Shaking Table Test And Finite Element Optimization Of Steeel Frame Bent Structure With Buckling Restrained Brace

As an important lifeline project,thermal power plant structure requires that its production function cannot be interrupted in an earthquake.The mass and stiffness distribution of such structures is very uneven,and local or even whole damage is likely to occur under earthquake.In this thesis,the actual 1000 MMW thermal power plant of class B seismic fortification in 8-degree areas is taken as the research object.the performance of the frame-bent structure of thermal power plant with bucklingrestrained braces is studied.The main work of this study includes:1.A scale shaking table test was carried out on the structure of the main power plant with buckling-restrained braces for class B seismic fortification in 8-degree areas.The acceleration response,displacement response,dynamic characteristics,column foot strain response and energy consumption of BRB of the structure under unidirectional,bidirectional,three directions,frequency earthquake,design earthquake,rare earthquake and super-rare earthquake and I1,II,III,IV site conditions are discussed.The results show that the inter-story displacement angle response of the structure meets the Chinese seismic code,and the longitudinal and transverse responses of the structure differ greatly,showing obvious whip effect at the top of structure,and the longitudinal displacement response of the structure is greater than that of transverse response.After the test,the longitudinal natural vibration period of the structure decreases slightly,and the longitudinal direction of the structure is weak.Some of the BRBs used in the test model remain elastic under frequent and design earthquakes,and show a certain viscous damping effect,and enter the plastic yield state under large earthquakes,indicating that the structure still has a certain reserve,which can resist earthquakes with greater intensity.2.The damage,acceleration response and displacement response of the thermal power plant with traditional steel braces and buckling-restrained braces are compared.The results show that the two types of structures meet the requirements of seismic fortification targets.However,under the design and rare earthquake,the traditional steel brace structure has been damaged by buckling,fracture and opening welding,and there is no obvious structural damage in the BRB structure except the visible residual deformation of some steel core at the sleeve end.The existing buckling-restrained braces schemes have shortcomings in the control scheme of lateral movement between floors,which mainly shows that the longitudinal and transverse seismic performance of the structure is not balanced.3.In order to explore the reasons for the large longitudinal displacement response of buckling-restrained brace structure,the simplified simulation method of BRB was improved,and this method can not only characterize the overall mechanical properties of BRB,but also reflect the stress of the working section of BRB core plate,Therefore,the cumulative plastic index can be used to directly reflect the damage of BRB.Based on this simplified method,the corresponding scaled finite element model was established by ABAQUS software,and the plastic evolution law of overall structure and weak parts are discussed,the analysis results show that the increase of the longitudinal interlayer displacement angle of the structure is related to the fact that the BRB of coal hopper layer first enters the plasticity.4.Four optimization schemes are proposed and corresponding finite element models are established by referring to the working principle of ‘mega-frame’ and adjusting the lateral stiffness ratio of the structure.Taking into account computational efficiency,SAP2000 software was used to establish the nonlinear analysis model of finite element model,and the results of shaking table test and finite element modeling were compares and verified,which were in well agreement,the finite element models of corresponding optimization schemes are established,the longitudinal displacement,acceleration and the proportion of BRB energy dissipation of six group of seismic waves under 8-degree rare(400Gal)and extremely rare(600Gal)earthquakes are compared and analyzed for the five models.The results show that when the lateral stiffness of the structure suddenly decreases,the full distribution of BRB and the approximately “complementary” lateral stiffness ration distribution can effectively alleviate the sudden change of the structural story-drift ratio,and the reduction of the overall BRB lateral stiffness ration can reduce the structural acceleration response.