Flat-slab building structures exhibit significant higher flexibility compared with traditional frame structures, and shear walls (SWs) are vital to limit deformation demands under earthquake excitations. The objective of this study is to identify an appropriate finite element (FE) model of SW dominant flat-plate reinforced concrete (R/C) buildings, which can be used to study its dynamic behavior. Three-dimensional models are generated and analyzed to check the adequacy of different empirical formulas to estimate structural period of vibration via analyzing the dynamic response of low- and medium-height R/C buildings with different cross-sectional plans and different SW positions and thicknesses. The numerical results clarify that modeling of R/C buildings using block (solid) elements for columns, SWs, and slab provides the most appropriate representation of R/C buildings since it gives accurate results of fundamental periods and consequently reliable seismic forces. Also, modeling of R/C buildings by FE programs using shell elements for both columns and SWs provides acceptable results of fundamental periods (the error does not exceed 10%). However, modeling of R/C buildings using frame elements for columns and/or SWs overestimates the fundamental periods of R/C buildings. Empirical formulas often overestimate or underestimate fundamental periods of R/C buildings. Some equations provide misleading values of fundamental period for both intact and cracked R/C buildings. However, others can be used to estimate approximately the fundamental periods of flat-plate R/C buildings. The effect of different SW positions is also discussed.

Among different approaches developed for structural damage detection, changes in the measured static response have shown promise for locating structural damage. In this paper, an analytical study of the relationship between damage characteristics (location and severity) and changes in displacement curvatures is presented. Then a parametric study is carried out on using changes in displacement curvatures in structural damage detection. The influence of many parameters are investigated and applied numerically to two examples; an overhanging beam (statically determinate structure) and a two-span continuous beam (statically indeterminate structure) with different damage characteristics. The numerical results clarify that the displacement curvature, has the characteristic of localization at the damaged region. Also, the obtained results show that the displacement curvature, derived from static response only, can accurately locate single and multiple damages with different damage characteristics for specific load case. The merits as well as the disadvantages of using displacement curvature in structural damage detection are also discussed.

This paper investigates the application and reliability of using high-order mode shape derivatives especially, the fourth derivative in damage detection of plate-like structures. Numerical analyses have been carried out for low- and high-order mode shapes of simply supported and cantilever steel plate models. Six scenarios of damages are studied for plate models to represent different damage characteristics. The influence of artificial noise on the damage identification using changes in fourth derivative of mode shapes has been investigated. Based on the numerical studies, it is shown that the fourth derivative of mode shape is promising in detecting and locating structural damage in plate-like structures since it is localized at the damage locations even for a small amount of damage using only one of the mode shapes. Both low- and high-order mode shapes give successful results. Also, damage indices of the fourth derivatives give smoother localization and consequently better damage identification than those of curvature of mode shapes. Furthermore, using high-order modes (which can be measured by advanced sensors) does not improve the results of damage identification using the fourth derivative. Unfortunately, damage detection using changes in fourth derivative of mode shapes is sensitive to measurement noise.

A novel online capacitance estimation method for a DC-link capacitor in a three-phase back-to-back pulse width modulation (PWM) converter is proposed. A controlled AC current with a frequency lower than the line frequency is injected into the input side, which then causes AC voltage ripples at the DC output side. With this AC voltage component extracted by band-pass filters, the capacitance is estimated by the support vector regression method without measuring the DC-link current. A function that defines the relation between a given capacitor power and its corresponding capacitance is determined using a set of training data. This function is then used to predict the output for the given input which is not included in the training set. The proposed method can simply be implemented with only software and no additional hardware. Experimental results confirm that the estimation error is less than 0.146%.