The Mobility Judgement And System Optimization Of Radial Retractable Roof

With the improvement of people's living standards,their need for the sports venues is also increasing day by day.People hope to enjoy the sunshine and breeze when the weather is nice and avoid stopping the sports activities when the weather is not good.Compared with conventional sports venues,the sports venues with retractable roof can betterly meet people's need so that the it is becoming a development trend.Among the retractable roofs,the radial retractable roof based on angulated rod scissor-like-element is attracting more and more favor from domestic and foreign scholars for its advantages of less weight with higher strength,large opening ratio,simple unit,beautiful shape and high adaptability for the architecture shape.However,the research results of radial retractable roof structure mainly focus on geometry and set the morphological research as a focus.Few scholars study the mechanical properties of radial retractable roof especially the three-dimension radial retractable roof.As the combination of mechanism and structures,few scholars have conducted systematic research of the uncertainty and reliability of this kind of retractable roof.In order to overcome the disadvantages above,the freedom of Hoberman radial retractable roof is calculated based on the method of screw theory and the divergence point during the movement process is found.The results show that divergence point of the Hoberman linkage mechanism appears when the system expands to the limit state.The freedom of the system is 1 before the divergence point and changes as 4 after the point.Based on the screw theory,three other types of angulated rods elements which can meet the radial movable condition is also derived.These angulated rod SLEs are separately GAE ? angulated rod SLE?GAE? angulated rod SLE and non-crossing angulated rod SLE.The motion law and opening ratio of the linkage mechanism formed by these angulated SLEs is analyzed.The results show that the Hoberman linkage mechanism is more suitable for actual engineers for its smaller initial closing degree and larger opening ratio.Based on the loop increment method which considers the deviation correlation,the position deviation expression of general node in Hoberman linkage can be obtained.The sensitivity analysis of node position deviation is carried out and the results show that the influence of initial rod length deviation on the node position deviation is increasing with the distance between fixed node and the rod decreases.The curve of the reliability of different nodes and the input angle is obtained based on FOSM.The curve shows that the reliability of one node is larger when the system is at initial period and becomes much smaller at the end.By comparing node reliability of different position,it is found that the reliability decreases with the distance increases.The influence of different coordinate calculation path,rod length,number of angulated rods,radial position of nodes on the reliability of target nodes is analyzed and the result shows that the reliability of the node has no sensitivity to the node coordinate calculation path and rod length of the system but the reliability of the node in the same relative position decreases with the increase of the number of rods and radial distance.The two-objective optimization function of system reliability and processing cost is constructed and the expression of the initial gap is obtained when the objective function is at its minimum.The result shows that the optimal solution of the initial gap is related to the weighting factor ?,the processing coefficient K,the sensitivity in the target node deviation expression and the objective function reaches the minimum when the target node deviation sensitivity is at its minimum.Based on the two-dimension Hoberman radial retractable grid,a three-dimensional Hoberman radial retractable shell is constructed,and the mechanical properties of this 3-D roof is analyzed by using the finite element analysis software ABAQUS.It turns out that by choosing reasonable geometrical parameters and finite element parameters,the three-dimensional Hoberman radial retractable roof can meet the requirements of the bearing capacity and normal use requirements.On the basis of the basic model,the influence of the parameters such as the rods number,the number of straight rods in one angulated rod,the rise-span ratio and shape coefficient to the structural mechanical properties is analyzed.Results are as follows:firstly,the increase in the rod number have a beneficial effect on the mechanical properties of the structure,and will have a negative effect on the economic performance.Therefore,it is found that when the number of angulated rods is 18-20 the weight and structural response are both small.The reduction of the number of straight rods in one angulated rod will have a beneficial effect on the mechanical properties,the use performance and the economic performance.However,under the influence of the construction and transportation difficulty and drive condition,4 to 5 is more reasonable.Thirdly,The increase of the span ratio is benefitial to the mechanical properties of the closed state of the structure but have a negative effect on the mechanical properties during the opening process and also has some negative effects on the economic performance.Lastly,the increase in the plane shape factor of the structure will have a beneficial effect on the mechanical properties opening rateio and economic performance of the structure.