thickness all affect the ultimate bearing capacity significantly,and that the proposed formula is applicable and feasible for design.

Key words: negative eccentricity, ultimate bearing capacity, gusset plate connection, rib-reinforced steel tube