Experimental investigation on monotonic bending behaviour of TSOBs bolted beam to hollow square section column connection with inner stiffener

Abstract In the reported research results on T-head Square-neck One-side Bolts (TSOBs) bolted Endplate Connection (TSOB-EC), the failure of TSOB pulling-out due to the punching shear failure of Hollow Square Section Column (HSSC) wall is typical, which should be avoided. Two types of inner stiffeners that have H-section and double channel section are used to improve the punching shear resistance of the HSSC wall. At the same time, the inner stiffeners are used as connection splices to connect the upper column and the lower. The effect of the length and plate thickness for the stiffener on the connection performance are also studied. A total of six TSOBECs with stiffeners were tested under monotonic bending moment. The test results show that the stiffeners can avoid the bolt pulling-out failure and improve the deformation capacity of TSOBEC. The yield bending moment and peak bending moment of TSOBEC can be increased by 8.1%∼31.8% and 11.6%∼21.7% by double channel stiffeners, respectively, and improved by 69.3%∼72.6% and 22.5%∼39.4% by H-steel stiffeners, respectively. The analytical models for predicting the bending moment capacity of TSOBEC with stiffeners are proposed and the prediction results are accurate with an error within 5%. In addition, extended H-steel stiffener is recommended for designing the strengthened TSOBEC, and the cross-section of the stiffener needs to be calculated by the proposed models to ensure that the H-steel stiffener and HSSC do not deform even if the joint fails.