Nonlinear Mechanical Performance Analysis Of Concrete Folded Plate Quasi-spherical Reticulated Shells

The concrete folded plate quasi spherical reticulated shell is formed by surface cutting spherical shell and remeshing,which can be regarded as a new structure composed of multi-ribbed plates intersecting at the ridge.For this kind of structure,the static and dynamic analysis and elastic stability analysis are mainly carried out at present,without considering the influence of non-linearity.Due to the small cross-section size of components and the significant influence of material nonlinearity of concrete,it is possible to make the combination of geometric and material nonlinearity,or even the combination of two kinds of nonlinearity,become the controlling factor affecting the engineering application.Therefore,considering the influence of nonlinearity,how to accurately calculate the stability bearing capacity of structure is a necessary problem for structural design.Based on the basic theory of finite element method,This paper use the arc length method tracing the whole load deflection curve,significantly analysing the static performance,geometric nonlinearity,material nonlinearity and dual nonlinearity of the structure.The results show that:(1)The concrete folded plate quasi spherical latticed shell continues the good spatial stress characteristics of arch structure.The displacement of the slab around the structure is large,which is the weak area of structural rigidity,and is elastic supported on the spine beam,and the displacement of the top of the structure is small.(2)The change of the rise-span ratio has a great influence on the static performance and the nonlinear critical load of the structure.When the static performance analysis,the axial force of the spine beam changes with the rise-span ratio;The rise-span ratio should be controlled between 1/7.5 and 1/5 when considering geometric nonlinearity;Considering the material nonlinear rise-span ratio should not be less than 1/7,and the rise-span ratio should be controlled between 1/7 and 1/5 when considering the double nonlinear.(3)The stiffness of the ring beam has little influence on the geometric nonlinear analysis,but has a great influence on the static performance,the material and the double nonlinearity.In practical engineering application,the height of the bearing ring beam section should not be less than 1/60 of the span;The stiffness of the spine beam has a great influence on the static and nonlinear properties of the structure.In practical engineering application,the height of the section of the spine beam should be 1/100-1/80 of the span.(4)The material consumption of multi ribbed beam and roof slab is relatively large in the structure,but the stress is relatively small.Too large section size will significantly increase the weight of the structure.It is suggested that the section height of the multi ribbed beam should be 1/144?1/120 of the span,and the thickness of the roof slab should not be less than 1/400 of the span.(5)As far as the structure is concerned,excessive up-convex buckling is beneficial to the structure.In this paper,the sixth order negative buckling mode is taken as the initial geometric defect for analysis.When considering geometric nonlinearity,the initial geometric defect should not be larger than 1/225 of the span.The analysis considering material nonlinearity and double nonlinearity is not sensitive to the initial geometric imperfections.In practical engineering application,it can be guaranteed that the geometric defect is no more than 1/300 of the span.(6)The approximate calculation formula of nonlinear critical load fitted in this paper has sufficient engineering accuracy.