Research On Performance-Based Design Theory Of Spatial Latticed Shell Structures

With the developments of spatial latticed shell structures towards larger span, higher height, more expensive equipments and deeper influence, the losses of buildings caused by the disasters are becoming more terrible. Many scholars' have paid abroad attentions to the new problem.To this problem, the study frame of the performance-based design theory of spatial latticed shell structures is constructed according to the idea of performance-based design and the characters of spatial latticed shell structures in this paper. The study frame synthesizes the idea of performance-based design, the theory of dynamical failure and the theory of loads and their combinations. Thorough and specific researches are carried out in the following chapters of the paper.The theory of dynamical failure of spatial latticed shell structures and the theory of loads and their combinations are the bases of performance-based design theory. Therefore, the exploring researches on the theory of dynamical failure are presented after the research advances are summarized. The paper expounds the two kinds of failure mechanisms of spatial latticed shell structures subjected to dynamic actions, the dynamic instability and the dynamic strength failure. Aiming at the problem of dynamic instability, a new judgment method—stress rate method is proposed. About dynamic strength failure, a double control criterion based on maximum displacement and plastic accumulative dissipated energy is proposed. Moreover, the dynamical failure index is presented to judge the different extent of dynamical strength failure of spatial latticed shell structures. The whole process, mechanism, and characters of dynamic failure of spatial latticed shell structures with different initial parameters are analyzed roundly. According to the theory researches and experiments accomplished by foregone scholars, the five levels (good condition, slight damaged, middling damaged, seriously damaged, collapse) of spatial latticed shell structures are proposed, and the corresponding dividing indexes are presented.Then, this paper presents exploring and deep researches to the evaluation of lifecycle-costs of spatial latticed shell structures and cost-effectiveness criterion based optimum design methods. The mathematics model for calculating initial building cost of spatial latticed shell structures is proposed by analyzing the structural constitutes and unit price of materials. The mathematics model for calculating maintenance cost of spatial latticed shell structures is established by investigations to latticed shell structures in existence. The calculating method of failure costs of spatial latticed shell structures is constructed by analyzing the engineering value and society value after the exploring researches on the theory of dynamical failure. Furthermore, the calculating process and applying program of lifecycle-cost calculation are accomplished.The characters of nonlinear, many variables, few constraint, disperse variables for optimum design of spatial latticed shell structures are analyzed. The paper proves that the stiffness of spatial truss structure is largest configured by the full stress principle with the same quantity of steel, and then a full stress adjusting optimum method is proposed, which considers structural building cost, maintenance cost and failure cost synthetically. The method quotes adjusting coefficient λ. to adjust the control stress of full stress design, and obtains the structural configurations of full stress design with different coefficient λ.. Then the lifecycle-costs of these configurations are calculated and the minimum is the optimum configuration. By applying the above calculating program of lifecycle-cost and full stress adjusting optimum method, the optimum spatial latticed shell structures are achieved which take the least lifecycle-cost as target, and the corresponding optimum parameters such as target reliability index, target controlling displacement, rise-span ratio, and so on, are achieved too.The paper provides comprehensive analysis to the Keiwitt single layer latticed shell structure according to the above theory and methods, and comparison between the results and those of Chinese national codes are carried out. The concept of structural performance-based importance coefficient is put forward and corresponding reference values are provided too. So the idea of performance-based design is embodied by structural performance-based importance coefficient, and Chinese national codes and performance-based design are integrated effectively.This paper introduces the idea of performance-based design to the field of spatial structures, and some groping research works is accomplished. Some useful results and conclusions are obtained, which are referenced to practice engineering, guild regulations and further researches. This paper provides some valuable references to fulfill the whole performance-based design of spatial latticed shell structures.