The Study On Partial Repair Technology Of Light-weighted Composite Bridge Deck Composed Of Steel And UHPC Layer

There are two major problems existing in orthotropic steel plates such as steel fatigue cracking and pavement damage. To deal with the problems above, our team proposed a new type composite bridge deck system that consists of an orthotropic steel deck and a thin reinforced Ultra-high performance concrete(UHPC) layer through stud shear connectors, named ultra-high performance light-weighted composite deck structure, the performance of bridge deck has been improved greatly. But the thickness of UHPC layer on Ultra-high performance light-weighted composite deck structure is typically only 35 ~ 80 mm, there are dense bars inside, need overall cast and high temperature steam curing, so the construction of UHPC layer require Higher, and thus the construction errors can not be avoided absolutely. In addition, it may cause partial damage on the UHPC layer of the bridge deck structure such as serious overloading of vehicles, earthquake and so on after the deck put into use. To meet the requirement above and consider the factors of human and material. This paper presents a local repair technique for UHPC layer of light-weighted composite deck and completed the following works:Firstly, with the Dongting Lake bridge as the background, full scale test models with the ball flat steel ribs were produced. A method of dismantling damaged UHPC layer by pulling out the bar in UHPC layer is proposed, and a new form of partial repair joint welding tensioned bar to steel plate is designed. To demonstrate the feasibility of the demolition scheme and verify the performance of the joint between old and new UHPC, utilized full-scale experimental model to complete the demolition of designated UHPC areas and carried out two full-scale model experiments to research the mechanical properties of horizontal and vertical joints respectively. The result shows that this method can complete the demolition of damaged UHPC area quickly. The new repair joint form reduces the stress of UHPC layer and improves the tensile properties effectively. the tensioned bar and steel plate bear the loads together by welding tensioned bars to steel plate in the position of the joint. The cracking stresses measured from the experiments of horizontal and vertical joints are 21.8MPa and 17.4MPa, 73.4% and 67.1% of the cracking strength of the cast in place UHPC section, transverse joint strength is greater than the longitudinal joint strength and they are all larger than 9.8MPa the cracking strength of conventional joint and close to the strength of 21.9MPa and 23.5MPa in tongue and groove joint and profiled steel joint, it can prove that this joint structure can significantly improve the strength of the seam cracking.Secondly, the calculation of the finite element analysis of Dongting Lake Bridge is completed using FE software Midas Civil and ANSYS, including calculation of local FE analysis models and full-bridge global. Comprehensive two part of the calculation results, the maximal horizontal and vertical tensile stresses are 17.6MPa and 6.9MPa, less than the tensile stress measured. The new repair joint completely meets the requirement of the UHPC layer maximal tensile stress. At the same time, it can reduce the tensile stress effectively by positioning the joint in the middle of the diaphragm plates and away from the position of longitudinal ribs, this can improve the reliability of the joints.Thirdly, based on the maintenance test on the experimental models to measure the shrinkage of UHPC layer under different curing conditions.After 48 hours steam curing, shrinkage strain is 82??, due to the constraints of steel panels, steel bars, shear studs, significantly less than 161?? shrinkage strain under nature curing after 28 days. And steam curing can be completed the most of shrinkage in a relatively short period of time, greatly reducing the follow curing work, this proves steam curing has more advantage for UHPC layer on light-weighted composite bridge deck. Meanwhile, after 48 hours steam curing, it will produce 3.50 MPa shrinkage stress in the UHPC layer by theoretical calculation, it provides a reference for the actual projects.