Full-scale FRP-concrete-steel Double-skin Tubular Arch: Investigation On Construction Methods And Behavior Under One-point Loading

Fiber Reinforced Polymer(FRP)is a new high-performance material with the advantages of light weight,high strength and good corrosion resistance.It has been widely used in practical engineering.FRP-concrete-steel double skin tubular member(DSTM)is a new type of composite structural component.The new composite structure consists of FRP outer tube,steel inner tube and the concrete infill between the two tubes which has higher compressive strength and better deformation capacity than the unconstrained concrete due to confinement provided by the two tubes.Because the steel tube is constrained by both the outer concrete and the FRP tube,local buckling can be effectively avoided and its strength can be fully used.In addition,steel tube and FRP tube can also be used as the formwork for casting concrete,which can exempt the formwork cost during the construction process.FRP tubes can also protect steel inner tubes and concrete from corrosive environment.With the said advantages,the new composite structure is especially suitable for the construction of bridge structures and long-span structures in areas with seismic resistance requirements and/or in corrosive environment.However,the research on this new composite structural member is mainly focused on beams and columns,and the research on arch structure using DSTM has been rather limited and the related application has not been documented yet.Under this background,the following research is carried out in this research program:1.Design of specimens and loading devicesAccording to the FRP-concrete-steel double-skin tubular arch bridge to be built on the new campus of Lu’an No.1 High School Anhui,two full-scale arch specimens were designed and constructed.The arch span was 12.31 m,the arch height was 1.175 m,Ф299×12mm,Q355 C steel tubes were used as inner tubes,and FRP tube with rounded corners were used as outer tubes.The self-compacting concrete of grade C40 with expansive agents were used in for concrete.At the same time,a self-balancing steel beams for arch loading test was designed by based on current design guideline and finite element analyses.Loading device includes three parts: self-balancing steel bottom beam,arch support and arch foot.2.Study on cast-in-place and prefabricated construction technologyTwo construction methods,namely cast-in-place and precast construction methods were developed respectively.Two FRP-concrete-steel double-skin hollow arches were cast in a steel factory using the above two methods respectively.The cast-in-place arches were constructed by positioning and connecting the steel tube and FRP tube to form the arch tubes and then casting concrete in one time.The precast arches were constructed by fabricating three DSTC tubes first(the process also includes positioning,connecting steel and FRP tube and casting concrete)and connecting them to for a whole arch.3.Experimental study on the behavior of FRP-concrete-steel double-skin tubular arch under one-point loadingThe behavior of FRP-concrete-steel double-skin tubular arches,constructed with two different construction techniques,under one-point loading was studied and compared.The one-point loading was applied in the mid-span.The test phenomena and failure mode in the whole testing process were observed and test data recorded,based on which load-displacement curvess,load-strain curve,specimen deformation diagrams and strain development in steel and FRP tube were obtained.The influences of two construction methods on the behavior of FRP-concrete-steel double skin tubular arch bridge were compared and discussed.