Form Finding And Static Mechanical Behavior Of The Beam (Truss) String Structures

The beam (truss) string structure is a sort of long-span space structures. Because of its excellent static mechanical characteristics, it has been studied and used widely. At present, it mainly focuses on the research into form finding and static mechanical behavior of beam (truss) string structures. This paper is also aimed at the two issues.In the paper the problem of form finding of the beam (truss) string structures is studied and the method named offload by steps is put forward in accordance with the mechanical behavior of the structures. The method is applicable to not only the beam (truss) string structures stretched at one end, but also to the structures stretched at both ends. The form of unstrained state can be found based on that of pre-stressed state straightly, i.e. it need not assume the form of unstrained state firstly by means of offload by steps approach, whose precision has been tested by the numerical solution of loading by steps. Furthermore, the forms of unstrained state relative to two different stretching construction methods are compared and it comes to the conclusion that the stretching patterns have no effect on the form of unstrained state. Besides, the friction force of tension bed has also been taken into account in the paper, and it shows that the influence of friction force on form finding can be neglected under certain conditions. The calculating model in reference to Zhengzhou International Center of Conference and Exhibition has been established, and the form related to the unstrained state has been found by offload by steps method. It means that the form finding method proposed in the paper is also applicable to the spatial string structures.The effects of four parameters such as pre-stressed value of cable, rise-span ratio of arch and rag-span ratio of cable, moment of inertia of arch (height of truss section), and the number of struts, on static mechanical characteristics of the beam (truss) string structures are analyzed in the most disadvantage work condition. Finally, some available conclusions are achieved.Based on the above research work, some suggestions of design, as well as of construction are put forward.