Pitch Motion Stability Analysis Of Ship Chamber For Hoist Vertical Shiplift

The hoist vertical shiplift is a large and complex system consisting of concrete structure,electric drive,mechanical transmission,hydraulic control and fluid.At present,the 200 m level high-lift hoist vertical shiplift which is pre-researched in the lower reaches of the Jinsha River in China has the largest single-stage lift height.According to the navigation requirements,it will lift the ship chamber of 17,200 t,the water and the 3000 t level ship at an altitude of nearly 200 m,and its operational safety cannot be compromised.However,domestic and foreign researches on the pitch motion stability of the ship chamber during operation is still unclear.The design and verification basis of the critical distance of suspension points is insufficient,and the pitch motion stability safety margin is difficult to evaluate.In order to solve the above engineering problems,the following research has been carried out:Multi-modal equations for shallow water sloshing in the ship chamber are established,and shallow water sloshing characteristics under different conditions of pitch motion and longitudinal earthquake are analyzed.Aiming at the shallow water sloshing in the ship chamber under pitch motion,a simplified method based on the Housner theory and an analytical method based on the multi-modal theory are proposed,and the formulas for calculating the capsizing moment are derived,respectively.The simulation results show that the multi-modal theory only needs to retain the first order(n=1)to ensure that the capsizing moment calculation error is less than 5%,which is much higher than the 20% error of Housner theory.For the shallow water sloshing under longitudinal earthquake,the calculation accuracy of multi-modal theory and equivalent mechanical model are compared.The results show that the calculation results of multi-modal theory are closer to the simulation values,while the convergence accuracy of the equivalent mechanical model is poor.For the currently widely used hydraulic static levelling,a numerical method for judging the pitch motion stability of the ship chamber and the calculation of critical distance of suspension points are proposed.The mechanical-chamber-fluid(MCF)coupling dynamics model considering the system damping is established,which contains the main hoist mechanical system,the ship chamber and the shallow water sloshing.Combining with the Lyapunov motion stability criterion,the pitch motion stability is judged and the numerical calculation method of the critical distance of suspension points is proposed.The rationality of the method is verified by engineering examples.The influence factors of the torque counterweight,the wire rope stiffness,the synchronous shaft stiffness and the wire rope elastic modulus tolerance on the pitch stability are analyzed.The results show that the calculation accuracy of the critical distance of suspension points is increased by about8.7%～20.8% compared with the previous model without the counterweight system.For the200 m level high-lift hoist vertical shiplift,the design parameters can ensure the pitch stability of ship chamber(safety factor is 1.3),increasing the wire rope stiffness by 30% can improve the pitch stability by about 5.3%,increasing the synchronous shaft stiffness by 30 %can enhance the pitch stability by about 6.68%.Numerical method for judging the pitch motion stability and the calculation of critical distance of suspension points are proposed for the hydraulic dynamic levelling.The mechanical-hydraulic-chamber-fluid(MHCF)coupling dynamics model of the main hoist mechanical system,the hydraulic levelling system,the ship chamber and the shallow water sloshing is established considering the system damping ratio.The Lyapunov motion stability criterion is adopted to judge the pitch motion stability,and the critical distance of suspension points is calculated.Comparing with the calculation results of the variable step Runge-Kutta method,the rationality of presented method is validated.The results show that comparing with the hydraulic static levelling,the hydraulic dynamic levelling will decrease the pitch stability(about 15%～44%),but the pitch stability can still be ensured(safety factor is 1.1).The stability of each system which affected by the distance of suspension points from low to high is shallow water sloshing,ship chamber motion,main hoist system and hydraulic levelling system.Under the hydraulic dynamic levelling,increasing the synchronous shaft stiffness by 30% can enhance the pitch stability by 6.2%,increasing the water boundary layer damping ratio can effectively improve the pitch stability.For the extreme longitudinal earthquake,the numerical method for judging the pitch motion stability and analyzing the time-history response are proposed.A TMHCF coupled dynamic model considering tower,main hoist mechanical system,hydraulic levelling system,ship chamber and shallow water sloshing is established.The fourth-order fixed-step RungeKutta method is used to calculate the seismic time-history response of the tower and the zero-input response of the coupling system.It verifies the seismic level of the tower and the pitch motion stability.The method is verified by comparison with the reference and engineering data.The results show that the design parameters of the 200 m level hoist vertical shiplift tower in the pre-research can ensure that the longitudinal deformation still meets the requirements of the regulations under the level 7 seismic fortification intensity,and it can ensure the pitch motion stability with safety factor approximately 1.088.The pitch motion stability under the longitudinal earthquake is lower than that during normal operation,and the maximum reduction occurs when the ship chamber is lifted to the highest range(about8.4%).With the increase of the lift height,the response speed of each part of the TMHCF coupling system gradually increases.The shortest adjustment time from initial disturbance to steady state is the tower system.Through the research,the shallow water sloshing characteristics under pitch motion and longitudinal earthquake is revealed.A set of numerical analysis methods for judging the pitch motion stability of the ship chamber,the calculation of critical distance of suspension points,and the evaluation of stability safety margin are proposed.It effectively solves the engineer’s needs for analysis of hydraulic static levelling,hydraulic dynamic levelling,and extreme conditions of longitudinal earthquake.