Study On Dynamic Deflection Signal Features Of Long-span PC Beam Bridge

Long-span PC beam bridge girder span of widespread deflection, effects the vehicle ride comfort and safety, but also affects the bridge landscape and the service life of the bridge and safe of operation. The concrete shrinkage and creep, prestress loss and the construction method are ones of the main factors causing bridge midspan deflection..However, Time-variation and uncertainty of the concrete shrinkage and creep and prestress loss, and complexity of construction method, to accurately grasp the characteristics of bridge dynamic deflection signal is still very difficult.In this paper, based on Calculation method with finite element and Fu Li-ye transformation, The long-span PC beam bridge later concrete shrinkage and creep, prestress loss deflection signal characteristic, and the impact of construction method to bridge the redistribution of internal force and deflection are studied.The results as follows:(1) The characteristics of the deflection signal caused by shrinkage and creep of concrete bridge are Studied, The deflection at mid-span section caused by concrete shrinkage and creep is growing faster at the beginning, bridged ten years to thirty years the deflection increment reduces gradually, and tends to be stable.Bridged ten years cumulative deflection accounted for bridge fifty years cumulative deflection77.6%-88.6%, bridged thirty years cumulative deflection accounted for bridge fifty years cumulative deflection86.4%-95.7%; the deflection signal frequency in0Hz～3Hz, belongs to the low frequency signal.(2) Aging characteristics of prestress loss is mainly due to the prestress loss caused by concrete shrinkage and creep. As early as in prestressed bridge girder mid-span deflection rise, with the passage of time, due to shrinkage and creep caused loss of prestress, the mid-span deflection appeared slowly.Bridged five years relative deflection accounted for bridge thirty years relative deflection75.4%～99.3%, bridged ten years relative deflection accounted for bridge thirty years relative deflection75.4%～99.3%; the frequency mainly concentrated in the0Hz～1Hz, belongs to the low frequency signal.(3) Shrinkage and creep of concrete and prestressed and loss is coupled. At the early stage, in the common role of these two factors makes, the deflection at mid-span section rise, as time goes by, it gradually down and relative deflection value increment decreases, Bridged five years relative deflection accounted for bridge thirty years relative deflection41.5%～51.4%, bridged ten years relative deflection accounted for bridge thirty years relative deflection61.5%～71.9%; At the same time, the bridge span ratio (side span/span) has a certain effect on the bridge overall deflection of the deflection signal frequency; concentrated in the0Hz～1Hz, belongs to the low frequency signal.(4) The influence of the cantilever construction method of cantilever casting and cantilever erection of two kinds of construction process of internal force caused by shrinkage and creep of concrete bridge late redistribution and deflection change; The value of bending moment of bridge control section by the cantilever erection method is significantly larger than that of cantilever construction method, the method of cantilever castings’ bridge deflection is larger in late.