Behaviors Of Thread-fixed One-side Bolted Connection Under Bending Moment And Shear Force

The technology of using threaded holes with internal threads instead of nuts to achieve bolt anchoring is relatively mature in the machinery industry.For actual structural joints,there is an obvious interaction relationship between bending and shear capacity.Therefore,it is necessary to study the mechanical performance and calculation methods of the joint under the combined action of bending moment and shear force.This paper conducted experimental research on the influence of bending moment and shear force on the mechanical performance of the thread-fixed one-side bolts bolted joints and traditional nut-fixed double-sides bolted connections for comparison.Two failure modes including bolt fracture and column wall failure were found.For the thread-fixed one-side bolts bolted joints,the internal thread of the thread hole was cut off.For the raditional nut-fixed double-sides bolted connections,the failure mode was column wall yielding failure.The bending capacity of joint would weakened by the shear force.Parametric analysis of thread-fixed one-side bolts bolted joints under bending moment and shear force was carried out utilizing finite element model verified by the tests’ results.The influence of shear force against bending performance was discussed,meanwhile,the interactive relationship between bending and shear capacity was drawn.When the bolt fracture occurred,the bearing capacity of the thread-fixed one-side bolts bolted joints was similar to that of traditional nut-fixed double-sides bolted connections.When the column wall failure occurred,the bearing capacity of the former was less than that of the latter.Further study was conduct on the mechanical performance of thread-fixed one-side bolts bolted T-stubs under tension and shear force through finite element method.Studied parameters included column wall thickness,bolt diameter and bolt spacing distance.The results showed that increasing the column wall thickness could improve the stiffness,strength and the thread anchoring length of joints,while increasing the diameter of bolt could increase the bolt bearing capacity.Therefore,the failure mode and bearing capacity of joint could be affected by both of them.Five kinds of failure types might occur and the interactive relationship between tension and shear capacity was obtained.When the tube wall was thin,the deformation of the thread hole under shear force would weaken the anchoring force and cause the joint failure in advance.The failure type should be avoided by increasing the tube wall thickness or adopting strengthening method.The second-order deformation of tube wall would lead to the bending of bolts and the deformation of bolt holes,which would weaken the thread anchoring condition and reduce the bearing capacity of joint.Design method for calculating the resistance under tension and shear force was proposed based on the current design equation for traditional nut-fixed double-sides bolt.Considering that the shear force would lead to the deformation of the thread hole,the tension capacity of the joint under tension and shear load was modified.When the tension force of the joint was greater than 0.9 times of the tension capacity,the thread-fixed one-side bolts bolted T-stubs should not bear shear load,which was different from the traditional nut-fixed double-sides bolt.At this point,the formula no longer applied.The comparison between the predicted values of the modified formula and the finite element simulation showed that the modified formula was safer and more reliable.