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This paper investigates the effects of the loading rates of high damping seismic isolation rubber bearing on earthquake responses.
For this purpose, a seismically isolated system is formulated by the Runge-Kutta numerical algorithm with nonlinear rate model
of high damping rubber bearing to carry out the seismic time history response analysis. Resu...
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... the input motion, the synthetic earthquake data, shown in Fig. 4, which is made by the measurement data in Mexico, 1985 and tentative design response spectrum (lshida etal., 1989), is used. This earthquake is often used in design and evaluation of seismically isolated system due to its long period components. The maximum peak acceleration of the Mexico earthquake is actually 316 gal but in this ...
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This report briefly presents the development of the deformable connection of an earthquake-resistant building structural system in which the lateral force resisting system (LFRS) is connected to the gravity load resisting system (GLRS) using this type of connection instead of a rigid connection. The GLRS and LFRS are able to move relative to each o...
Citations
... So, the next key question needs to answer is why the phase shift is so pronounced in mode 1 whereas is rarely observed in mode 2. Our experimental results on sandstones found that the transition from a higher stressing rate (either loading or unloading rate) to a lower one will yield a pronounced elastic after-effect (Song et al. 2022b). The damping will be more pronounced as a result if the stressing rate dramatically alters (Koo and Ohtori 1998). Our tests on sandstones and coal in this work further elaborate the effect of stressing rate on damping and phase shift during differential cyclic loading (DCL) and reveals the fact that a pronounced phase shift is responsible for the larger value of DER. ...
Stability of coal pillar (walls) is of great importance to security of underground mining. Periodic excavation and water table variation subject coal pillars (walls) to cyclic load with varying stressing rates and wetting–drying (WD) circumstances. Therefore, investigation on mechanical responses of coal exposed to effects of WD and compressive differential cyclic loading (DCL) was conducted to experimentally reveal coal’s mechanical behaviors. 22 cylindrical coal samples, 7 WD schemes (natural, soaking, 0, 10, 20, 30, 40 WD cycles) and 2 DCL loading modes (loading rate is 4 times of unloading rate and vice versa) were applied. The measurements covered mass loss, P-wave velocity, energy dissipation, crack characterization and hysteretic phase shift. P-wave velocity shows an exponential attenuation versus WD cycle. Mode 1 possessing loading rate 4 times of unloading rate corresponds to a higher rate of premature failure, incurring 4 out of 7 samples failed in cyclic stage, whereas all 7 samples survived in cyclic stage in mode 2 with opposite stressing rates. Stressing rate induced impact on deformation and energy dissipation is qualitatively revealed, with 6 out of 7 groups exhibiting more dissipated energy (approx. 10–50% larger than mode 2) in mode 1. More dissipated energy is attributed to a pronounced phase lag incurred by a higher loading rate and elastic-after effect. WD action induced meso-cracks were characterized and the width of crack is proportional to applied WD cycles. The testing results can provide practical guidance for in-situ application, such as evaluating the stability of coal mine based ground water reservoirs.
Highlights
he DCL test is first time applied on coal.
WD action has a pronounced effect on P-wave attenuation for coal.
Dissipated energy is influenced by loading pattern in DCL.
A modulus related parameter is proposed to predict coal failure.
... Seismic isolation is a protective measure against high earthquake risk exposure and is now seeing increased applications all over the world [1]. Various studies have investigated the different aspects of seismic isolation systems whether pertaining to the theory, development, behavior or the applications of such systems [2]- [6]. These included investigating the feasibility of production and implementation of low cost rubber bearings comparable in efficiency to commercial rubber bearings [7]. ...
... This system has emerged as a viable structural option in seismic zones to reduce the vulnerability of structural systems subjected to earthquakes, such as computer center, chip fabrication factories and hospital. The importance of the base isolation design is recognized to protect structures from the strong earthquakes after 1994 Northbridge earthquake and researchers have considerable attention (Koo, 1998: expensive to apply to low-cost house. The conventional seismic isolators consist of rubber and steel layers. ...
This paper proposes a new type of bearing system. In this study, a method for design of on elastomeric bearing system and
its mechanical property analysis are carried. Experimental and theoretical studies of the elastomeric bearings with fiber
reinforcement were proved effective new lightweight bearing system. The fibers in the bearings for isolation are assumed to
be flexible in extension, in contrast to the steel plates in the conventional bearing system. Several kinds of bearing systems
in the form of long strips are designed, fabricated and tested. The results suggest that it is possible to produce the economical
and effective fiber-reinforced elastomeric bearing that matches the behavior of a steel-reinforced bearing. Feasibility and
advantages of the proposed bearings are illustrated by the application of the analytic procedure to the structure system.
Results obtained here are reported to be an efficient approach with respect to bearing system and design of bearing against
shock absorbing system when compared with other conventional one.
The response of rock to dynamic loading is critical to the stability of underground engineering. This study experimentally investigated the mechanical responses of sandstone exposed to incremental and decremental frequency under compressive cyclic loading. The impact of loading frequency on amplitude of strain variation between the upper and lower bounds of cyclic stresses are revealed. The result shows that a higher frequency can incur a larger-amplitude variation of axial and volumetric strains between two bounds of cyclic stresses. The inelastic axial and radial strain ratios (defined in text) both exhibit good performance in early warning of rock failure. The cyclic loading stage (CLS) with the lowest inelastic strain ratio can be defined as the critical phase. This also applies to the evolution of secant modulus, the CLS with the peak secant modulus is used as the point to emit warning signals. The phase shift between stress–strain is frequency-dependent, a lower frequency results in a larger phase-shift. The evolution of damping ratio and dissipated energy ratio are almost frequency independent and both decrease with the ongoing of cycle.
Recently, laminated rubber bearings are widely used as seismic isolators for road bridges. Although many studies have been conducted on the dynamic model of High Damping Rubber (HDR) bearings, few models can reflect phenomena such as the dependency of experienced shear strain on initial history. To develop a model that can represent the dependency of the experienced shear strain of HDR and a dynamic loading test was conducted using HDR specimens. The hysteresis characteristics of HDR was measured by applying a horizontal vibration using a hybrid actuator under a constant vertical load. Based on the cyclic shear test, the mechanical properties of HDR were calculated such as absorbed energy, hysteresis loop area, equivalent stiffness, equivalent damping ratio. Dynamic analysis was also performed from the experimental results. The dynamic model applied in program analysis is a bilinear type double-target model. This model can express the nonlinear characteristics related to the initial history of HDR bearings. The parameters required for dynamic analysis were determined from the experimental results. Through this dynamic analysis, the effectiveness of the bilinear type double target model was verified. In this research, a high damping rubber specimen was used.
In this paper, the effects of shape factors on the buckling loads in the laminated rubber bearing (LRB) are investigated to
guide the design of LRB in determination of the rubber plate thickness and the total rubber height. To substantiate the application
of LRB to the seismic isolation of nuclear power plants, the seismic analyses and shaking table tests are carried out for
a seismically isolated structure using four LRBs. The parameter equations of seismic isolation frequency are obtained from
the shaking table tests and the quasi-static tests of LRB itself to investigate the effects of the LRB characteristics in
prediction of maximum peak acceleration responses by analysis. From the comparison of the maximum peak acceleration responses
obtained from numerical analyses and experiments, it is verified that the horizontal stiffness variations of LRB should be
considered in seismic analysis to get more accurate results.
Key Wordsthe Laminated Rubber Bearing(LRB)-Seismic Isolation Desgn-Stability-Buckling Load
