基于最优化理论的大跨异形曲面结构单轴旋转法

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

近十年来,国内兴建了大量的机场、高铁站、会展中心等工程,具有建筑造型新颖、平面尺寸大(超大面宽、超大进深和较大高差)等特点,一般采用原位拼装提升或累积提升的施工工艺。由于上述施工方法存在拼装高度较高、高空作业量大、工艺复杂等问题,导致施工效率低、安全风险大、质量控制难。虽然旋转提升法对于降低拼装高度有显著的效果,但是多应用于跨度小、结构规整、提升吊点数量少的结构中,同时旋转过程中同步性较差,经常导致提升器窝缸甚至局部杆件受力过大而弯曲破坏的现象,针对大跨曲面屋盖钢结构施工仍处于技术空白期,存在适用局限性。依托杭州西站项目,系统介绍了大跨异形曲面结构确定旋转轴及旋转角度的两种方法,即双轴反复旋转法和基于最优化理论的单轴旋转法,并从经济性、安全性、实操性方面对两种方法及原位拼装提升法进行了对比:1)经济方面,基于最优化理论的单轴旋转法较双轴反复旋转法节省胎架用量5.8%,较原位拼装提升节省胎架用量406.8%。2)安全方面,采用单轴旋转施工与原位拼装提升施工结构杆件应力比差值不到0.05,而双轴旋转施工(换杆前)与原位拼装提升施工结构杆件应力比差值达1.31,这是由于采用双轴旋转施工,结构需分别绕两个方向旋转,旋转过程态与结构设计态位形差异较大,导致杆件内力分布不均匀,从而导致部分构件应力比较大,虽然可通过换杆加固的方式解决,但设计施工成本会相应增加。结构施工过程中虽然单轴旋转法的构件应力比与原位拼装提升法的差别不大,但是原位拼装提升法所设胎架高度高,存在大面积高空作业,工人施工安全性较差。3)实操方面,采用旋转提升可有效解决原位拼装提升带来的拼装胎架安装高度高、高空作业多等施工复杂性问题。而基于最优化理论的单轴旋转法相较于双轴反复旋转法,其可通过自编程序一步得到旋转提升参数的最优解,省时省力。且由于其确定的旋转轴及旋转角度是唯一的,施工时结构仅需绕单轴进行旋转,操作更为简便。结果表明:基于最优化理论的单轴旋转法更佳,其较好地弥补了原位拼装提升法、双轴反复旋转法在大跨异形曲面屋盖钢结构应用中的技术缺陷和不足,为以后类似曲面屋盖结构的施工提供参鉴。

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 in-situ 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.