Investigation On Some Problems Of Long–span Cable Domes

Cable domes are flexible tension structures system of highly efficiency,which at present,have become one of hot spots of research and application in engineering.Some scientific problems such as force finding analysis method,cable-strut rupture and construction simulation analysis of cable domes,are investigated in this paper,and the main contents are summarized as follows.(1)A new method of force-finding based on the ratio updating for cable domes is proposed by using the ratio relationship of cable-strut prestress,and verified by examples.When considering self-weight,results of force finding are compared with each cable segment was divided into one unit and multiple units.The results show that the method of force finding based on the ratio updating has fast computational speed,small geometric shape deviation and high precision.Self-weight should be considered during the prestress design of cable domes,when each cable segment was divided into one unit and three units respectively,the difference between the results of force finding analysis is small,so each cable segment can be divided into only one unit to simplify the solving process for force finding of similar structures in the engineering practice,and the calculation results can satisfy the accuracy requirement.(2)The equation of cable shape is derived,and it is proposed that the horizontal component force of the cable can be used to describe the prestress distribution of a cable dome when its self-weight is considered.On this basis,a new approach,named component force balancing method,which is based on catenary equation is proposed for force finding of cable domes,by using the balance relationship of nodes,which is verified by examples.Besides,it is compared with the method of force-finding based on the ratio updating,The results show that component force balancing method based on catenary equation has clear mechanical concepts and easy solving process.Thus,the method can provide a new idea for force finding of cable domes.The difference in the results of force finding between the above two kinds of methods is small,and both can be used for force finding of cable domes,It is suggested to adopt the method of force-finding based on the ratio updating to solve the prestress distribution for purpose of application convenience,whose results can satisfy the accuracy requirement,and we can use component force balancing method based on catenary equation to check if necessary.(3)The influences due to local cable-strut rupture on the internal force of other struts,the reaction of support and the vertical displacement of the node are studied with transient dynamic analysis method,A new method and indicator of sensitivity analysis of cable domes due to cable-strut rupture based on the strain energy is proposed,and the definition of sensitivity coefficient is given.They are used in sensitivity analysis of Levy domes due to cable-strut rupture,and compared with indicator of other papers.The results show that the rupture of local cable-strut may make the internal forces of other struts,the reaction of supports and the vertical displacement of the node to fluctuate,whose amplification effects in the process of vibration should be focused on.Sensitivity coefficient due to the outer hoop cable rupture is maximal,sensitivity coefficient due to the middle strut rupture comes second.Therefore,we should focus on improving the safety stock of hoop cables and the middle strut.The indicator proposed is more suitable for the flexible cable domes,which can thoroughly consider the vibration condition due to cable-strut rupture and show the sensitivity degree of structure to cable-strut rupture from a macro point.(4)Using the traditional tensioning construction schemes to construction simulation analysis of Levy domes.On this basis,carring on the improvement,two new tensioning construction schemes are proposed,and compared with the traditional construction schemes.The results show that internal forces of cables and struts in the process of tensioning are not greater than the initial prestress with different tensioning schemes,the cable of the smallest initial prestress should be tensioned in last place for construction simulation analysis of similar structures,and tensioning orders should be reasonably arranged,so that to reduce demands for tensioning tools,and improve the efficiency of economy.