Research On Characteristic And Mechanism Of Force And Deformation Of Immersed Steel Shell Concrete Tube

With the increase of waterway traffic and the complication of water environment,traditional bridging and immersed reinforced concrete tube cannot meet requirements,while immersed steel shell concrete tube having high intensity,large section,long durability and prefabricability becomes the preference of area having advanced seacrossing engineering technology.However,domestic technology of immersed tube starts relatively late,research on immersed steel shell concrete tube is less,and almost no research is related to force and deformation of whole structure,which is matching actual engineering.Based on the first steel shell immersed tube project in China,ShenZhong passageway,this paper makes a series of studies on the force and deformation from whole to detail by using the finite element numerical simulation method.(1)The actual three-dimensional model is established to simulate sit-on-bottom pouring.Pouring in layers in order of baseplate-vertical wall-roof is better method.The calculation results show that the bottleneck includes the middle of the long-span floor when pouring floor,the bottom of lateral wall when pouring wall,the junction of the roof and lateral wall when pouring roof,and the middle of the long-span roof.In structural design,attention should be paid to the diameter and arrangement of the transverse steel bar enclosing the steel plate in the opposite tension middle wall,as well as the thick Ness of the long-span mediastinal plate.(2)The actual three-dimensional model is established to simulate floating pouring.Floating pouring must be carried out in layers,and the pouring sequence is the same as sit-on-bottom pouring.Bottleneck includes the bottom diaphragm of the middle wall when pouring floor,the bottom of lateral wall and the top of lateral wall when pouring the wall at one time,and the junction of the roof and lateral wall when pouring the roof.The matters needing attention in structural design are the same as the bottom pouring.Floating pouring is safer during pouring baseplate,covering less area and simplifying process,while environment,equipment and technology generate more influence.(3)Based on the equivalent principle of bending stiffness,a three-dimensional composite model of simplified practical engineering is established,the dimensions of temporary components are designed,and the floating transportation,locking backfilling and top backfilling of pipe segments are simulated.In structural design,attention should be paid to the design of the form and arrangement of temporary component end door sealing and floating anchor.Among the three main working conditions during the construction period after pipe joint forming,the bottleneck includes the middle of longspan bottom plate during pipe top backfilling and the junction between middle wall and bottom plate.(4)Detailed concrete damage plastic model considering bond slip is established in the middle of driveway-baseplate,and the bond slip strength of steel-concrete interface is high,which means interface will not be damaged due to failure.The interface between concrete and longitudinal impedance partition generates vertical cracks due to tension,and the concrete in tension area generates oblique cracks due to tension.The concrete in the tension area reaches the tensile strength,the concrete in the compression area is close to the compressive strength,and the steel plate bears greater tensile stress and compressive stress,but it is safer.The strength check is carried out at the junction of the central vertical wall with complex stress state,and the bending and shear capacity meet the strength requirements,but the shear force of the section is close to the shear capacity,which becomes the controlling factor.