Research On Key Joints Of Large-span Spoke Wheel Structure With Middle Compression Ring

The radial cables,radial girders,and V columns in the large-span spoke wheel system with middle compression ring are primary components for roof structure.Pin connected joints and spherical plain bearing joints between cables,girders and columns play an important role in transferring force.However,joint failure can easily result in continuous collapsing of the roof structure.Joint design and constructed detail determine the structural safety,integrity and economy.The research on the key joints not only boosts project construction,but also lays a solid foundation for subsequent research on these systems.In this paper,combined with the steel structure roof of Shanghai Pudong Football Stadium under construction,SAP2000 is used for the overall analysis and calculation of the roof.Use ANSYS to analyse mechanic performance for pin connected joints of radial cable and girder,pin connected joints of radial girders and V columns inner branch,V column base spherical plain bearing joints,V column inner branch and outer branch spherical plain bearing joints.Then investigate compressive bearing capacity of V column base spherical plain bearing joint by means of full scale experiment.Finally introduced construction of radial cables,radial girders,and V columns from processing technology,assembling process and pretension method.Compared and analyze the construction site monitoring data and theoretical values.The conclusions are listed as follows:(1)Calculate and analyze the serviceability limit state and ultimate limit state of the roof by SAP2000 software.The results show that the vertical deformation of the roof under the action of temperature and earthquake is small,and the flexible light structure has good seismic performance,but the effects of wind load and asymmetric live load are great,we should pay more attention on when design the roof.Optimized radial girders in order to control the stability stress ratio of them within 0.85.After optimization,buckling factor of first local buckling mode reached 5.61,and the local stability met the design requirements.(2)Use ANSYS software to analyze mechanic performance of pin connected joints of radial cable and girder.The results show that thickening the flange at 200 mm on both sides of the transverse diaphragm can greatly reduce the stress level at the connection between the outer side of the lower flange and the lug plate,and the connection between the inner side of the lower flange and the transverse bulkhead;increasing the radius of the lug plate chamfering arc can be effective Reduce the stress level at the joint between the root of the ear plate and the lower flange.The pin connecting nodes of the radial beam and the inner limb of the V shaped support column are in an elastic state under 1 times the design load,and the design margin is1.4 times or more.(3)Use ANSYS software to analyze mechanic performance of V column base spherical plain bearing joints.middle ear plate,outer ear plate,and bearing cap of the joint have good compressive load bearing performance.Verified joint compressive load bearing performance by means of full scale experiment.The results show that plane strain intensity in elastic stage of monitoring points obtained by experiment and ANSYS agree with each other in terms of numerical value and change trend.(4)Use ANSYS software to analyze mechanic performance of V column inner branch and outer branch spherical plain bearing joints.The results show that under 2 times the design load,the pressure-bearing surface of outer ear plate of the inner column,the middle ear plate and the outer ear plate of the outer column partially enter yield,but the plasticity development is not large.Joints of the inner and outer column still have the load-bearing capacity for meeting the design requirements.(5)Use strain gauges,EM sensors and acceleration sensors for construction site monitoring.The construction site monitoring data shows that the stress monitoring values of the radial girders,the middle compression ring,the V columns,and the columns do not exceed the theoretical value under the static load combination.The error rates between the actual measured value and the theoretical value of the first three modes of natural frequency is within15%,and the error rates between the measured value and the theoretical value of the cable force is within 13%.The calculation result of SAP2000 software are valuable references.