Seismic Fragility Analysis Method For Gravity Dams Based On Deformation And Damage

Earthquake is one of the major disasters causing the dam failure, so it is necessary to carry out the research on seismic safety of the dam. Seismic fragility analysis can predict the probability of failure of gravity dam under different levels of earthquakes, which can provide a basis for seismic safety evaluation of the dam structure, loss estimation and seismic disaster reduction strategy. In this paper, as the resistance index parameter is sensitivity and difficult to obtain, and difficult to quantitative grading classification of seismic damage grade, the deformation and damage of gravity dam are chosen as the resistance index, and the related level standards are proposed in seismic fragility analysis of gravity dam. The fragility analysis of gravity dam based on deformation and damage is carried out with the probabilistic analysis method of SAC-FEMA (Method of the Federal Emergency Management Agency) based on the above content. The main contents are as follows:(1) The effect of energy dissipation, crack paths ratio and crack position are considered to establish the seismic fragility analysis method of gravity dam based on damage in this paper. Firstly, the effect of energy dissipation, crack paths and crack position are introduced to the overall damage indexes, and the overall damage index is selected as the resistance index. A five-level classification standard of seismic damage and the related level states are proposed according to the relationship between the resistance indexes and the failure mode, and the method of the existing damage grade classification. By using nonlinear dynamic time history analysis to calculate resistance indexes, and combining with the probabilistic analysis method of SAC-FEMA to obtain the failure probability, the method of damage-based seismic fragility analysis is established.(2) The deformations along river at dam crest and neck are selected as the resistance indexes to establish the seismic fragility analysis method of gravity dam based on deformation in this paper. Firstly, the advantages and disadvantages of the existing damage index of gravity dam are comparative studied, and the deformations along river at dam crest and neck are selected as the resistance indexes. Then, a five-level classification standard of seismic damage and the related level states are proposed according to the relationship among the resistance indexes, the failure mode and the damage index. By using nonlinear dynamic time history analysis to calculate resistance indexes, and the probabilistic analysis method of SAC-FEMA to obtain the failure probability, the method of deformation-based seismic fragility analysis is established. The procedure can be used to evaluate the failure probability, and to provide basic information for hazard prediction and risk analysis.(3) The correlations between the ground motion parameters PGA and structural response and the correlations between the ground motion parameters Sa with structural response were compared, and Sa is suggested as the seismic parameter in the seismic fragility analysis of gravity dam. The correlation between the ground motion parameters PGA with structural response, and the correlation between the ground motion parameters Sa with structural response were compared based on the correlation parameter ζ=βSIM/b in the seismic fragility analysis of the dam according to indicate that correlation between Sa and the structural response of gravity dam is higher than that of PGA, and it is suggested that Sa is used as ground motion parameter in the seismic fragility analysis of gravity dam.