This paper focuses on the investigation of a hybrid seismic isolation system with passive variable friction dampers for protection of structures against near fault earthquakes. The seismic isolation can be implemented...This paper focuses on the investigation of a hybrid seismic isolation system with passive variable friction dampers for protection of structures against near fault earthquakes. The seismic isolation can be implemented by replacing the conventional columns fixed to the foundations by seismic isolating ones. These columns allow horizontal displacement between the superstructure and the foundations and decouple the building from the damaging earthquake motion. As a result, the forces in the structural elements decrease and damage that may be caused to the building by the earthquake significantly decreases. However, this positive effect is achieved on account of displacements occurring in the isolating columns. These displacements become very large when the structure is subjected to a strong earthquake. In this case, impact may occur between the parts of the isolating column yielding their damage or collapse. In order to limit the displacements in the isolating columns, it is proposed to add variable friction dampers. A method for selecting the dampers＇ properties is proposed. It is carried out using an artificial ground motion record and optimal active control algorithm. Numerical simulation of a sevenstory structure shows that the proposed method allows efficient reduction in structural response and limits the displacements at the seismic isolating columns.展开更多
Shaking tables with moving platforms are widely used in laboratory testing of structural models and full-sized devices. In most cases, the platform＇s movement should reproduce real ground acceleration records. Howeve...Shaking tables with moving platforms are widely used in laboratory testing of structural models and full-sized devices. In most cases, the platform＇s movement should reproduce real ground acceleration records. However, the stroke of the platform, required for reproduction of real records, is usually rather large. This limitation does not allow an accurate realization of the ground motion by the shaking table. Commonly, in order to overcome this problem, original records are modified, which causes a significant change in the acceleration records＇ spectra. That is why structural responses to the original and to the modified records are different. A new method for modification of original acceleration records is proposed, in which the original record is corrected by an additional artificial one that changes the shaking platform＇s displacement. The corrected record is obtained as a sequence of impulses, The magnitude and duration of each impulse, as well as their location on the time scale, are obtained by an optimization procedure. The optimization is implemented according to a performance index, aimed to minimize the influence of the correcting acceleration record on the specmam of the original one. The proposed method has higher reproduction accuracy, compared to other known methods. Its effectiveness is demonstrated by comparison of response spectra and dynamic behaviors of three multi-story structures subjected to natural and modified seismic excitations.展开更多
This paper provides a first indication that this is true for a system comprised of a static structure described by hyperbolic partial differential equations and is subjected to an external random input force. The syst...This paper provides a first indication that this is true for a system comprised of a static structure described by hyperbolic partial differential equations and is subjected to an external random input force. The system deforms the randomness of an input force sequence in proportion to its algorithmic complexity. The authors demonstrate this by numerical analysis of a one-dimensional vibrating elastic solid （the system） on which we apply a maximally-random force sequence （input）. The level of complexity of the system is controlled via external parameters. The output response is the field of displacements observed at several positions on the body. The algorithmic complexity and stochasticity of the resulting output displacement sequence is measured and compared against the complexity of the system. The results show that the higher the system complexity, the more random-deficient the output sequence.展开更多
文摘This paper focuses on the investigation of a hybrid seismic isolation system with passive variable friction dampers for protection of structures against near fault earthquakes. The seismic isolation can be implemented by replacing the conventional columns fixed to the foundations by seismic isolating ones. These columns allow horizontal displacement between the superstructure and the foundations and decouple the building from the damaging earthquake motion. As a result, the forces in the structural elements decrease and damage that may be caused to the building by the earthquake significantly decreases. However, this positive effect is achieved on account of displacements occurring in the isolating columns. These displacements become very large when the structure is subjected to a strong earthquake. In this case, impact may occur between the parts of the isolating column yielding their damage or collapse. In order to limit the displacements in the isolating columns, it is proposed to add variable friction dampers. A method for selecting the dampers＇ properties is proposed. It is carried out using an artificial ground motion record and optimal active control algorithm. Numerical simulation of a sevenstory structure shows that the proposed method allows efficient reduction in structural response and limits the displacements at the seismic isolating columns.
文摘Shaking tables with moving platforms are widely used in laboratory testing of structural models and full-sized devices. In most cases, the platform＇s movement should reproduce real ground acceleration records. However, the stroke of the platform, required for reproduction of real records, is usually rather large. This limitation does not allow an accurate realization of the ground motion by the shaking table. Commonly, in order to overcome this problem, original records are modified, which causes a significant change in the acceleration records＇ spectra. That is why structural responses to the original and to the modified records are different. A new method for modification of original acceleration records is proposed, in which the original record is corrected by an additional artificial one that changes the shaking platform＇s displacement. The corrected record is obtained as a sequence of impulses, The magnitude and duration of each impulse, as well as their location on the time scale, are obtained by an optimization procedure. The optimization is implemented according to a performance index, aimed to minimize the influence of the correcting acceleration record on the specmam of the original one. The proposed method has higher reproduction accuracy, compared to other known methods. Its effectiveness is demonstrated by comparison of response spectra and dynamic behaviors of three multi-story structures subjected to natural and modified seismic excitations.
文摘This paper provides a first indication that this is true for a system comprised of a static structure described by hyperbolic partial differential equations and is subjected to an external random input force. The system deforms the randomness of an input force sequence in proportion to its algorithmic complexity. The authors demonstrate this by numerical analysis of a one-dimensional vibrating elastic solid （the system） on which we apply a maximally-random force sequence （input）. The level of complexity of the system is controlled via external parameters. The output response is the field of displacements observed at several positions on the body. The algorithmic complexity and stochasticity of the resulting output displacement sequence is measured and compared against the complexity of the system. The results show that the higher the system complexity, the more random-deficient the output sequence.
