Study On Key Technologies Of Green Prefabricated Precast Concrete Girder Bridge

Green bridge is able to minimize the usage of natural resources and the pollution to environment in their whole life cycle from construction to operation,and then effectively control the adverse effects on the environment after bridge construction and operation.According to the principle of optimum utilization of resources,the key points of green bridge are modular design method in bridge design and prefabricated construction technology in bridge construction.At present,there are more researches and applications about modular precast concrete components overseas,while domestic researches and applications mainly involve the precast concrete girder and that of other prefabricated components are relatively few.In this paper,based on green bridge concept and part of the research and application achievements of prefabricated bridges,we put forward the key technologies of green prefabricated precast concrete girder bridge.Key processes of green bridge are green design and construction.As for green bridge design,one of the key points is to develop the principles and main points of green bridge design;And for green bridge construction,we should pay attention to saving energy,land,water and material as well as environmental protection.It is suggested that the government,research organization,designers and contractors develop regulations and standards of green bridge,establish green consrtruction management mode and assessment system of green bridges and promote related policies of green bridge.Modular precast concrete components of green bridge,such as precast slab,precast girder and precast pier,are produced in prefabrirated field.For this reason,it is necessary to determine a rational component size considerating its fabrication,lifting,transportation,storage and using conditions.Precast concrete slab is usually connected with precast concrete girder,steel girder or directly connected with the pier,and is apt to show uncoordination of stress and deformation between precast slab and girder as a result of the material difference,temperature effect and concrete shrinkage and creep,etc.Therefore,it is critical that connection details between precast concrete slab and other prefabricated components perform well with reliable connection method,which is the ensurance of safety and durability of precast concrete bridge.Precast concrete girder,especially the precast prestressed concrete girder,usually has a long span and relatively large sectional size.Therefore,it is nessesary to consider the influence of the torsion,stability,shear lag effect,distortion,loss of prestress and anti arch on the stress and deformation during design and construction of precast concrete girder.Multi-girder bridge system is offen used in precast concrete bridge,and the single piece of main girder will be connected as a whole along the longitudinal and transverse,rely on the diaphragm,prestressed technology or the bridge slab.Therefore,except sufficient strength and rigidity between joints,it must have a good connection detail between defferent girders to make sure of reliable serviceability,safety and durability of the bridge.In the implementation of green bridge,precast concrete pier column is also a good choice.The bridge pier could be designed and constructed as an integral pier or segmental piers according to actual requirements of the project.Therefore,reliable connection is required between pier column and foundation,pier column and bent cap and defferent segmental piers.In order to make sure that the precast concrete pier or column performs a good ductility and energy dissipation capacity,energy dissipation bars can be used at the bottom of precast pier columns,or to utilize steel pipe concrete,steel reinforced concrete to improve the ductility and energy dissipation of the pier.