In this study, the progressive collapse behaviour of a cable dome structure was analysed and evaluated according to the importance of element. First, the dynamic response and collapse mode caused by the removal of different types of cables and struts from a cable dome structure were studied using the instantaneous unloading method of full dynamic equivalent load. Second, a method was developed for element importance classification based on collapse modes, and the importance coefficient was introduced after comparing the node displacements before and after the removal of different elements. On this basis, the correlations of the importance coefficient of an element with its importance classification and the collapse mode caused by its removal were examined. Third, the influences of some design parameters on the resistance of cable dome structures to progressive collapses and on the importance coefficients of components were analysed and evaluated. Finally, a method was proposed to determine the critical value of the element importance category. The results of this study indicated that Cable-Strut elements differed in their antiprogressive collapse effects and importance coefficients, and thus produced different dynamic responses and collapse modes when they were removed. Cable domes differed in their critical importance coefficients for Cable-Strut elements, and design parameters differed in their influence on the antiprogressive collapse resistance of cable domes.
In this paper, the security of spatial database access is studied, which discusses security problems about spatial database access and transmission, and presents a solution to guarantee spatial data access security and solve some problems, including identity authentication and security transmission of secret data. We present a solution to avoid the shortcoming of SSL protocol. At the same time, a new concept is introduced in this paper, which is certificate and private key cruising. Finally, we give an application to verify the solution. It is found that our solution is very convenient to users and can make sure the security of spatial database.
Construction errors are unavoidable in actual cable-bar tensile structures. Construction error analysis, evaluation, and especially adjustment theories were still in their infancy. For the improvement of the situation, based on the equilibrium equation, physical equation, and geometric equation for pin-joint structures, the member length deviation was adopted as the variable, and the relationship between the pre-stress deviation and member length deviation was determined. On this basis, an adjustment method was devised for the pre-stress deviations under three different conditions, and an evaluation of the effectiveness for pre-stress deviation adjustment was proposed. Finally, a 5-m diameter cable-bar tensile structure model was designed and constructed for simulation. The research results demonstrated that the adjusted pre-stress deviations of measuring points can be effectively corrected, and the theoretical results generally coincided with the experimental results. The adjustment effects of pre-stress deviation varied with the number of adjustment cables, and the adjustment effectiveness gradually decreased with the reduction of the number of adjustment cables. Different adjustment schemes produced different structural deformations, and it was necessary to prioritize the adjustment scheme that resulted in lower peak values of internal forces and shape changes during the adjustment process. The research results indicated that the correctness and validity of the proposed error analysis and adjustment method of pre-stress deviation, and its practical application in the guidance of construction errors analysis, pre-stress deviation adjustments, and evaluation of adjustment results of actual pretension structures.
Since the literature lacks an effective analysis method of collapse mechanisms and optimisation design theory for progressive collapse resistance of cable dome structure, a structural performance-based optimisation approach was proposed to improve the progressive collapse resistance for cable dome structures in this study. First, the dynamic response and collapse model of a cable dome structure were analysed after its members were removed using Ansys LS-DYNA and the full dynamic equivalent load-based instantaneous unloading method. Second, the importance coefficients of the members were calculated to determine the contribution of each member to the progressive collapse resistance of the structure. Finally, a stepwise optimisation solution was proposed by integrating a global optimisation model, which uses the mean of the importance coefficients of all members as the optimisation index, with a local optimisation model, which minimises the maximum member importance coefficient. The results indicated that different members exhibited varying levels of importance in the progressive collapse resistance of the structure, with the inner and outer hoop cables demonstrating the highest levels of importance, followed by the inner upper string of the tension hoop. The other members had low levels of importance. Compared with the cable dome structure based on the Geiger topology, the cable dome structure based on the Levy topology was more resistant to progressive collapse; such resistance decreased as the number of cable-truss frames decreased. Additionally, the local optimisation approach based on the genetic algorithm reduced the maximum member importance coefficient (i.e., that of the outer hoop cable) by 60.26%.
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