Analysis Of Construction Control And Temperature Effect Of Long-span Cable-stayed Bridge With Unequal Height Pylons

In recent years,with the continuous development of modern urban traffic in China,the cable-stayed bridge with unequal height pylons has been wildly accepted and applied because of its unique advantages in adaptability and aesthetics.The cantilever pouring method is generally used in construction of cable-stayed bridge,whose construction state is closely related to the finished state.However,the actual construction state is not always consistent with the reasonable construction state due to the influence of various factors,which makes the alignment and internal force of the actual finished state easily deviate from the reasonable finished state.In addition,the construction of long-span prestressed concrete cable-stayed bridge will take a long time,during which it will inevitably be affected by natural environment temperature change and solar radiation.Owing to the lack of research on construction control and temperature effect of cable-stayed bridge with unequal height pylons at home and abroad,this paper takes Qingxikou Qujiang River Bridge as the engineering background,a construction control system for long-span cable-stayed bridges with unequal height pylons is established,and the methods of parameter identification and state prediction are emphatically studied.Meanwhile,the temperature effect is analyzed by finite element method.The following conclusions can be obtained:(1)The structural characteristics and some well-known engineering examples of cable-stayed bridge with unequal height pylons are introduced,and the research status of construction control and temperature effect of cable-stayed bridge is summarized by consulting a large number of documents.(2)According to the design and construction characteristics of cable-stayed bridge with unequal height pylons and the experience in construction control of constructed cable-stayed bridge with equal height pylons,a self-adaptive construction control system of long-span cable-stayed bridge with unequal height pylons is established from three aspects: calculation model,monitoring scheme,technology and organization system.(3)Through parametric sensitivity analysis,it can be determined that the main design parameters of cable-stayed bridge with unequal height pylons in construction control are the self-weight of the concrete girder and the elastic modulus of the stay cable,then the least square method is used to modify these parameters.It can be found that the modified calculation model is more in line with the actual situation,the difference between the measured and theoretical deflection of the girder is within 10 mm.(4)The residual modification GM(1,1)based on Markov chain is established by using the measured deflections of the constructed beam segments,and is used to predict the deflection of the next beam segement during construction.Combining with the grey prediction results,a formula for calculating the erection elevation of formwork based on the self-adaptive control principle is put forward.The analysis and verification results of a actul bridge show that the elevation predicted by residual modification GM(1,1)based on Markov chain has high accuracy and reliability,and can meet the requirements of construction control.(5)The influence of temperature difference between day and night,temperature gradient of main girder,temperature gradient of pylons,temperature difference among stay cable,pylons and main girder on the stress and deflection of main girder and cable force at the construction stage of the longest one-side cantilever and the longest two-side cantilever of the cable-stayed bridge with unequal height pylons is analysed by using the finite element software Midas Civil.Furthermore,according to the calculation results of temperature effect,some suggestions for the construction control of cable-stayed bridge with unequal height pylons are put forward.