The Analytic Theory And Experimental Research Of Double-Arch Gate

Double-arch gate is a new gate made up of spatial tubular trusses, designed based on the idea of spatial structure. The load-bearing members of the gate are double-arch fish-alike trusses, which are capable of bearing bilateral load. The double-arch truss is composed of the main-arch, the minor-arch, the chord, and the wed-member. The double-arch gate is made up of multiple double-arch trusses. It has more rigidity and larger load-bearing capacity than the traditional gate made up of solid wed girder, because most of its members sustain axial stresses. As a result, this double-arch gate can save much steel consumption under the same condition.The analytic theory and experimental research for the new gate were presented in the paper. At first, the original idea of double-arch truss was introduced and the double-arch gate was designed. It was compared with the traditional gate made up of solid wed girder. The new gate was first adopted in Caoe River gate as tidal barrage and sluice .The Caoe River gate bore tremendous tidal bore strike in Qiantang River. Analyses showed that the new gate performed better than the traditional gate in the project because it saved about 30% steel consumption under the same condition.Then the analytical methods under dead-load are studied. Comparisons are made between two methods: one of them is FEM regarding the gate as spatial structure and the other is simplified formula regarding the gate as independent plain substructure. The stress of gate is preliminarily analyzed from the result.At the same time, for optimization, the significant designing parameters of the gate such as the number of the double-arch truss, the line style of arch axis, the thickness of double-arch were analyzed.Further, the scale-model experiment was also conducted in the paper. The research included three procedures: static test, repetitive loading, and cyclic experiment. Result of the static test showed that the result from experiment was consistent with the result from FEA analysis .The repetitive loading experiment verify that fatigue failure cannot appear in Caoe River Gate during serviceable life. In cyclic experiment it is found that the bearing-status is divided into three stages: the elastic stage, the local plastic stage and the failure stage withdifferent local yield points and structural yield points. The arch-springing joints and the locations where the main-arches and minor-arches are jointed are the first to be damaged.The gate usually bears the dynamic load, so the dynamic property of gate is also researched. The research includes two contents. Firstly, the vibration mode of gate was analyzed by numeric method in consideration of the situation with and without water. Secondly, a numerical analysis of the gate under the load spectrum of the tidal bore strike is carried out. The fluid-structure interaction is considered in the analysis.It is shown that arch-springing joints and the locations where the main-arches and minor-arches are joined are relatively weak in the structure. So the detailed experiments on the joints where the main-arches and minor-arches are joined were carried out. Three types of X-shape joints, namely unreinforced joints, rib-plate-reinforced joints and sleeve-reinforced joints, were proposed and studied in experiments. Through the analysis of stress distribution and bearing-capacity of joints, it could be found the sleeve-reinforced joints have the best performance. Also, for the arch-springing joints, the designing principle was proposed, and those on Caoe River Gate were improved and optimized. Moreover, the methods of fatigue analysis were proposed and the fatigue life of the key joints of Caoe River gate was analyzed. At last, the fabrication process and inspection of the double-arch gate were proposed. The fabrication of Caoe River gate was introduced.