earticle

영어

The evaluation of joint stiffness is very important to design the space frames with ball-bolted joints. In this paper, the characteristics of stress distribution and neutral axis on the sleeve of ball-bolted joint at space frame are analyzed for the evaluation of the stiffness by the experimental approach. Six types of pipes, ∅42.7×2.3, ∅48.6×2.8, ∅60.5×3.2, ∅89.1×3.2, ∅114.3×4.5, and ∅139.8×4.5, are selected, and so the test models with the detailed partial specifications which are widely used in the domestic construction field are constructed for the bending test of joints. The strains of the joints are measured by the strain gages attached to the sleeves and pipes to investigate the characteristics of mechanics in it, and the deflection of the test models are also measured by LVDT positioned in the lower middle of the ball. In results, after initial phase of loading, the compressive stresses are concentrated at the upper surface of the sleeve with the gap in the lower boundaries of the ball and sleeve, and the sleeve and cone. Also, the neutral axis is nearly positioned at the nearest strain gage position from the middle axis of the sleeve cross section. It shows the tendency that the neutral axis moves from the compressive zone to the tensile one according to increasing the load. It is founded that the distribution of compressive strains from the neutral axis is not linearly distributed on the sleeve, and the strain on the extreme fiber of sleeve shows the state of concentrated stress. The maximum strains on the extreme fiber are 1.24 times of the linearly distributed strain fiber in BS427m12, 1.27 times in BS486m16, 1.4 times in BS605m20, 1.15 times in BS891m24, 1.72 times in BS1143m30, and 1.46 time in BS1398m36.