A Blade Loss Response Spectrum for Flexible Rotor Systems

1985 ◽  
Vol 107 (1) ◽  
pp. 197-204 ◽  
Author(s):  
M. Alam ◽  
H. D. Nelson
Keyword(s):  
Response Spectrum ◽  
Damping Ratio ◽  
Response Spectra ◽  
Flexible Rotor ◽  
Peak Displacement ◽  
Rotor Systems ◽  
Displacement Response ◽  
Modal Damping Ratio ◽  
Whirl Speed ◽  
Blade Loss

A shock spectrum procedure is developed to estimate the peak displacement response of linear flexible rotor-bearing systems subjected to a step change in unbalance (i.e., a blade loss). A progressive and a retrograde response spectrum are established. These blade loss response spectra are expressed in a unique non-dimensional form and are functions of the modal damping ratio and the ratio of rotor spin speed to modal damped whirl speed. Modal decomposition using complex modes is utilized to make use of the unique feature of the spectra for the calculation of the peak blade loss displacement response of the rotor system. The procedure is applied to three example systems using several modal superposition strategies. The results of each are compared to true peak displacements obtained by a separate transient response program.

scholarly journals A Multi-Objective Ground Motion Selection Approach Matching the Acceleration and Displacement Response Spectra

2018 ◽  
Vol 10 (12) ◽  
pp. 4659 ◽  
Author(s):  
Yabin Chen ◽  
Longjun Xu ◽  
Xingji Zhu ◽  
Hao Liu
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Structural Response ◽  
Response Spectra ◽  
Computationally Efficient ◽  
Ground Motion Selection ◽  
Displacement Response ◽  
Rc Frames ◽  
Selection Approach ◽  
Displacement Response Spectra

For seismic resilience-based design (RBD), a selection of recorded time histories for dynamic structural analysis is usually required. In order to make individual structures and communities regain their target functions as promptly as possible, uncertainty of the structural response estimates is in great need of reduction. The ground motion (GM) selection based on a single target response spectrum, such as acceleration or displacement response spectrum, would bias structural response estimates leading significant uncertainty, even though response spectrum variance is taken into account. In addition, resilience of an individual structure is not governed by its own performance, but depends severely on the performance of other systems in the same community. Thus, evaluation of resilience of a community using records matching target spectrum at whole periods would be reasonable because the fundamental periods of systems in the community may be varied. This paper presents a GM selection approach based on a probabilistic framework to find an optimal set of records to match multiple target spectra, including acceleration and displacement response spectra. Two major steps are included in that framework. Generation of multiple sub-spectra from target displacement response spectrum for selecting sets of GMs was proposed as the first step. Likewise, the process as genetic algorithm (GA), evolvement of individuals previously generated, is the second step, rather than using crossover and mutation techniques. A novel technique improving the match between acceleration response spectra of samples and targets is proposed as the second evolvement step. It is proved computationally efficient for the proposed algorithm by comparing with two developed GM selection algorithms. Finally, the proposed algorithm is applied to select GM records according to seismic codes for analysis of four archetype reinforced concrete (RC) frames aiming to evaluate the influence of GM selection considering two design response spectra on structural responses. The implications of design response spectra especially the displacement response spectrum and GM selection algorithm are summarized.

Study on Relationship of Seismic and Pseudo Response Spectrums

2012 ◽  
Vol 238 ◽  
pp. 844-847
Author(s):  
Gong Lian Chen ◽  
Wen Feng Liu ◽  
Gang Li
Keyword(s):  
Design Theory ◽  
Seismic Waves ◽  
Response Spectrum ◽  
Response Spectra ◽  
The Real ◽  
Displacement Response ◽  
Dynamic Relationship ◽  
Performance Based Seismic Design ◽  
The Difference ◽  
Velocity Response Spectrum

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.

scholarly journals Preliminary results of ground-motion characteristics

2012 ◽  
Vol 55 (4) ◽  
Author(s):  
Francesca Bozzoni ◽  
Carlo Giovanni Lai ◽  
Laura Scandella
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Response Spectrum ◽  
Field Tests ◽  
Response Spectra ◽  
Ground Acceleration ◽  
Preliminary Results ◽  
Emilia Earthquake ◽  
Particle Orbit ◽  
2012 Emilia Earthquake

The preliminary results are presented herein for the engineering applications of the characteristics of the ground motion induced by the May 20, 2012, Emilia earthquake. Shake maps are computed to provide estimates of the spatial distribution of the induced ground motion. The signals recorded at the Mirandola (MRN) station, the closest to the epicenter, have been processed to obtain acceleration, velocity and displacement response spectra. Ground-motion parameters from the MRN recordings are compared with the corresponding estimates from recent ground-motion prediction equations, and with the spectra prescribed by the current Italian Building Code for different return periods. The records from the MRN station are used to plot the particle orbit (hodogram) described by the waveform. The availability of results from geotechnical field tests that were performed at a few sites in the Municipality of Mirandola prior to this earthquake of May 2012 has allowed preliminary assessment of the ground response. The amplification effects at Mirandola are estimated using fully stochastic site-response analyses. The seismic input comprises seven actual records that are compatible with the Italian code-based spectrum that refers to a 475-year return period. The computed acceleration response spectrum and the associated dispersion are compared to the spectra calculated from the recordings of the MRN station. Good agreement is obtained for periods up to 1 s, especially for the peak ground acceleration. For the other periods, the spectral acceleration of the MRN recordings exceeds that of the computed spectra.<br />

Research on Seismic Displacement Response of Cable Stayed Bridge without Back Stays

2014 ◽  
Vol 919-921 ◽  
pp. 1039-1042
Author(s):  
Liang Lv ◽  
Bin Liang ◽  
Wen Sheng Wang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Seismic Wave ◽  
Natural Vibration ◽  
Peak Displacement ◽  
Seismic Displacement ◽  
Displacement Response ◽  
Cable Stayed Bridge ◽  
Element Method ◽  
Design And Construction

Seismic displacement response of cable stayed bridge without back stays was studied in this paper. Based on the cable stayed bridge without back stays on Zhenshui Road in Xinmi City, finite element method (FEM) was applied to calculate and analyze natural vibration and peak displacement response of the structure. The results show that with regard to mid-span and consolidation of pier and main tower, uniaxial seismic wave input results in peak displacement response of corresponding direction is bigger than that of any other direction. Peak displacement response of the top of the main tower is bigger than those of mid-span and consolidation of pier and main tower in any seismic wave input cases, which indicates that the top of the tower needs to be focused in the process of design and construction. Seismic wave along triaxial direction has the biggest impact on the structure. Keywords: cable stayed bridge without back stays; seismic displacement response; seismic wave input; peak displacement response

A Virtual Bearing Method for Optimal Bearing Placement of Flexible Rotor Systems

2017 ◽  
Author(s):  
Shibing Liu ◽  
Bingen Yang
Keyword(s):  
Optimization Problem ◽  
Optimization Method ◽  
Rotor System ◽  
Problem Solution ◽  
Flexible Rotor ◽  
Rotor Systems ◽  
Real Coded Genetic Algorithm ◽  
Minimum Number ◽  
Distributed Transfer Function ◽  
Flexible Rotor Systems

Flexible multistage rotor systems have a variety of engineering applications. Vibration optimization is important to the improvement of performance and reliability for this type of rotor systems. Filling a technical gap in the literature, this paper presents a virtual bearing method for optimal bearing placement that minimizes the vibration amplitude of a flexible rotor system with a minimum number of bearings. In the development, a distributed transfer function formulation is used to define the optimization problem. Solution of the optimization problem by a real-coded genetic algorithm yields the locations and dynamic coefficients of bearings, by which the prescribed operational requirements for the rotor system are satisfied. A numerical example shows that the proposed optimization method is efficient and accurate, and is useful in preliminary design of a new rotor system with the number of bearings unforeknown.

Response spectral matching of horizontal ground motion components to an orientation-independent spectrum (RotDnn)

2020 ◽  
pp. 875529302097098
Author(s):  
Luis A Montejo
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Time History ◽  
Response Spectra ◽  
Major Axis ◽  
Component Level ◽  
Nonlinear Characteristics ◽  
Target Spectrum ◽  
Horizontal Ground Motion ◽  
Median Spectrum

This article presents a methodology to spectrally match two horizontal ground motion components to an orientation-independent target spectrum (RotDnn). The algorithm is based on the continuous wavelet transform decomposition and iterative manipulation of the two horizontal components of a seed record. The numerical examples presented follow current ASCE/SEI 7 specifications and therefore maximum-direction spectra (RotD100) are used as target for the match. However, the proposed methodology can be used to match other RotDnn spectra, like the median spectrum (RotD50). It is shown that with the proposed methodology the resulting RotDnn from the modified horizontal components closely match the smooth target RotDnn spectrum, while the response spectrum for each horizontal component continue to exhibit a realistic jagged behavior. The response spectra variability at the component level within suites of spectrally matched motions was found to be of the same order than the variability measured in suites composed of amplitude scaled records. Moreover, the spectrally matched records generated preserved most of the characteristics of the seed records, including the nonlinear characteristics of the time history traces and the period-dependent major axis orientations.

Structural behaviour of water sloshing damper with embossments subject to random excitation

2004 ◽  
Vol 31 (1) ◽  
pp. 120-132 ◽  
Author(s):  
Young-Kyu Ju
Keyword(s):  
Standard Deviation ◽  
Vibration Control ◽  
Structural Model ◽  
Structural Characteristics ◽  
Damping Ratio ◽  
Tall Buildings ◽  
Random Excitation ◽  
Water Tank ◽  
Structural Behaviour ◽  
Peak Displacement

To improve the serviceability of tall buildings, several types of vibration control systems have been developed. The tuned liquid damper (TLD) has advantages, such as simple adjustment of natural frequency, easy installation, and low maintenance. Since water tanks at the top of tall buildings can be directly modeled as a TLD system, it is more practical than any other vibration control system in Korea. Since most of the tanks in Korea have embossments on the wall, the structural characteristics are different from those of tanks used in other countries. As the damping ratio of the TLD depends on several factors, such as the magnitude and frequency of applied load, the shape of the tank, wall roughness, and so forth, it is difficult to evaluate the control performance of the tank exactly. In this study, the characteristics of the water sloshing damper with embossments (WSDE) are evaluated and the equation for equivalent damping ratio is proposed. To clarify the damping effect of a high-rise building with a damping device subject to random excitation, an experiment of a coupled structural model with a water tank was conducted. The parameters were mass ratio of water to model structure, number of wire screens, and shape factor of the water tank. The peak displacement, acceleration response, and standard deviation of the experimental results are analyzed. The coupled structural model with a water tank shows lower maximum and standard deviation responses than those of the structural model alone.Key words: water sloshing damper with embossment, vibration control, structural test, tall buildings.

Analytical Determination of Shock Response Spectra for an Impulse-Loaded Proportionally Damped System

Volume 1 ◽  
2004 ◽  
Author(s):  
R. David Hampton ◽  
Nathan S. Wiedenman ◽  
Ting H. Li
Keyword(s):  
Transient Response ◽  
Shock Loading ◽  
Response Spectrum ◽  
Response Spectra ◽  
Analytical Determination ◽  
System Response ◽  
Mechanical Shock ◽  
Shock Response ◽  
Mass Spring ◽  
The Impact

Many military systems must be capable of sustained operation in the face of mechanical shocks due to projectile or other impacts. The most widely used method of quantifying a system’s vibratory transient response to shock loading is called the shock response spectrum (SRS). The system response for which the SRS is to be determined can be due, physically, either to a collocated or to a noncollocated shock loading. Taking into account both possibilities, one can define the SRS as follows: the SRS presents graphically the maximum transient response (output) of an imaginary ideal mass-spring-damper system at one point on a flexible structure, to a particular mechanical shock (input) applied to an arbitrary (perhaps noncollocated) point on the structure, as a function of the natural frequency of the imaginary mass-spring-damper system. For a response point sufficiently distant from the impact area, many Army platforms (such as vehicles) can be accurately treated as linear systems with proportional damping. In such cases the output due to an impulsive mechanical-shock input can be decomposed into exponentially decaying sinusoidal components, using normal-mode orthogonalization. Given a shock-induced loading comprising such components, this paper provides analytical expressions for the various common SRS forms. The analytical approach to SRS-determination can serve as a verification of, or an alternative to, the numerical approaches in current use for such systems. No numerical convolution is required, because the convolution integrals have already been accomplished analytically (and exactly), with the results incorporated into the algebraic expressions for the respective SRS forms.

scholarly journals Design Earthquake Response Spectrum Affected by Shallow Soil Deposit

2019 ◽  
Vol 2019 ◽  
pp. 1-18 ◽  
Author(s):  
Dong-Kwan Kim ◽  
Hong-Gun Park ◽  
Chang-Guk Sun
Keyword(s):  
Soil Depth ◽  
Site Response ◽  
Response Spectrum ◽  
Soft Soil ◽  
Response Spectra ◽  
Earthquake Response ◽  
Ground Acceleration ◽  
Site Class ◽  
Shallow Soil ◽  
Short Period

Site response analyses were performed to investigate the earthquake response of structures with shallow soil depth conditions in Korea. The analysis parameters included the properties of soft soil deposits at 487 sites, input earthquake accelerations, and peak ground-acceleration levels. The response spectra resulting from numerical analyses were compared with the design response spectra (DRS) specified in the 2015 International Building Code. The results showed that the earthquake motion of shallow soft soil was significantly different from that of deep soft soil, which was the basis of the IBC DRS. The responses of the structures were amplified when their dynamic periods were close to those of the site. In the case of sites with dynamic periods less than 0.4 s, the spectral accelerations of short-period structures were greater than those of the DRS corresponding to the site class specified in IBC 2015. On the basis of these results, a new form of DRS and soil factors are proposed.

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