scholarly journals A Modified Newmark Method for Calculating Permanent Displacement of Seismic Slope considering Dynamic Critical Acceleration

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Yulong Cui ◽  
Aijuan Liu ◽  
Chong Xu ◽  
Jun Zheng
Keyword(s):  
Time History ◽  
Reduction Process ◽  
Improved Method ◽  
Permanent Displacement ◽  
Critical Acceleration ◽  
Seismic Slope Stability ◽  
Sliding Method ◽  
Slide Block ◽  
Important Index ◽  
Real Value

Newmark permanent displacement is an important index for evaluating seismic slope stability, which has been widely used in recent years. The traditional Newmark sliding method assumes that the critical acceleration is constant but does not consider the inhomogeneity and dynamic reduction process of shear strength on the sliding surface, presumably leading to underestimation of the permanent displacement. In this paper, this problem is analyzed, and a new method for calculating permanent displacement of seismic slope considering dynamic critical acceleration is proposed, in which the Monte Carlo simulation is used. Example calculations indicate that this approach permits to show the dropping cohesion and the dynamic critical acceleration of the slide block during the earthquake time history. The improved method for calculating seismic slope permanent displacement presented in this paper solves the problem that the calculated value from the Newmark sliding method is smaller than the real value and is a useful improvement.

Fling-step recovering from near-source waveforms and ground displacement attenuation models

2020 ◽  
Author(s):  
Maria D'Amico ◽  
Erika Schiappapietra ◽  
Giovanni Lanzano ◽  
Sara Sgobba ◽  
Francesca Pacor
Keyword(s):  
Low Frequency ◽  
Time History ◽  
Strong Motion ◽  
Response Spectra ◽  
Ground Displacement ◽  
Permanent Displacement ◽  
Processing Scheme ◽  
Long Period ◽  
Fling Step ◽  
Attenuation Models

<p>We present a processing scheme (eBASCO, extended BASeline COrrection) to remove the baseline of strong-motion records by means of a piece-wise linear de-trending of the velocity time history. Differently from standard processing schemes, eBASCO does not apply any filtering to remove the low-frequency content of the signal. This approach preserves both the long-period near-source ground-motion, featured by one-side pulse in the velocity trace, and the offset at the end of the displacement trace (fling-step). Hence, the software is suitable for the identification of fling-containing strong-motion waveforms. Here, we apply eBASCO to reconstruct the ground displacement of more than 400 three-component near-source waveforms recorded worldwide (NESS1, http://ness.mi.ingv.it/; Pacor et al., 2019) with the aim of: 1) extensively testing the eBasco capability to capture the long-period content of near-source records; 2) calibrating attenuation models for peak ground displacement (PGD), 5% damped displacement response spectra (DS), permanent displacement amplitude (PD) and period (Tp). The results could provide a more accurate estimate of ground motions, to be adopted for different engineering purposes such as performance-based seismic design of structures.</p><p>Pacor F., Felicetta C., Lanzano G., Sgobba S., Puglia R., D’Amico M., Russo E., Baltzopoulos G., Iervolino I. (2018). NESS v1.0: A worldwide collection of strong-motion data to investigate near source effects. Seismological Research Letters. https://doi.org/10.1785/0220180149</p>

Dynamic Stability of Large-Span Suspen-Domessubjected to Seismic Excitations

2011 ◽  
Vol 378-379 ◽  
pp. 209-212 ◽  
Author(s):  
Hui Juan Liu ◽  
Lu Feng Yang ◽  
Yong Feng Luo
Keyword(s):  
Mechanical Behavior ◽  
Critical Point ◽  
Dynamic Stability ◽  
Theoretical Investigation ◽  
Stability Theory ◽  
Time History ◽  
Improved Method ◽  
Seismic Excitations ◽  
Response Curves ◽  
Time History Response

Dynamic stability of suspen-domes is analyzed in the paper. Theoretical investigation is conducted based on the Lypumov dynamic stability theory. Based on B-R criterion, an improved method to evaluate the dynamic stability of suspen-domes is proposed. According to the method and time-history response curves, the dynamic stability of the suspen-domes is evaluated under horizontal seismic excitations. The dynamic stability characteristics, stability mode and cable mechanical behavior of the suspen-domes with different rise-span ratios are analyzed. The results show that the effect of the rise-span ratios on the dynamic stability is different. When the exciting acceleration approaches the critical point, some cables may relax, but they may be tensed again.

Stochastic Finite-Fault Simulation of the Ms 7.0 Lushan Earthquake Based on Frequency- and Distance-Dependent Radiation Patterns

2021 ◽  
Author(s):  
Tianjia Wang ◽  
Xu Xie ◽  
Longfei Ji
Keyword(s):  
Radiation Pattern ◽  
Ground Motion ◽  
Low Frequency ◽  
Time History ◽  
Lushan Earthquake ◽  
Radiation Patterns ◽  
Improved Method ◽  
High Frequencies ◽  
Finite Fault ◽  
Finite Fault Method

ABSTRACT The stochastic finite-fault method (EXSIM) has been extensively used for simulating ground motion at high frequencies. However, its poor performance in low-frequency simulations is a limiting factor that restricts its engineering application. Refining the representation of the radiation pattern in the finite-fault method is an effective strategy to improve low-frequency simulations; to this end, a frequency-dependent radiation pattern has been considered by several researchers. However, this strategy fails to provide an accurate simulation of seismic-wave propagation at distances beyond the near-fault region. Researchers have proposed various approaches for characterizing the radiation pattern variation with distance. This study introduces frequency- and distance-dependent radiation patterns of S waves to the EXSIM. The near-field acceleration records in the east–west and north–south directions of the 2013 Ms 7.0 Lushan earthquake were reconstructed. The proposed method was verified by: (1) comparing broadband simulation results obtained by the improved method with observed results, (2) conducting a misfit analysis to compare the model bias between the improved and original methods, and (3) comparing the observed and simulated peak ground acceleration data with the predicted values of the ground-motion prediction equations (GMPEs) to verify the effectiveness of the GMPEs in describing the regional ground-motion attenuation. The results indicated that the 5%-damped pseudo spectral accelerations at high frequencies (1–20 Hz) and acceleration time history simulated by the improved method were consistent with the observed values. Furthermore, the improved method effectively optimizes the simulation effect at low frequencies (0.05–1 Hz) compared with the original method. Thus, the improvement in the representation of the radiation pattern in EXSIM can better estimate broadband ground motion in the study area.

Upgrading Seismic Behaviors of R/C Frames with Shaped Memory Alloys Based Braces

2020 ◽  
Vol 3 (2) ◽  
pp. 993-1002
Author(s):  
Ali Reza Allahverdizade ◽  
Serenay Kara ◽  
Savaş Erdem
Keyword(s):  
Earthquake Engineering ◽  
Smart Materials ◽  
Intelligent Systems ◽  
Structural Engineering ◽  
New Technologies ◽  
Time History ◽  
Damping Capacity ◽  
Base Shear ◽  
Permanent Displacement ◽  
Structural Fatigue

Intelligent systems in structural engineering are systems that are capable of automatically adapting structural behavior in response to instantaneous loads, thereby ensuring the safety of extended structural life and performance. One of the new technologies that makes it possible to achieve these goals is the production and development of smart materials. Examples of these smart materials used in structural engineering include piezo-ceramics, magnetorheological fluids, electrorheological fluids, and form-memory alloys. Shaped Memory Alloys (SMAs) are new materials that have been used in various fields of science and engineering in recent decades. In recent years, these materials attracted the attention of researchers in the field of building and earthquake engineering due to their properties such as high damping capacity, low permanent displacement and structural fatigue resistance. One of the application areas of these materials is that they are used as a brace in the structures, so the research results have shown the acceptable performance and operability of such structural systems. In this study, shape memory bracelets and steel bracelets installed as structural brackets were used as a lateral load system in the seismic improvement of concrete bending frames and factors such as residual displacement and base shear in these two load-bearing systems are compared.  The model under studying is a 6-story frame that has been subjected to time history analysis. SeismoStruct software was used to analyze the model.

scholarly journals A Modified Newmark Methodology for Permanent Deformation Analysis of Rock-Fill Dams

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Hongjun Li ◽  
Hong Zhong ◽  
Zuwen Yan ◽  
Jianming Zhao
Keyword(s):  
Shear Strength ◽  
Safety Evaluation ◽  
Time History ◽  
Deformation Analysis ◽  
Vertical Acceleration ◽  
Seismic Safety ◽  
Critical Acceleration ◽  
Cyclic Shear ◽  
Rock Fill ◽  
Seismic Safety Evaluation

Newmark sliding block approach has been extensively studied by many researchers in the past decades. Significant progress has been made to alleviate its deficiencies and overcome its simplifying assumptions, but some aspects such as the cyclic shear strength and time history vertical acceleration in the Newmark sliding displacement analysis are seldom considered strictly. In the presented research, a modified Newmark methodology for sliding deformation analysis of rock-fill dams subjected to strong earthquake is proposed. In order to make the seismic safety evaluation of dams more realistic, the influence of cyclic shear strength (earthquake-induced reduction of shear strength) and time history vertical acceleration obtained from the dynamic response analysis on the critical acceleration and accumulative sliding displacement of the flexible sliding body is considered. Detailed comparison between the proposed method and existing methods is performed via the analysis of two typical dams, that is, a virtual rock-fill dam with a height of 100 m which is assumed to be situated on rock formation and a real core rock-fill dam with a height of 150 m built on deep overburden layers. It is demonstrated that the cyclic shear strength and time history vertical acceleration within flexible sliding body, as highlighted in the proposed method, have significant effect on the seismic safety evaluation, critical acceleration, and accumulation of sliding deformation of rock-fill dams subjected to strong earthquake loading. The existing approaches tend to provide unconservative evaluation on the consequences of earthquakes on rock-fill dams.

scholarly journals Fling-Step Recovering from Near-Source Waveforms Database

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 67
Author(s):  
Erika Schiappapietra ◽  
Chiara Felicetta ◽  
Maria D’Amico
Keyword(s):  
Low Frequency ◽  
Time History ◽  
Strong Motion ◽  
Response Spectra ◽  
Ground Displacement ◽  
Permanent Displacement ◽  
Flat File ◽  
Processing Scheme ◽  
Long Period ◽  
Fling Step

We present an upgraded processing scheme (eBASCO, extended BASeline COrrection) to remove the baseline of strong-motion records by means of a piece-wise linear detrending of the velocity time history. Differently from standard processing schemes, eBASCO does not apply any filtering to remove the low-frequency content of the signal. This approach preserves both the long-period near-source ground-motion, featured by one-side pulse in the velocity trace, and the offset at the end of the displacement trace (fling-step). The software is suitable for a rapid identification of fling-containing waveforms within large strong-motion datasets. The ground displacement of about 600 three-component near-source waveforms has been recovered with the aim of (1) extensively testing the eBASCO capability to capture the long-period content of near-source records, and (2) compiling a qualified strong-motion flat-file useful to calibrate attenuation models for peak ground displacement (PGD), 5% damped displacement response spectra (DS), and permanent displacement amplitude (PD). The results provide a more accurate estimate of ground motions that can be adopted for different engineering purposes, such as performance-based seismic design of structures.

Effect of Airfoil Clocking on Noise of LP Turbines: Part II — Modal Structure Analysis

2014 ◽  
Author(s):  
Adolfo Serrano ◽  
José Ramón Fernández
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Time History ◽  
Reduction Process ◽  
Acoustic Power ◽  
Acoustic Energy ◽  
Modal Structure ◽  
Low Pressure Turbine ◽  
Multistage Turbine ◽  
Noise Measurements

The clocking effect on noise is investigated experimentally in a multistage turbine high speed rig. It consists in a three stages state of the art Low Pressure Turbine (LPT). The work is a continuation of a first part in which efficiency and noise are addressed together for the same test [1]. Due to the large amount of data acquired in the experiment, noise results presented in [1] are based on averaged Sound Pressure Level (SPL) at the exit. The present paper goes beyond that analysis and aims to get the modal structure and its sensitivity to clocking. Noise measurements are taken ‘in-duct’ immediately downstream the LPT by a continuously and slowly rotating device denominated Noise Measurement Module (NMM). Previous experimental studies [2] [3] demonstrate this as an effective way of characterizing the LPT noise source in an engine, provided that the necessary hot to cold conversions and propagation effects are included. The rotation of the NMM allows the identification of the spinning modes responsible of the tone noise. The axial dependence acquired by the different sensors along the duct gives the radial structure of the spinning modes. The modal decomposition allows the estimation of the acoustic energy, which is the proper magnitude for observing the clocking dependence. The data reduction process from time history signals to the acoustic power estimation is described in detail. Special attention is paid on the applicability limits and uncertainty analysis. Results from the first part [1] suggest that efficiency is weakly affected by clocking whereas noticeable influence of some tone noise is observed. The acoustic power and modal structure dependence of the same tones observed in [1] will allow the comprehension of the noise clocking mechanisms in future. Although this is out of the scope, results suggest some physical explanation described here.

Seismic Design and Safety Evaluation Analysis of Reinforced Slope with Geogrid in 200m High Core Rock-Fill Dams

2012 ◽  
Vol 204-208 ◽  
pp. 2539-2549
Author(s):  
Hong Jun Li ◽  
Zu Wen Yan ◽  
Yan Yi Zhang
Keyword(s):  
Seismic Design ◽  
Ant Colony Algorithm ◽  
Permanent Deformation ◽  
Evaluation Criteria ◽  
Safety Evaluation ◽  
Time History ◽  
Vertical Acceleration ◽  
Rock Fill ◽  
Sliding Method ◽  
Fill Materials

The reinforcement technique with strengthening geogrid has been widely used in modern seismic design of 200m high rock-fill dams. However, how to evaluate accurately the effects of reinforcement in seismic design and safety evaluation has become a key problem. As compared with the minimum safety factors which are conventionally employed as the evaluation criteria, the earthquake-induced deformation can better reflect the characteristics of rock-fill materials, input motion and the performance of reinforced dams for the earthquake loading. In the improved Newmark sliding method, the effects of reinforcement in enhancing the stability of slope in high rock-fill dams and restricting the permanent deformation of dams are investigated. Firstly, the limit tensile intensity and limit coordinating strain of reinforcement is determined based on the stress-strain relationship of reinforcement-composite and rock-fill materials. Secondly, the location of critical failure face is determined via a combination of ant colony algorithm and Holland method. The yielding acceleration of potential sliding bodies, which considers the limited stress of reinforcement layers and time-history vertical acceleration, is obtained. Finally, the transient movements are accumulated for all the overloadings. It is guaranteed that the reinforcement can reduce the permanent deformation up to 80% and improve the seismic design and safety evaluation of high rock-fill dams subjected to strong ground motion effectively.

scholarly journals An improved method of Newmark analysis for mapping hazards of coseismic landslides

2019 ◽  
Author(s):  
Mingdong Zang ◽  
Shengwen Qi ◽  
Yu Zou ◽  
Zhuping Sheng ◽  
Blanca S. Zamora
Keyword(s):  
Factor Model ◽  
Area Under The Curve ◽  
Infrastructure Development ◽  
Improved Method ◽  
Permanent Displacement ◽  
Coseismic Landslides ◽  
Ludian Earthquake ◽  
Slide Surface ◽  
Improved Performance ◽  
Using Data

Abstract. Coseismic landslides have been responsible for destroyed buildings and structures, dislocated roads and bridges, cut off of pipelines and lifelines, and tens of thousands of deaths. Accurately mapping the hazards of coseismic landslides is an important and challenge work. Newmark's method is widely applied to assess the permanent displacement along a potential slide surface to determine the coseismic responses of the slope. This paper considers the roughness and size effect of the potential slide surface-unloading joint, and then presents an improved method of Newmark analysis for mapping hazard of coseismic landslides. The improved method is verified using data from a case study of the 2014 Mw 6.1 (USGS) Ludian earthquake in Yunnan Province, China. The permanent displacement yielded from this method range from 0 to 122 cm. Comparisons are made between the predicted displacements and a comprehensive inventory of landslides triggered by the Ludian earthquake to map the spatial variability using certainty factor model (CFM). Confidence levels of coseismic landslides indicated by certainty factors range from −1 to 0.95. A coseismic landslide hazard map is then produced based on the spatial distribution of the values of certainty factors. Area under the curve analysis is used to draw a comparison between the improved and conventional method of Newmark analysis, revealing the improved performance of the method presented in this paper. Such method can be applied to predict the hazard zone of the region and provide guidelines for making decisions regarding infrastructure development and post-earthquake reconstruction.

Seismic-induced permanent displacement of geosynthetic-reinforced segmental retaining walls

1996 ◽  
Vol 33 (6) ◽  
pp. 937-955 ◽  
Author(s):  
Z Cai ◽  
R J Bathurst
Keyword(s):  
Key Words ◽  
Failure Mechanism ◽  
Earth Pressure ◽  
Retaining Walls ◽  
Wall Structure ◽  
Displacement Method ◽  
Permanent Displacement ◽  
Interface Shear ◽  
Critical Acceleration ◽  
Potential Failure

This paper describes the application of conventional displacement methods to estimate seismic-induced permanent displacements of geosynthetic-reinforced segmental retaining walls constructed on firm foundations. Permanent displacements associated with three sliding mechanisms are investigated: (1) external sliding along the base of the total wall structure; (2) internal sliding along a reinforcement layer and through the facing column; and (3) block interface shear between facing column units. A pseudostatic method based on the Mononobe-Okabe earth pressure theory is used to determine the value of critical acceleration associated with each potential failure mechanism. Newmark's sliding block displacement method and a number of emperical methods are briefly summarized and can be used to estimate the permanent displacements of segmental retaining walls. An example is given to illustrate the application of the methods presented. Key words: segmental retaining walls, geosynthetics, seismic, Newmark, sliding block, displacement methods.

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