Analysis and Design of a Complex Single⁃Layer Aluminum Alloy Daylighting Roof Grid Structure

The film and television research base， located in the Changchun Film and Television Cultural Innovation Incubation Park， has a long span of 85 m and a short span of 61 m. The daylighting roof features a peculiar shape and is directly supported by irregularly distributed peripheral frame columns， resulting in highly complex stress conditions. Two schemes were mainly considered in the selection of daylighting roof structure， namely steel truss structure and single-layer aluminum alloy latticed shell structure. In view of the advantages of light weight， beautiful appearance， and low construction difficulty， the single-layer aluminum alloy latticed shell structure was ultimately adopted. Further structural analysis and design were carried out accordingly. Due to the complex structure of the single-layer aluminum alloy latticed daylighting roof， the MIDAS/Gen model and the RFEM model were used for structural calculations， and the accuracy of the models was verified by comparing the computation results. The calculation results showed that the first three modes of the two models were highly consistent with the first three buckling modes， and the errors in their natural vibration periods and eigenvalues were very small， indicating that the accuracy of both models met the calculation requirements. Further analysis revealed that both the natural vibration modes and the buckling modes of the daylighting roof latticed shell were characterized by global vibration and global buckling， indicating a reasonable structural arrangement. The MIDAS/Gen model was used to caary out an elastic analysis of single-layer aluminum alloy latticed shells. The results showed that the maximum stress in the members was 112 MPa， while the stress in most members remained below 80 MPa， meeting the requirements of the Code for Design of Aluminium Struectures（GB 50429‒2007）. Under the standard load combination （dead load + live load）， the maximum displacement of the structure was 119 mm， resulting in a displacement-to-span ratio of 1/512， which was less than the limit of 1/400 in the Technical Specification for Space Frame Structures（JGJ 7‒2010） . These analysis results demonstrated that the structure could satisfy both strength and stiffness requirements. The RFEM model was used to conduct a double-nonlinear stability analysis of the structure and to evaluate its stability bearing capacity. The distribution form of initial defects was based on the lowest buckling mode corresponding to each working condition， with a defect magnitude set at 1/300 of the span. After calculation， the minimum value of the load critical coefficient under each working condition was 2.5， which was greater than the limit of 2.0 in the Load Code for the Design of Building Structures（GB 50009‒2012）. The progressive collapse resistance of the project was analyzed using the component removal method. The collapse condition selected the two members that had failed first in the double nonlinear stability analysis as the initially failed members. According to the collapse analysis results， when the first two members failed， the stress level of the overall grid structure remained largely unchanged， indicating that progressive collapse did not occur. Key members were extracted for characteristic buckling analysis. The effective length coefficient， calculated as 1.47 according to Euler’s formula， was input into the overall design model to check the strength of the key members. The calculation results showed that the stress ratio of most members was less than or equal to 0.5， and the structure had sufficient safety reserves. A finite element analysis model of a typical joint was established to obtain the stress state of the joint under the action of the load design value. It was confirmed that the stress in each part met the requirements of the code and had a large safety reserve. The structural design concept of "strong joint and weak member" was satisfied.