scholarly journals The Effect of the Vertical Acceleration on Stability Assessment of Seismically Loaded Earth Dams

2016 ◽  
Vol 63 (2-3) ◽  
pp. 101-120 ◽  
Author(s):  
Aleksandra Korzec
Keyword(s):  
Slope Stability ◽  
Vertical Component ◽  
Vertical Acceleration ◽  
Permanent Displacement ◽  
Ground Acceleration ◽  
Safety Criterion ◽  
Acceleration Time ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Block Approach

AbstractIn the assessment of slope stability, the vertical component of acceleration is commonly neglected. However, signal analyses performed on a large number of acceleration time histories have revealed that the vertical peak ground acceleration can be as high as the horizontal one. In this paper, a method of slope stability analysis regarding the vertical component of acceleration is proposed. It considers a rigid body system affected by the acceleration time histories in both horizontal and vertical directions. In a general case, the strength of the contact between acceleration components is time dependent. Parametric analysis was performed on the basis of cyclic harmonic loading, assuming a safety criterion in the form of permanent displacement. The results, for both harmonic and real acceleration time histories, were compared with the results of the commonly used Newmark’s sliding block approach, which revealed significant differences in permanent displacements calculated by the two methods.

scholarly journals Stability evaluation of Sermo dam, Yogyakarta, using two components acceleration time histories causes by Java subduction earthquake scenarios

2018 ◽  
Vol 195 ◽  
pp. 03020
Author(s):  
Windu Partono ◽  
Undayani Cita Sari
Keyword(s):  
Seismic Sources ◽  
Seismic Load ◽  
Seismic Loads ◽  
Maximum Magnitude ◽  
Ground Acceleration ◽  
Acceleration Time ◽  
Earthquake Scenarios ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
East West

Dam assessment under a specific earthquake event is one of the most important approaches to dam evaluation. The assessments are usually performed by running two different models of seismic loads: spectral acceleration and acceleration time histories. The first model is implemented using seismic load information developed from a national code. The second approach is implemented using earthquake scenarios by conducting acceleration time histories. The National Center for Earthquake Studies 2017 suggested that a shallow crustal fault and subduction are the two most dangerous seismic sources of Yogyakarta Province. This paper presents an evaluation of Sermo dam in terms of dam displacement and peak ground acceleration (PGA) under the Java subduction source earthquake scenarios. The evaluation was performed by conducting twocomponent (north-south and east-west directions) acceleration time histories from Java subduction seismic sources. Due to incomplete data, all acceleration time histories used in this study were collected and modified from worldwide earthquake data bases. Based on the average displacement and PGA values it can be predicted that Sermo dam is strong enough to resist an earthquake with a maximum magnitude of 8.4 Mw and minimum epicentre distance of approximately 160 Km caused by the Java subduction source.

Comparison of Seismic Analysis of Jacket Structures Using Response Spectrum and Time Domain Procedures

2013 ◽  
Author(s):  
Partha Chakrabarti ◽  
Atul Rikhy
Keyword(s):  
Linear System ◽  
Ground Motion ◽  
Time Domain ◽  
Response Spectrum ◽  
Ground Acceleration ◽  
Soil System ◽  
Soil Stiffness ◽  
Acceleration Time ◽  
Acceleration Time Histories ◽  
Time Histories

In seismically active areas of the world an offshore jacket structure has to be designed for seismic loads. Since the structure must meet both strength and ductility requirements, a two stage design for Strength Level Earthquake (SLE) and Ductility Level Earthquake (DLE) is generally used. Normal procedure for designing such a structure for SLE condition is to use Response Spectrum method of analysis (RSA). The main advantage of RSA is that it is computationally very efficient. Time Domain Analysis (TDA) is used mostly to analyze DLE condition. A response spectrum depicts the maximum response to a ground motion of a single degree of freedom system having different natural periods but the same degree of damping. A design response spectrum is a smoothened average of several earthquake motions. It is a property of the ground motion with a given recurrence interval at the particular region of interest. RSA is a frequency domain analysis technique based on mode superposition approach. API RP 2A specifies that the modal responses be combined using a Complete Quadratic Combination (CQC) of modal responses. For the directional response combination, API RP 2A recommends applying 100% of the spectral acceleration for the two orthogonal lateral directions and 50% for the vertical and using the Square Root of Sum of Squares (SRSS) combination to obtain the maximum response. With this approach it is possible to conduct only one analysis, with any reference system, and the resulting structure will have all members that are designed to equally resist earthquake motions from all possible directions. RSA based on mode superposition is valid strictly for a linear system. A jacket structure with its pile-soil system is not truly a linear system due to soil nonlinearity. Therefore, linearization of the pile-soil system is necessary. The stiffness of a pile is dependent on the pile head loads. Thus the response from the RSA will be very much load or deformation dependent for the pile-soil stiffness. Software used here for the analyses has an iterative analysis option for obtaining the appropriate linearized stiffness. TDA is a step by step time integration procedure for the entire system including the piles and there is no linearization involved for the foundation stiffness as the pile-soil stiffness at discrete points of the pile are calculated at each time instant within the program. The TDA is more precise for the given time history but more time consuming as a series of ground acceleration time histories are normally required for the TDA approach. The results from RSA are expected to be conservative especially for the design of piles. However, this can only be confirmed from a series of TDA performed using ground acceleration time histories. This paper demonstrates that more accurate and less conservative results can be obtained by using a combination of RSA and TDA even for SLE condition. However, several simulations for TDA are required for confidence in the design to ensure that all structural elements have achieved the maximum conditions. Essentially, RSA can be used for jacket member design and TDA can be used specifically for pile design. Thus the authors believe the design of an entire jacket could be more economical if this combined approach is judiciously used.

Metrics for the Comparison of Acceleration Time Histories

2017 ◽  
Author(s):  
Nithyagopal Goswami ◽  
Mourad Zeghal ◽  
Majid Manzari ◽  
Bruce Kutter
Keyword(s):  
Acceleration Time ◽  
Acceleration Time Histories ◽  
Time Histories

Selection and Scaling Time History Records for Performance-Based Design

2017 ◽  
pp. 1-35
Author(s):  
Yasin M. Fahjan ◽  
F. İlknur Kara ◽  
Aydın Mert
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Time History ◽  
Design Code ◽  
Uniform Hazard Spectra ◽  
Acceleration Time ◽  
Acceleration Time Histories ◽  
Recent Developments ◽  
Time Histories ◽  
Strong Ground

Recent developments in performance-based analyses and the high performance of computational facilities have led to an increased trend for utilizing nonlinear time-history analysis in seismic evaluation of the performance of structures. One of the crucial issues of such analysis is the selection of appropriate acceleration time histories set that satisfy design code requirements at a specific site. In literature, there are three sources of acceleration time histories: 1) recorded accelerograms in real earthquakes scaled to match design code spectrum/uniform hazard spectra/conditional mean spectrum, 2) artificial records generated from white noise spectra to satisfy design code spectrum, and 3) synthetic records obtained from seismological models. Due to the increase of available strong ground motion database, using and scaling real recorded accelerograms is becoming one of the most contemporary research issues in this field. In this study, basic methodologies and criteria for selecting strong ground motion time histories are discussed. Design code requirements for scaling are summarized for ASCE/SEI-7-10, EC8 and Turkish Seismic Codes. Examples for scaling earthquake records to uniform hazard spectra are provided.

Pilot and Observer Performance in Simulated Low Altitude High Speed Flight

1965 ◽  
Vol 7 (3) ◽  
pp. 257-265 ◽  
Author(s):  
Ben Schohan ◽  
Harve E. Rawson ◽  
Stanley M. Soliday
Keyword(s):  
Atmospheric Turbulence ◽  
High Speed ◽  
Target Identification ◽  
Observer Performance ◽  
Acceleration Time ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Low Altitude ◽  
Vertical Accelerations

Responses of experienced pilots and aerial observers were studied in simulated low-altitude, high-speed (LAHS) flight. The pilots “flew” three-hour surveillance missions at airspeeds of .4M and .9M in different degrees of simulated atmospheric turbulence. Flying ability decreased from .4 to .9M; however, intensity of vertical accelerations did not seem to affect flying ability except at the most severe levels. Target identification was unimpaired by either turbulence or airspeed. The observers also flew three-hour missions while experiencing acceleration time histories recorded from the pilot's flights. Target identification deteriorated as airspeed increased from 0.4 to 0.9 Mach. Gust intensity did not affect performance of any of their tasks. Performance efficiency on all tasks did not deteriorate from beginning to end of the missions of both pilots and observers.

scholarly journals Development of two components acceleration time histories for Semarang, Indonesia, due to Semarang fault earthquake scenarios using 30 meters soil deposit model

2018 ◽  
Vol 159 ◽  
pp. 01043
Author(s):  
Windu Partono
Keyword(s):  
Site Response ◽  
Historical Earthquakes ◽  
Structure Design ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Acceleration Time ◽  
Earthquake Scenarios ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Deposit Model

Development of surface acceleration time histories is important for dynamic analysis of structure design and evaluation. Acceleration time histories usually developed from seismograph records due to specific earthquake event. Following the research conducted by Team for Revision of Seismic Hazard Maps of Indonesia 2010 and 2016, Lasem fault and Semarang fault are two closest and dangerous shallow crustal fault earthquake sources which must be taken into account for seismic mitigation of Semarang. This paper presents the development two components surface acceleration time histories for Semarang caused by Semarang fault earthquake scenarios, with magnitude from 6 Mw to 7 Mw and maximum epicentre distance 15 Km. This research was performed by conducting deterministic hazard analysis, response spectral matching and site response analysis to obtain a pair of modified acceleration time histories. Site response analysis was performed by conducting 30 meters soil deposit model by taking the assumption that the position of bedrock elevation is 30 meters below the surface layer. Modified acceleration time histories were developed from a pair time histories (North-South/NS and East-West/EW direction) collected from worldwide historical earthquakes. Modified time histories were developed due to limited time histories data caused by Semarang fault earthquake source.

Development of Target Power Spectral Density Functions Compatible With Design Response Spectra

2015 ◽  
Author(s):  
Jinsuo R. Nie ◽  
Jim Xu ◽  
Joseph I. Braverman
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Seismic Analysis ◽  
General Procedure ◽  
Response Spectra ◽  
Acceleration Time ◽  
Power Spectral ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Spectral Shapes

For seismic analysis of nuclear structures, synthetic acceleration time histories are often required and are generated to envelop design response spectra following the U.S. Nuclear Regulatory Commission, Standard Review Plan (SRP) Section 3.7.1. It has been recognized that without an additional check of the power spectral density (PSD) functions, spectral matching alone may not ensure that synthetic acceleration time histories have adequate power over the frequency range of interest. The SRP Section 3.7.1 Appendix A provides a target PSD function for the Regulatory Guide 1.60 horizontal spectral shape. For other spectral shapes, additional guidance on developing the target PSD functions compatible with the design spectra is desired. This paper presents a general procedure for the development of target PSD functions for any practical design response spectral shapes, which has been incorporated into the recent SRP 3.7.1, Revision 4.

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