Structural Seismic Damage Assessment Method Based on Structural Dynamic Characteristics

The seismic damage state of building structure can be evaluated by observing the fundamental period change of structure. Firstly, the fundamental period calculation formula that adapts to the deformation pattern and distribution mode of horizontal seismic action for reinforced concrete frame structure is derived. Secondly, the seismic damage assessment standard of building structure considering period variation is established. Then, the seismic damage assessment method of building structure is constructed. Finally, the seismic damage example is used to verify the established evaluation method. The results show that the established research method has high accuracy and good engineering practicability.

Estimation of the Seismic Damage Potential of RC Frames Using Seismic Parameters

Variation of the fundamental period is regarded as one of the methods to assess the damage of the structures under earthquakes. The inter-relationship among seismic parameters and variation of the fundamental period can identify the potential structural damage of an earthquake. For this purpose, the present paper aimed to study the relations among main seismic parameters, incorporating a variety of information about ground motion and variation of fundamental period. Three RC frames were analyzed under far-fault earthquake records by nonlinear dynamic analyses and mathematical methods applied to assay the correlation between seismic parameters and variation of fundamental period. Based on the results, high correlations were observed between some seismic parameters and variation of fundamental period. Further, based on regression equations, new parameters with a very strong correlation with variations of fundamental periods were achieved, which can be regarded as appropriate indices to estimate the potential structural damage of an earthquake.

Prediction of terrestrial and extraterrestrial parameters by modelling and extrapolating their natural regularities

Extrapolation of dominant modes of fluctuations after fitting suitable mathematical function to the observed long period time series is one of the approaches to long-term weather or short-term climate prediction. Experiences suggest that reliable predictions can be made from such approaches provided the time series being modeled possesses adequate regularity. Choice of the suitable function is also an important task of the time series modelling-extrapolation-prediction, or TS-MEP, process. Perhaps equally important component of this method is the development of effective filtering module. The filtering mechanism should be such that it effectively suppresses the high frequency, or unpredictable, variations and carves out the low frequency mode, or predictable, variation of the given series. By incorporating a possible solution to these propositions a new TS-MEP method has been developed in this paper. A Variable Harmonic Analysis (VHA) has been developed to decompose the time series into sine and cosine waveforms for any desired wavelength resolution within the data length (or fundamental period). In the Classical Harmonic Analysis (CHA) the wavelength is strictly an integer multiple of the fundamental period. For smoothing the singular spectrum analysis (SSA) has been applied. The SSA provides the mechanism to decompose the series into certain number of principal components (PCs) and then recombine the first few PCs, representing the dominant modes of variation, to get the smoothed version of the actual series. Twenty-four time series of terrestrial and extraterrestrial parameters, which visibly show strong regularity, are considered in the study. They can be broadly grouped into five categories: (i) inter-annual series of number of storms/depressions over the Indian region, seasonal and annual mean northern hemisphere land-area surface air temperature and the annual mean sunspot number (chosen cases of long term/short term trends or oscillation); (ii) monthly sequence of zonal wind at 50- hPa, 30-hPa levels over Balboa (representative of quasi-biennial oscillation); (iii) monthly sequence of surface air temperature (SAT) over the India region (strongly dominated by seasonality); (iv) monthly sequence of sea surface temperature (SST) of tropical Indian and Pacific Oceans (aperiodic oscillations related to El Nino/La Nina); and (v) sequence of monthly sea level pressure (SLP) of selected places over ENSO region (seasonality and oscillation). Best predictions are obtained for the SLP followed by SAT and SST due to strong domination of seasonality and/or aperiodic oscillations. The predictions are found satisfactory for the lower stratospheric zonal wind over Balboa, which displays quasi-periodic oscillations. Because of a steep declining trend a reliable prediction of number of storms/depressions over India is possible by the method. Prediction of northern hemisphere surface air temperature anomaly is not found satisfactory.

A simplified fundamental period equation for RC buildings

Considering the huge differences in the prediction and organization of equations available in the literature, this paper aims at developing a reliable equation including mass and stiffness parameters. Microtremor (ambient vibration) measurements were taken from 23 RC buildings and their fundamental periods were compared to the dynamic analysis results. Building models were then calibrated to account for the infill wall effect. After that, 156 RC buildings were 3D modelled and their dynamic analysis results were used to calibrate the proposed fundamental period equation.