Study on Active Vibration Control of Seismic Isolation Structure With Variable Gain Using Spectrum Monitoring

In this research, the seismic isolation structure which can switch the active control gains by the characteristics of the earthquake is proposed. As the number of high-rise buildings in urban areas in has increased in recent years, damage due to long-period earthquakes is expected to increase. In this paper, the focus is on the area of velocity response spectrum as an index of long-period earthquake. Then we design the time varying weighting coefficient from the area of the velocity response spectrum obtained from the seismic wave. The long periodicity of the earthquake is judged from the area of the velocity response spectrum calculated from the seismic wave arriving from moment to moment. In addition, we aim to improve the performance of the control system by inputting appropriate control power. We also aimed for energy saving of control by not performing control input within the range where the earthquake does not have a long period. We proposed a method of switching control using time varying weighting factor, designed time varying weighting factor, and confirmed its effectiveness by performing time history response analysis on actual seismic waves.

Statistical Analysis for Platform Height Ratio of Horizontal Components in Bedrock Seismic Oscillation Velocity Response Spectrum

Based on the strong ground motion records of the bedrock, the overall feature of ratio (H1/H2) of the platform height of two horizontal components in velocity response spectrum was analyzed. The results show that: (1) The platform height values of two horizontal components are different from each other; (2) H1/H2 decreases with the increasing of earthquake magnitude, decreases with the increasing of epicenter distance, and tends to be 1 in far field.

Ultimate Seismic Resistance Capacity for Long Span Lattice Structures under Vertical Ground Motions

Seismic resistance capacities of frame structures have been discussed with equilibrium of energies among many researchers. The early one is the limit design presented by Housner, 1956; that is, frame structures should possess the plastic deformation ability equivalent to an earthquake input energy given by a velocity response spectrum. On such studies of response estimation by the energy equilibrium, the potential energy has been generally abandoned, since the effect of self-weight or fixed loads on the potential energy is negligible, while ordinary buildings usually sway in the horizontal direction. However, it could be said that the effect of gravity has to be considered for long span structures since the mass might be concerned with the vertical response. In this paper, as for ultimate seismic resistance capacity of long span structures, an estimation method considering the potential energy is discussed as for plane lattice beams and double-layer cylindrical lattice roofs. The method presented can be done with the information of static nonlinear behavior, natural periods, and velocity response spectrum of seismic motions; that is, any complicated nonlinear time history analysis is not required. The value estimated can be modified with the properties of strain energy absorption and the safety static factor.

Study on Relationship of Seismic and Pseudo Response Spectrums

153 seismic waves were input into the elastic-dynamic differential equations of single degree of freedom system, the acceleration response spectrum, velocity response spectrum and displacement response spectrum in different site characteristic periods were obtained. According to the pseudo-dynamic relationship between acceleration, velocity and displacement response spectrum, the pseudo response spectra were obtained by the deduction of the 3 real response spectra from the frequency relation. Compared with the value of the real and the pseudo response spectra, the basic characteristics and differences were studied, the correction formulas of the difference between the real response spectrum and the pseudo response spectrum were obtained, the correction formula will contribute to the development of performance based seismic design theory.

Research on the Damage Fracture of Rock Blasting Based on Velocity Response Spectrum

The damage caused by blasting vibration on rock mass is an extremely complex process, and has certain impact on the mechanical properties and bearing capacity of the rock, which will affect the overall stability and safe operation of the construction. Therefore, studying on the damage effect of blasting vibration is very necessary. Taking Laxiwa hydropower station project as a background, the paper computed relative velocity response spectrum using monitoring and measuring blasting velocity as an excitation, then analysis was carried out to study the relationship between the depth of rock blasting and the integral value of relative velocity response spectrum as well as the index of cooperation of the integral value and the blast vibration’s duration time. The results show that using three-parameter (velocity, frequency, duration time) was clearly superior to two-parameter (velocity, frequency) on studying the damage fracture of rock blasting, and two-parameter was better than one-parameter (velocity) by analogy.

Real-Time Prediction of Liquid Sloshing of Oil Storage Tank Based on Earthquake Early Warning

For an efficient patrol to prevent and/or minimize secondary disaster such as fire breakout, diffusion of oil just after an earthquake, we investigated the possibility of real-time prediction of liquid sloshing of oil storage tank based on Earthquake Early Warning (EEW), and also investigated the estimation of volume of overflowed oil from a tank due to large liquid sloshing. As to velocity response spectrum prediction used in predicting liquid sloshing, we constructed the attenuation equation of spectral amplitude for far-field surface waves considering both the seismotectonics and the scaling law of the source characteristics. For estimation of the amount of overflowed oil, we executed experimental studies using a model tank of 7 m in diameter and proposed an empirical equation based on the velocity response spectrum and verified the validity of the formula for the past earthquakes. We applied these equations to the EEW in the 2008 Iwate/Miyagi inland earthquake (M7.2) for Sendai Oil Industrial Complex District, and obtained a good agreement between the predicted and the observed spectrum. Thus, it is expected that the information about the predicted sloshing behavior in a very early stage after a large earthquake using EEW, will be disseminated to person responsible for disaster countermeasures prior to communication congestion.

Assessing the Effectiveness of Soil Parameters for Ground Response Characterization and Soil Classification

The average shear wave velocity over the top 30 m of a soil profile ( VS,30) represents an usual parameter for soil classification in a modern building code for seismic design. In this work the ground response of about 100 soil profiles in Tuscany and Molise (Italy) is studied through 1-D numerical simulations in order to evaluate the reliability of European and Italian soil classifications based on the VS,30 criterion. The amplification factor, Fa, defined here as the ratio of the pseudo-velocity response spectrum intensity (Housner 1952) at the surface, S Is, to the pseudo-velocity response spectrum intensity at the rock outcrop, S Ir, is related to some soil parameters, such as VS,30, the fundamental frequency of vibration of the soil column, F0, and seismic impedance contrast, Iw. Analyzing the standard deviation of the residual obtained from regression analyses of Fa versus VS,30, F0, and Iw shows that F0 is the most helpful parameter for the prediction of Fa. Hence F0 appears to be more appropriate than VS,30 and Iw for the characterization of the seismic response of a site and, therefore, should not be disregarded in building code soil classifications.

Unique Method for Generating Design Earthquake Time Histories

A method has been developed which takes a seed earthquake time history and modifies it to produce given design response spectra. It is a multi-step process with an initial scaling step and then multiple refinement steps. It is unique in the fact that both the acceleration and displacement response spectra are considered when performing the fit (which primarily improves the low frequency acceleration response spectrum accuracy). Additionally, no matrix inversion is needed. The features include encouraging the code acceleration, velocity, and displacement ratios and attempting to fit the pseudo velocity response spectrum. Also, “smoothing” is done to transition the modified time history to the seed time history at its start and end. This is done in the time history regions below a cumulative energy of 5% and above a cumulative energy of 95%. Finally, the modified acceleration, velocity, and displacement time histories are adjusted to start and end with an amplitude of zero (using Fourier transform techniques for integration).