Construction Control Of Bridge Based On Large-scale Movable Scaffolding Systems Construction

The method of movable scaffolding construction has the ad vantages of short construction period, high economic efficiency, small traffic impact, process procedures, without foundation treatment, etc. which make it widely used in the construction of medium and small span concrete bridges. From the perspective of moveable scaffolding construction practice, this method still have many problems in the faulting control,, cracking control, etc. The safety and quality accidents of the movable scaffolding system have occurred from time to time during the construction process, which restrict the promoting use of the movable scaffolding system in bridge construction. Therefore, this paper adopted the movable scaffolding system of Wusi lake bridge in Hubei as the research object, and researched the stress analysis of the movable scaffolding system, load test, and the key technology of construction control of the box girder constructed by movable scaffolding system. The main research contents are as follows:(1)According to the possible load condition of the movable scaffolding system in construction, the whole construction process is analyzed by finite element simulation. The calculation results showed that: the strength and stability of the formwork were satisfied with the requirements of design and related standards. The torsion span ratio of the pouring conditions of the first span was 1/496, slightly larger than the design control value 1/500, it was recommended to strengthen the stiffness of the main beam. Under the pouring condition of the first span, the tensile stress at the bottom of the main girder was 210 MPa in the middle of the span, the top surface compressive stress of the main girder was 220 MPa, both of which were close to the specification standard limits. Therefore, it was recommended to take measures to strengthen the construction process and closely monitor the stress changes in the region.(2) In the preloading test process of movable scaffolding system, the deformation and stress of the main girder, the cross girder, the suspended beam and the hanger rod of were simulated and calculated under different loading conditions. Compared with the site measurement data of the preloading test, the manufacture quality and structural safety of movable scaffolding system were assessed. Results show that: the main beam were always in elastic range under loading test and sustained load;but the measured elasti c deformation value of the hanging beam is about 50%~125% of the theoretical value,and the actual stiffness of the bearing structure composed of the top rail, the suspended beam and the hanger rod was less than the design stiffness. It is recommended to ad opt a more scientific and reasonable structure to increase the stiffness of the structure. The residual deformation of suspended beam was large after unloading, so the loading test should be experimented to eliminate inelastic deformation before the movabl e scaffolding system is actually used.(3)According to the characteristics of the large-scale upstroke movable scaffolding system and the structure of Wusi Lake Bridge, the construction monitoring scheme for this project has been established. Firstly, thro ugh the movable scaffolding system preloading and according to the detailed construction control analysis results the linear was successfully controlled,and the error between the measured value and the theoretical value of each control was not more than 2c m. Under the premise of ensuring safety, the key technology for preventing faulting was proposed, which taken temporary support on cantilever. Through adopting this measure, the faulting between segments was reduced to 10 mm. Compared with not taking measures, the faulting was reduced by 49 mm. In addition, the results of the linear control in longitudinal and lateral directions and stress control of the whole bridge were good. The error between the measured value and the theoretical value of test points was mostly within ±20%. No concrete cracks appeared during construction, which indicated that the good effects were achieved in cracking control.