| The joint stiffness and joint structure form of single-layer spherical reticulated shell is a hot issue in academic research.The hub-shape inlay joint studied in this paper is often widely used in coal bunker,tank roof and other structures.It is a self-developed fabricated joint in China.At present,it is considered that the mechanical performance of this kind of joint is between the rigid joint and the hinged joint,that is,it has a certain bending stiffness and a certain rotation ability,which is a typical semi-rigid joint.However,there is no corresponding theoretical calculation and requirement for single-layer spherical reticulated shell with semi-rigid joints in the current code.Therefore,it is necessary to systematically analyze the mechanical performance of the hub-shape inlay joint,explore its semi-rigid characteristics,and comprehensively analyze the impact of the joint on the buckling mode and bearing capacity of the reticulated shell,so as to provide a theoretical reference for the design of single-layer spherical reticulated shell.Therefore,this paper mainly does the following research work:(1)Research on Modeling and mechanical performance of hub-shape inlay jointIn this paper,firstly,the hub-shape inlay joint is modeled in detail,and contact174 and target170 are selected as the contact pairs between the hub body and the rod insert.Then,by analyzing the mechanical properties of the joint under various working conditions,the failure mode and failure mechanism of the joint are determined.The results show that the ultimate bearing capacity of axial compression hub-shape inlay joint is higher than that of axial tension joint and the weak part of the joint under various load conditions is the tenon neck.The initial stiffness and ultimate bearing capacity of the axially compressed nodes increase with the increase of hub height,and the flexural capacity of the out of plane bending joints also increases.The results show that the ultimate bearing capacity increases with the increase of yield strength.The initial stiffness of the joint under in-plane bending is very small,and the ultimate bearing capacity under in-plane bending is also very low.Under constant pressure bending,when the axial compression ratio is less than 0.2,the ultimate moment bearing capacity under constant pressure bending will not change significantly due to friction effect,but when the axial compression ratio is greater than 0.2,the ultimate moment bearing capacity under constant pressure bending will not change significantly The results show that the ultimate bending moment will decrease with the increase of axial compression ratio,showing a linear change.The joint has good hysteretic characteristics,but the hysteretic curve has obvious pinch phenomenon,with the increase of axial compression ratio,pinch effect will gradually weaken,when the axial compression ratio exceeds 0.5,pinch phenomenon will disappear;Pinch effect in hysteretic curve will gradually decrease with the increase of hub diameter When the hub diameter exceeds 110 mm,the effect on the hysteretic behavior of the joint is very small.(2)The bilinear model of the stiffness of the hub-shape inlay joint is establishedOn the basis of the research on the bending effect of the joint,the size parameters of the joint are changed constantly during the elastic-plastic analysis,and the bending stiffness and torsional stiffness of the joint are obtained.The influence of different size parameters on the stiffness of the joint is analyzed.Based on the energy equivalent method,the bilinear model of the bending stiffness and torsional stiffness outside the plane of the joint is fitted.The results show that: the bending moment rotation curves of out of plane bending stiffness and torsional stiffness can be expressed by bilinear model,but they show large rotation angle at the initial stage under in-plane bending load,which is not in line with bilinear property.The hub height and hub diameter of hub-shape inlay joints have positive correlation with the joint stiffness,and the length of embedded tenon neck has positive correlation with out of plane bending and torsional stiffness Through regression analysis,the appropriate yield coefficient,stiffness coefficient,initial bending stiffness and initial torsional stiffness are determined,and the empirical formula for improving the ultimate bearing capacity is improved to fit the bilinear model of nodes under out of plane bending and torsion with high accuracy.(3)Study on global stability of single layer reticulated spherical shell with hub-shape inlay jointsFinally,based on the data of stiffness analysis of hub-shape inlay joint,the stability of single-layer spherical reticulated shell is studied,and the natural frequency,buckling mode and ultimate bearing capacity of semi-rigid reticulated shell under different structural parameters are compared and analyzed.The results show that the natural frequency,initial stiffness and ultimate bearing capacity of the reticulated shell decrease with the existence of the joint stiffness.The influence of bending stiffness on the natural frequency and ultimate bearing capacity is greater than that of axial stiffness.The first-order buckling mode of semi-rigid reticulated shells presents a symmetrical shape,the number of nodes with the largest displacement at the top of the reticulated shell increases with the rise span ratio,the deformation range of semi-rigid reticulated shells is larger than that of ideal rigid reticulated shells,the deformation range of the nodes in the first-order buckling mode decreases with the increase of rise span ratio and increases with the increase of span.The results show that the maximum ultimate bearing capacity of the hinged reticulated shell is less than one third of that of the rigid reticulated shell.With the rise span ratio decreasing from 1/4 to 1/8,the ultimate bearing capacity of semi-rigid latticed shells with different spans decreases by more than half;the sensitivity of the bearing capacity of latticed shells to the joint stiffness decreases with the increase of the structural span or rise span ratio,which proves the feasibility of considering the joint stiffness Compared with the ideal rigid connected reticulated shell,the model can accurately reflect the actual working condition of the structure. |
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