Uniaxial Rotation Method for Long Span Special-Shaped Curved Surface Structures Based on Optimization Theory

In the past decade, a large number of airports, high-speed rail stations, exhibition centers and other projects have been constructed in China, which have novel architectural designs, generally free form surface shapes, large plane dimensions, and characteristics such as super wide face, super deep depth, and large height differences. Therefore, the construction process of in-situ assembly lifting or cumulative lifting is generally adopted. The above construction methods have problems such as high assembly height, large high-altitude operations, and complex processes, resulting in low construction efficiency, high safety risks, and difficult quality control. Although the rotary lifting method has a significant effect on reducing the assembly of jig frames, it is often used in structures with small spans, regular structures, and a small number of lifting points. At the same time, the synchronization of the rotation process is poor, often leading to excessive bending and damage of the elevator cylinder and even local members. The construction of large-span special-shaped curved steel structures is still in a technical blank period, and there are applicability limitations. Based on the Hangzhou West Station project, the article systematically introduces two methods for determining the rotation axis and angle of large-span special-shaped curved steel structures, namely the double axis repeated rotation method and the single axis rotation method based on optimization theory. The two methods and the in-situ assembly and lifting method are compared in terms of economy, safety, and practicality. In terms of economy, the single axis rotation method based on optimization theory saves 5. 8% of the usage of tire racks compared to the double axis repeated rotation method, and improves the saving of tire rack usage compared to in-situ assembly by 406. 8% ; In terms of safety, the difference in stress ratio between single axis rotation construction and in-situ assembly lifting construction is less than 0. 05, while the difference in stress ratio between double axis rotation construction ( before pole replacement) and in-situ assembly lifting construction is 1. 31. This is because using double axis rotation construction requires the structure to rotate in two directions, and there is a significant difference in the configuration between the rotation process state and the structural design state, resulting in uneven distribution of internal forces in the members, As a result, some components have relatively high stresses, which can be solved by replacing rods for reinforcement, but the design and construction costs will correspondingly increase. Although the stress ratio of components during structural construction is not significantly different between the single axis rotation method and the in-situ assembly lifting method, the height of the jig frame set by the in-situ assembly lifting method is high, and there is a large area of high-altitude work, resulting in poor construction safety for workers. In terms of practical operation, the use of rotary lifting can effectively solve the construction complexity problems caused by the high installation height of the assembly jig frame and frequent high-altitude operations caused by insitu assembly lifting.compared to the dual axis repeated rotation method, the single axis rotation method based on optimization theory can obtain the optimal solution of rotation lifting parameters in one step through self programming, saving time and effort. And due to the unique rotation axis and angle determined, the structure only needs to rotate around a single axis during construction, making the operation more convenient. The results indicate that the single axis rotation method based on optimization theory is better, which effectively compensates for the technical defects and shortcomings of the in-situ assembly lifting method and the double axis repeated rotation method in the application of large-span special-shaped curved steel structures, and provides reference for the construction of similar curved roof structures in the future.