Research on Unloading Deformation of Multi-Blade Structures During Construction of Xi’an Tree Project

The Xi’an Tree Project is located in Qujiang New District, Xi’an City, on the urban axis of the millennium-old ancient capital Chang’an. The project adopts large and complex curved stainless steel building skins, and its complex geometric features as well as installation methods pose new challenges to the construction process of the building skin. In order to reduce the adverse effects on the building skin, the construction sequence of "pre-loading of the main structure-installation of skins-partial unloading-reloading" is adopted during construction. Therefore, it is necessary to simulate the entire construction process of building skins, and to study their relative deformation and stress situation with the main steel structure. This paper mainly focued on the effects of different unloading schemes of multiple blade on the unloading deformation between the main steel structure and the building skins after the installation of the building skins with the main structure being preloaded firstly, providing a valuable reference for the construction of this project. The SAP 2000 software was applied herein, and the unloading situations of two blades unloaded simultaneously, three blades unloaded simultaneously as well as the partial middle platform blades unloaded simultaneously at different positions were considered, in which the unloading deformations of key nodes of the blades were extracted and analyzed. It was indicated that in case of two blades unloaded simultaneously, its adverse effects were the minimal with a deformation displacement of less than 1.0 mm, and it was suggested to be prioritised; In case of simultaneous interval unloading for three blades, it was suggested to be adopted in the ST layer where the overall displacements of the blades were small; In case of partial middle platform blades unloaded simultaneously, it had a maximum deformation displacement of 25.9 mm, which needed to be carefully considered in conjunction with specific conditions.