This site intends to present technical proposals on hydraulic steel structures such as hydraulic gates,
　intake and discharge equipments, silt/sand dischargers etc. which are provided harbour entrances, docks
　and locks along waterways, or dams, weirs, floodgates and power stations on rivers, or irrigation systems.

PROPOSAL１　【STORM GATE・・TORSION TYPE】

Drilling 1:Mitigation of Warping & Optimum Design

　This page proposes the technology of a super large storm gate of torsion type structure.

１．Estimation of Proposed Technology

　The result of estimation on the top page is as follows.
（１）The initial cost is equal to or less than 1/3〜1/2 of the ordinary technology.
（２）There is no risk which prevents the proposal from being realized. Details are as below.
　1) The structural analysis of torsion type gate is studied enough. *1 (Fun. Sub.)
　2) The strong operational equipment to drive the gate is feasible. (Tec. Dev.)
　3) The large torsional structures in ocean environment have worked for 37 years. *2 (Pro. Ver.)
　4) Interests of the beneficiaries coincide with the proposer's. (Bus. His.)
（３）The engineering level is �U (Pre.) and secondary subjects remain.
The boundary subjects we can see now are shown at item ６. For the mark *, refer to the notes below.
Notes *1：material 3 & 4 in item ７
　　　　*2：material 1 & 2 in item ７

２．Image of Large Storm Gate

　Fig.-1 thru 4 show image of large storm gates. They were constructed to protect people and properties in sea side areas against storm tides or tsunamis. Their necessity has more increased due to the recent amplification of weather changes and probability rise of tsunami occurrences.

３．How Come Torsion Type Structures?

　There have been many idea proposals of the super large storm gates and Table-1 shows their examples. In this table, the proposals are classified by type of structures, storage areas and the cost axes, and the proposals having a common content are grouped into a group. The table also shows each group's top two big applicable conditions by their number and name. The applicable condition is a condition without which the group can not be applicable to any waterway and Table-2 shows each condition's number, name and content. The cost ranking and the applicable conditions of the proposal groups in Table-1 are presented on the cost axes of Fig.-5. The cost ranking shows only qualitative supremacy of cost and dose not intend to show absolute cost values or relative cost rates. "Still Sea" and "Ship col." on Fig.-5 mean that the idea proposal is applicable to the waterways "where the gate can be operated at still sea condition" and "where no ship collision occurs" respectively. But there is no waterway which meets these applicable conditions. Fig.-6 shows the result of group screening by this viewpoint and shows that the torsion type structure is profitable among other ordinary technologies. Fig.-7 gives gate image of the five proposals shown on Fig.-6. Table-3 shows, for reference, examples of design conditions set up for this screening. Furthermore Fig.-7' was added to show superiority in cost of the torsion type gate. This figure shows the challenge target line for design optimization of it. The target line coincides with the power approximation curve of its actual weight records. Comparison of the target line to the red colored marks on the figure shows its superiority well.

４．Difference between Torsion Type Structure and Bending Structure

　Fig.-8 shows characteristic deformations of the torsion type structure and the bending structure. L in the figure is clear span of the structures. Suppose deformation of the bending structure is characterized by parallel movement of the structural section, that of the torsion type structure can be characterized by rotation of the structural section in its plane. The rotation center of the section is the restriction point of movement. In short, a structure can be either torsion type or bending type according to existence of the restriction or not. But the structural character of the two types are remarkably different when sectional shape of the structures are closed like a box beam. The bending structure resists against loads on the span with the sectional moment of inertia whereas the torsion type structure resists with a second power of the closed area. The load transmittal routes are also different. The load on the bending structure is taransmitted to the span terminals with the structural shearing rigidity,

whereas the load applied to a section of torsional structure is transmitted to the restriction point of the section and the torsional moment composed of the load and the restriction force of the section is transmitted to the span terminals with the structural torsional rigidity. The bending type is 3 dimensional structure and the torsion type may be classified into 2.5 dimensional structure. The torsion type structure has various merits due to the structural characters different from the bending type and the merits become more remarkable as the structural span become longer.

５．Super Large Storm Gate of Torsion Type Structure

　Fig.-9 shows image of a torsion type super large storm gate. This case is rail slide type and its clear span is 600 meters. The four locomotives and auxiliary hydraulic equipment on the storage dock top are implemented for the gate opening and closure operation. The figure shows the left hand side half span of a gate.

６．Remained Subject Without Solution

　Table-4 shows the remained subjects which can be seen now. It is quite ordinary that tremendous number of secondary subjects has to be solved by realization of new gate types.

７．Reference Materials