A new method of robust damper design is presented for elastic-plastic multi-degree-of-freedom(MDOF)building structures under multi-level ground motions(GMs).This method realizes a design that is effective for various ...A new method of robust damper design is presented for elastic-plastic multi-degree-of-freedom(MDOF)building structures under multi-level ground motions(GMs).This method realizes a design that is effective for various levels of GMs.The robustness of a design is measured by an incremental dynamic analysis(IDA)curve and an ideal drift response curve(IDRC).The IDRC is a plot of the optimized maximum deformation under a constraint on the total damper quantity vs.the design level of the GMs.The total damper quantity corresponds to the total cost of the added dampers.First,a problem of generation of IDRCs is stated.Then,its solution algorithm,which consists of the sensitivity-based algorithm(SBA)and a local search method,is proposed.In the application of the SBA,the passive added dampers are removed sequentially under the specified-level GMs.On the other hand,the proposed local search method can search the optimal solutions for a constant total damper quantity under GMs’increased levels.In this way,combining these two algorithms enables the comprehensive search of the optimal solutions for various conditions of the status of the GMs and the total damper quantity.The influence of selecting the type of added dampers(oil,hysteretic,and so on)and the selection of the input GMs on the IDRCs are investigated.Finally,a robust optimal design problem is formulated,and a simple local search-based algorithm is proposed.A simple index using the IDRC and the IDA curve of the model is used as the objective function.It is demonstrated that the proposed algorithm works well in spite of its simplicity.展开更多
The authors presented an interesting aspect in viscous or visco-elastic damper optimization under earthquake excitation. They also reviewed the research development in the field of passive damper optimization.
On March 11, 2011, eastern Japan was shaken by the 2011 off the Pacific coast of Tohoku Earthquake (the Great East Japan Earthquake). Almost 30 000 people have been killed or are missing as a result of that earthquake...On March 11, 2011, eastern Japan was shaken by the 2011 off the Pacific coast of Tohoku Earthquake (the Great East Japan Earthquake). Almost 30 000 people have been killed or are missing as a result of that earthquake and the subsequent monster tsunami, as of April 11, 2011. This paper reports several aspects of this devastating earthquake. It has been reported that long-period ground motions, which had been predicted by many researchers, occurred in Tokyo, Nagoya and Osaka. The response characteristics of high-rise buildings to the recorded long-period ground motions are discussed from the viewpoint of resonance and critical excitation. It is shown that high-hardness rubber dampers are very effective in the reduction of vibration duration in addition to the reduction in vibration amplitude.展开更多
This study introduces measures to identify resonant (concentration of energy in a single or a few frequencies) or unfavorable earthquake ground motions. Probabilistic measures based on the entropy rate and the geometr...This study introduces measures to identify resonant (concentration of energy in a single or a few frequencies) or unfavorable earthquake ground motions. Probabilistic measures based on the entropy rate and the geometric properties of the power spectral density function (PSDF) of the ground acceleration are developed first. Subsequently, deterministic measures for the frequency content of the ground acceleration are also developed. These measures are then used for identifying resonance and criticality in stochastic earthquake models and 110 acceleration records measured at rock, stiff, medium and soft soil sites. The unfavorable earthquake record for a given structure is defined as the record having a narrow frequency content and dominant frequency close to the structure fundamental natural frequency. Accordingly, the measures developed in this study may provide a basis for selecting records that are capable of producing the highest structural response. Numerical verifications are provided on damage caused to structures by identified resonant records.展开更多
Temporal variation of dynamical modal properties of a base-isolated building is investigated using earthquake records in the building. A batch processing least-squares estimation method is applied to segment-wise time...Temporal variation of dynamical modal properties of a base-isolated building is investigated using earthquake records in the building. A batch processing least-squares estimation method is applied to segment-wise time-series data. To construct an input-output system,an auto-regressive model with exogenous input (ARX) of second-order including a forgetting coefficient as a weighting coefficient is used for the estimation of modal parameters. The fundamental and second natural frequencies and the damping ratios of the fundamental and second natural modes of the base-isolated building are identified in the time domain. The identified results are consistent with the results obtained from the micro-tremor vibration data,forced-vibration test data and earthquake records in the present base-isolated building in the case of taking into account the amplitude-dependency of the isolators and viscous dampers. It is finally pointed out that several factors,e.g.,amplitude dependency of the isolator and damper system and special characteristics of the series-type viscous damper system,may be related complicatedly with the temporal variation in modal properties of the above-mentioned system.展开更多
It has often been reported that, when building structures are subjected to near-fault earthquake ground motions, horizontal and vertical impulsive inputs may cause critical damage during the first few seconds. In prac...It has often been reported that, when building structures are subjected to near-fault earthquake ground motions, horizontal and vertical impulsive inputs may cause critical damage during the first few seconds. In practical design of building structures, however, the safety check, taking into account the effect of multi-component ground motions, is hardly conducted except the design of important structures such as high-rise buildings and nuclear power plants. Ftirthel＇more, it is not clear how the correlation of multi-component ground motions influences the actual safety of structures. In this paper, the detailed property of critical excitation is discussed in association with the relationship between the characteristics of ground motions and those of structures. The properties of various auto power spectral density （PSD） functions of the horizontal and vertical ground motions are investigated, and those of the critical cross PSD function of these two-directional ground motions are found by a devised algorithm in a feasible complex plane. A closed-form expression is derived from the critical relation of the auto PSD functions of the simultaneous inputs. This critical excitation method provides us with a new approach for earthquake-resistant design against the possible future earthquake which causes the critical damages to buildings.展开更多
基金Part of the present work is supported by the Grant-in-Aid for Scientific Research(KAKENHI)of the Japan Society for the Promotion of Science(Nos.18H01584,JP20J20811)This support is greatly appreciated.
文摘A new method of robust damper design is presented for elastic-plastic multi-degree-of-freedom(MDOF)building structures under multi-level ground motions(GMs).This method realizes a design that is effective for various levels of GMs.The robustness of a design is measured by an incremental dynamic analysis(IDA)curve and an ideal drift response curve(IDRC).The IDRC is a plot of the optimized maximum deformation under a constraint on the total damper quantity vs.the design level of the GMs.The total damper quantity corresponds to the total cost of the added dampers.First,a problem of generation of IDRCs is stated.Then,its solution algorithm,which consists of the sensitivity-based algorithm(SBA)and a local search method,is proposed.In the application of the SBA,the passive added dampers are removed sequentially under the specified-level GMs.On the other hand,the proposed local search method can search the optimal solutions for a constant total damper quantity under GMs’increased levels.In this way,combining these two algorithms enables the comprehensive search of the optimal solutions for various conditions of the status of the GMs and the total damper quantity.The influence of selecting the type of added dampers(oil,hysteretic,and so on)and the selection of the input GMs on the IDRCs are investigated.Finally,a robust optimal design problem is formulated,and a simple local search-based algorithm is proposed.A simple index using the IDRC and the IDA curve of the model is used as the objective function.It is demonstrated that the proposed algorithm works well in spite of its simplicity.
文摘The authors presented an interesting aspect in viscous or visco-elastic damper optimization under earthquake excitation. They also reviewed the research development in the field of passive damper optimization.
基金Project (No. 21360267) supported by the Grant-in-Aid for Scientific Research of Japan Society for the Promotion of Science
文摘On March 11, 2011, eastern Japan was shaken by the 2011 off the Pacific coast of Tohoku Earthquake (the Great East Japan Earthquake). Almost 30 000 people have been killed or are missing as a result of that earthquake and the subsequent monster tsunami, as of April 11, 2011. This paper reports several aspects of this devastating earthquake. It has been reported that long-period ground motions, which had been predicted by many researchers, occurred in Tokyo, Nagoya and Osaka. The response characteristics of high-rise buildings to the recorded long-period ground motions are discussed from the viewpoint of resonance and critical excitation. It is shown that high-hardness rubber dampers are very effective in the reduction of vibration duration in addition to the reduction in vibration amplitude.
基金Project (No. JSPS-P-08073)supported by the Japanese Society for the Promotion of Science
文摘This study introduces measures to identify resonant (concentration of energy in a single or a few frequencies) or unfavorable earthquake ground motions. Probabilistic measures based on the entropy rate and the geometric properties of the power spectral density function (PSDF) of the ground acceleration are developed first. Subsequently, deterministic measures for the frequency content of the ground acceleration are also developed. These measures are then used for identifying resonance and criticality in stochastic earthquake models and 110 acceleration records measured at rock, stiff, medium and soft soil sites. The unfavorable earthquake record for a given structure is defined as the record having a narrow frequency content and dominant frequency close to the structure fundamental natural frequency. Accordingly, the measures developed in this study may provide a basis for selecting records that are capable of producing the highest structural response. Numerical verifications are provided on damage caused to structures by identified resonant records.
基金supported by the Grant-in-Aid for Scientific Research (No. 10650562) from the Ministry of EducationScience, Sports and Cul-ture of Japan, the Grant-in-Aid for Scientific Research (No. 16560496) from the Japan Society for the Promotion of Sciencethe Col-laboration Project between Kyoto University and Obayashi Corpora-tion (1998-2002), Japan
文摘Temporal variation of dynamical modal properties of a base-isolated building is investigated using earthquake records in the building. A batch processing least-squares estimation method is applied to segment-wise time-series data. To construct an input-output system,an auto-regressive model with exogenous input (ARX) of second-order including a forgetting coefficient as a weighting coefficient is used for the estimation of modal parameters. The fundamental and second natural frequencies and the damping ratios of the fundamental and second natural modes of the base-isolated building are identified in the time domain. The identified results are consistent with the results obtained from the micro-tremor vibration data,forced-vibration test data and earthquake records in the present base-isolated building in the case of taking into account the amplitude-dependency of the isolators and viscous dampers. It is finally pointed out that several factors,e.g.,amplitude dependency of the isolator and damper system and special characteristics of the series-type viscous damper system,may be related complicatedly with the temporal variation in modal properties of the above-mentioned system.
基金supported by the Grant-in-Aid for Scientific Research of Japan Society for the Promotion of Science (Nos. 18360264 and 21360267)
文摘It has often been reported that, when building structures are subjected to near-fault earthquake ground motions, horizontal and vertical impulsive inputs may cause critical damage during the first few seconds. In practical design of building structures, however, the safety check, taking into account the effect of multi-component ground motions, is hardly conducted except the design of important structures such as high-rise buildings and nuclear power plants. Ftirthel＇more, it is not clear how the correlation of multi-component ground motions influences the actual safety of structures. In this paper, the detailed property of critical excitation is discussed in association with the relationship between the characteristics of ground motions and those of structures. The properties of various auto power spectral density （PSD） functions of the horizontal and vertical ground motions are investigated, and those of the critical cross PSD function of these two-directional ground motions are found by a devised algorithm in a feasible complex plane. A closed-form expression is derived from the critical relation of the auto PSD functions of the simultaneous inputs. This critical excitation method provides us with a new approach for earthquake-resistant design against the possible future earthquake which causes the critical damages to buildings.
