LocationLicang, Qingdao, Shandong, China
Structural analysis and InspectionSSDI
Text description provided by the architects. The future Qingdao North Railway Station is located on reclaimed land overlooking the bay of Jiaozhou, 500 meters from the shore of the Yellow Sea, in northern Qingdao.
The roof structure is composed by 10 identical frames parallel to the tracks called “arches”, reaching a maximum span of 140 meters. The arches support main roof transverse beams every 22 m with inclined columns called “brackets”. The brackets, the arches and the transverse roof beams are braced together in order to form rigid triangles (figure 1).
The beams and the arches are offset to form the curvature of the roof, and rotated in a vertical plan perpendicular to the arrival (figure 2). In the middle of the station, the space is narrower, but higher.
In the longitudinal section (figure 3), the structure is composed by “V” columns supporting the transverse beams. In the central section of the station, the V brackets are connected to each other, and create a very stiff double-W system to resist horizontal forces perpendicular to the tracks while enabling the structure to expand under thermal variation.
The system of beams and the arches are connected longitudinally at the top of the structure by a central ridge beam (figure 4). This beam has a triangular section of 5 m x 3.80 m.
All three facets of webs of the triangular box beam are pierced with rectangular holes to reduce its weight. This beam is designed as a 3-dimensional Vierendeel truss, reinforced with diagonals where shear forces must be counteracted.
The use of many identical frames made standardization possible, and thus allowed to develop complex details such as cable-reinforced brackets.
The brackets are stiffened by a self-balanced system that stabilises them against buckling while increasing the slenderness ratio of each member to reduce the weight and cost of construction (figure 6).
The brackets are connected to the arch through pin connection plates (figure 7):
The arches, “V” branches, and “V” columns supporting the waiting room structure are connected on a single foundation, formed as a concrete buttress. (figure 8)
In China, structures spanning more than 120 m, and those with a maximum dimension longer than 300 m must submit to the “National Commission of Structure Seismic Design Beyond Code Limits. (全国建筑结构超限抗震审查委员会)”.
In compliance with this commission’s requirement, the roof structure must resist wind pressure up to 700 kg/sqm on the cantilevered sections, due to its vicinity to the sea.
The utilization of folded plate technology allows the creation of original structural forms through the dense deformation of plate steel sheets. With many densely-packed folding axes the production of conical shapes are possible. The technique was initially developed and utilized successfully on the Shanghai South Station, a project we completed in 2006. The entire steel structure was fabricated in Nanjing and shipped to the building site.
The arch is built with 20 mm bent plates in order to form a cylindrical shell stiffened every 5.500 m by interior plates (figure 9).
The roof transversal beam comprises 1 upper flange of 400 mm x 30 mm, and a lower chord designed as an elliptic cylindrical shell (figure 10).
10.8 km of cables (diameter varying between 50 and 120 mm) are used to stabilize the brackets connecting transversal beams and arches against buckling. 5.5 km of cables are used for the diagonal bracing.