January 17 — The first "clustered-anchor steel crossbeam" of the south main bridge of the Anhui Chizhou Yangtze River Highway Bridge was recently hoisted successfully, a world first that opened the curtain on construction of the bridge's upper pylon columns.
It is reported that the Anhui Chizhou Yangtze River Highway is 41.2 km long in total. Contract Section 04 of the Chizhou Yangtze River Highway Bridge, undertaken by China Road and Bridge Construction Co., Ltd. (hereinafter referred to as "CCRB"), is 2.626 km long and includes a cable-stayed bridge with a main span of 828 m, a continuous rigid-frame bridge of 110+200+110 m, and a continuous-beam river-crossing bridge of 3×80+2×45 m. It is a representative project characterized by complex bridge types and diverse foundations.
To improve development quality and build a quality project, and drawing on the distinctive regional culture of Jiuhua Mountain in Chizhou City, Anhui Province, the construction team of the Chizhou Yangtze River Highway Bridge, guided by the concept of deep integration of design and construction, proposed two new technologies for the pylon columns: "skin-function concrete" and a "new-type steel crossbeam clustered anchor." Over the more than three years since the bridge broke ground, the CCRB project team has tackled key technologies one by one and successfully applied them, fully advancing the project's construction.
Distinctive Craftsmanship: Mastering "Skin-Function Concrete" Construction Technology
The main navigation-span bridge of the Chizhou Yangtze River Highway Bridge is an asymmetric hybrid-girder twin-tower cable-stayed bridge with a main span of 828 m. The south main pylon rises 243 m, equivalent to a 90-story building, towering into the clouds.
The bridge's main pylon "skin-function concrete" adopts composite technology using inner and outer layers of concrete with different properties, continuously varying material composition and structure to eliminate internal component interfaces, ease interface stress, and form a new heterogeneous composite concrete material with gradient changes in properties and function. This improves the crack resistance, durability, and appearance of the pylon concrete structure, optimizing both structural function and economy.
As there was no prior experience to draw on for skin-function concrete technology, the CCRB project team carried out in-depth technological innovation. Through more than 600 mix-proportion tests, over 20 process verifications, and more than 30 scheme discussions, they successfully overcame a number of key technical challenges. During construction, two mixing systems were deployed to mix the black and white concretes separately using two mixing processes; steel wire mesh was used to separate the inner and outer layers of concrete during pouring; and the "dual-feed synchronous pouring" process and a "multi-point balanced feeding system" were used for synchronous lifting and vibration, creatively solving such challenges as the bonding at the interface between black and white concrete, consistency of strength grades, and matching of the pouring rates of the two concretes. This comprehensively improved the concrete's mechanical properties, crack resistance, durability, and aesthetics.
Striving for Excellence: Pioneering "Steel Crossbeam Clustered Anchor" Construction Technology
The Chizhou Yangtze River Highway Bridge adopts the world's first "new-type steel crossbeam clustered anchor technology." Because the steel crossbeams are huge in volume, the working space is cramped, the procedures are complex, and precision requirements are extremely high, the hoisting construction combines "novelty, height, weight, size, narrowness, complexity, precision, and difficulty," posing numerous challenges to on-site construction.
The bridge's steel crossbeams are box structures, with a single steel crossbeam weighing up to 315 t in total and hoisted in four sections. The interior space of the crossbeams is narrow, with work carried out on high-altitude platforms 160 m to 230 m above ground. The steel box girder structure is complex and the procedures are cumbersome: a single steel crossbeam alone has 10,960 high-strength bolts and 248 splice plates, with a maximum of 600 bolts in a single connecting plate, 168 anchor rods on one side, and the heaviest single anchor rod weighing 309 kg. Moreover, affected by the main reinforcement, stirrups, and hook bars of the main pylon, the installation space for the steel crossbeam anchor rods is relatively complex, making quality control difficult. Large tower cranes are used for ultra-high-altitude, heavy-tonnage, large-component hoisting operations, entailing high safety risks. In addition, installation precision requirements are extremely high, with allowable deviations in plan position and elevation both within 2 mm.
Facing these numerous challenges, the CCRB project team planned ahead and constructed meticulously. Both ends of the pylon columns and steel crossbeams are anchored and connected to steel structure anchor plates embedded in the concrete pylon columns via high-strength nuts, ensuring the stability of the entire upper pylon column structure. When a steel crossbeam segment was positioned onto the steel buttresses above the load-bearing frame, on-site personnel each performed their duties, using the three-directional adjusting jack positioning system to initially position the steel crossbeam segment in plan and elevation. After a single steel crossbeam was assembled into a whole, the three-directional adjusting jacks were used for secondary precise positioning, after which the anchor rod anchoring system, pylon column reinforcement, and formwork were installed, precisely installing each section of the steel crossbeam at a height of 160 m.
The Chizhou Yangtze River Highway Bridge is a key project in Anhui's "four vertical and eight horizontal" expressway network crossing the Yangtze River. Its early completion is of great significance for supporting the national Yangtze River Economic Belt development and enhancing regional economic growth.