| The rapid development of China’s transportation construction has been continuously improving the technical level of bridge construction. Bridges with large width and great complexity are emerging one after another, while the cast-in-place cantilever method of a continuous beam is progressing toward maturity. This article mainly relies on the construction project of Malin Bridge on the A3 section of the connecting line of Changchun-Shenzhen Expressway in Sanming city, Fujian Province, contracted to China Railway 17 Bureau Group Co. Ltd. Malin Bridge is a bridge with disconnected and dislocated right-side and left-side bridges. The right-side bridge roadway is a 4×26.5+(42+76+42)+3×40+4+4×30)=514m cast-in-place prestressed concrete continuous rigid frame+ prestressed concrete T beam bridge; while the left-side bridge is a 3×30+(42+76+42)+5×40+2×30=523.5m cast-in-place prestressed concrete continuous rigid frame+prestressed concrete T beam bridge. The main bridge is designed as a (42+76+42) =160m prestressed concrete continuous rigid frame bridge stretching over a canyon, with 3% cross slope of the bridge floor. The cross section of box girder uses the single-box double-room vertical web cross section. The width of the box girder roof is 25.25m, the width of the bottom plate is 17.25m, while the length of the cantilever is 4.0m. This project aims to resolve problems in bridge construction, such as steep terrain, complicated construction road, poor transportation, and low in-situ vertical lifting capacity. The bridge floor is designed with a 3% ultra-high cross slope; the main beam is a 25.25m single-box double-room prestressed concrete box girder; the height difference between neighboring webs on box girder is 25.5m; the width of the main bridge floor is 25.25m, and the length of the bottom plate is 17.25m. Under the work condition of hanging baskets, the distance between the two hanging points on the low and rear cross beam is over 25.5m, so low and rear cross beams with great rigidity will be needed to meet the requirements of hanging basket deformation. How to optimize the structure-type or supporting-type layout form of low and rear cross beams for basket hanging, so as to decrease the sectional dimensions of low and rear cross beam, thus lowering the desi.This paper combines with the technical problems to be addressed in the actual construction process of Malin Bridge and uses methods such as theoretical analysis, numerical simulation, expert reasoning, laboratory experiment, field experiment and monitoring to study the design and optimization of the special-shaped triangle hanging basket of Malin Bridge, and the risk analysis and risk control of the main beam cantilever construction. Main results are concluded in the following aspects:(1) Design a new hanging basket-special-shaped triangle hanging basket incombination with the advantages of both triangle and rhombus; optimize the primary truss design of the special-shaped triangle hanging basket, replace the previous formed steel construction with the higher-strength 16Mn steel pulling plate as tension member of the primary truss to save steel materials; meanwhile use pin rolls and bolts to unite the main components to simplify the assembly process; address the discrepancy in elevation between neighbouring main trusses, caused by wide girder and large cross slope, through the step-like layout and connection of the three-piece main truss, to improve the versatility and efficiency of the hanging basket. 2) Increase a longitudinal sliding beam under the basket bottom cross beam as the supporting component of the bottom beam, which effectively reduces the load-bearing span of the bottom beam, solves the need of large-width cantilever construction for bottom beam with strong stiffness, and also improves the security of walking in the basket.(3) Put forward the innovative staggered platform hinge joint (layout method) form of the front beam of the multi-truss basket to solve the elevation differences of the three-piece main truss of the bridge floor with large cross slope and large width.Finally, this study solves the design and construction problems about the main bridge basket caused by the high pier, super-wide beam surface, large bridge cross slope, transportation hoisting difficulty, and other factors of Malin Bridge, bringing in significant social and economic benefits. |
