Test and analyses of a new double-arch steel gate under cyclic loading

A new double-arch steel gate used as tidal barrage and sluice was adopted in the Caoe River Dam in China. It was a new application of a spatial structure in hydraulic gate to bear bilateral loading. To study the mechanical property of the gate, a scale-model cyclic test was conducted. The test data of the model under the bilateral designing load were analyzed and it was found that the load-bearing members mainly bore axial force and the value of axial force varied a little along the span. Thus the design of the gate was appropriate. The bearing capacity of the model was analyzed through load–deflection envelope curve. The curve was divided into three stages: the elastic stage, the local plastic stage and the failure stage by the local yield point and structural yield point. The local plastic strain in the joints had minor influence on the load–deflection curve of the structure before the joints were damaged. There were local yield strength and structural yield strength in the gate model and both of their values were bigger than that of the designing load. Therefore, the gate was safe enough for the projects. Arch-springing joints and the places where the main arches and minor arches were joined were the key joints because they were subject to damages. Moreover, fatigue analyses of the joints were performed and those which failed to meet the fatigue requirement were redesigned.