Mechanical Properties Analysis Of Concrete Ribbed Conical Reticulated Shells

As a traditional space structure,the concrete thin shell structure,due to its using of concrete material,has the advantages of good durability and fire resistance,easy availability of materials.However,the traditional concrete thin shell structure has the disadvantage of difficult formwork for curved surface construction.But the folding plate reticulated shell intersected by multi-ribbed plate can reduce the difficulty of surface construction to a great extent.At present,the researches on this kind of shells mainly include herringbone,quasi-spherical,quasi-flat shells and curtain reticulated shells,and this paper mainly focuses on the research of conical reticulated shells.Concrete multi-ribbed conical reticulated shell is bisected by triangle ribbed plate,after the intersection in the space form of large-span umbrella structure.This structure is modelling beautiful,plane strong of comfort,and reasonable of structure stress.The construction is simple and has good prospects for development.The internal forces and mechanical properties of multi-ribbed conical reticulated shell are significantly changed due to the different arrangement of the multi-ribbed beam and whether the multi-ribbed flat plates are sloped or not.Therefore,three kinds of concrete multi-ribbed conical reticulated shells are analyzed in this paper.The multi-ribbed conical reticulated shell of the multi-ribbed beam which is arranged in the ort Hogonal straight way and formed by the ridge line is called structure type I.The multi-ribbed beams which are arranged in an orthogonal oblique way are called structural type II.On the basis of the structure type I,the triangular multi-ribbed plate is arched to make the ridge(valley)line form the conical multi-ribbed reticulated shell of the spatial broken line beam,which is called the structure type III.Based on the method of numerical simulation,the static characteristics of three kinds of multi-ribbed conical reticulated shell structures are studied respectively,and the influences of such factors as the rise-span ratio,the stiffness of side beam,ridge beam,multi-ribbed beam and roof plate on the static performance of the structures are discussed.The results show that the maximum deflection of type I and II structure occurs at the center of gravity of the ribbed slab,while the maximum deflection of type III structure occurs in the middle span of the valley line after the ribbed slab is arched from the middle.There are both axial force and bending internal force in the structure,so the influence of eccentric axial force should be considered in the bearing capacity design.The dynamic performance of type I structure is studied by subspace iteration method.The results show that the main vibration mode of type I structure is vertical vibration.The vertical vibration appears earlier in the middle and lower region of the multi-ribbed folded plate.Because of the uniform distribution of structural stiffness,the frequency is repeated many times and there are obvious jump points.The response spectrum method of mode decomposition is used to analyze the seismic response of type I structure in different directions,and then the dynamic internal forces of the structure under earthquake action are simplified.The results show that the structure is greatly affected by the vertical seismic action,and the increase of the ratio of span to span to a certain extent will reduce the feature that the structure is dominated by the vertical seismic response.The arc length method was used to track the equilibrium path of type III structure for geometrical nonlinear stability analysis,and the uniform defect mode method was used to apply initial defects to the structure.According to different control parameters,the critical load of the structure is calculated,and the approximate calculation formula of the structure stability bearing capacity is put forward.The results show that the nonlinear buckling of the structure has the characteristics of the shell structure,the bearing capacity decreases sharply after the jump instability,and the post-buckling ductility is weak.Initial defects have little influence on the ultimate bearing capacity of the structure,and L/300 is taken as the maximum acceptable initial defects of the structureThe analysis results in this paper can provide reference for similar engineering applications.