Seismic Fragility Of Free-standing Contents In Buildings

The free-standing contents in buildings may be damaged due to sliding or overturning under the action of the floor motion caused by the earthquake,thereby causing economic damage,affecting the normal use of the building,or even causing casualties.The characteristics of the sliding and rocking response of free-standing contents in buildings are examined in this paper and the corresponding seismic fragility curves of the sliding and overturning damage are established.The fragility curve is the function relationship of the probability of exceedance of the contents sliding or overturning damage and the intensity measure of the floor motion.The thesis mainly completed the following works:1)A numerical model for simulating the sliding motion of free-standing contents is established and the reliability of the model in predicting the maximum sliding distance is verified by comparison with the shaking table tests.Based on a large number of numerical calculation results,a modified floor motion intensity measure,considering the effective duration of the sliding motion,is proposed to assessment the maximum sliding distance of free-standing contents.The fragility model of sliding damage is established.The analysis results show that there is a better linear relationship between the modified floor motion intensity measure and the maximum sliding distance of contents.2)A simplified single lumped mass numerical model with local damping for correctly simulating the energy dissipation of the rocking motion of free-standing contents is established.Compared with the free rocking test and the overturning acceleration spectrum obtained by the rigid block model,the new simplified model proposed in this paper has a clear physical concept,which can better simulate the attenuation of the amplitude of the free rocking motion,and can also reproduce the more complex behaviors such as direct overturning or overturning after rocking under the excitation of different frequencies and different intensities.3)A dimensionless peak floor displacement as the floor motion intensity measure is proposed to assessment the overturning damage of free-standing contents.Based on a large number of numerical calculation results,there is a better linear relationship between the new intensity measure and the maximum rocking angle of contents.Based on the new intensity measure,the probability tree method and the incremental dynamic analysis method were used to establish the fragility model of contents overturning damage.The analysis results show that the fragility analysis result of the probability tree method is related to the strip division method,which leads to lack of objectivity.Therefore,it is recommended to use the incremental dynamic analysis method for fragility analysis.