| The application of long-span lattice arches is becoming more and more popular in recent years. Both Simple lattice arches and mixed structural system get extensive adoption in industrial and public building. This makes the investigation on the stability of lattice arches very important. Compared with solid arch, the shear deformation of lattice arch is not small any more,so its effects on the critical load must be taken into consideration. Furthermore, to what degree the effect of shear deformation on the critical load is determined mainly by the dimension and arrangement of lacing bar. The purpose of this paper is to investigate how the shear deformation influences the overall buckling of the long-span lattice arch. However, there is a lack of researches on the stability of lattice arch both domestically and internationally. The coefficient of arbitrary axes arch's equilibrium differential equation is variable, and this equation is so difficult to solve directly that usually approximate method have to be adopted, such as evolutionary method, finite difference method etc. Since shear deformation should be taken into consideration on the stability research of arch in this paper, and the above approximate methods neither work well nor can be adopted, the main research works are as follows: (1)Based on the basic equations for calculating the arch deformation curve derived from the basic arch equations and the basic principle of CDC method, a new method for calculating the critical load of parabola arch ——Arch Deflection Curve Method (ADC method for short) is obtained in this paper. With this method, the critical load of parabola arch under uniform vertical loads are worked out,and the value matches well with the results of current literature and of FEM. It has proved the ADC method to be accurate, also shows many advantages of the ADC method. (2)Through introducing the shearing deformation into the basic equations of the ADC method successfully,the ADC method develops further into a new method that can calculate critical load including shearing deformation; After making some simplification and tentative, the lattice arch is changed successfully into equivalent solid arch, hence the ADC method can be used to process an approximate analysis of lattice arch;Through the single factor and multi-factor analysis of the parameters, the laws of the shearing deformation's influence on the critical load of two-legs or three-legs lacing arch are obtained. (3)For the sake of simplifying the calculation of the lattice arch's critical load,combining the theoretical derivation and the numerical integration,a formula for equivalent slenderness ratio of the lattice arch is put forward in this paper. Hence the lattice arch can be converted into equivalent solid arch and critical load can be worked out simply;Finally,the simulation of actual lattice arch structure with finite element method is completed, and the contrast between the results of ADC method and the results of the formula is done. As a result, the analysis according to this paper's thoughts and methods is right and reasonable. This paper applies the CDC method principles to the stability analysis of the arch, and gets the ADC method of calculating the critical load is just a beginning. The ADC method still can be further developed. Like the CDC method for the stability analysis of straight beam-column, the ADC method can continue to develop further into a general method to analyze stability problem of curve beam-column. Besides, the stability problem of the large-span lattice arch still needs further experimental studies and more accurate theoretical second-order analyses.
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