Earthquake is a kind of sudden and destructive random excitation in nature.It is significant to determine the probability distribution characteristics of the corresponding dynamic indicators to ensure the safety and t...Earthquake is a kind of sudden and destructive random excitation in nature.It is significant to determine the probability distribution characteristics of the corresponding dynamic indicators to ensure the safety and the stability of structures when the intensive seismic excitation,the intensity of which is larger than 7,acts in train-bridge system.Firstly,the motion equations of a two-dimensional train-bridge system under the vertical random excitation of track irregularity and the vertical seismic acceleration are established,where the train subsystem is composed of 8 mutually independent vehicle elements with 48 degrees of freedom,while the single-span simple supported bridge subsystem is composed of 102D beam elements with 20 degrees of freedom on beam and 2 large mass degrees of freedom at the support.Secondly,Monte Carlo method and pseudo excitation method are adopted to analyze the statistical parameters of the system.The power spectrum density of random excitation is used to define a series of non-stationary pseudo excitation in pseudo excitation method and the trigonometric series of random vibration history samples in Monte Carlo method,respectively solved by precise integral method and Newmark-βmethod through the inter-system iterative procedure.Finally,the results are compared with the case under the weak seismic excitation,and show that the samples of vertical acceleration response of bridge and the offload factor of train obeys the normal distribution.In a high probability,the intensive earthquakes pose a greater threat to the safety and stability of bridges and trains than the weak ones.展开更多
As capacity design philosophy suggests, the best way to achieve a safe seismic response of multistory buildings, under strong earthquakes, is to uniformly spread the inelastic deformation demands throughout the buildi...As capacity design philosophy suggests, the best way to achieve a safe seismic response of multistory buildings, under strong earthquakes, is to uniformly spread the inelastic deformation demands throughout the building structure. Unfortunately, this type of mechanism is difficult to be reached due to the abundant presence ofinfill wall panels on buildings, which under strong earthquakes show severe cracks and strength degradations, thus complicating the seismic response of buildings. In order to avoid these brittle mechanisms of failure, studies were made toward development of new seismic protection system which would completely protect the infill walls from any cracks and strength degradation manifestations and simultaneously improve the seismic response of the entire structure. Utilization of the ＂IDRIZI＂ seismic protection system, would greatly contribute to many important aspects, like the increase of structural seismic performance, drastic reduction of damages under strong earthquake events and avoiding any unpredictable local failure mechanisms on buildings.展开更多
On April 20, 2013 at 8：02 am, a magnitude 7.0 earthquake occurred in Lushan County, Sichuan Province, China, which induces massive landslides, causes great losses to life and property. Based on the locations of after...On April 20, 2013 at 8：02 am, a magnitude 7.0 earthquake occurred in Lushan County, Sichuan Province, China, which induces massive landslides, causes great losses to life and property. Based on the locations of aftershocks provided by the China Earthquake Network Center and the characteristic of Longmenshan active faults system, combined with the current preliminary focal mechanism solution, the fault rupture direction is determined. With the finite fault inversion method, we invert the rupture process of the Lusban Ms7.0 earthquake by teleseismic waveforms data. The inversion results indicate that the main shock is dominated by thrust fault component and the rupture initiated at depth of 15 km, and most of slip ruptured around the hypocenter with the peak slip of about 1.5 m. Most of rupture slips released at the first 20 s and the main rupture occurred at the first 10 s after the onsets of the mainshock. Most of seismic energy released near the hypocenter with a length of 28 km, especially on both sides of the hypocenter with the range of 20 km, and the seismic energy released relatively smaller in other areas. There is a large area with weak slip between the main rupture and another two asperities on both sides of the hypocenter; it may imply that the accumulated strain on the rupture fault has not been completely released. Therefore, there is a significant possibility of having strong aftershocks in the areas where energy is not fully released. This is also the main reason why there are a lot of moderate to strong aftershocks in the Lushan aftershock sequence. In addition, there is an earthquake vacant zone with a length of about 50 km between the Wenchuan Mw7.9 earthquake and this event, which is of high earthquake risk and is deserved to be paid close attention to.展开更多
基金Project(52178101) supported by the National Natural Science Foundation of China。
文摘Earthquake is a kind of sudden and destructive random excitation in nature.It is significant to determine the probability distribution characteristics of the corresponding dynamic indicators to ensure the safety and the stability of structures when the intensive seismic excitation,the intensity of which is larger than 7,acts in train-bridge system.Firstly,the motion equations of a two-dimensional train-bridge system under the vertical random excitation of track irregularity and the vertical seismic acceleration are established,where the train subsystem is composed of 8 mutually independent vehicle elements with 48 degrees of freedom,while the single-span simple supported bridge subsystem is composed of 102D beam elements with 20 degrees of freedom on beam and 2 large mass degrees of freedom at the support.Secondly,Monte Carlo method and pseudo excitation method are adopted to analyze the statistical parameters of the system.The power spectrum density of random excitation is used to define a series of non-stationary pseudo excitation in pseudo excitation method and the trigonometric series of random vibration history samples in Monte Carlo method,respectively solved by precise integral method and Newmark-βmethod through the inter-system iterative procedure.Finally,the results are compared with the case under the weak seismic excitation,and show that the samples of vertical acceleration response of bridge and the offload factor of train obeys the normal distribution.In a high probability,the intensive earthquakes pose a greater threat to the safety and stability of bridges and trains than the weak ones.
文摘As capacity design philosophy suggests, the best way to achieve a safe seismic response of multistory buildings, under strong earthquakes, is to uniformly spread the inelastic deformation demands throughout the building structure. Unfortunately, this type of mechanism is difficult to be reached due to the abundant presence ofinfill wall panels on buildings, which under strong earthquakes show severe cracks and strength degradations, thus complicating the seismic response of buildings. In order to avoid these brittle mechanisms of failure, studies were made toward development of new seismic protection system which would completely protect the infill walls from any cracks and strength degradation manifestations and simultaneously improve the seismic response of the entire structure. Utilization of the ＂IDRIZI＂ seismic protection system, would greatly contribute to many important aspects, like the increase of structural seismic performance, drastic reduction of damages under strong earthquake events and avoiding any unpredictable local failure mechanisms on buildings.
基金supported by Chinese Seismic Array Detecting Project (Grant No.201008001)National Natural Science Foundation of China (Grant Nos.41174086,40974034,41021003)
文摘On April 20, 2013 at 8：02 am, a magnitude 7.0 earthquake occurred in Lushan County, Sichuan Province, China, which induces massive landslides, causes great losses to life and property. Based on the locations of aftershocks provided by the China Earthquake Network Center and the characteristic of Longmenshan active faults system, combined with the current preliminary focal mechanism solution, the fault rupture direction is determined. With the finite fault inversion method, we invert the rupture process of the Lusban Ms7.0 earthquake by teleseismic waveforms data. The inversion results indicate that the main shock is dominated by thrust fault component and the rupture initiated at depth of 15 km, and most of slip ruptured around the hypocenter with the peak slip of about 1.5 m. Most of rupture slips released at the first 20 s and the main rupture occurred at the first 10 s after the onsets of the mainshock. Most of seismic energy released near the hypocenter with a length of 28 km, especially on both sides of the hypocenter with the range of 20 km, and the seismic energy released relatively smaller in other areas. There is a large area with weak slip between the main rupture and another two asperities on both sides of the hypocenter; it may imply that the accumulated strain on the rupture fault has not been completely released. Therefore, there is a significant possibility of having strong aftershocks in the areas where energy is not fully released. This is also the main reason why there are a lot of moderate to strong aftershocks in the Lushan aftershock sequence. In addition, there is an earthquake vacant zone with a length of about 50 km between the Wenchuan Mw7.9 earthquake and this event, which is of high earthquake risk and is deserved to be paid close attention to.
