Research On The Applicable Index For Fragility Analysis Of Prestressed-Energy-Dissipating Fabricated Concrete Structures

With the increasing progress of the overall process of national construction industrialization,the proportion of prefabricated buildings in the number of domestic buildings has been increasing year by year.The prefabricated concrete structure has the advantages of high efficiency,energy saving,green and sustainable development,which accords with the basic strategic policy of national ecological civilization construction,and is an important structural form to promote the process of building industrialization in the future,and gradually lead the whole construction industry to the direction of green,information and intelligence.According to whether there is a post-cast zone in the connection area of its beam-column joint,it can be divided into"wet"fabricated concrete structures and"dry"fabricated concrete structures.In the development process of early prefabricated buildings,"wet"prefabricated concrete structures are widely used in a large number of engineering practices due to their excellent performance equivalent to cast-in-place.With the arrival of the intelligent and information age of the building industry,compared with the"wet"type,the"dry"prefabricated concrete structure has no post-pouring concrete work,high construction efficiency and rich combination forms,which is more conducive to giving full play to the advantages of assembly technology,and it is an inevitable way to promote the transformation and upgrading of the construction industry in the new century.The prestressed-energy-dissipating prefabricated concrete structure is a typical"dry"prefabricated concrete structure,because it has the advantages of small residual displacement,small damage,strong energy dissipation and self-resetting ability,as well as rapid replacement and repair after the earthquake.It is more in line with the efficient and convenient development concept of prefabricated structures and meets the development trend of building industrialization.However,due to the diversification of structural forms of prestressed-energy-dissipating prefabricated concrete structures,the stress mechanism and behavior characteristics are more complex,and the corresponding codes and seismic design theories are not perfect.The seismic action and structural fragility analysis of this kind of structure need to be further studied.At the same time,the traditional seismic fragility analysis methods lack refined structural damage indicators to fully reflect the performance characteristics of prestressed-energy-dissipating prefabricated concrete structures,and the research on applicable ground motion intensity measures is also relatively scarce.Therefore,this paper combs the research status of prestressed-energy-dissipating prefabricated concrete structures,and expounds in detail the development process from pure prestressed system to prestressed-energy-dissipating system.At the same time,it combs the research status of structural seismic fragility analysis and fragility analysis index.On this basis,the applicable indexes for fragility analysis of prestressed-energy-dissipating prefabricated concrete structures are studied.The main research contents and achievements are as follows:（1）A structural seismic fragility analysis method based on multi-parameter combination seismic performance index is proposed.Considering the performance characteristics of prestressed-energy-dissipating prefabricated concrete structures,two kinds of comprehensive structural damage measures with multiple index parameters are proposed.The first kind is the comprehensive structural damage measure based on the combination of the maximum interstory displacement angle and the maximum residual interstory displacement angle,which comprehensively considers the stiffness and self-reset characteristics of the structure,and accords with the mechanical characteristics of prestressed-energy-dissipating prefabricated concrete structures.In addition,the calculation is simple and fast,so it is suitable for practical engineering.The second type is a more refined comprehensive structural damage measure based on the combination of the overall damage coefficient based on the Park-Ang model,the maximum inter-story displacement angle and the maximum residual inter-story displacement angle,which comprehensively considers the energy dissipation,stiffness and self-reset characteristics of the structure from the two levels of members and structures.It can more comprehensively reflect the performance characteristics of prestressed-energy-dissipating prefabricated concrete structures,but the calculation is relatively complex,so it is suitable for the study of foundation seismic theory system.（2）On the basis of the comprehensive structural damage measure proposed in this paper,the multi-story and high-rise frame numerical analysis models of prestressed-energy dissipating prefabricated concrete structures and cast-in-place structures are established based on the Open SEES finite element software platform,and the structural fragility analysis based on incremental dynamic analysis is carried out.In this paper,the applicability and limitation of using a single engineering demand parameter as a structural damage measure to describe the seismic performance of structures are studied.The feasibility of the structural fragility analysis method based on multi-parameter combination seismic performance index and two kinds of comprehensive structural damage indexes proposed in this paper are verified.The research results show that the seismic performance analysis based on the structural damage measure of single parameter is difficult to fully reflect the performance characteristics of the structure,and the seismic performance analysis of the structure based on the comprehensive structural damage measure proposed in this paper can comprehensively reflect the performance characteristics of prestressed-energy-dissipating prefabricated concrete structures and show its performance advantages from a quantitative point of view,which is reasonable and practical.（3）On the basis of comprehensive structural damage measure,the suitable ground motion intensity measure of prestressed-energy-dissipating prefabricated concrete structures is explored.Considering the influence of the discreteness of structural seismic response on the results of fragility analysis,the applicable ground motion intensity measure of prestressed-energy-dissipating prefabricated concrete structures is studied.Considering the influence of the uncertainty of ground motion on the evaluation results,100 ground motion records with a wide range are selected for time-history analysis.On the basis of the results of structural time-history analysis,the applicability of 26 kinds of ground motion intensity measures are evaluated from the aspects of efficiency,correlation,practicability and proficiency.The results show that the average spectral acceleration index I_Npis a suitable ground motion strength index for prestressed-energy-dissipating prefabricated concrete structures.（4）The seismic fragility analysis of structures considering the strength index of vector ground motion is carried out.Eight kinds of vector ground motion intensity measures are constructed from the point of view of peak value and frequency spectrum of ground motion.The discreteness of the three-dimensional probabilistic seismic demand model established from the vector ground motion intensity measure and its correlation with the fragility surface are used to evaluate the applicability of the eight vector ground motion strength measures.The results show that the vector-valued intensity measure(PGV,I_Np/PGV)is more suitable for the fragility surface evaluation and analysis of prestressed-energy-dissipating prefabricated concrete structures.The fragility surfaces of structures under different performance levels are established.From the point of view of fragility surface,the seismic performance of prestressed-energy-dissipating prefabricated concrete structures is evaluated and compared with the univariate fragility curve based on single scalar ground motion intensity measure,and the advantage of fragility surface in seismic performance evaluation of structures is verified.