Research On Static And Dynamic Performance Of Tensairity Truss Structures

Tensairity,proposed in recent years,is a new kind of structural system which is composed of rigid upper cord,low pressure airbag and cable.The object of research,Tensairity Truss,applies the triangular truss to replace the solid-web upper cord of original structure in order to improve its spanning capacity.The design model for hybrid structure,composed of airbag and cable,is complicated,so it is necessary to propose a corresponding static design method and simplified design model.Considering the fact that the structural response for long-span structure is influenced by earthquake action and wind load,but the research work in Tensairity Truss is still limited.This work discusses the mechanical characteristics at first,makes parametric analysis for the static performance and proposes the design principle and simplified design model.Structural dynamic to static ratio in earthquake and wind vibration coefficient in wind load are analyzed in this work.The major work and conclusions are included in several aspects:1.Three major factors influencing the static performance of Tensairity Truss,pressure of airbag and rise and prestress of cable,are investigated.The formula of airbag's vertical rigidity is derived,and static simplified design model is proposed.There is 15 percent difference between the proposed model and original model on design limit state,and structural mechanical behavior could be predicted by the proposed model.2.The structural dynamic performance of Tensairity Truss is analyzed as the change of span,pressure,rise and prestress of cable.The structural response in vertical and horizontal earthquake action are analyzed by response spectrum method and time history analysis method,and the applicability of response spectrum method is verified.The horizontal earthquake action has little effects for the structural response.The dynamic to static ratio of upper cord,membrane and cable are calculated as the change of span,pressure of airbag,rise,prestress of cable and damping ratio in vertical earthquake action by model-superposition response spectrum method.The recommended value for dynamic to static ratio of truss and airbag is 0.25,and the dynamics effect of cable could be ignored.The failure mode of structure under three direction ground motion components is dynamic instability.3.The wind vibration coefficient of structural components is discussed as the change of wind direction,pressure of airbag and prestress of cable for closed structure based on the data of wind tunnel experiments,and wind vibration coefficient is based on maximum structural total response.The recommended value for wind vibration coefficient of stress for upper cord is 2.0 and wind vibration coefficient of displacement for upper cord is 3.0.The structural along-wind displacement is 1/27 of the span of structure and the structural across-wind displacement is 1/98 of the span of structure based on the analysis of the unidirectional and bidirectional fluid-structure interaction for Tensairity Truss with 4 meters' span.The rigid components are recommended to replace the cable.