Study On Dampers Setting Of A Prestressed Concrete Cable-stayed Bridge(Nanping Min River Bridge) With Single-way Longitudinal Grade

Cable-stayed bridges were firstly selected by the engineer because of their beautiful configuration,powerful wind resisting capability,good dynamic and fast construct speed.Usually,the cable-stayed bridges were designed as two-way longitudinal slop,cable-stayed bridge with a single-way longitudinal was rare.The existence of unidirectional slop would cause the movement of main girder,also produce certain longitudinal forces.At present,the dampers were often used to control the longitudinal displacement of the bridge.The vibration-reduction control based on viscous damper is a new technology which is effective.It is more and more widely used in long-span cable-stayed bridges.In this thesis,according to a PC cable-stayed bridge with a single-way longitudinal grade,Nanping Min River Bridge,the parameters of dampers were investigated.The main contents and results are as follows:(1)The principle,advantages and disadvantages of fluid viscous damper were introduced,and the applications of viscous dampers in cable-stayed bridge were reviewed.(2)The static characteristics of main girder of Nanping Min River Bridge in construction and service stages were analyzed.The results showed that in the process of construction,the edge stress of main girder met the specification requirements.Under the influence of live load,the deflection of main girder and the displacement of main tower met the specification requirements.Affected by 1.15%single-way longitudinal grade,in the process of construction,horizontal force caused by structure weight focused on one side of main girder,and vehicle braking forces in service stage would exacerbate the impacts.(3)Stress of main girder of Nanping Min River Bridge in construction and service stages was analyzed.The results showed that in the process of construction and service,the main girder would produce longitudinal force and displacement.Therefore,dampers were needed to control the vibration and displacement.Fluid viscous dampers were suggested in this thesis.Through the calculation and adjustment,the final parameters of the fluid viscous dampers were setting as follows:damping coefficient C=1400kN/(m/s),damping rate index a=0.3,the maximum damping force was 1000kN and the maximum stroke was ±500 mm.The numbers and location of viscous dampers were optimized,and two fluid viscous dampers were suggested placing between lower cross beam and main girder(3#and 4#)for each other.(4)Construction monitoring of Nanping Min River Bridge was studied.The results showed that the main parameters of main girder in accordance with the design value,reached the predetermined target.The measured results of construction system of converting showed that the fluid viscous damper could effectively control the longitudinal displacement of main girder,the effect was good.