Consecutive lifting and lowering electrohydraulic system for large size and heavy structure

Most of hydraulic strand jacks cannot fulfill consecutive motion of lifting or lowering. Non-consecutive motion will generate additional inertial force that probably changes initial stress distribution of large and heavy structure in addition to be time-consuming. To solve the problem, an electrohydraulic system and corresponding strand jack were developed. The new strand jack uses two lifting cylinders to alternate lifting (lowering). The velocity difference between the two lifting cylinders is a key parameter to achieve smooth transferring-load and consecutive motion. The working principle of lifting is different from that of lowering. Electrohydraulic system is presented. To get the least values of velocity difference and the transferring-load stroke, the method of double-objective optimum is applied. Test results verify that the strand jack and electrohydraulic system can fulfill consecutive motion of lifting and lowering.