Research On The Key Technology Of Main Cable Erection Of Suspension Bridges By Air Spinning

Nowadays,with the vigorous development of sea-crossing engineering in China,the suspension bridge with the strongest crossing capacity becomes the first choice,and how to achieve the breakthrough of its span has also become one of the most important issues.However,the improvement of the span of suspension bridges is bound to lead to a substantial increase in the weight of main cable strands.There is no doubt that a higher requirement is put forward for the cable strand transportation and traction equipment.Because the main cable of suspension bridges is commonly erected by the prefabricated parallel wire strand method(PPWS method)in China.The air spinning method(AS method)is the construction technique of directly braiding into cable on site,which skillfully solves the problem.At present,only the main cable of Tsing Ma Bridge has been constructed by AS method among all suspension bridges built in China.It shows that the understanding of AS method is relatively poor.In order to promote the development and application of AS method in China,there are still many important problems to be solved.In view of the above problems,this paper relies on Yangbaoshan Bridge,the first suspension bridge independently constructed by AS method in China,to carry out a series of researches around AS method.The main contents are as follows:Firstly,AS method,including its traction system,composition and layout of common construction equipment and key construction steps,is summarized systematically through the study of a large number of completed suspension bridges.AS method and PPWS method are compared and analyzed from the main cable quality,cost consumption,construction time,equipment demand and other aspects.The results show that AS method is a more economical and efficient construction method for the super-long-span suspension bridges and it is more suitable for the construction of suspension bridges in special topography.Secondly,taking three-span-continuation catwalks for AS method as the research object,the main contents of construction control calculation of catwalks are summarized,and the rules,the change of temperature,span and tower height affecting erection curves of the catwalk in different spans,are studied.A method that can be used to control the erection curve of catwalks is put forward.The verification of several suspension bridges shows that the proposed method has high control accuracy and can meet the construction requirements.Thirdly,after the establishment of three-dimensional finite element model of cables including catwalk structure,the spinning process of main cables by constant tension AS method is studied in detail.A set of calculation methods for important parameters,which can guide the main cable erection by AS method,is summarized.The measured results of the supporting project show that the calculation method is practical and accurate.Finally,the single variable method is used to study main influencing factors in the construction process of main cables by constant tension AS method,including the catwalk deformation,spinning tension,temperature difference between catwalk and steel wire,wind load,etc.A set of construction control indexes suitable for the main cable erection by AS method of suspension bridges is proposed.The results show that the catwalk deflection caused by the self-weight of the strand has the greatest impact on the spinning curve.The temperature difference between catwalk and steel wire leads to the uncoordinated deformation and mutual influence.Reasonable control of the spinning tension is an important means to improve the erection accuracy of the strand and work efficiency.The proposed AS method construction control indexes fill the blank in the related fields of the domestic main cable erection.