| Due to the needs of the production process,irregular frame and frame structures are inevitable in the structural design of power plants.Theoretical studies and experience with seismic hazards have shown that the irregular nature of the structure can lead to a reduction in seismic performance and sometimes even to more than expected damage.It is therefore of great theoretical and practical importance to optimise the existing structure to create a relatively regular,seismic and economical frame structure.This thesis analyses the main plant frame and rack structure of natural gas power plants based on irregular frame and row frame structure,combined with China’s seismic design code,and carries out seismic performance analysis and seismic reduction control studies on it.The main contents include the following:(1)Firstly,PKPM-SATWE structural design software is used to determine the structural calculation model and analyse the dynamic characteristics of the calculated structure.The SATWE model was imported into SAP2000 to calculate the dynamic characteristics,bearing capacity and deformation characteristics of the irregular frame row frame structure under the action of reaction spectrum seismic action and time analysis.It can be obtained that the mass stiffness analysis of the irregular structure floor is not uniform,the torsional component in the self-oscillation cycle of the structure is relatively large,the axial pressure at the bottom of the structure is relatively large and the spatial integrity of the structure is poor.(2)In view of the structural characteristics of the irregular main plant of the natural gas power plant and the problems that existed in the project,the original structure was strengthened by increasing the lateral stiffness of the model structure(increasing the cross-sectional size of the model frame columns and adding a small number of shear walls)to carry out a comparative analysis of the seismic performance of the structure before and after strengthening.(3)As the traditional method of increasing the lateral stiffness of the structure increases the bottom shear force borne by the floor structure,which leads to premature cracking of the structure under earthquake action is not conducive to the seismic resistance of the structure,so the seismic damping technique is used to improve the seismic performance of the structure.In order to reduce the impact of seismic waves on the structure during earthquakes,seismic isolation bearings are installed at the bottom of the structure to absorb the seismic energy,thus ensuring the maximum structural integrity.A comparative analysis of the model before and after seismic damping shows that the installation of seismic isolation bearings absorbs the energy transferred to the structure by the earthquake and reduces the structural damage;the installation of BRB anti-buckling braces and viscous dampers reduces the self-oscillation period of the structure and limits the inter-story displacement,and the seismic performance of the structure is significantly improved after the installation of the damping devices.(4)Based on the results of the seismic isolation analysis in Chapter 4,a performance-based seismic design of the model structure is carried out,with reference to the relevant codes and the structural characteristics of the main plant of the irregular power plant,four different seismic performance levels are assigned to the structure and quantified.The performance-based combined seismic isolation design of the structure and the design process of the isolated structure are proposed for reference in similar projects.The performance-based seismic analysis study using seismic isolation bearings shows that the seismic reduction effect of the isolation bearings becomes more and more obvious as the seismic intensity increases. |
