Rather than viewing earthquake-induced structural damage as a single index of maximal deformation, it can be viewed as a combination of two indices, that is, the deformation demand and dissipation of energy. A method for evaluating the earthquake-induced damage of multi-storey buildings is presented that considers the maximal storey drift and the storey hysteretic energy. In this method, the maximal storey drift is estimated by means of the strength reduction factor spectrum, pushover analysis and distribution formula of deformation along structural storeys, which is based on the modal decomposition hypothesis in the nonlinear response stage of structures. For estimating the storey hysteretic energy demand, the normalized hysteretic energy spectrum of constant ductility factors is established, where the normalized hysteretic energy is defined as the ratio of the hysteretic energy to the square of the peak ground acceleration, and the formula for the distribution of hysteretic energy along structural storeys is derived based on the relation of the simplified internal forces of structures. For demonstrating the process of the proposed method and verifying its accuracy, an example is implemented, and the analysis results of the example indicate the following: (1) the method proposed in this article is a simple and easily implemented method for evaluating the structural damage induced by earthquakes and (2) the distribution formulas of the maximal drift and hysteretic energy along structural storeys derived in this article are relatively accurate.Keywords damage index, displacement demand, hysteretic energy, nonlinear response history analysis, pushover analysis, storey drift
The current research on the damage-based strength reduction factor has been completely based on the inelastic single-degree-of-freedom systems that are more suitable for two-dimensional analyses. Therefore, it is necessary to construct damage-based strength reduction factor spectra for systems subjected to bidirectional ground motions. In this study, an inelastic single-mass bi-degree-of-freedom (SMBDOF) system subjected to the orthogonal bidirectional ground motions with the hysteretic property of two-dimensional yield-surface plasticity function is presented, and the x-component of the system is used to construct the damage-based strength reduction factor spectra of the system ( R b spectra). The Park-Ang damage model is used to determine the constant damage index of the R b spectra. In addition, 178 ground motion records for site classes C, D, and E are considered as ground excitations of the SMBDOF system to construct the mean R b spectra with the format of R b- D- T for a given ductility capacity and R b- μ u- T for a given damage level. The R b spectra of the SMBDOF system is compared with the corresponding R spectra of the SDOF system. Statistical analysis considering different values of the natural period, ductility capacity, damage index, period ratio, and site condition is conducted. Analysis results show that the coupling of two-component responses of an inelastic system could increase the strength demand of the system in certain cases; the trend of the R b spectra presented in this study is approximately consistent for different site classes, but the spectral values have the characteristic of site conditions. Therefore, the influence of the period ratio should be considered because a large period difference between two components of the SMBDOF system could aggravate seismic damage in certain situations. Based on the statistical analysis, the expression of R b spectra curves with a period ratio γ = 1 is derived using the regression analysis, and the correction expression is obtained considering the influence of the period ratio on the R b spectra. Then, the construction procedure of the R b spectra is introduced. The predicted R b spectra obtained by the proposed procedure is compared with the actual mean spectra, and comparison results indicate a good match.
With the development of science and technology, manipulators are increasingly used in industrial production and daily life. The manipulator with traditional control mode has high requirements for operators, complicated operation, and human-computer interaction is inconvenient. In this paper, an intelligent manipulator system based on gesture control is designed. FPGA is used as the control core of the system. We apply the improved Canny algorithm processing, which can automatically recognize gesture information. After judgment, the control signal is sent to the manipulator to control the manipulator to complete the specified action. Through experimental testing, the system can successfully recognize all kinds of gestures, and can well control the manipulator to complete all kinds of actions. The human-computer interaction is more real, which greatly improves the intelligence of the manipulator system and helps to improve the work efficiency.
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