Research On The Mechanical Performance And Design Method Of Segmentally Prestressed Cylindrical Reticulated Mega-structures

The large-span structure is produced as a result of mankind’s quest for activity space.It is continuously developed with the needs of human production and living conditions change over time.In modern society,people have put forward higher requirements for large-span structures with technological progress.One of the most important manifestations is that the structural spanning capacity to cover large support-free areas has increased continuously.Evolving from large-span to super large-span has become an inevitable trend of spatial structures.Therefore,it is necessary to explore the reasonable structural form of the super large-span spatial structure,namely innovate from the structure system,and to conduct in-depth studies on the mechanical performance of this new type of super large-span spatial structure,so as to realize the super large-span in a more reasonable and economical way.These also have great significance and practical application value for the super large-span spatial structure.To address these issues,this dissertation introduced prestressing technology into reticulated mega-structures.The arrangement methods of the cable-strut system in super large-span prestressed reticulated mega-structures were developed,and then the mechanical performance and design method of the prestressed cylindrical reticulated mega-structures were thoroughly researched.The major research contents are listed as follows:(1)A new type of prestressed cylindrical reticulated mega-structure with a three-segmental cable-strut system was proposed.The mechanism and detailed layout of the three-segmental cable-strut system were presented.And another two transformed structure forms were further proposed.Based on the concept of segmentation,the three structure forms were uniformly named as segmentally prestressed cylindrical reticulated mega-structure.The static properties and stability of the prestressed cylindrical reticulated mega-structure with the proposed three-segmental cable-strut system were studied.The reasonable ranges of key arrangement parameters were obtained,and the influences of initial geometric imperfection(IGI)on different levels were studied.(2)The effects of member buckling on the overall stability of the structure and its propagation rule were investigated.The method for preventing member buckling and thus enhancing the overall structural stability was presented,and its improvement effects on the overall structural stability were further discussed.It is found that member buckling not only has a significant adverse effect on the overall structural stability,decreasing over 20%,but also can remarkably decrease the improvement effect of the cable-strut system.After substituting buckling-resistant members for buckling members,the ultimate load-bearing capacity of the structure can promote to more than 90% of that of the ideal structure.Hence,it is a feasible method to solve the memebre buckling by substituding buckling-resistant members for buckling members,substitutsubstitut.The adverse influence of member buckling thus can be reduced to an almost negligible degree.(3)The possible overall buckling forms of the segmentally prestressed cylindrical reticulated mega-structures with different cable-strut systems,structural layouts,and values of structural parameters were researched.And thus a method for avoiding out-of-plane stability and improving the overall structural stability was put forward.Moreover,two simplified calculation models for the stability capacity of the overall structure were proposed,which show high calculation accuracy and computation efficiency.(4)The simplified analysis model for the out-of-plane stability of a single latticed arch in the overall structure was proposed.The Equivalent section parameters of latticed arches were calculated.And then the out-of-plane stability equations of the latticed arch with lateral supports and arch segments between the supports w ere derived.The semi-empirical and semi-theoretical formulas for calculating the critical numbers and stiffness of the longitudinal latticed beam were put forward based on the relationships between the in-plan and out-of-plane stability of the overall structure.Finally,a stepwise stability design method from in-plane to out-of-plane stability for the segmentally prestressed cylindrical reticulated mega-structure was proposed.(5)The selection method of seismic records based on the energy distribution of seismic records was proposed.The basic seismic performance of the structure under uniform excitation was studied firstly.The reasonable components of the seismic wave that should be considered,the mode combination method,and its combined order were recommended for this kind of segmentally prestressed cylindrical reticulated mega-structures.Besides,the influences of earthquake ground motion on seismic performance were further studied.The critical apparent wave velocity was thus obtained.And then the relevant design suggestions were put forward for the simplified analysis method of structural seismic performance considering the influence of earthquake ground motion.The proposed three-segmental cable-strut system and thereby the formed segmentally prestressed cylindrical reticulated mega-structures in the dissertation can greatly enrich the structural forms of super large-span prestressed reticulated mega-structures,which also can provide more alternatives for the form selection of the super large-span prestressed spatial structure.The proposed method and relevant measures to improve the structural stability,the recommended reasonable ranges for structural parameters,and the presented simplified calculation models,analysis methods and design suggestions can also provide theoretical and design guidance to the actual engineering application of this kind of structure.