Research On Mechanical Properties And Seismic Performance Of Innovative String Reticulated Mega-structures

With the development of human society, the construction of modern large-scale venues has put out higher requirement of the spans of spatial structures, so as to meet the needs of modern large-scale venues construction. However, single type structure cannot meet the need of super large-span any more. Therefore, scientific and technological workers of all nations continue to study and explore, combining different types of structure to improve their stress performance and increase the span. Beam string structure is a type of pre-tensioned long span spatial structure widely applied in practical projects, which is composed of an upper structural member and a lower string with struts. The cylindrical reticulated mega-structure, an innovative spatial structure which has been presented and studied recently, comprises of two levels. The first level, which is a large grid structure and is referred to as the main structure, bears all the loads, and transfers them to the supporting structure. The second level, composed of substructures embedded in the large grids of the main structure, bears only the loads within the corresponding large grid and transfers them to the main structure. Based on the concepts of beam string structures and cylindrical reticulated mega-structures, an innovative string cylindrical reticulated mega-structure is proposed. The introduction of cable-strut system improves the mechanical and seismic performances of the structure, constrains structural deformation effectively, enhances the structural rigidity, makes full use of material characteristics, therefore the string cylindrical reticulated mega-structure has the ability to across larger space economically and reasonably. Based on the above benefits, the innovative structure will be widely applied in long span engineering. A systematic theoretical research is carried out on the cable-strut arrangement, the elastic static performance and stability, the dynamic characteristics and the seismic performance of the structure.For the innovative structure, five types of cable-strut arrangements are presented, the influence of rise-span ratio on structural deformation in different cable-strut arrangement styles is investigated. An optimal scheme is obtained through a comprehensive comparison that includes static performances of the structures such as the member internal force, the deflection, the ultimate load and the buckling mode of the structure.For the optimal cable-strut arrangement scheme, a large-scale parametric analysis is performed to investigate the parameters such as, the deformation, internal force, ultimate bearing capacity and each rate of change. The responses are compared to the corresponding ones for a structure without cables, and the reasonable values of structural parameters are presented. The optimal pre-stress value of several string cylindrical reticulated mega-structure with different span, ratio of rise to span, height of the latticed 3D beams are presented. In addition, the influence of half-span loading on the structural stability is investigated.The basic dynamic characteristics of the structure are analyzed. Comparative analysis of the natural vibration period and the corresponding mode of vibration are carried out between the case of the main structure bearing loads cooperatively with the substructures and that of the main structure bearing loads alone. A series of parametric analyses are carried out for the sequence of the first modes of different directions and the corresponding natural vibration period, the results are compared to those for a structure without cables. The influence of the parameters on the structure stiffness of different directions has been obtained.The influence of the one-dimensional and more-dimensional seismic actions on seismic performance of the structures are studied. For the one-dimensional seismic action, the structural seismic performances in the case of the main structure bearing loads alone in different directions of seismic waves are investigated by using time history method and response spectrum method respectively. Comparison is then made to the structural seismic performances in the case of the main structure bearing loads cooperatively with the substructures. A series of parametric analysis further studies the seismic response of member internal force and structural deformation. For the more-dimensional seismic action, the distribution laws of the structural seismic performances are first studied. The behaviors of the structure under seven kinds of multi-component seismic actions are analyzed, and the reasonable component of the seismic action that should be considered in design are thus obtained. Parametric analysis is then carried out for the seismic responses of internal force and deflection of the structure, and the reasonable values of structural parameters are recommended.