bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-Linear Time Domain Method to Predict Tube-to-Tube Support Plate Fretting Wear in Steam Generators
Authors: Burgess J. A. , Au-Yang M. K. , Chandler C. K.
Published: July 2008

Fretting-wear of nuclear heat exchanger equipment is addressed at the design stage to demonstrate that the tube and tube support plate components will meet their design life. AREVA has developed a method to predict the progression of fretting-wear using a combination of the predicted work-rates determined from the non-linear interaction of the tube and tube support plates caused by turbulence-induced vibration and the forces associated with fluid-elastic instability. The wear rate is then computed based upon the work-rate and the experimentally determined wear coefficient of the material pair. This solution is performed with a time domain analysis using a time history modal superposition method. Time history forcing functions are first obtained by the inverse Fourier transform of the power spectral density function used in classical turbulence-induced vibration analysis. The fluid-structure coupling force, which is dependent on the cross-flow velocity, is linearly superimposed onto the turbulence forcing function. The tube responses are then computed by direct integration in the time domain. The results of the analysis show that the highest work-rates occur at the design tube-to-tube support plate clearance configuration and become progressively lower over the life of the heat exchanger. The work-rates and the turbulence-induced vibration response of the tube are computed at several mid-life time steps based upon the increased tube-to-tube support plate clearances resulting from the tube wear.
Structural Dynamics and Response of Roof Tiles Under Wind Loading
Authors: Okamoto Satoru
Published: July 2008

A series of wind tunnel tests was conducted on the vibration and scattering behavior of full-sized model of roof tiles, which were used widely for roofings of Japanese wooden dwellings. This study has investigated the nature and source of the vibrating and scattering behavior of roof tiles with the aim of providing a better insight to the mechanism. The roof tiles were set up on the pitched roof in the downstream of the flow from the wind tunnel. The vibrations for the roof tiles were measured by the Laser Doppler Vibrometry and the accelerometer, and the practical natural frequencies of the roof tiles were analyzed by the impulse force hammer test method. The motions of the vibration and scattering were observed by the high-speed video camera. Based on the consideration on the results of the measurements, there is a basic mechanism which can lead to flow-induced vibrations of the roof tiles. This mechanism is similar to that of the so-called fluttering instability, which appears as the self-excited oscillation in the natural mode of the structure at the certain critical flow speed. The values of the frequencies for the oscillating relate to the values of natural frequencies of the vibration.
Passive Seismic Control Using Shape Memory Alloy Springs
Authors: Yamashita Yoshitaka , Masuda Arata , Sone Akira
Published: July 2008

In this paper, seismic response analysis is made both experimentally and numerically for a passive isolation device with pseudoelastic shape memory alloy (SMA) spring as a restoring force component. Thanks to the material nonliniarity and the geometrical nonliniarity, the SMA spring used in the device has well-defined softening, or “force limiting”, property that can suppress the acceleration response of the superstructure by limiting the seismic force transmitted from the ground. To illustrate how the presented device can suppress the acceleration response under the prescribed level, shaking table tests of a reduced-scale model of uniaxial isolator are carried out with seismic inputs appropriately scaled both in time and in amplitude. Then, a Preisach model of the SMA spring is constructed for the purpose of design study, and verified by comparing the simulated seismic responses with the experimental ones.
Evaluation of Non-Vibrating Utility Burner/Furnace Systems for Resistance to Thermoacoustic Oscillations
Authors: Eisinger Frantisek L. , Sullivan Robert E.
Published: July 2008

Six burner/furnace systems which operated successfully without vibration are evaluated for resistance to thermoacoustic oscillations. The evaluation is based on the Rijke and Sondhauss models representing the combined burner/furnace (cold/hot) thermoacoustic systems. Frequency differences between the lowest vulnerable furnace acoustic frequencies in the burner axial direction and those of the systems’ Rijke and Sondhauss frequencies are evaluated to check for resonances. Most importantly, the stability of the Rijke and Sondhauss models is checked against the published design stability diagram of Eisinger [1] and Eisinger and Sullivan [2]. It is shown that the resistance to thermoacoustic oscillations is adequately defined by the published design stability diagram to which the evaluated cases generally adhere. Once the system falls into the stable range, the frequency differences or resonances appear to play only a secondary role. It is concluded, however, that in conjunction with stability, the primary criterion, sufficient frequency separations shall also be maintained in the design process to preclude resonances. The paper provides sufficient details to aid the design engineers.
Experimental Study for Identifying Stiffness of Bridge Slab by Using Wavelet Transform
Authors: Imanishi Naoto , Sone Akira , Masuda Arata
Published: July 2008

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.
Effect of Acoustic Resonance on the Dynamic Lift Forces Acting on Two Tandem Cylinders in Cross-Flow
Authors: Mohany Atef , Ziada Samir
Published: July 2008

Direct measurement of the dynamic lift force for the case of two tandem cylinders in cross-flow during acoustic resonance is performed. Two spacing ratios inside the proximity interference region, L/D = 2.5 and 3, are considered. During the tests, the acoustic transverse-modes of the duct housing the cylinder are self-excited. In the absence of acoustic resonance, the measured dynamic lift coefficient agrees well with those reported in the literature. When the acoustic resonance is initiated, a drastic increase in the dynamic lift coefficient is observed, especially on the downstream cylinder. This is associated with abrupt changes in the phase between the lift forces and the acoustic pressure. The dynamic lift forces on both cylinders are also decomposed into in-phase and out-of-phase components, with respect to the resonant sound pressure. The lift force components for the downstream cylinder are found to be dominant. Moreover, the out-of-phase component of the lift force on the downstream cylinder is found to become negative over two different ranges of flow velocity and to virtually vanish between these two ranges. Acoustic resonance is therefore generated over two ranges of reduced velocity separated by a non-resonant range near the velocity of frequency coincidence. The out-of-phase lift component of the downstream cylinder is found to control the occurrence of acoustic resonance, whereas the in-phase lift component seems to cause slight variations in the acoustic resonance frequency.
Flow Excited Acoustic Resonance of Two Side-by-Side Cylinders in Cross Flow
Authors: Hanson Ronald , Mohany Atef , Ziada Samir
Published: July 2008

The aeroacoustic response of two side-by-side cylinders in cross-flow is investigated experimentally. In order to investigate the effect of the gap between the cylinders on the acoustic resonance mechanism, six spacing ratios between the cylinders have been investigated. These spacing ratios are in the range of T/D = 1.25 to 3, where D is the diameter of the cylinders and T is the center-to-center distance between them. Special attention is given to the bi-stable flow regime, which is reported in the literature for intermediate spacing ratios. During the tests, the acoustic cross-modes of the duct housing the cylinders are self-excited. For the intermediate spacing ratios, T/D = 1.25, 1.35, 1.46 and 1.75, two distinct vortex shedding frequencies at the off-resonance conditions are observed. These are associated with the wider and narrower wakes of the cylinders, as described in the literature. In this case, acoustic resonance occurs at a Strouhal number that is between those observed before the onset of resonance. In addition, the acoustic resonance synchronizes vortex shedding in the two wakes and thereby eliminates the bi-stable flow phenomenon. For large spacing ratios, T/D = 2.5 and 3, vortex shedding occurs at a single Strouhal number at which the acoustic resonance is initiated.
Seismic Control of Structure Using Energy Absorption by Elasto-Plastic Hysteresis Loop Characteristics
Authors: Aoki Shigeru
Published: July 2008

Reduction of seismic response is one of the most important problems of aseismic design of the structures. When the structures are subjected to excess seismic load, force-displacement relation has hysteresis loop characteristic. In this paper, seismic control of structure using energy absorption by elasto-plastic characteristic is examined by analytical method. As elasto-plastic characteristic, bilinear hysteresis loop is used. The equation of motion is equivalently linearized. The maximum value of the mean square value and absorbed energy are obtained for some values of the damping ratio, the natural period, the yield displacement and the stiffness ratio. It is found that the maximum value of the mean square value of the response decreases with the decrease of the yield displacement and the stiffness ratio. It is also found that the maximum value of the mean square value decreases with the increase of absorbed energy. The proposed method is applied to the secondary system and the same results are obtained.
Power Lines Real Time Monitoring
Authors: Lilien J. L. , Gue´rard S. , Godard B. , Feiereisen J. M. , Destine´ J.
Published: July 2008

Nowadays, the electricity demand keeps increasing. To adapt to this request, an increase in the production of electricity, as well as in transmission and distribution capacities is necessary. Whereas the construction of a new site of energy production is relatively easy, it is extremely long and difficult to manage to build new overhead lines. Consequently, electricity companies are searching for means to maximize the transport capacity of their lines while preserving the minimal distances to the ground and the mechanical reliability of the lines. Real time monitoring of the line ampacity is one of the means which make it possible to optimize the use of high voltage lines.
Numerical Simulation of a Non-Linear Coupled Fluid-Structure Problem With Implicit and Explicit Coupling Procedures
Authors: Sigrist Jean-Franc¸ois , Abouri Driss
Published: July 2008

The present paper deals with the numerical simulation of a non-linear coupled fluid-structure problem with finite element/finite volume coupled technique and mainly focus on the time coupling algorithm: the coupling procedure lies on a staggered explicit or implicit strategy. A simple coupled case is studied; namely a non-linear elastic beam coupled with an incompressible fluid with free surface effects. The structure problem is solved with a finite element approach. The nonlinear discrete structure problem is integrated in time with the non-linear Newmark scheme with a fixed-point procedure. The fluid problem is solved with a finite volume approach. The non-linear discrete fluid problem is solved with the PISO (Pressure Implicit by Splitting Operator) algorithm. The coupled problem is solved with two different approaches. At first, an explicit approach is proposed, based on a step by step alternate integration of the structure and fluid non-linear problems. As expected the method is found to be numerically dissipative and potentially unstable. An implicit approach is then proposed, using inner coupling iterations. The proposed algorithm is proved to be stable and less dissipative. Implicit and explicit approaches are presented. Numerical calculations are performed on the elementary studied case. Results are presented and compared for the two time-integration procedures, highlighting the numerical qualities of each procedure in terms of numerical damping, stability and precision.
Effect of Velocity Ratio on Vortex Shedding From a Short Stack
Authors: Adaramola M. S. , Oladeinde A. O. , Sumner D. , Bergstrom D. J.
Published: July 2008

The influence of the jet-to-cross-flow velocity ratio, R, on vortex shedding from a cylindrical stack of aspect ratio AR = 9 was investigated using hot-wire anemometry. The cross-flow Reynolds number was ReD = 2.3×104 and R was varied from 0 to 3. The stack was partially immersed in a flat-plate boundary layer, where the boundary layer thickness-to-height ratio at the location of the stack was δ/H = 0.5. In the downwash flow regime, when R < 0.7, a single Strouhal number (e.g., St = 0.167 at R = 0) was measured along the entire stack height. In the crosswind-dominated flow regime, when 0.7 ≤ R < 1.5, a higher Strouhal number was obtained (e.g., St = 0.185 at R = 1.0). In the transitional and jet-dominated flow regimes, a jump in Strouhal number (e.g., from St = 0.176 to 0.193 at R = 2.0), occurred within the flat-plate boundary layer. The power spectra showed that the shape and strength of the vortex shedding peak changed along the stack height. In general, the peak was more broad-banded near the base of the stack, became sharper and more distinct within the middle of the combined stack and jet wakes, and then reduced in strength in the jet wake and jet regions. In the transitional and jet-dominated flow regimes, the jump in Strouhal number was seen as a gradual change in dominance between two closely spaced peaks, with both peaks co-existing near the edge of the boundary layer.
Flow Excitation of Diametral Acoustic Modes of Axisymmetric Cavities
Authors: Awny Kareem , Ziada Samir
Published: July 2008

Flow-excited resonances of the acoustic diametral modes of a cylindrical pipe housing an axi-symmetric shallow cavity are investigated experimentally. The aeroacoustic response of the cavity-pipe combination is studied up to a Mach number of 0.4 and for several ratios of cavity length to its depth. Although the diametral modes do not have a preferred orientation because of the system axi-symmetry, they are found to be strongly excited by any of the first three instability modes of the cavity shear layer. Intense acoustic pressure levels, up to 170 dB, and wide lock-in resonance ranges have been observed. The acoustic pressure and its phase are measured along the cavity circumference to examine the orientation of the excited diametral modes within the un-preferential domain of the axi-symmetric cavity. Preliminary results suggest that the excited modes are stationary at low flow velocities, but they switch to spinning mode pattern at higher velocities.
Simplified Elasto-Plastic Response Analysis of Piping: Considering In-Plane, Out-of-Plane and the Mixed Bending of Elbow
Authors: Otani Akihito , Toyoda Syozaburo , Nakamura Izumi , Takada Hajime
Published: July 2008

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.
The Studies of the High Seismic Performance RC Shear Walls
Authors: Liao Wen-I. , Mo Yi-Lung
Published: July 2008

In order to improve the ductility of shear walls under earthquake loading, high seismic performance shear walls have been proposed to have steel bars in the same direction as the principal direction of applied stresses in the critical regions of shear walls. This paper presents the test results and model-based simulation of two shear walls under shake table excitation and two shear walls under reversed cyclic loading. Based on the experimental results, the tested shear walls with reinforcement oriented close to the principal tensile direction of applied stresses have greater ductility than that of the conventional shear wall. The model-based simulation based on the Cyclic Softened Member Model (CSMM) is performed and compared with the test results. The comparison shows that CSMM can well predict the seismic behaviors of the shear walls.
Cross-Flow Past a Pair of Staggered Cylinders With the Upstream Cylinder Subjected to a Transverse Harmonic Oscillation
Authors: Price Stuart J. , Pai¨doussis Michael P. , Krishnamoorthy Srikanth
Published: July 2008

The results of an experimental investigation are presented for the cross-flow past a pair of staggered circular cylinders, with the upstream cylinder being subject to forced harmonic oscillation transverse to the flow direction. Flow-visualization of the wake-formation region and hot-film measurements of the wake spectra are reported. Experiments were conducted in a water tunnel for Reynolds numbers, based on upstream velocity, U, and cylinder diameter, D, in the range 1440 ≤ Re ≤ 1680. Results are presented for the case where the longitudinal separation between cylinder centres (for the mean position of the upstream cylinder) is L/D = 2.0, with the transverse separation being T/D = 1.0. As shown by Sumner et al. [1] this configuration corresponds to either the gap vortex pairing and enveloping or gap vortex pairing, splitting and enveloping regimes. The results show that the oscillation of the upstream cylinder causes considerable modification of the flow patterns and regimes compared to what is obtained when the cylinder is fixed. In particular, depending on the frequency of oscillation of the upstream cylinder, sub- and super-harmonic resonances are obtained between the vortex formation frequency and oscillation frequency, as well as the usual fundamental lock-in. These resonances and accompanying wake regimes are examined in detail in the paper.
Flow Induced Acoustic Resonances of an Annular Duct With Co-Axial Side Branches
Authors: Arthurs David , Ziada Samir , Bravo Rafael
Published: July 2008

This paper investigates the aeroacoustic response of an annular duct with co-axial side branches, and examines the effect of several passive countermeasures. The investigated geometry is inspired by the design of the Roll Posts in the Rolls-Royce LiftSystem® engine, which is currently being developed for the Lockheed Martin Joint Strike Fighter aircraft. The effects of design parameters, such as diameter ratio, branch length ratio and thickness of the annular flow on the frequency and resonance intensity of the first acoustic mode are studied experimentally. Numerical simulations of the acoustic mode shapes and frequencies are also performed. The annular flow has been found to excite several acoustic modes, the strongest in all cases being the first acoustic mode, which consists of an antisymmetric quarter wavelength along the length of each branch. The ratios of the branch length and diameter, with respect to the main duct diameter, have been found to have strong effects on the frequency of the acoustic modes. The effects of passive measures to weaken the acoustic coupling between the co-axial branches have been also investigated. These include detuning the co-axial branches, by decreasing the length of one branch, and installing a pair of splitter plates in the annular flow duct.
Methods of Evaluating Vibration Induced Stress of Small-Bore Piping
Authors: Noda Michiyasu , Suzuki Michiaki , Maekawa Akira , Sasaki Toru , Suyama Takeshi , Fujita Katsuhisa
Published: July 2008

The vibration induced fatigue failure of small-bore piping is one of the common causes of failure trouble at nuclear power plants. This failure used to be prevented by calculating and screening vibration induced stresses using the accelerations measured by portable vibrometers, which are easy to handle in the working areas. Though the conventional evaluation method for calculating the vibration induced stress of small-bore piping often adopts the single-mass model, the stresses calculated by the model may be different from the actual ones because of being too simplified. So the purpose of this study is to develop the calculation methods of vibration induced stress for the screening preventing from fatigue failure troubles of small-bore piping using portable vibrometers. Firstly, for comparatively simple small-bore piping using the mock-up model simulating actual simple small-bore piping, shaking table experiments are conducted using sine wave and the field response wave measured on-site. By comparing the vibration induced stresses measured by the strain gauges and calculated using the accelerations, at first the validity of a single-mass model was conducted, and then the evaluation of a two-mass model developed as an improvement calculation model was conducted. As results of comparison, the single-mass model was found to be useful only for screening although the calculated stresses had the deviations and the tendency of an underestimate, and the two-mass model was found to be utilized as better screening because the calculated stresses had better agreement with the measured ones. Next, for small-bore piping with typical pattern configurations consisted of several masses and supports, the model considering the supports and the center of gravity being out of pipe centerline was developed and proposed. Finally, for the more complex small-bore piping with general piping configurations consisted of many bends, branches or joints, the method based on the finite element method analysis and the values measured by a portable vibrometer was developed. In this method, the analytical model was optimized, and the stresses were obtained considering vibration modes as dynamically. Judging from the results checked by numerical analysis, this method was found to be accuracy enough to use for screening, because the analytical model was optimized smoothly and the estimated stresses became to be from 1.1 to 1.4 times to the original true ones that corresponds to the actual ones measured in site.
Spectrographic Analysis for the Modal Testing of Nonlinear Aeroelastic Systems
Authors: Marsden Catharine C. , Price Stuart J.
Published: July 2008

The spectrograph is a signal processing tool often used for the frequency domain analysis of time-varying signals. When the signal to be analyzed is a function of time, the spectrograph represents the frequency content of the signal as a sequence of power spectra that change with time. In this paper, the usefulness of the technique is demonstrated in its application to the analysis of the time history response of a nonlinear aeroelastic system. The aeroelastic system is modeled analytically as a two-dimensional, rigid airfoil section free to move in both the bending and pitching directions and possessing a rigid flap. The airfoil is mounted by torsional and translational springs attached at the elastic axis, and the flap is used to provide the forcing input to the system. The nonlinear system is obtained by introducing a freeplay type of nonlinearity in the pitch degree-of-freedom restoring moment. The airfoil is immersed in an aerodynamic flow environment, modeled using incompressible thin airfoil theory for unsteady oscillatory motion. The equations of motion are solved using a fourth-order Runge-Kutta numerical integration technique to provide time-history solutions of the response of the airfoil in the pitch and plunge directions. Time-histories are obtained for the nonlinear responses of the linear and nonlinear aeroelastic systems to a sine-sweep input. The time-histories are analyzed using the spectrographic technique, and the frequency content of the response is plotted directly as a function of the input frequency. Results show that the combination of the sine-sweep input with the spectrographic analysis permits a unique insight into the behaviour of the nonlinear system with a minimum of testing. It is shown that the frequency of the nonlinear system response is a function of the input frequency and one other characteristic frequency that can be associated with the limit cycle oscillations of the same nonlinear system subject to a transient input.
The Material Behavior and Isolation Benefits of Ball Pendulum System
Authors: Tsai C. S. , Tsou Ching-Pei , Lin Yung-Chang , Chen Mei-Ju , Chen Wen-Shin
Published: July 2008

Earthquake ground motions often result in significant seismic disasters. Strong ground motions will not only cause damage, but may also cause the collapse of structures. People have to face up the suffering from the earthquake damage, and the indirect loss which may be more serious than the damage itself. For example, the antique breaks in museum, and the equipment damages in hi-tech industries are often in huge loss. Therefore, in addition to promoting the earthquake-resistant capacity of a structure, it is also important to ensure the safety of the ancient valuable objects and the instruments in structures. For this reason, this study is aimed at a new damped rolling type base isolation system named the ball pendulum system (BPS) to be installed under the motion sensitive equipment and proceeding all related studies. The isolation device can isolate earthquake from buildings or equipments in any direction by rolling motions and damping materials. This study has conducted a series of component tests and shaking table tests for examining the behaviors of materials and earthquake proof benefits. From the experiment results, it is found that this device can reduce more than 80% of acceleration response under earthquakes with peak ground acceleration of 450 gal. So, the new rolling isolation system with a damping material can be recognized as a feasible and promising way in mitigating the seismic response of equipment.
Application of Optimal Design Methodology on the Seismic Design of Piping Systems Supported by Elasto-Plastic Dampers
Authors: Ito Tomohiro , Michiue Masashi , Fujita Katsuhisa
Published: July 2008

In this study, the optimal seismic design methodology which can consider the structural integrity of both the piping systems and the elasto-plastic supporting devices are developed. This methodology employs genetic algorithm and can search the optimal conditions such as the supporting location, the capacity and stiffness of the supporting devices. The lead extrusion damper is treated here as a typical elasto-plastic damper. Four kinds of evaluation functions; stress of piping systems, energy absorption, lead melt of dampers and energy absorbing balance are considered and each optimal condition is clarified and discussed. As the results, it is found that the optimal seismic design methodology proposed here is very effective and can be applied to the actual seismic designs for the piping systems supported by the elasto-plastic dampers, and can be also applied to the piping systems exposed to the actual earthquake waves which have various frequency components and the piping systems with a heavy local mass.
Nonlinear Vibration Response of a Cylindrical Water Storage Tank Caused by Coupling Effect Between Beam-Type Vibration and Oval-Type Vibration: Part 1 — Vibration Experiment
Authors: Maekawa Akira , Suzuki Michiaki , Fujita Katsuhisa
Published: July 2008

In this study, a vibration experiment with a reduced scale model of a large-size cylindrical water storage tank has been performed in order to investigate the nonlinear vibration responses of the cylindrical tank when the beam-type vibration and the oval-type vibration are coupled. In the vibration experiment, a sinusoidal sweep test was performed by using a shaking table on the reduced scale model of the cylindrical water storage tank filled with water to the 95% level. The test was conducted by varying the input acceleration from smaller to larger input in several steps to identify the vibration modes and evaluate the vibration behaviors of the beam-type vibration and the oval-type vibration. As a result, the resonance curves showed that the resonance frequency shifted to the lower frequency region and the response magnification factor became smaller when the input acceleration level became higher. When the magnitude of the input acceleration increased furthermore, the resonance curves were changed to be duller from the sharp peak and the resonance points became unclear. The measured displacements and strains of the sidewall of the model tank showed that the oval-type vibration was excited in the vicinity of the beam-type resonance frequency and that the amplitude of the oval-type vibration increased too significant to be ignored when larger input was applied. It was verified that the oval-type vibration with a subharmonic resonance of order one-half was excited when larger input was applied. This phenomenon was not observed when small input was applied. This shows that the vibration behaviors caused by coupling effect between beam-type vibration and oval-type vibration depend on the magnitude of input excitation. From these results, it can be assumed that the oval-type vibration is closely related to the nonlinear vibration response phenomena of a cylindrical water storage tank.
A Design Overview for the Engineering of an Onshore Extension of the Natural Gas Transmission System (NGTS) in the Northern Greece
Authors: Kokavessis Nikos K. , Anagnostidis George S.
Published: July 2008

This paper describes the framework developed for the geological investigation and crossings design of an onshore pipeline project being implemented in Northern Greece. Scientific and technological concepts for geological investigation are based on the results provided by local engineering companies and research institutes specialized in applied geotechnical and geophysical research. The basics of the crossings design are developed such as, the evaluation of the suitable pipe wall thickness and the design of the technically essential pipeline encroachments with railways, roads, channels, rivers, underground utilities, active faults and soils prone to liquefaction. Special reference has made to the seismic hazard assessment required for evaluation of the seismic characteristics at crossing areas, as well as the finite element study performed to define pipeline stresses and strains developing in active fault areas. Finally the severe seismic conditions of Greece entailing particular design requirements and protection measures for the buried pipeline are demonstrated.
A Dynamic Behavior of the Frame Structure Allows the Columns to Uplift
Authors: Mikoshiba Tadashi , Minowa Chikahiro , Sato Takanori , Shao Li , Chiba Toshio
Published: July 2008

To investigate the dynamic behavior of the frame structure which allows the columns to uplift, a shaking table test was conducted by using a 4-story frame structure model. The effect of the absence or presence of the uplift and the damper in the column on the dynamic behavior of the structure were clarified. Dynamic response of the traditional frame structure with damper was compared to that of structure with damper in the columns. By using damper in the columns, the seismic impact of the structure was controlled. It is confirmed that the frame structure which is allowed the columns to uplift has an adequate seismic ability.
Seismic Qualification of Nuclear Plant Components Using PSHA-Based Spectra
Authors: Bhargava Divakar , Dwivedy Keshab K.
Published: July 2008

With the prospect of a revival of nuclear power industry after a long hiatus, there is an emphasis on designing the next breed of nuclear plants in the US using seismic spectra derived from a probabilistic seismic hazard analysis (PSHA). The methods available in guidance documents to establish Safe Shutdown Earthquake (SSE) spectral shapes at a site using PSHA invariably show that the risk-based spectra have high peaks, high zero period accelerations (ZPA), and significant energy content at higher frequencies when compared to the previous deterministic spectra at the same site. It is well known that earthquakes in Central and Eastern United States (CEUS) will typically contain some high frequency energy. While the early site permit applications and reactor supplier’s design certifications for new plants are expected to use the PSHA-based spectra for their seismic design, existing nuclear plants designed to deterministic spectra may also need to be reviewed for the probabilistic seismic spectra at their sites. This paper considers the implications of a probabilistic hazard spectrum for the seismic qualification of equipment and components for an operating plant and suggests a procedure for conducting a review. Amplification of ground spectra through nuclear plant structures and other intervening systems such as a piping system or an electrical cabinet are calculated using conventional linear dynamic analysis methods in much the same way as was done in the past for high frequency hydrodynamic loads in the Boiling Water Reactor (BWR) containments. Electrical and mechanical equipment, including devices such as relays that may be sensitive to high frequency vibratory loads are evaluated. While the spectral peaks at equipment mounting location are high at higher frequencies, the damage potential is considerably low. For an existing plant, a limited review of the previous seismic analyses and testing with the redefined seismic spectra concludes that the previous design has sufficient seismic margin. Implications of the PSHA based spectra for seismic qualification of equipment for new plants is not expected to be as severe as once believed. Additional assurance of safety can be obtained by updating or conducting a plant-specific seismic probabilistic risk analysis.
A Decrement Method for Quantifying Nonlinear and Linear Damping in Multi-Degree of Freedom Systems
Authors: Meskell Craig
Published: July 2008

A method is presented which can estimate the linear and non-linear damping parameters in a lightly damped multi-degree of freedom system. This in effect allows the system to be decomposed into a set of single degree of freedom nonlinear systems. Only a single response measurement from a free decay test is required as input. This ensures that the magnitude of the damping parameters is not compromised by phase distortion between measurements. The response is band-pass filtered in the time domain, with the pass band centered on each of the natural frequencies. This provides a set of free response measurements, one for each mode. However, it does introduce a restriction in that the natural frequencies must be distinct and separated somewhat. The instantaneous energy of each trace is used to describe the long-term evolution of the mode. Practically this is achieved by using only the peak amplitudes in each period. In this way the stiffness and inertial forces are effectively ignored, and only the damping forces are considered. For this reason, the method is not unlike the familiar decrement method, which can be used to estimate the viscous damping in linear systems. The method is developed in the context of a weakly non-linear, lightly damping two degree-of-freedom system, with both linear and Coulomb damping. Simulated response data is used to demonstrate the accuracy of the technique.
Detailed and Simplified Approaches for Inelastic Seismic Analysis of Piping Systems
Authors: Iijima Tadashi , Sakakida Takaaki , Ono Satoru
Published: July 2008

We examined two approaches for predicting the inelastic responses of piping systems. The first enabled us to evaluate accurate responses using nonlinear time-history analysis. We focused on a material model in this approach. Plastic deformation might exhibit a cyclic-hardening effect, which is dependent on the strain ranges, and this hardening affects the dynamic responses of piping systems. Therefore, we improved the hardening model developed by Ohno and Wang (OW model), which is one of the most sophisticated models for producing kinematic hardening behavior. We modified it to produce cyclic-hardening behavior dependent on strain ranges. The second was a simplified approach to evaluate inelastic responses without time-consuming time-history analysis. We developed a tool using equivalent linearization. The tool used analysis techniques including a model of elastic beam elements using flexibility factors for pipe elbows, and modal response spectrum analysis. Equivalent linearization made it possible to apply modal analysis to inelastic analysis. We demonstrated how applicable the approaches were by conducting test simulations.
Estimate of Inelastic Excursions in Hysteretic Structures by Wavelet Transform of Acceleration Responses
Authors: Hashimoto Yuito , Masuda Arata , Sone Akira
Published: July 2008

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.
A Study on the Damage Degree of Shield Tunnels Submerged in Overburden Soil During the Thrust Fault Offset
Authors: Lin Ming-Lang , Jeng Fu-Shu , Huang Tisan-Hwei , Chung Chun-Fu , Lee Hung-Hwei
Published: July 2008

When an under-lain thrust fault slips, especially triggered by earthquakes, the overburden soil may deform and fail so that a fault zone also develops inwardly. The research about the deformation and the failure of the overburden soil is an essential issue to evaluating the safety of ground or underground structures near the potential faulted zone. In this study, a MRT tunnel, closed to a thrust fault and fault dip 60 degree, is considered, both of the sandbox experiment and the numerical analyses are adopted to discuss the damage degree of a tunnel submerged in an overburden soil under the thrust faulting. In the numerical analyses, a small-scale model, simulation of the sandbox, is justified according to the experimental results and used to discuss the base behavior of the overburden soil. In addition, a full-scale model is used to evaluate the damage degree of tunnel segments by defining a dangerous factor. Moreover, considering the real behaviors of sand particles, the distinct element method is adopted as well. In the sandbox experiment, the results indicate that the development of the shear zone was apparently hindered by the existence of a model tunnel near the fault tip, and induced significant deformation of the tunnel. In addition, the results from numerical analyses, the finite element method and the distinct element method, are similar to the experimental results. The numerical analysis results of the full-scale model indicate that the damage degree is increased while the tunnel is close to the fault tip, and the footing wall is more dangerous than the hanging wall. The defined dangerous factor is able to reflect the damage degree of the tunnel. In the distinct element analysis, the full-scale model, it can be observed that a fault zone extends from the fault tip to the ground surface, but discussions on the distribution of stress and moment in the tunnel are not included and will be considered in the future study.
Robust Design Method of Multi-Degree-of-Freedom Passive Tuned Mass Damper by Control Theory
Authors: Iba Daisuke , Masuda Arata , Sone Akira
Published: July 2008

This paper proposes a design method of a multi degree of freedom passive tuned mass damper with robust performance. In this study, the passive tuned mass damper is designed from the view of feedback control theory. Design parameters of the general passive tuned mass damper can be thought to be a feedback gain, and designed by replacing the design problem of the passive tuned mass damper with the output feedback control problem. Moreover, for giving the tuned mass damper robustness, an extended model is constructed by two main systems that have maximum and minimum natural frequencies in the given variable domain of parameters, and one static output feedback H∞ controller reduces the maximum value of frequency response of the extended plant. In this paper, it was confirmed to be able to design the single-degree-of-freedom tuned mass damper with robustness by this method. Moreover, this method was enhanced to the design problem of the multi-degree-of-freedom tuned mass damper that was placed on the multi-degree-of-freedom vibration system, and finally a numerical simulation confirmed the effectiveness.
Symmetric Vortex Shedding From a Circular Cylinder Under Periodic Flow Forcing
Authors: Konstantinidis E. , Balabani S.
Published: July 2008

This paper describes an experimental study of the near wake of a circular cylinder subjected to streamwise flow forcing. The wake field is examined by PIV and LDV for excitation frequencies in which symmetric shedding is likely. The results show that symmetric formation of vortex pairs occurs close to the cylinder synchronized with the oscillatory component of the flow. The symmetric mode rapidly breaks down and gives rise to an antisymmetric arrangement of single vortices further downstream. The number of cycles for which the symmetrical vortices persist in the near wake is a probabilistic function of the excitation frequency and forcing amplitude. Details of the related wake kinematics and frequencies are shown and the findings are discussed in relation to symmetric vortex formation occurring in self-excited streamwise oscillations.
Study of Cycloidal Pendulum Dynamic Absorber for Vibration Control of Structures
Authors: Komatsuzaki Toshihiko , Iwata Yoshio
Published: July 2008

The dynamic absorber has been widely used for suppressing vibration in structures. In practical application, the optimal tuned absorbers are designed and used in terms of natural frequency and additional damping so that resultant frequency response may become fully reduced. Among various types of dynamic absorber, the pendulum type is preferable due to its simple constitution and performance reliability. However, damping performance of ordinal pendulum system may be influenced by levels of excitation because of intrinsic nonlinearity in system which leads to slight change in natural frequency. The present paper deals with a study of new type pendulum dynamic absorber. It is known that pendulum moving along cycloidal curve strictly keeps uniform period. Both analytical and experimental investigations show that a strict optimal damping condition can be satisfied in cycloidal pendulum damper, in conjunction with better damping performance compared with normal pendulum.
Seismic Behavior of High-Tech Facility Isolated With a Trench Friction Pendulum System
Authors: Tsai C. S. , Lin Yung-Chang , Chen Wen-Shin
Published: July 2008

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.
Component Tests and Simulation of Advanced Buckling Restrained Braces
Authors: Tsai C. S. , Chen Wen-Shin , Chen Bo-Jen
Published: July 2008

Recently, the earthquake proof technology has been acknowledged to be able to ensure the safety of the structures effectively during earthquakes. In this paper, two advanced buckling restrained braces (BRBs) that include multi-curved reinforced BRB and simplified reinforced BRB are presented. These two braces not only improve the disadvantages of traditional buckling restrained braces but also are more economic than the traditional ones. In order to understand the behaviors of advanced buckling restrained braces, the component tests of the advanced buckling restrained braces were carried out in the Department of Civil Engineering, Feng Chia University, Taichung, Taiwan. The experimental results illustrate that the behaviors of the advanced buckling restrained braces were very stable, as well as the maximum tension forces are close to the maximum compression forces. Furthermore, the Wen’s model in an increment form was utilized to simulate the behaviors of the advanced buckling restrained braces under cyclic loadings. The comparison between the experimental and numerical results shows that the mathematical model could simulate the behaviors of the advanced BRBs well.
Effects of Local Site Conditions on Seismic Responses of a Reactor Containment Structure
Authors: Chen Jian-Chu
Published: July 2008

The effect of local site conditions on soil-structure interaction (SSI) responses of a pressurized water reactor (PWR) containment building founded on different site conditions was investigated using substructure SSI analysis procedure. The structure was analyzed for both surface and embedded foundation conditions for each site with an exception for one half-space site with shear wave velocity 5000 fps. Only the surface foundation was analyzed for this very stiff half-space site. A total of 23 analyses are presented in this paper. Responses including peak ground accelerations and response spectra at selected locations were compared. The results indicate that the local site conditions have a significant influence on SSI response particularly for the structure founded on the surface of shallow soil deposit overlying competent rock. For thick soil sites having shear wave velocity larger than 1000 fps and having soil thickness greater than 3.5 times the radius of the structure, the effect of the soil thickness is not important.