The design calculation for this project is based on a space bar finite element method program. The grid structure is divided into seven distinct areas: A, D, and G are classified as the first type of frame based on their size, while B, C, E, and F are categorized as the second type. Each joint is modeled as a hinge, and all members are analyzed as axial force bars. The yield strength of the steel used is 235 N/mm², with a design stress of 200 N/mm². The allowable slenderness ratio for the members is set at 150 to ensure structural stability.
The grid uses high-frequency welded pipes with different diameters and thicknesses for various parts. Specifically, 60×3.5, 76×3.75, 89×4.0, 114×4.0, and 159×6 mm sections are used. Bolt ball nodes are made from 45 steel, while high-strength bolts are fabricated from 40Cr steel. Sealing plates, supports, and support blocks are constructed using A3 steel, and sleeves are made from Q235, 16Mn, or 45 steel. The support system plays a critical role in the grid's performance. It is designed as a pressure-bearing support that can handle both compressive and tensile forces, ensuring the hinge characteristics of the upper grid structure.
The large grandstand roof at the Zhuhai International Circuit features a long cantilever structure with an asymmetrical layout and a 22-meter overhang. Due to its complexity, deflection testing was conducted to verify the safety of the grid. A Leica TC1700 total station was used to measure the coordinates of the grid supports, with horizontal angles observed in two rounds and distances measured four times for accuracy. Elevation measurements were taken using a Soka BZ precision level, following fourth-level surveying standards.
Deflection observations were carried out in three stages: (1) after the grid support was completed, elevation, axis coordinates, and offsets were recorded; (2) after truss assembly but before roof installation, and again after the roof was covered; and (3) settlement and displacement were monitored every half month, with additional checks after strong typhoons.
Measuring points were placed on the upper chord nodes. Each area was divided into four longitudinal deflection lines, with four measuring points on each line. The deflection results for the C and D areas showed close agreement with the calculated values, with a maximum deviation of 28 mm. The data indicated that the structure was symmetrical in design, but slight asymmetry was observed in the C area, with the right side showing slightly more deflection than the left.
Since the upper chords were not visible, measuring points were placed on the roof surface. Each section had two edges and three deflection lines along the length, with numbering similar to the roof covering but not identical. Due to lost reference points, relative deflections were measured based on elevation differences between the average of points 2 and 4 and the midpoint of the three points. The results showed some discrepancies at certain points, possibly due to deformation caused by typhoon conditions.
Overall, the deflection measurements revealed minor errors at some locations, but the majority aligned well with calculations. Except for the E area, most zones showed a tendency for greater deflection on the right side, indicating slight lateral inclination in the frame structure. However, the entire grid remained safe and stable throughout the observation period.
In conclusion, the Zhuhai International Circuit’s grandstand grid is a large-scale bolted node structure that can be accurately modeled and analyzed using the space bar finite element method. Deflection tests were conducted at multiple stages, confirming the structure’s integrity. Observations also revealed small lateral tilts in certain areas, but these did not compromise the overall safety of the grid.
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