Creep Effects On Internal Force Evolution Of Continuous Girder Bridge Constructed By Different Methods

Prestressed concrete continuous girder is widely used in various tranportation systems.It is applicable to both small span bridges(10-40m)and large span bridges(200-300m).There are mainly four construction methods for continuous girder bridges:full support method,simple supporting to continuous method,cantilever construction method and incremental launching method.Some studies have been conducted on the structural internal force of bridges constructed by different methods,and concluded that difference among the internal force does exist.The internal force of bridge constructed by full support method has little difference with that of bridge constructed by incremental launching method.The internal force of continuous girder bridge constructed by simple supporting to continuous method is similar to that of simple supported girder bridge with identical span.The internal force of the continuous girder bridges constructed by cantilever construction method is similar to that of cantilever beam with the same span.However,the influential factors resulting in the above mentioned differences have not been identified.In this study,concrete creep was considered as an dominant factor and the creep of bridges constructed by different methods were studied.Firstly,finite element models of the continuous girder bridges constructed by different methods were established and internal force evolution of these bridges were analyzed.The influence of prestress tendons on the internal forces was also studied.Secondly,effects of concrete creep on the internal forces on the typical sections of concrete bridges were also investigated.Heuristic theory was adopted to analyze the internal force of bridge constructed by full support method,and the results were compared with that obtained by finite element method.It can be observed that the two results are indentical.Thirdly,none stress state method was used to analyze the influence of the construction process on the internal force of the bridge constructed by cantilever method.The reliability of the model was verified by the comparison between the predicted value and measured values on a case bridge.It can be concluded from the results that there is little change in the internal force of bridges with prestress tendons.The internal force of bridges without prestress tendons tend to the internal force of once-formed structures when using simple supporting into continuous construction method or cantilever construction method.There is little change in the internal force of the bridges constructed by full support method.It also can be concluded that the existence of prestress tendons in continuous girder bridges has a coordinating effect on creep secondary internal force.