| As the main support of air-cooled condenser equipments, the seismic safety ofair-cooled condenser structure system concerns operation of the whole thermal powerplant. In order to meet the requirements of million kilowatts air-cooled condenserstructure in thermal power plant in high earthquake intensity areas, a new air-cooledcondenser structure of steel truss-umbrella brace is proposed in this paper. And theseismic performance of the new structure and seismic design methods based onperformance are analyzed through pseudo-dynamic test, pseudo-static test andelastic-plastic time history analysis. The main work of this paper is as follows:(1) Based on investigation and analysis, the main air-cooled condenser structuresare summarized as: steel frame-brace structure, reinforced concrete structure, solidabdomen beam-umbrella brace structure, steel truss-reinforced concrete pipe column,and the merits and faults of these structures are given. Finally, the steel truss-umbrellabrace air-cooled condenser structure is proposed considering the seismic performance,vibration and economic performance.(2) SAP2000finite element software is used to build the calculation model ofsteel truss-umbrella brace air-cooled condenser structure, mechanical properties ofstructure under vertical load and wind load, structural spectrum response, elastictime-history response and torsion performance of the structure are analyzed, charactersof mechanical properties and seismic stress distribution, laws of internal forcedistributing under multi dimensional earthquake ground motions are achieved, thestructure’s seismic effect calculating methods which considering torsion effect areproposed. Effectiveness of setting diagonal bracing to decrease the deflection of steel truss overhang and the lateral displacement is analyzed.(3) Selecting a1/4substructure, constructing a1/8scale model of steel truss-umbrella brace air-cooled condenser structure. Loading and measuring schemes aredesigned, through dynamic characteristics test, pseudo-dynamic test and pseudo-statictest to acquire the structural natural vibration frequencies, model shape and dampingratio, observe the development process of crack and failure mode of the structure,acquire the time-history curve of structure under earthquake waves action withdifferent peak accelerations, strain distribution of key areas, hysteretic curves andskeleton curves. The fundamental period of vibration, damping vibration rule, dynamicmagnification factor vibration rule, regularity of rigidity degeneration, hystereticproperty, energy dissipation, ductility, bearing capacity and capacity of wholedeformation of the steel truss-umbrella brace air-cooled condenser structure are studied,the mechanical performance of classic members which contain reinforced concretepipe column, A-type frame, steel truss, bracket members is analyzed. Throughcomparison of model test results of traditional steel truss-reinforced concrete pipecolumn, study the influence of umbrella on structural failure model, stiffnesscharacteristics, deformation behavior and carrying capacity.(4) The simplified principles and modeling approaches of the steel-concretehybrid structure are proposed through comparison of model test results, finite elementsoftware ABAQUS is used to build the elastic-plastic model of steel truss-umbrellabrace air-cooled condenser structure, base shear response time history curves,displacement response time history curves, displacement envelop curves and damageof reinforced concrete columns under different intensity of earthquake are acquired.And the seismic performance of steel truss-umbrella brace air-cooled condenserstructure is studied furthernlly combined with the model structure seismic test.(5) Design methods of air-cooled condenser structure considering the safety of theequipment are proposed. Firstly, the selection principles of air-cooled condenserstructure system and components of structure are given; secondly, performance leveland indexes are proposed considering the safety of technology equipment; thirdly, thevalues of performance that based on experimental and theoretical analysis are given;finally, structural requirements apply to different ductility requirements of reinforced concrete pipe column and seismic tectonic measures of connecting parts of steel trussand pipe column, connecting parts of umbrella brace and corbel of pipe column aregiven.The aim of this paper is to solve the technical problems that appear in the realproject. The steel truss-umbrella brace air-cooled condenser structure system which isproposed in this paper has excellent structural performance and could meet therequirements of large-capacity units in high earthquake intensity arears, so as to playan important role to promote the direct air-cooled technology. |
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