Research On The Setting Of Temporary Piers Of Long Span Hybrid Girder Cable-stayed Bridges

In order to reduce the construction risk of large-span cable-stayed bridges in the large cantilever state,and improve the overall stability of structure,usually adopt the method of setting temporary piers in the side span.The temporary piers of the cable-stayed bridge generally set near 0.6 times of the side span from the main tower,so the temporary piers can give full play to the role Tibet PoLongGou bridge is a hybrid cable-stayed bridge,the structural arrangement of which is(156 + 430 + 156)m.Due to auxiliary piers of side span is not set,the proportion of side span and the main span smaller,the temporary pier was set in a place,27.5m(about 0.18L)away from the center line of the main tower,which can’t give full play to the role of the temporary piers.So the security and mechanical behavior of the bridge in construction process is very unfavorable.Therefore,it is necessary to have simulation calculation and construction monitoring of the bridge construction process.Thus,it is imperative to undertake a study into the setting position and analysis whether set or not,in order to explore the feasibility of other programs.Through simulation calculation and construction monitoring,get the following main conclusions1.Tibet PoLongGou bridge is the National Firs asymmetric equilibrium system hybrid cable-stayed bridge,which using the construction method that side span cantilever casting and mid-span cantilever assembling.The method that composite beam leading side beam can effectively control the unbalanced torque of the main tower.2.Through the simulation calculation of construction process and field monitoring and feedback control,the error of the main monitoring parameters between the measured and predicted values meet the requirements,such as the deformation and stress of the main tower and main girder deformation and stress,the internal force of the stay cables.3.The calculated values and measured values of the reaction on the temporary piers are reflects the temporary piers not give full play to its functions,namely the temporary piers in most construction under the condition of no reaction,its role is very limited for overall structure,and the maximum reaction of temporary piers is 173.3 T,isfar less than its design using value(800 T),in a safe state.4.Through the coMParative analysis of the temporary piers set programs of PoLongGou bridge,obtained that: when the temporary piers set in 3L/4,L2/3,3L/5,L/2,may be effectively to reduce the horizontal displacement of the main tower,root stress of the main tower and the displacement of main girder,But the location of temporary piers have less effect on the stay cable force and the stress of main girder;When the temporary piers set at27.75m、L/3、2L/5,in the most later construction process,there is no reaction,and when set at 3L/4,it unable to provide favorable effect at early construction process.5.The static calculation results show that the geological conditions permitting,the temporary piers of PoLongGou bridge set in the side span L2/3 is more reasonable,and without temporary pier won’t affect the static security of full-bridge structure.