Test Verification Of Three-Degree-Freedom Loading Control Method Based On Hytest

In recent years,with the trend of large-scale structure development in the civil industry,various universities have developed and built their own large-scale multi-functional loading system,the most prominent representative of which is the three-degree-of-freedom loading system.Initially,scholars simply considered that the horizontal displacement of the test specimen was only produced by the horizontal actuator while the vertical displacement of the test specimen was only produced by the vertical actuator.However,with the increase of the size of structural test specimens and the complexity of the working conditions of the specimens,there is a higher requirement for the loading accuracy of the specimens in the test.The original three-degree-of-freedom loading system is controlled by MTS 793 software.The purpose of the software itself is to control the actuator,so the software can only visually see the output and displacement of the actuator in the loading process;it can not visually reflect the loading situation of the specimen and the coupling effect of the three actuators.Therefore,the main contents and conclusions of this paper are as follows:(1)Improve the three-degree-of-freedom loading control method considering the coupling effect,and realize the three-degree-of-freedom loading control method considering the coupling effect in the quasi-static test of HyTest hybrid experimental platform.HyTest hybrid experimental platform is used to simulate and analyze the three-degree-of-freedom loading control process.The simulation results show that the loading control method and HyTest pseudo-static test software can be well applied to the three-degree-of-freedom multi-function loading test device.(2)The pseudo-static test of reinforced concrete column is carried out to judge the effectiveness of the whole loading system.Three-degree-of-freedom quasi-static test is carried out by using the three-degree-of-freedom multi-functional loading test device of Harbin University of Technology.The validity of the control method is judged by comparing the difference between the generalized displacement or the generalized force of the specimens and the target working condition on the three-degree-of-freedom.From the experimental data obtained,it can be seen that the loading errors on the three degrees of freedom are small.(3)In order to further test the loading effect of the whole loading system,a pseudo-static test is carried out to determine whether the loading control method can solve the problem of base slip in the test loading.However,during the test,it is found that the bottom warpage of the specimen will seriously affect the displacement and force recovery during the unloading process,which leads to the failure of the test.It can be seen from the test that when the target command does not have a turning angle,the test can be carried out and there are acceptable errors.When the target command has a turning angle,the test error is large and the test can not be completed.(4)In order to apply this three-degree-of-freedom loading method to 3000-ton test loader,a feasible loading scheme is proposed for 3000-ton test loader and a hybrid simulation analysis is carried out.From the simulation analysis,it can be seen that the loading control method and HyTest pseudo-static test software can be applied to 3000-ton test loader with high accuracy.