Mechanical Performance Analysis Of Large Span Corrugated Steel Web-UHPC Combined Continuous Box Girder Bridge

The traditional prestressed concrete box girder has a limited span application range due to its weight.The span of the continuous beam should not exceed 150 m,and the span of the continuous rigid frame is limited to 200 m.In the construction and operation of large-span prestressed concrete box girder,the cracking phenomenon of the web and bottom plate is serious.Owing to insufficient information reagrding the concrete shrinkage and creep and the deformation of the main girder during its construction stage,an excessive midspan deflection is a common phenomenon at domestic and abroad.To address above problem,this paper proposes the structural concept of "long-span corrugated steel web-UHPC composite continuous box girder bridge".The use of corrugated steel webs to replace the concrete webs can not only reduce the self-weight of the structure and thus address the problem of concrete web cracking,but also improve the introduction rate of prestressing of top and bottom decks is greatly improved;the application of ultra-high performance concrete(UHPC)to replace the top and bottom concrete decks can further reduce the structural self-weight and avoid the cracking of bottom deck.UHPC has extremely low shrinkage and creep after steam curing,which is used to construct the main beam to solve the problem of excessive mid-span deflection due to creep.The corrugated steel web-UHPC combined continuous box girder is expected to break through the technical bottleneck of the traditional corrugated steel web-PC combined box girder bridge,and become a very competitive structure selection in the long-span continuous box girder bridge.In this paper,the long-span corrugated steel web-UHPC composite continuous box girder bridge is proposed as the research object.By means of theoretical analysis and finite element structural analysis,the overall mechanical profermance,local structural behaviors,economic analysis and optimization are carried out.The main conclusions are derived as follows:(1)Compared with the prototype design scheme and PC box girder bridge,corrugated steel web-UHPC composite box girder bridge can significantly reduce the dead weight of the structure and the dead load of the bridge;Under the longest cantilever condition,the internal forces are considerably reduced,and the safety and stability of construction are greatly improved.Under the combinations of various actions,the principal tensile stress and principal compressive stress of corrugated steel web-UHPC composite box girder bridge meet the requirements of bridge design code,and the mid-span deflection is far less than the allowable deflection of bridge code design.(2)The local buckling stability,the overall buckling stability and the combined buckling stability all meet the requirements of related design code.The maximum shear stress of corrugated steel webs of proposed composite continuous box-girder bridge is only 50% of its shear strength.The shear bearing capacity of stud connectors meets the requirements of related design code,and the safety reservation is large.(3)The excellent mechanical performance of corrugated steel web-UHPC composite continuous box girder is verified from the aspects of constant live load ratio,settlement adaptability,structural dynamics and lateral eccentric load analysis of bridge deck.(4)The initial cost and the life cycle cost of corrugated steel web-UHPC composite continuous box girder bridge is competitive.With a reducing thickness of UHPC web,a reducing box-girder height at supports,a reducing thickness of UHPC deck and a growing spacing of UHPC diaphragm,the technical economy of the propsed design scheme is improving.The corrugated steel web-UHPC composite continuous box girder bridge has excellent overall mechanical performance,local structural behaviors,construction convenience,and thus it is feasible technically.It is expected to become a competitive bridge type of long-span continuous beam bridge.