At 15:55 on November 28, the Anjiazhuang Grand Bridge of the National Highway 109 New Line Expressway, which crosses over the Fengsha Railway, completed a 47-minute high-altitude rotation of its left and right main spans, with both spans precisely aligned. This marks the world's first successful dual-span synchronous rotation atop high piers for a curved steel truss cable-stayed bridge, making "China Bridge" a new calling card renowned worldwide once again.

The National Highway 109 New Line Expressway runs through seven towns in Mentougou District. Once completed, the travel time along the entire route will be shortened from over 2 hours to under 1 hour. Since 2018, China Railway Design Group has undertaken the design and research of the Anjiazhuang Grand Bridge, a controlling project of this line. The bridge site is located in a high-intensity seismic zone of degree 8, with steep mountains on both sides, strong instantaneous winds and variable wind directions in the valleys. The left and right spans lie on curves with radii of 1,600 meters and 1,500 meters respectively, and must simultaneously cross the busy Fengsha Railway, the existing National Highway 109, and the Yongding River, which has flood discharge requirements and is a Class I water source protection area. The bridge deck is nearly 50 meters above the normal water level. The construction conditions are extremely demanding, and both design and construction are highly challenging.

"To minimize the impact on Fengsha Railway operations and Yongding River flood discharge while meeting seismic and wind resistance requirements, we innovatively designed a large-span curved steel truss girder and adopted a ten-thousand-tonne pier-top rotation construction method. The steel truss girder was designed and manufactured according to the principle of 'curved beams made curved.' The left and right main spans respectively adopt a (248.95+248.95) m steel truss cable-stayed bridge and a (171.95+171+75.25) m continuous steel truss girder bridge, making them the largest-span curved steel truss cable-stayed bridge and curved steel truss girder bridge in the world. This is the first application of curved steel truss girder pier-top rotation technology, with the left and right spans synchronously rotated into place in a single integral operation. The rotation weights were 15,570 tonnes and 9,320 tonnes respectively, and the left span's horizontal rotation length reached 498 meters, a world record. Numerous difficulties and challenges were overcome in controlling the attitude and precision during rotation and in reasonably matching the spherical hinge, support feet, and steel truss girder structure. The main piers use concrete-filled steel tubular piers with a diameter of 4 meters, a wall thickness of 90 millimeters, and Q500 steel; the design diameter and wall thickness of the steel tubes are unprecedented both domestically and internationally, resolving a series of technical challenges such as the force-transfer structure at both ends of concrete-filled steel tubular piers," said Li Yanming, head of the bridge project at China Railway Design Group, with great pride.

The left and right spans, different in style yet harmoniously staggered, stand majestically among the mountains, imposing and vigorous. The curved girder bodies complement the bridge tower shapes, further highlighting a balance of rigidity and softness in their lines. The white exterior is bright and lively, blending perfectly with the surrounding mountain scenery and water. The rotation construction site was orderly, with all participating parties cooperating closely. The bridge slowly rotated under everyone's gaze like two dancers performing, and the two spans finally joined hands above the Yongding River, drawing cheers and applause.

"The curved steel truss girder structure of this bridge is exceptionally complex. The steel towers have semi-elliptical variable cross-sections, and the spatial positioning of nearly ten thousand truss members must fit together perfectly. To accurately express every detail, we adopted a BIM forward-design approach, explored an integrated design workflow of design-modeling-drawing generation, developed automated modeling functions and an intelligent drawing generation system, and provided construction companies and steel girder manufacturers with high-precision models and batch drawings. This precisely conveys complex structural information and design intent, opens up the information transfer path across the entire design-manufacturing-construction process, and effectively saves time and cost," Peng Lanping, chief engineer in charge of the bridge project at China Railway Design Group, told us about the latest intelligent design methods used for the bridge.

As the first expressway in the western Beijing region and a key livelihood project in Beijing, the National Highway 109 New Line Expressway project will become a new rapid transportation corridor connecting Hebei and Beijing upon completion. It will serve as a new trunk line alleviating traffic pressure in northwestern and southwestern Beijing, driving the region's economic and social development to "accelerate," and bringing new opportunities for high-quality development in Mentougou District's revitalization of red tourism resources, development of traditional characteristic villages, and inheritance of intangible cultural heritage. The Anjiazhuang Grand Bridge will become a landmark building of Mentougou.