Research On Dynamic Stability Of Radial Steel Gate

The reason causes the failure of radial gate is that the arm loses dynamic stability when it is excited by longitudinal exciting force and parametric resonance happens. The dynamic stability should be paid attention to. Recently, preliminary study of dynamic stability of arm was done by some scholars, and some useful conclusions were achieved. Only transverse planar vibration of arm which was considered as two ended hinged joint column under longitudinal periodical force was analyzed based on traditional dynamic stability theory. The dynamic stability of radial gate arm is different from that of other compressed columns because of the complexity of radial gate. In this paper, further research on dynamic stability of the arm is done based on previous work. The main work and conclusions show as follows:(1) The dynamic stability of radial gate arm which is considered as two ended hinged joint column subjected to longitudinal periodical force and bending moment, and the amplitude of parametric resonance of the arm was derived.(2) Numerical example shows as follow: parametric resonance of arm happens which leads to the failure of radial gate for some combinations of parameters of longitudinal exciting force, and parametric resonance does not happen for other combinations. The dynamic load amplitude which causes parametric resonance becomes smaller when the frequency of exciting force is closer to natural vibration frequency of the arm. Parametric resonance suddenly happens when the relationship between frequency of exciting force and natural vibration frequency of the arm satisfies some kind of conditions. The amplitude of parametric resonance before which the amplitude of transverse vibration is very small suddenly increases which leads to dynamic instability. It is very important to consider parametric resonance in practical engineerings.(3) Space dynamic stability of I-section arm with two symmetrical axes was analyzed. Dynamic differential equation was derived and the concept of excitation rate was defined. The boundary of main dynamic instability region was obtained by which the three main dynamic instability regions could be determined.(4) Optimization model was established based on rational structure arrangement of surface radial gate with three arms. Dynamic stability constraint of the arm was considered on the basis of static constraints to void parametric resonance of arm when a certain relationship between frequency of exciting force and natural vibration frequency of the arm was satisfied.(5) M language of MATLAB software was used to develop a general optimization program to design the main frame based on rational structure arrangement of surface radial gate with three arms. Numerical example was used to verify the effectiveness of the program which can provide a effective design method for surface radial gate with three arms.