Analysis Of The Influence Of Geometric Nonlinearity On Long-span Cable-stayed Bridges In Completion And Construction Stage

The lower reaches of the Yangtze River have large surface and the shipping on it are very busy.Cable-stayed bridges can easily connect the two sides of the river with economical cost,which can meet the needs of social development.Geometric nonlinearities are important characteristics of long-span cable-stayed bridges.The nonlinear will increase with the bridge span.The influence of the geometric nonlinearities Oon the response of long-span cable-stayed bridge is necessary to be analyzed during the construction and completion stage in order to ensure the quality and safety.In this paper,the causes of geometric nonlinearities are analyzed firstly.The bridge model of a long-span cable-stayed bridge is established.The cable forces are adjusted to achieve a reasonable completion state.The influences of three geometric nonlinearities(sag effect,second-order effect,large displacement effect)on the displacements,internal forces and stresses of the cable-stayed bridge in completion state are analyzed,and the main causes of nonlinear increment are discussed.Secondly,the construction methods of the long-span cable-stayed bridge are introduced,and the solution method of the reasonable state in the construction stage is analyzed.The construction stage model of the cable-stayed bridge is established,and the reasonable construction state is obtained by the unstressed state method.The influences of three geometric nonlinearities on the displacements,internal forces and stresses of the cable-stayed bridge during construction stage are analyzed.Finally,the displacement calculation results of the large-span cable-stayed bridge considering geometric nonlinearities under static wind loads are analyzed.The influence law of three geometric nonlinearities under different wind speeds is studied.The results show that:the three geometric nonlinearities have different effects on the displacements,internal forces and stresses of the main girder and the pylon.The nonlinearities mutually influence each other,and result in the increment static response of the bridge.In the completion state,the sag effect is the main nonlinearity that causes a significant increase in the static response of the main beam and the pylon.During the construction stage,the influence of geometric nonlinearities on the structure increase with the construction progresses:In the double cantilever construction stage,the influence of geometric nonlinearity on the structure is much smaller than that of the single cantilever construction stage,in which period the influence on the displacement of the cantilever section of the main beam is greater than that of the closed section.The effect on the internal force shows opposite phenomenon.Lateral static wind loads mainly cause lateral and torsional deformation of long-span cable-stayed bridges.In general,the influence of geometric nonlinearities on the torsional displacement of the main beam is greater than that on the lateral displacement.In addition,the three geometric nonlinearities have different influences on the displacements:In the completion state,the sag effect has the most significant effect on the transverse and torsional displacement of the main girder;in the construction stage,the large displacement and the second-order effect are the main factors of the lateral displacement of the main beam,and sag effect is the main factor of the torsional displacement.as the wind speed increases,the degree of influence of geometric nonlinearities on the displacements also increase as well.