Study On The Key Technology Of The Steel Pylon's Construction Survey Of Super-huge Bridge

Nanjing Third Yangzi River Bridge is the first cable-stayed bridge in China of which the main tower is in the form of steel structure. This paper focuses on the crucial survey technology applied in the construction of steel-pylon, and in combination with requirements of engineering practices some researches have been done in order to advance effective survey methods and measurements. The following are the key researches:(1) According to the precision requirement of the steel-pylon's assembly and the circumstances in the construction site, the control network for the construction of steel-pylon, which is based on the first-degree control network, is built. And the control network design is also made to meet the requirement of high-precision when the steel-pylon is assembled.(2) In view of the construction methods which are applied when the steel-pylon is assembled section by section, miniature control network needs to be built in the construction site. Then the vertical matching surveying between sections and the error accumulation management are carried out to examine the manufacturing circumstances of every steel-pylon's section and also they will be used to direct the assembly in the construction site.(3) The observational factors in the construction site are complicated, so inner controlling method, outer controlling method and the method combined inner controlling method and outer controlling method are applied respectively according to different sections, different precision requirements and different construction factors so as to achieve the expected precision and construction progress.(4) Considering that atmosphere refraction has some effect on the steel-pylon's fixing survey during the night, the study of the atmosphere refraction of one-way triangulated height experiment at night is especially done in order to effectively correct the data.(5) In the course of steel-pylon's construction, difference will appear comparing the assembled steel-pylons with the assembling ones because of the effect of the external environment and the construction errors. In view of this kind of specific property of the steel-pylon, a precision management program for the construction is developed in order to monitor and control the steel-pylon's posture and predict and adjust the posture of the following sections in time.