[China Motor] The steel structure was successfully unloaded

Recently, the roof unloading of the central core area of the steel structure project of the China Motorcycle (Chongqing) Project Phase III and Phase IV (entertainment complex project) undertaken by Jinggong Steel Structure was successfully completed. This marks the successful completion of the steel structure construction of the project, and the project construction has achieved important phased results.

The steel structure of the project includes three parts: the steel roof of the central core area, the steel roof of rain eaves, and the steel structure of commercial skylights. The central core area of the project is the world's largest and Asia's first Nick theme park with an area of nearly 30,000 square meters. After completion, it will bring you 14 sets of super international IPs such as the popular Wang Wang team, SpongeBob SquarePants, Ninja Turtles, Dora the Explorer, etc., including 29 sets of IP story lines and image packaging for children, excitement, and family. Entertainment equipment.

Chongqing China Motor uses a super-large-span, double-layer free-form surface, orthogonal, vertical grid structure, surrounded by 44 steel columns and central steel diagonal braces to form a supporting system. The upper steel roof of the central core area of the project is a curved large-span orthogonal truss structure, with a north-south span of 150m and an east-west span of 250m. The central elevation of the roof is 65m and the roof height is about 35m. The entire roof falls on a bent column composed of steel columns and diagonal braces at the lower part, and the top of the column is connected with the roof through a one-way sliding steel support to release the radial horizontal thrust of the roof truss.

The bearing of this project is designed in accordance with European standards and has a large circumferential horizontal reaction force. It is the first in China to adopt imported sliding materials with high strength and low friction coefficient-high-performance modified ultra-high molecular weight polyethylene. After testing, the performance of the sliding material far exceeds that of the conventional PTFE material, the compressive strength is up to 180MPa, the lateral shear force of the support exceeds 15000kN, and the friction coefficient meets the design requirements.

Since the finished supports around the structure are all one-way sliding supports, they cannot bear the horizontal reaction force along the sliding direction. Therefore, in the roof unloading stage, when the structure changes from the multi-point support state to the surrounding support state, the support will inevitably produce horizontal displacement. In order to ensure that the support is in the center after the unloading construction is completed, and to reduce the additional bending moment generated on the supporting column, the deformation of the entire roof structure is calculated through finite element analysis before construction, and the design, processing, and installation are deepened. The overall pre-deformation of the roof structure is carried out at this time. When the support is processed, it is necessary to produce and fix the slidable part of the upper top plate in advance according to the pre-deflection value requirements, and perform the pre-deflection installation in the pre-deformed posture during installation, and the maximum pre-deflection value of the support is 80mm. After the unloading of the on-site roof is completed, the bearing reset is in good condition, the actual slippage is basically consistent with the theoretical pre-bias value, and the deviation is controlled within the design requirements. In the early stage of construction, through repeated comparisons of various schemes, the construction scheme of "multiple points in the middle + hoisting around" was finally adopted. In order to reduce the assembly height of the steel structure, the intermediate lifting zone is divided into three cumulative liftings. The maximum lifting height is 46m and the maximum lifting weight is about 3000t.

Due to the structural characteristics of the roof, in order to reduce the deformation of the structure during the lifting process, a dense lifting point + pole-style lattice lifting frame is adopted. Each group of lifting frames is equipped with a lifting lifting point at both ends to lift the two lower trusses separately. The construction accuracy is better guaranteed. The project has 28 sets of lifting frames, 52 lifting points, and the maximum height of the lifting frames is 70m.

After the roof is lifted and closed, more than 100 temporary support points of different types need to be unloaded, and the maximum unloading amount is 120mm. There are two types of support points for the entire roof: the outer ring is the hoisting area, a total of 118 sets of four-sided lattice support frames are set up, and the inner ring is supported by 52 hoisting points. Through the simulation analysis and comparison of various unloading sequences, and the special unloading construction experts' demonstration, the method of “the support frame of the hoisting area is unloaded in batches, and the lifting point of the hoisting area is unloaded after grading” is finally selected. During the unloading process, real-time stress and strain monitoring and deformation measurement were performed on the roof at the same time. The monitoring results are basically consistent with the theoretical analysis, with small deviations, which effectively guarantees the safety of the construction and subsequent use of this special structure.

The park is located in the central core area of the building, and the area of the construction site below is smaller than the projected area of the steel roof. There are only reserved access channels on the north side of the construction area and the outside. The site is narrow and construction organization is difficult. In order to solve the impact of the site on the construction organization, BIM-based information management technology was used in the project. Among them, in the project planning stage, the construction process is simulated through the information-based dynamic site organization simulation technology, and a reasonable construction sequence and dynamic road site planning are determined to provide a reliable basis for subsequent construction. In addition, the on-site material storage is strictly controlled through the information-based material supply platform and the logistics management platform, and the material organization is tracked in real time, and information-based feedback, evaluation and early warning are carried out to avoid the situation of insufficient on-site supply or excessive stacking. Through the above-mentioned multiple information technology, the effective use of every inch of space in the projectile land is realized.

The commercial skylights located at the four corners of the central amusement area adopt a stringed beam structure. Compared with the conventional stringed structure, the prestressed struts of the stringed beams of this project use non-swing triangular fixed struts, which makes the cables unable to be pre-biased in the conventional form. . During the construction of the project, a cable design with adjustable length at both ends is adopted, and the pre-stressed construction is carried out by synchronous tensioning at both ends; at the same time, in order to avoid the unsynchronized tension of the two ends, the unbalanced force of the cable clamp is too large. Sliding, and the triangular fixed brace is damaged by excessive horizontal force. The subdivision level synchronous tension control technology is used to ensure the smooth establishment of the prestress.

Chongqing China Motorcycle is the first world-class travel shopping complex in Asia that integrates shopping, leisure, entertainment, culture and sports. The roof enclosure structure adopts air pillow type ETFE membrane structure.

This article is reproduced from: Jinggong Steel Structure Group