Calculation Research Of Load-Transferring Mechanism Of The Long Nut Column Of Three-Gorge Ship Lift

As one of the permanent navigation facilities of the Three Gorge project, the ship lift has such characteristics as large lifting capacity, large lifting height, huge variation of the upstream water level, and significant changing rate of the downstream water level. With its technical difficulties and large construction scale both taking the first place in the world, it is of great importance and necessity to make scientific calculation and analysis to insure its safe operation.The long nut column, which is one of the important part to ensure the safety of the ship lift, is studied in this paper by calculation and analysis of FEM.In the paper the arc reinforcement element is automatically generated, and the module forming element information of both the line and arc reinforcement of either detached or combined type is added into the former program. Based on the calculation and analysis with the program, the stress status of the long nut column structure of the ship lift is studied. The influences of several key factors to the stress status are analyzed, including each load component, diameter of the short bolt and both tonnage and layout form of the prestressed anchor strands. The chief results are:(1) The vertical load is the main factor to generate the principal stress of the concrete, the maximum tensile stress of the over-joint reinforcement, and the maximum shear of the short bolt. With the vertical load, the structural deformation has a shape that is large in the upper position and small in the lower.(2) The diameter alteration of the short bolt has little effect on the concrete, the steel bracket, the over-joint reinforcement, and the prestressed anchor strands. At the same time, the increment of the diameter of the short bolt increases the safety factor, and is favorable to the structure.(3) The tonnage and layout form of the prestressed anchor strands have even less effect on the nut column structure. On the other hand, the eccentric stress caused by the vertical load is not sustained by the prestressed anchor strands as expected, but by the bottom of the steel bracket and the shear of the short bolt in the horizontal direction.(4) The principal tensile stress of the grouting joint decreases and the principal compressive stress increases with the decrease of the column temperature. It is concluded that the temperature decrease is favorable to the stress status. (5) The former design of the long nut column is satisfactory. Meanwhile, the design diameter of the short bolt in the part above 90m height is of some redundancy, and so is the safety factor. It is advised that the diameter of the short bolt in the part above 90m is changed to 20mm.