Study On Long-span Continuous Beam Bridge Construction Using Combination Of Full Cantilever And Full Staging Method

Long-span continuous bridges has become one of the most popular bridge types due to its own advantages.Form cantilever method(FCM)and full staging method(FSM)are the most used and developed construction method for continuous bridges.However,in order to meet work-time transportation,construction efficiency and other requirements,contractors has combined those two methods and put in use.FCM and FSM have many differences in pre-stress design,structure system and boundary conditions so it is of necessarity to analyze stress and deformation of bridges using combined construction method and study its construction control.This paper use Guangzhou Wenquan Liuxihe Bridge as a construction example and results achieved are as follows:(1)Based on case study and construction example,characteristics of FCM and FSM has been studied and presented,including construction cost,technics and length of time.Advantages and also feasibility of combined method are also discussed,which provide information for method choosing in actual construction.(2)Midas Civil FEA beam model has been created based on construction example.It was used to analyze differences of stress and deformation of continuous bridges during and after construction which are using FCM,FSM and combined method.Two kinds of pre-stress design are also compared.Changes in stress resulting from incomplete detachment of scaffolding and beam after pretension are also studied.(3)Effect of construction sequences,including sequence of closure,timing of dismantling scafold and timing of pretension,on stress and deformation of continuous bridge under combined method are studied and analyzed.Results shows that when beams are not symmetry,multiple times of pretension might lead to displacement differences between beams.Effects of sequence of closure are very similar between FCM and combined method,the most reasonable way to close beams is to start from both sides towards the center.(4)On-site construction control system of combined method is introduced.Based on data collected from the site,the differences of stress and deformation between FEA calculation and actual testing data are studied.Besides errors and minor differences,calculation and actual data matches positively.Due to the complexity of bridge construction,it is very important to use control measures to keep construction in order.