Study On Energy-based Seismic Performance Evaluation Method For RC Frames

The energy-based seismic design method fuses the force and the displacement,which can fully reflect the effect of earthquake actions on structures. However, how touse the energy concept for the seismic design of specific structures is still a challengingsubject.In this thesis, the energy-based method for evaluating seismic performances of RCFrames is studied and the main achievements are as follows:The general distribution rules of the duration response of each energy component,the total earthquake input energy, the instantaneous input energy for four types of SDOFsystems are discussed. Then the differences between the total earthquake input energy,maximum instantaneous input energy and appearing time expressed by absolutedisplacement and relative displacement are discussed.In this paper, a method of determining the normalized equivalent velocity spectrumfor the elastic-plastic single-degree-of-freedom (SDOF) systems is proposed.220seismic records, as the input, were selected from American PEER database andclassified according to Chinese site classification. And a three-piece normalizedequivalent velocity spectrum for SDOF systems is suggested, basing on a complexintensity index. The effects of stiffness reduction factors, ductility factors and dampingratios for SDOF systems for five types of site soils on the normalized equivalentvelocity spectrum are analyzed. On this basis, a method to determine the normalizedequivalent velocity spectrum according to Chinese site classification is proposed.The demand and the distribution coefficient of the cumulative plastic deformation energy are deduced. Based on the energy balance principle and multimodal equivalentsingle degree of freedom system(ESDOF) systems, cumulative plastic deformationenergy required for multi-degree-of-freedom(MDOF) systems and its distributioncoefficient along the layer are deduced. Then the sensitivity analysis of16conditions isanalyzed. The results show that the distribution coefficient of cumulative plasticdeformation energy is mainly determined by the mass, the yield coefficient of shear, thestiffness and the cumulative plastic deformation ratio. And the change of top-levelparameters has no obvious effect on the distribution of the cumulative plasticdeformation energy. The cumulative plastic deformation energy along the layer ispositively associated with the yield coefficient of shear and the accumulated ductilitycoefficient, but is negative associated with the stiffness. The cumulative plasticdeformation energy released from the weak intermediate layer redistributes to theadjacent two layers, according to the ratio of the original cumulative plastic deformationenergy.A semi-analytical and semi-numerical two-parameter damage model based onlayers is proposed. The existing two-parameter damage models have shortcomings inthe overall or the story damage assessment, because of a great deal of work andcumulative errors. Meanwhile, the results are greatly affected by the combinations ofthe coefficients. Combining with the results in the fourth chapter, a semi-analytical andsemi-numerical two-parameter damage model is proposed based on the layer. Thismodel makes up for the huge computational effort of the existing damage model. Finally,the damage models ban injury pattern between the layers received by damage model inthis paper is compared with the computed result of Park-Ang model, which verifies theeffectiveness of the model in this paper.The demand and the distribution of the cumulative plastic deformation energy ofRC frames are studied. Different Period Time Deduction Factor is using to consider theinfluence of the filled wall and the simplified calculating method is proposed. On thebasis of the nonlinear time history analysis, the distribution of the cumulative plasticdeformation energy along the floor is obtained. Based on this, the formula of thedistribution coefficient of the cumulative plastic deformation energy which is obtainedin the fourth chapter is adjusted. Based on the energy-based seismic design method, the energy-based seismicperformance evaluation method for RC frames is suggested. This method is adequatefor the damage and safety evaluation of RC frames under strong earthquakes.Combining with the research results in the previous chapters, the typical procedure ofthis method is provided. Then the implementation of this method is illustrated through acase study.