Performance Analysis And Design Of Heavy Duty Cast Steel Universal Hinged Supports

Heavy-duty universal hinged supports are being more and more widely used in modern large-span structures. They offer extremely huge individual load carrying capacity and universal rotation ability which are preferable to release temperature effects and to improve boundary conditions of lower structures. Yet the bearing capacities of the currently available universal hinged supports under tension and shear are relative low, which is hard to satisfy the increasing engineering requirements. On the other hand, the Chinese code about cast steel node design has just been released, and there are issues needed to be further investigated. So, this dissertation presents the design, full-scale experiment and analysis on a kind of heavy duty cast steel universal hinged supports with the bearing capacity up to 6000kN. The main research contents are as follows:(1) A three-dimensional finite element model is developed by using the 3D entity modeling software SolidWorks, the preprocessing software HyperMesh, and the commercial software ANSYS with consideration on material, geometrical and contact nonlinearities. The model is validated against the experimental results reported in a reference and the verification suggests that the model can well predict mechanical behaviors of the supports.(2) With reference to the available universal hinged supports and based on a patented design, an innovative heavy duty cast steel universal hinged support with the bearing capacity up to 6000kN is designed. The supports designed in this dessertation are of the largest bearing capacity in China. The performance of the supports under three typical load combinations is analyzed and evaluated against the Chinese national code'Technical specification for application of connections of structural casting steel (CECS 235:2008)'. The effects of loading angle and initial deformation are also discussed. It is concluded that the designed supports can satisfy the requirements of the Chinese code under the design load combinations.(3) An innovative self-balanced loading system is designed and realized by updating the available loading ring in the Lab. Full-scale experiments in three load cases are carried out successfully. Tests results show the support has reasonable design and manufacture details, direct force path, and reliable performance. The three tests also verify the numerical model, and the verification further confirms the applicability of the model.(4) The effects on the mechanical performance and economical efficiency are duscussed for supports under compression, tension and shear; the parameters include depth of the cake of the upper component, depth of the top plate of the bottom component, yield strength of the material etc. The analysis shows that, in the range of the parameters analyzed, when the support is in compression, the parameters such as depth of the top plate, depth of the ribs of the bottom component and yield strength of the material have great effects on the mechanical performance of the support. When the support is under shear, the parameters such as depth of the cake of the upper component and yield strength of the material have a great effects on the mechanical performance of the support. When the support is in tention, the parameters such as depth of the cake of the upper component and yield strength of the material have a great effect on the mechanical performance of the support.(5) Methods for reducing stress in contact regions and stress concentration regions are investigated, and the research is also carried out for the ultimate bearing capacity calculation considering the effects of the material strengthening modulus in the model. It is shown that the difference between the radiuses of the two contact objects has the largest effect on the contact stress. The proper design of local refinement, force path change, and local stiffness distribution modification can effectively reduce stress concentration. And among the above three methods, the local refinement method is the most effective. When the Code is used to determine the bearing capacity of cast steel nodes, it is suggested to check stress state of the nodes. The material strengthening modulus in the calculation model has great effect on the bearing capacity of the supports, therefore the material strengthening modulus from coupon tests is highly recommended in the calcultion. When cast steel nodes are made up of several cascade connected components, it is suggested to determine bearing capacity of each components separately, and select the minimum one as the bearing capacity of the cast steel nodes.