Shaking Table Tests of Critical Equipment With Simple Isolators

Because the earthquake is one kind of non-predictable calamity and happens suddenly, its disaster and consequence are larger than other calamities. Mankind must face not only the emotional effects caused by earthquakes, but also the damage to the structure and substructure systems. The fire, damaged pipeline systems cased by earthquake and the destruction of the semiconductor, equipment or microelectronics in high-tech factories will cause an enormous and a chain of economic losses. Therefore, there is a need of an economical and efficient method to protect equipments from earthquake damage. Namely, in addition to promoting the earthquake-resistant capacity of structures, it is also important to ensure the safety of the expensive equipment and facilities. In this study, it is aimed at developing a new simple isolator with appropriate damping for critical equipment. The basic principle of the simple isolator is to lengthen the natural period of equipment, and simultaneously to reduce the earthquake-induced energy and the displacement of the isolator by additional damping. A series of shaking table tests for critical equipment isolated with simple isolators were carried out in the Department of Civil Engineering, Feng Chia University, Taichung, Taiwan. From these test results, it is illustrated that the simple isolator can reduce more than 80% responses of accelerations under earthquakes with peak ground acceleration of above 0.450g. Therefore, the simple isolator can be recognized as a feasible and promising way in mitigating the seismic responses of equipment. In addition, the simple isolator possesses enough energy absorbing capacity to reduce its maximum displacement and the restoring force to bring the isolator back to the original position without significant residual displacement.

Simplified Elasto-Plastic Response Analysis of Piping: Considering In-Plane, Out-of-Plane and the Mixed Bending of Elbow

When piping systems are subjected to extreme seismic excitation, they undergo a plastic deformation that produces a large damping effect via energy dissipation. Based on our studies of the damping effect of the elasto-plastic response of piping, we have presented a simplified method for predicting the elasto-plastic response of piping in PVP conferences over the last several years. The method has taken the plastic deformation of in-plane bending elbows into consideration. The elasto-plastic response predicted by the method resulted in good agreement with piping model excitation tests. In this paper, we report an additional method to consider out-of-plane bending elbow and the mixed bending of in-plane and out-of-plane bending. The simulation results by this method and the comparisons with 3D piping model excitation tests are also reported.

Load Discontinuity and Its Remedy in Step-by-Step Integration

The discontinuity at the end of an impulse will lead to an extra impulse and thus an extra displacement. Consequently, an amplitude distortion is introduced in the numerical solution. The difficulty arising from the discontinuity at the end of an impulse can be overcome by using a very small time step to perform the step-by-step integration since it reduces the extra impulse and thus extra displacement. However, computational efforts might be significantly increased since the small time step is performed for a complete step-by-step integration procedure. A remedy is devised to computationally efficiently overcome this difficulty by using a very small time step immediately upon termination of the applied impulse. This is because that the extra impulse caused by the discontinuity is almost proportional to the discontinuity value at the end of the impulse and the step size. The feasibility of this proposed remedy is analytically and numerically confirmed herein.

A Partitioned Algorithm of Dynamic Fluid-Structure Interaction for Elephant Foot Bulging of Tanks

A partitioned coupling algorithm is presented in this paper to solve the dynamic large-displacement fluid-structure interaction (DFSI) problems. In this algorithm, the program based on arbitrary Lagrangian Eulerian (ALE) and fractional two-step method is developed to calculate computational fluid dynamics (CFD) and computational mesh dynamics (CMD). ABAQUS is used to calculate computational structure dynamics (CSD). Some user subroutines are implemented into ABAQUS and the data are exchanged among CSD, CFD and CMD. Numerical results including elephant foot bulging (EFB) of the liquid storage tank are obtained under dynamic waveform.

Seismic Behavior of High-Tech Facility Isolated With a Trench Friction Pendulum System

Seismic mitigation of high-tech facilities is a very important issue in earthquake prone areas such as Taiwan, Japan, U.S.A., etc. In order to lessen vulnerability of earthquake damage of high-tech equipment, base isolation seems to be a good choice. This paper mainly explores the possibility of using a new base isolation system named the trench friction pendulum system (TFPS) to reduce seismic responses of high-tech facilities. The main reasons, from a engineer’s point of view, to use this system for protecting high-tech equipment from earthquake damage are high efficiency and low cost. A series of shaking table tests for a high-tech facility isolated with TFPS isolators were carried out in the Department of Civil Engineering, Feng Chia University, Taichung, Taiwan, ROC. The experimental results show that the proposed system provides a good protection for the high-tech facility during strong earthquakes.

Experimental Study for Identifying Stiffness of Bridge Slab by Using Wavelet Transform

In health monitoring of bridge slabs, it is suitable to identify the change in their stiffness. The authors have been proposing the method to identify the spring constant of slab by wavelet transform of an excitation force and acceleration response. In previous paper, the method to identify the spring constants of slabs is theoretically investigated under the noisy conditions. The method to find the specific values of constant α in an analyzing wavelet by which the most reliable value of the spring constant is given according to the graphic form showing the relation between identified mass and constant α. In this paper, the effectiveness of the method is proven from the experiment results using the reinforced concrete panel specimen.

Seismic Analysis and Design of RC Frame With New Metallic Dampers

Earthquake can make structures damaged and crumble. The traditional approach to seismic design has been based upon providing a combination of strength and ductility to resist the imposed loads. Thus, the level of the structure security cannot be achieved, because the disadvantage of the designing method is lack of adjusting capability subjected to an uncertain earthquake. The presence of some damping (energy dissipation) in buildings has been recognized and studied by professional researchers. Passive energy-dissipated system, as a category of vibration control methods, lead the inputting energy from earthquake to special element, thereby reducing energy-dissipating demand on primary structural members and minimizing possible structural damage. In this paper, a new idea of designing metallic damper is presented and realized through the improved dampers that are of a certain bearing forces in plane of plate and suitable energy-dissipating capability by making metallic dampers in different shapes. New types of metallic dampers are called as “dual functions” metallic damper (DFMD), because it not only provides certain stiffness in normal use for a building, but also are of good ability of the seismic energy-dissipation. The structural configuration and mechanical characteristics of the models and prototypes of the DFMDs are analyzed and experimented so as to verify the seismic performance of the dampers. Finally, the DFMDs applied to a new building in China are introduced and numerical results demonstrate the effectiveness of the DFMD.

Passive, Semi-Active, and Active Tuned-Liquid-Column Dampers

The dynamic characteristics of the passive, semi-active, and active tuned-liquid-column dampers (or TLCD’s) are studied in this paper. The design of the latter two are based on the first one. The water-head difference of a passive TLCD is pre-set to form the so-called semi-active one in this paper. The water-head difference is released at a proper time instant during an earthquake excitation to enhance the vibration reduction of a structure. Two propellers are installed along a shaft inside and at the center of a passive TLCD to form an active one. These two propellers are driven by a servomotor controlled by a computer to provide the control force. The seismic responses of a five-story shear building with a passive, semi-active, or active TLCD are computed for demonstration and discussion. The results of this building with a tuned mass damper (or TMD) are also included for comparison.

Finite Element Models for Computing Seismic Induced Soil Pressures on Deeply Embedded NPP Structures

This paper discusses computations of seismic induced soil pressures using finite element (FE) models for deeply embedded and/or buried (DEB) stiff structures, such as those appearing in the conceptual designs of structures for advanced reactors. For DEB structures, the soil-structure interaction (SSI) effect is expected to have a strong influence on the estimate of the seismic induced soil pressures, especially for stiff structures embedded in soft soil strata. In this paper, two FE models are developed using the SASSI and LS-DYNA computer programs, representing respectively the substructure subtracting method and explicit FE algorithm. SASSI utilizes the wave propagation theory and the principle of superposition to treat the SSI phenomenon. In the LS-DYNA analysis, an attempt is made to apply the direct approach to the SSI effect, which treats the near field soil with an explicit FE mesh that is connected to a transmitting boundary to approximate wave propagation in the half-space. The structural model used for the study is derived from the characteristics of a conceptual design for an advanced reactor. The structure is founded in a soft soil overburden underlain by a rock and the input seismic motion is specified at rock outcrop and has a zero period acceleration (ZPA) equal to 0.3 g, typical of review level earthquakes for nuclear power plant structures in the Central and Eastern United States. Various depths of burial (DOB) for the structure are considered in the analysis to afford an assessment of the DOB effect on the seismic induced soil pressure estimates determined by these methods. Comparisons and discussions of the analysis results computed by the two approaches are provided.

Estimate of Inelastic Excursions in Hysteretic Structures by Wavelet Transform of Acceleration Responses

In this paper, we present the method to estimate inelastic behavior of structures by wavelet transform. In the presented method, we focus on the singularity, which appears in acceleration responses when the restoring force of structures enters into an elastic region from a plastic region. And we confirm numerically and experimentally that we can estimate the inelastic excursions to the elastic region from the plastic region by performing the wavelet transform on the absolute acceleration response. The experiment is carried out using the five-story structural model installed by lead rubber bearings (LRBs) with hysteretic characteristics of restoring force. The experiment results show that wavelet transform makes it possible to estimate the inelastic excursions, when a non-stationary wave is inputted into the structure.