| The air-cooled platform is a substantial structure of the directly air-cooledthermal power plant. Its structure form is monotonous to some extent. One of thenew forms is the steel bracing beam and column structure. This system is assembledby reinforced concrete tube columns, platform beams, Y-shape supporting andA-shape frames, and has significantly uneven vertical mass and stiffness distribution.Therefore, its seismic performance should be given considerable attention. Besides,related research has rarely been conducted both home and abroad at present. So, it isof great importance to research deeply on the damage properties, deformationproperties and mechanical characteristics of the system under rare earthquake.Using the finite element numerical simulation method, the elastic-plasticdynamic analysis was carried out to research the damage properties, deformationproperties and mechanical characteristics of the structure under rare earthquake. Thefollowing works have been done:(1) Two kinds of3-D finite element models were established, corresponding tomodels with different combinations of seismic precautionary intensity andconnection assumption, i.e. the hinged connection scheme and the rigid schemeunder7degree intensity;(2) The modal analysis was carried out using the method of finite elementnumerical simulation to get the nature vibration characteristics of the structure;(3) The elastic-plastic dynamic analysis was carried out to research the damageproperties, deformation properties and mechanical characteristics of the structureunder rare earthquake;(4) The incremental dynamic time history analysis was conducted to study theductility of the air cooled platform structure under rare earthquake.Results show that, the free vibration of the structure is mainly translationalmotion in two orthogonal directions with some torsion effects, thus, the influencesof torsion coupling should be consided; the interaction between A form frame andcolumn or steel frame could not be considered in global analysis of the air cooledplatform structrue; the plastic hinge of steel bracing beam and column structure willappear in the column roots and nearby the upper bracing joints, the deformability ofweak parts should be strengthened to make it better seismic behavior; the hingedconnection scheme has advantages on earthquake resistant behaviour to the rigidscheme in terms of the top displacement of A form frames; the bracing systemprovides significantly effect on strengthening the steel frame, it is feasible to use theY-shape supporting. At last suggestions were given based on the theory analysis and numericalresults. These suggestions including strengtheing the construction measure ofconnection parts among columns and bracings, canceling dislocation connections ofbracings or paritcularly reinforcing the construction of connections in order to makenode have better load-bearing and deformation capacity. |
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