A Frequency-based Analytical Method Of Component Importance Of Cable-strut Tensile Structures

In recent years, cable-strut tensile structure has been widely used in large-span stadium, exhibition center and other buildings because of its light weight, high material utilization and large span and other characteristics. Cable-strut tensile structure is a kind of flexible structure. Analyzed by traditional geometric composition, the structure usually belongs to statically indeterminate structure or variable geometry structure. Pre-stressed stiffening makes it a stable structure which can withstand the load. Therefore, the cable-strut tensile structure also has the characteristics of low redundancy, vulnerability and strong features. In order to ensure the safety of the structure in the emergency situation(such as terrorist attacks, bombing etc.),an accurate assessment of the degree of importance of different components of the structure, and taking measures to weaken the importance of key components, improving the robustness of structure, are of great significance for this type of structure. At the same time, because of the special nature of the flexible structure, the method to analyze the importance of the component of rigid structure is not completely suitable for the flexible structure. Hence, in view of cable-strut tensile structure, this paper used the the structure self vibration frequency as the breakthrough point to analysis the importance of component.First of all, in reference to large abundant literatures, this paper summarizes the characteristics and application of cable-strut tensile structure, and also analyze the scope of application of the current research methods of component importance both in domestic and abroad, as well as their advantages and disadvantage. Meanwhile, based on the characteristic of the flexible structure, a kind of new analysis ideas, regarding regard structure natural frequency of vibration as cutting point, is used.Secondly, quoted the previous research results, the relationship between the structure of the circular frequency and the structure stiffness is made clear.Subsequently, this paper derived a computing formula about how to measure the importance of the component, which based on structure natural frequency of vibration. This formula take descent rate of the structure natural frequency of vibration after the component damaged as evaluation index. At the same time, due to the limitation of the application of the “removing concept method” to importance analysis of component, this paper referenced the concept of stiffness reduction, avoiding computation convergence caused by direct "remove" components. By calculating four examples, plane frame structure and cable net structure, cable dome and tower tensegrity, this paper verify the applicability and rationality of the formula.Finally, combing with a wheel of large span tension structure engineering, this paper analyzes the vibration characteristics of the structure and studies the influence of the degree of pre-stress to the natural frequency of the structure; carrying on the component importance analysis to this structure with the method in this paper, and pointing out the hoop cable is the key component of the structure. In this paper, a new concept-weakening the importance of key component is uesd, and proceeding weakening of the importance of the hoop cable by separating cable approach meanwhile, measuring the effect of the importance weakening. The calculation results indicates that the cable separation method can effectively reduce the degree of importance of the key components. In addition, the paper proposes the effects of the cable separation can be effective evaluated by the quantitative computation method of component importance and it also can provides a reference for determining the number of sub-index in the project.