Experiment on Rotational Stiffness for Joints with Different Structural Forms of Cuplock Steel Tubular Formwork Support
In order to study the rotational stiffness characteristics of the joints with different structural forms of the cuplock steel tubular formwork support,a test scheme is proposed to measure the rotational stiffness of corner joints,side joints,and middle joints of the formwork support,corresponding to the joint rotational stiffness test for 2,3 and 4 inserted horizontal tubes respectively.Based on the rationality of the scheme verified by the corresponding coupler joint test,the elastic modulus of the cuplock steel tubes randomly purchased in the local market is measured.The M-θ curve of the cuplock joint is fitted by the tri-linear model,and the influence of different numbers of horizontal tubes on its rotational stiffness and its failure characteristics are analyzed.The results show that:(1)The rotational stiffness of the corner joints and side joints of the cuplock steel tubular formwork support is 77.93％and 92.14％of that of the middle joints respectively,and both are higher than the recommended value of 25 kN·m·rad-1 given in the code.The rotational stiffness of corner joints and side joints is relatively weak,which has a significant influence on the overall stability of frame.(2)The elastic modulus of cuplock steel tubes randomly purchased in the local market has decreased to varying degrees compared with the new,with a maximum decrease of about 30％.(3)The failure order of cuplock joints is the horizontal tube,the bell shape cap,the standing tube,and the bowl shape socket.The failure of the joints occurred at the joint of the horizontal tube,where should be strengthened in the quality control.The relevant conclusions can provide a reference for determining the rotational stiffness of similar semi-rigid joints.
cuplock formwork supportelastic modulus of steel tuberotational stiffness of jointfailure characteristic of joint
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