Most reinforced concrete (RC) frames would exhibit different degrees of damage after mainshock ex... more Most reinforced concrete (RC) frames would exhibit different degrees of damage after mainshock excitations, and these mainshock-damaged RC (MD-RC) frames are highly vulnerable to severe damage or even complete collapse under aftershock excitations. In the present study, the effectiveness of utilizing soft steel damper (SSD) as a passive energy dissipation device for seismic retrofitting of MD-RC frame under aftershock actions was investigated. A common three-story RC frame in the rural area was employed and a numerical evaluation framework of retrofitting analysis of the MD-RC frame was also proposed. Based on proposed evaluation framework, nonlinear dynamic time history analysis of the MD-RC frame with and without retrofitting schemes was conducted to evaluate the retrofit effect of the retrofitting schemes on the MD-RC frame. The results revealed that the retrofitting schemes could effectively improve the natural vibration characteristics of the MD-RC frame, especially the first-o...
Abstract Loss predictions and assessments for residential building groups are crucial processes d... more Abstract Loss predictions and assessments for residential building groups are crucial processes during extreme events such as wind hazards. The primary purpose of the present work is to improve the existing loss assessment methodology for residential building groups under wind hazards by considering the wind-induced interference effects between building groups, such as those based on the building locations, area density, wind direction, and wind speed. The failure characteristics of the envelope components under complex and strong wind loads are obtained, and the failure laws of the envelope components caused by strong winds are revealed as the wind speed, wind direction, and building area density are changed. The results can provide advice for government departments and residents regarding the arrangement of buildings and reinforcement of envelope components.
Abstract This study investigates the effect of near-surface soil properties on the topographic am... more Abstract This study investigates the effect of near-surface soil properties on the topographic amplification of ground motions, based on the seismic response analysis of a 2D slope model with horizontally stratified soil medium. Finite difference simulations are performed to calculate the nonlinear elastoplastic response of the slope model, using strong motion records as excitation. Then a series of parametric analyses are carried out to quantitatively evaluate the influence of several factors, such as the shear-wave velocities of the superficial layers, thickness of the surface layer and soil material of the surface layer. The numerical results indicate that the decrease in the average shear-wave velocity of superficial layers would enhance the topographic effect in the area close to slope crest. In order to further assess the influence of different superficial soil profiles, seismic response analysis is conducted for a group of 2D slope models, which are built based on borehole data. The regression analysis of simulation results further confirms that the intensity of topographic effect gradually increases with decreasing VS30. Finally, the results of numerical analyses are compared with current seismic code provisions.
The effect of pulse characteristic of near-fault ground motions on multistory reinforced concrete... more The effect of pulse characteristic of near-fault ground motions on multistory reinforced concrete frame structures is investigated by means of a synthetic broadband ground motion model (SBGM). A simplified analytical pulse model is used to describe the low-frequency components of ground motions, while a stochastic simulation method based on wavelet packet is adopted to simulate the highfrequency components of ground motions. First, the time histories, response spectrum, and structural response of synthetic ground motions are compared with those corresponding to recorded nearfault ground motions. The good agreement indicates that the SBGM model used in this article is a suitable and efficient tool for evaluating the structural response. Sensitivity analysis on structural response of 2-, 4-, 8-, and 12-story building models to the SBGM model input parameters is then performed to identify the key ground-motion parameters which control the main structural response indicators, that is, interstory drift ratio and maximum interstory drift ratio. Final results indicate that the amplitude of velocity pulse in the SBGM model has a significant influence on structural drift demands. Nevertheless, for low-rise buildings, the maximum drift demands would effectively decrease with increasing proportion of high-frequency components. Moreover, the ratio of pulse period to structural fundamental period and number of oscillations impose a large drift demands to the structure under near-fault pulse-like ground motions.
The design earthquake is usually specified as a single event in most of modern seismic codes. How... more The design earthquake is usually specified as a single event in most of modern seismic codes. However, one earthquake is often followed by a series of aftershocks called seismic sequence. Such cases are quite common, especially in near-fault regions, which could cause additional accumulated damage to structures. In this paper, a new methodology for evaluating the effect of near-fault seismic sequences on the accumulated damage of reinforced concrete (RC) frame structure is proposed, in which different initial damage levels (i.e., postmainshock global damage index) of structure after the mainshock are considered. Meanwhile, a quantitative description of the damage demands and the relative intensity index between mainshock and aftershock are provided. For this purpose, the nonlinear dynamic response of an eight-story RC frame structure subjected to single earthquake and seismic sequence is compared in terms of structural performance indices (collapse capacity, story damage demands, postmainshock damage level and normalized hysteretic energy) and relative intensity index. The results indicated that seismic sequences lead to reduced collapse capacity of postmainshock-damaged structures. Moreover, the near-fault pulselike aftershock records would induce larger structural story damage demands than ordinary (i.e., non-pulse-like) aftershock records. Furthermore, the relative intensity index proposed in this paper has significant effects on the structural story damage demands, incremental dynamic analysis curves of aftershock and normalized hysteretic energy.
Most reinforced concrete (RC) frames would exhibit different degrees of damage after mainshock ex... more Most reinforced concrete (RC) frames would exhibit different degrees of damage after mainshock excitations, and these mainshock-damaged RC (MD-RC) frames are highly vulnerable to severe damage or even complete collapse under aftershock excitations. In the present study, the effectiveness of utilizing soft steel damper (SSD) as a passive energy dissipation device for seismic retrofitting of MD-RC frame under aftershock actions was investigated. A common three-story RC frame in the rural area was employed and a numerical evaluation framework of retrofitting analysis of the MD-RC frame was also proposed. Based on proposed evaluation framework, nonlinear dynamic time history analysis of the MD-RC frame with and without retrofitting schemes was conducted to evaluate the retrofit effect of the retrofitting schemes on the MD-RC frame. The results revealed that the retrofitting schemes could effectively improve the natural vibration characteristics of the MD-RC frame, especially the first-o...
Abstract Loss predictions and assessments for residential building groups are crucial processes d... more Abstract Loss predictions and assessments for residential building groups are crucial processes during extreme events such as wind hazards. The primary purpose of the present work is to improve the existing loss assessment methodology for residential building groups under wind hazards by considering the wind-induced interference effects between building groups, such as those based on the building locations, area density, wind direction, and wind speed. The failure characteristics of the envelope components under complex and strong wind loads are obtained, and the failure laws of the envelope components caused by strong winds are revealed as the wind speed, wind direction, and building area density are changed. The results can provide advice for government departments and residents regarding the arrangement of buildings and reinforcement of envelope components.
Abstract This study investigates the effect of near-surface soil properties on the topographic am... more Abstract This study investigates the effect of near-surface soil properties on the topographic amplification of ground motions, based on the seismic response analysis of a 2D slope model with horizontally stratified soil medium. Finite difference simulations are performed to calculate the nonlinear elastoplastic response of the slope model, using strong motion records as excitation. Then a series of parametric analyses are carried out to quantitatively evaluate the influence of several factors, such as the shear-wave velocities of the superficial layers, thickness of the surface layer and soil material of the surface layer. The numerical results indicate that the decrease in the average shear-wave velocity of superficial layers would enhance the topographic effect in the area close to slope crest. In order to further assess the influence of different superficial soil profiles, seismic response analysis is conducted for a group of 2D slope models, which are built based on borehole data. The regression analysis of simulation results further confirms that the intensity of topographic effect gradually increases with decreasing VS30. Finally, the results of numerical analyses are compared with current seismic code provisions.
The effect of pulse characteristic of near-fault ground motions on multistory reinforced concrete... more The effect of pulse characteristic of near-fault ground motions on multistory reinforced concrete frame structures is investigated by means of a synthetic broadband ground motion model (SBGM). A simplified analytical pulse model is used to describe the low-frequency components of ground motions, while a stochastic simulation method based on wavelet packet is adopted to simulate the highfrequency components of ground motions. First, the time histories, response spectrum, and structural response of synthetic ground motions are compared with those corresponding to recorded nearfault ground motions. The good agreement indicates that the SBGM model used in this article is a suitable and efficient tool for evaluating the structural response. Sensitivity analysis on structural response of 2-, 4-, 8-, and 12-story building models to the SBGM model input parameters is then performed to identify the key ground-motion parameters which control the main structural response indicators, that is, interstory drift ratio and maximum interstory drift ratio. Final results indicate that the amplitude of velocity pulse in the SBGM model has a significant influence on structural drift demands. Nevertheless, for low-rise buildings, the maximum drift demands would effectively decrease with increasing proportion of high-frequency components. Moreover, the ratio of pulse period to structural fundamental period and number of oscillations impose a large drift demands to the structure under near-fault pulse-like ground motions.
The design earthquake is usually specified as a single event in most of modern seismic codes. How... more The design earthquake is usually specified as a single event in most of modern seismic codes. However, one earthquake is often followed by a series of aftershocks called seismic sequence. Such cases are quite common, especially in near-fault regions, which could cause additional accumulated damage to structures. In this paper, a new methodology for evaluating the effect of near-fault seismic sequences on the accumulated damage of reinforced concrete (RC) frame structure is proposed, in which different initial damage levels (i.e., postmainshock global damage index) of structure after the mainshock are considered. Meanwhile, a quantitative description of the damage demands and the relative intensity index between mainshock and aftershock are provided. For this purpose, the nonlinear dynamic response of an eight-story RC frame structure subjected to single earthquake and seismic sequence is compared in terms of structural performance indices (collapse capacity, story damage demands, postmainshock damage level and normalized hysteretic energy) and relative intensity index. The results indicated that seismic sequences lead to reduced collapse capacity of postmainshock-damaged structures. Moreover, the near-fault pulselike aftershock records would induce larger structural story damage demands than ordinary (i.e., non-pulse-like) aftershock records. Furthermore, the relative intensity index proposed in this paper has significant effects on the structural story damage demands, incremental dynamic analysis curves of aftershock and normalized hysteretic energy.
Uploads
Papers by FUJIAN YANG