Amplification factors in shock-turbulence interactions: Effect of shock thickness

2012 ◽  
Vol 24 (1) ◽  
pp. 011705 ◽  
Author(s):  
Diego A. Donzis
Keyword(s):  
Amplification Factors ◽  
Shock Thickness

scholarly journals Checking the site categorization criteria and amplification factors of the 2021 draft of Eurocode 8 Part 1–1

2021 ◽  
Author(s):  
Roberto Paolucci ◽  
Mauro Aimar ◽  
Andrea Ciancimino ◽  
Marco Dotti ◽  
Sebastiano Foti ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Shear Wave ◽  
Ground Motion ◽  
Shear Wave Velocity ◽  
Soft Soil ◽  
Site Amplification ◽  
Soil Conditions ◽  
Eurocode 8 ◽  
Site Specific ◽  
Amplification Factors

AbstractIn this paper the site categorization criteria and the corresponding site amplification factors proposed in the 2021 draft of Part 1 of Eurocode 8 (2021-draft, CEN/TC250/SC8 Working Draft N1017) are first introduced and compared with the current version of Eurocode 8, as well as with site amplification factors from recent empirical ground motion prediction equations. Afterwards, these values are checked by two approaches. First, a wide dataset of strong motion records is built, where recording stations are classified according to 2021-draft, and the spectral amplifications are empirically estimated computing the site-to-site residuals from regional and global ground motion models for reference rock conditions. Second, a comprehensive parametric numerical study of one-dimensional (1D) site amplification is carried out, based on randomly generated shear-wave velocity profiles, classified according to the new criteria. A reasonably good agreement is found by both approaches. The most relevant discrepancies occur for the shallow soft soil conditions (soil category E) that, owing to the complex interaction of shear wave velocity, soil deposit thickness and frequency range of the excitation, show the largest scatter both in terms of records and of 1D numerical simulations. Furthermore, 1D numerical simulations for soft soil conditions tend to provide lower site amplification factors than 2021-draft, as well as lower than the corresponding site-to-site residuals from records, because of higher impact of non-linear (NL) site effects in the simulations. A site-specific study on NL effects at three KiK-net stations with a significantly large amount of high-intensity recorded ground motions gives support to the 2021-draft NL reduction factors, although the very limited number of recording stations allowing such analysis prevents deriving more general implications. In the presence of such controversial arguments, it is reasonable that a standard should adopt a prudent solution, with a limited reduction of the site amplification factors to account for NL soil response, while leaving the possibility to carry out site-specific estimations of such factors when sufficient information is available to model the ground strain dependency of local soil properties.

scholarly journals Study on dynamic characteristics of leaf spring system in vibration screen

2021 ◽  
pp. 146134842110229
Author(s):  
Jiacheng Zhou ◽  
Chao Hu ◽  
Ziqiu Wang ◽  
Zhengfa Ren ◽  
Xiaoyu Wang ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Vertical Direction ◽  
Maximum Amplitude ◽  
Exciting Force ◽  
Mode Shapes ◽  
Leaf Spring ◽  
Amplification Factors ◽  
Simulation And Experiment ◽  
Exciting Forces ◽  
Spring System

By studying dynamic characteristics of the leaf spring system, a new elastic component is designed to reduce the working load and to a certain extent to ensure the linearity as well as increase the amplitude in the vertical and horizontal directions in vibration screen. The modal parameters, amplitudes, and amplification factors of the leaf spring system are studied by simulation and experiment. The modal results show that the leaf spring system vibrates in horizontal and vertical directions in first and second mode shapes, respectively. It is conducive to loosening and moving the particles on the vibration screen. In addition, it is found that the maximum amplitude and amplification factor in the horizontal direction appear at 300 r/min (5 Hz) while those in the vertical direction appear at 480 r/min (8 Hz), which are higher than those in the disc spring system. Moreover, the amplitude of the leaf spring system increases proportionally with the increase of exciting force while the amplification factors are basically the same under different exciting forces, indicating the good linearity of the leaf spring system. Furthermore, the minimum exciting force occurs in the leaf spring system under the same amplitude by comparing the exciting force among different elastic components. The above works can provide guidance for the industrial production in vibration screen.

The dynamic amplification factors for continuous beam bridges along high-speed railways

2021 ◽  
pp. 136943322110032
Author(s):  
Lin Ma ◽  
Wei Zhang ◽  
Steve C.S. Cai ◽  
Shaofan Li
Keyword(s):  
Fundamental Frequency ◽  
High Speed ◽  
Continuous Beam ◽  
Empirical Formulas ◽  
High Speed Railway ◽  
Amplification Factors ◽  
Girder Bridges ◽  
Continuous Beam Bridge ◽  
Train Speed ◽  
Dynamic Amplification

In this paper, the dynamic amplification factors (DAFs) of high-speed railway continuous girder bridges are studied. The vehicle-bridge interactions (VBIs) of 13 concrete continuous girder bridges with spans ranging from 48 to 130 m are analyzed, the influences of the train speed, the train marshalling and the bridge fundamental frequency on the DAF are investigated, and the DAF design standard for high-speed railway bridges is discussed. The results indicate that for the continuous beam bridge whose fundamental frequency is less than 3.0 Hz, the maximum DAF is no more than 1.15; while for the bridge examples with a fundamental frequency larger than 3.0 Hz, the maximum DAF reaches 1.25 because the resonance occurs at high train speed. The empirical formulas of the DAFs in the Japan Railway Technical Research Institute (JRTRI) code could provide a conservative estimation of the DAFs of high-speed railway continuous bridges.

Distribution of ground-motion intensity inferred from questionnaire survey, earthquake recordings, and microtremor measurements—A case study in Christchurch, New Zealand, during the 1994 arthurs pass earthquake

1997 ◽  
Vol 87 (2) ◽  
pp. 356-369
Author(s):  
Takumi Toshinawa ◽  
J. John Taber ◽  
John B. Berrill
Keyword(s):  
New Zealand ◽  
Ground Motion ◽  
Intensity Data ◽  
Amplification Factors ◽  
Areal Distribution ◽  
Local Site ◽  
Geological Conditions ◽  
The City ◽  
Microtremor Measurements

Abstract The areal distribution of seismic ground-motion intensity in the city of Christchurch, New Zealand, during the 1994 Arthurs Pass Earthquake (ML 6.6) was evaluated using an intensity questionnaire together with local site amplifications inferred from seismic recordings and microtremors. In order to estimate the intensity in parts of the city where no intensity data were available, intensity data were compared to relative levels of shaking determined from both weak-motion and microtremor recordings. Weak ground-motion amplification factors were determined using ratios of ground accelerations at five sediment sites with respect to a rock site. Microtremor amplification factors were determined from horizontal-to-vertical spectral ratios at a 1-km spacing throughout the city. A positive correlation between weak-motion and microtremor amplification factors allowed extrapolation of microtremor amplification to estimated MM intensity (EMMI). EMMI ranged from 3 to 6 and was consistent with the questionnaire intensity and geological conditions and showed detailed information on the areal distribution of ground-motion intensity in the city.

Investigation on the Robustness of Rotor/Stator Contact Interactions with Respect to Small Mistuning

2021 ◽  
Author(s):  
Florence Nyssen ◽  
Alain Batailly
Keyword(s):  
Degrees Of Freedom ◽  
Design Stage ◽  
Contact Interactions ◽  
Reduced Basis ◽  
Amplification Factors ◽  
Bladed Disk ◽  
Nonlinear Amplification ◽  
Rotor Stator Interaction ◽  
Bending Modes ◽  
The Impact

Abstract In this work, the impact of small mistuning on rotor/stator contact interactions is investigated. First, a detailed study of a rotor/stator interaction between the first bending modes and the second engine order is presented in the tuned case. Then, a numerical investigation on the effect of mistuning on the studied rotor/stator contact interaction is carried out. In particular, a stochastic analysis is performed to evaluate the robustness of the interaction with respect to the mistuning level. Simulations are conducted using a reduced order model (ROM) of an industrial bladed disk that combines both physical degrees of freedom (along blades tip for contact treatment) and modal coordinates. Mistuning is introduced in the tuned ROM by means of a modified version of the component mode mistuning method that allows to keep physical degrees of freedom within the reduced basis. Nonlinear amplification factors, i.e. the amplification factors in the context of contact nonlinearities, are compared with their linear counterparts, the latter are computed using a linear forcing on each blade using a two nodal diameters traveling wave excitation on the mistuned and the tuned bladed disk. The comparison between the linear and nonlinear amplification factor for each sample highlights that no correlation exists between a mistuning pattern leading to high amplifications in a linear context or when contact nonlinearities are taken into account. Therefore, dedicated analyses on the effect of mistuning should be undertaken with contact nonlinearities considerations at the design stage especially if intentional mistuning is considered.

Dynamic analysis of two dimensional simply supported orthotropic bridge decks

1978 ◽  
Vol 5 (1) ◽  
pp. 58-69 ◽  
Author(s):  
G. G. Kulkarni ◽  
S. F. Ng
Keyword(s):  
Theoretical Analysis ◽  
Forced Vibration ◽  
Vibration Analysis ◽  
Bridge Decks ◽  
Two Dimensional ◽  
Amplification Factors ◽  
Simply Supported ◽  
Forced Vibration Analysis ◽  
Critical Sections

Forced vibration analysis of two dimensional bridge deck structures involves complex mathematical procedures and therefore analysis is often based on beam idealization of equivalent plates. This simplification yields close agreement only for long span bridges where plate action is relatively insignificant. However, such a concept of beam idealization cannot be successfully utilized in the case of short span bridges where plate action is predominant and where the determination of the distribution of dynamic deflections and amplification factors at critical sections of such plates is of prime concern. The principal objective of the present investigation is the forced vibration analysis of longitudinally stiffened, simply supported orthotropic bridge decks utilizing a new concept of interconnected beam idealization. The theoretical analysis deals with determination of amplification factors and dynamic deflections along critical sections of the plate treated as a series of interconnected beams. The aspect ratios of the plates under investigation as series of interconnected beams are designed to cover a wide range of plate to beam transition. The theoretical analysis is supplemented by an extensive experimental programme.In conclusion, it is seen that this concept of interconnected beam idealization not only takes into account the plate action of the deck structure but also reduces greatly the complexity of mathematical formulation. A good comparison between the theoretical and the experimental results indicates that this concept can be used to advantage for analysis and, within certain limitations, for design purposes.

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