scholarly journals Selection of earthquake ground motion accelerograms for the continental margin of Southeastern Brazil

DYNA ◽  
2021 ◽  
Vol 88 (217) ◽  
pp. 228-236
Author(s):  
Cristian Soriano Camelo ◽  
Samuel Felipe Mollepaza Tarazona ◽  
Maria Cascão Ferreira de Almeida ◽  
Márcio de Souza Soares de Almeida ◽  
Ricardo Garske Borges
Keyword(s):  
Response Spectrum ◽  
Ground Motions ◽  
Southeastern Brazil ◽  
Earthquake Ground Motion ◽  
Synthetic Spectrum ◽  
Target Response ◽  
Acceleration Time ◽  
Acceleration Time Histories ◽  
Moderate Seismicity ◽  
Time Histories

Brazil is in an intraplate area of low to moderate seismicity, this means that few or no records of strong ground motions are available. Part of the site response analysis and seismic design of structures require the use of acceleration time-histories compatible with a specified target response spectrum. This study aims to utilize methodologies based on the use of existing earthquake records from a well-known database and synthetic accelerograms to obtain ground motions representative of the Brazilian Southeast Region, particularly in the offshore Campos Basin. Information from a probabilistic seismic hazard assessment performed in the interest area was employed as input to the methodologies applied in terms of target response spectrum and the dominant earthquake scenarios. Besides, the acceleration time-histories of two relatively recent earthquakes that occurred in the Brazilian Southeast were used to apply one of the approaches to obtain a synthetic spectrum compatible accelerogram.

Generation of Response Spectra Compatible Artificial Acceleration Time Histories

2012 ◽  
Author(s):  
Jukka Kähkönen ◽  
Pentti Varpasuo
Keyword(s):  
Response Spectrum ◽  
Response Spectra ◽  
Target Response ◽  
High Quality ◽  
Acceleration Time ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Quality Response

A procedure to generate artificial acceleration time histories compatible with predefined target response spectrum is presented. The procedure is demonstrated with three examples. It was found out that the generated artificial histories yield high quality response spectra for single-damping defined target spectra. A need for method that yields histories matching target spectra defined with multiple damping values was recognized.

Operations Management Strategy of Cable-supported Bridge using Seismic Accelerometer

2019 ◽  
Author(s):  
Seung Han Lee ◽  
Sung Woo Park ◽  
Kwang-Yeun Park ◽  
Do-Kyoun Kim ◽  
Byounghan Choi
Keyword(s):  
Operations Management ◽  
Disaster Response ◽  
Management Strategy ◽  
Response Spectrum ◽  
Free Field ◽  
Seismic Safety ◽  
Acceleration Time ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Gyeongju Earthquake

<p>This study presents the operations management strategy to respond to earthquake disasters using the acceleration records measured by seismic accelerometers installed on the primary structural elements of cable-supported bridges and those on the free fields around them. A two-step strategy in operations management is proposed for the urgent seismic safety assessment. In the first step, the seismic safety is evaluated with respect to the peak values in recorded acceleration time histories at the locations of the pylon foundation of bridge and the free field around it, and the corresponding management criteria for them are determined based on the existing disaster response manual for offshore bridges. In the second step, the peak values in displacement time histories, which are estimated from the recorded acceleration time histories, are utilized to assess the seismic safety at locations of the top and middle of pylon, and the center of girder of bridge, and the corresponding management criteria are determined based on the structural analyses under the response spectrum seismic loading. When an earthquake occurs, the safety of cable-supported bridge is evaluated urgently through comparisons of peak values in the recorded acceleration time histories and the estimated displacement time histories with the management criteria of accelerations and displacements determined in advance, respectively. The validity of the proposed strategy is verified though performing the safety assessments for several cable-supported bridges on service in Korea using the acceleration data recorded during recent Gyeongju earthquake in Korea.</p>

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.

scholarly journals Seismic Assessment of Footbridges under Spatial Variation of Earthquake Ground Motion (SVEGM): Experimental Testing and Finite Element Analyses

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1227 ◽  
Author(s):  
Izabela Joanna Drygala ◽  
Joanna Maria Dulinska ◽  
Maria Anna Polak
Keyword(s):  
Finite Element ◽  
Spectral Density ◽  
Earthquake Ground Motion ◽  
Density Functions ◽  
Acceleration Time ◽  
Kinematic Excitation ◽  
Acceleration Time Histories ◽  
Dynamic Analyses ◽  
Time Histories ◽  
Spectral Density Functions

In this paper, the seismic assessments of two footbridges, i.e., a single-span steel frame footbridge and a three-span cable-stayed structure, to the spatial variation of earthquake ground motion (SVEGM) are presented. A model of nonuniform kinematic excitation was used for the dynamic analyses of the footbridges. The influence of SVEGM on the dynamic performance of structures was assessed on both experimental and numerical ways. The comprehensive tests were planned and carried out on both structures. The investigation was divided into two parts: in situ experiment and numerical analyses. The first experimental part served for the validation of both the finite element (FE) modal models of structures and the theoretical model of nonuniform excitation as well as the appropriateness of the FE procedures used for dynamic analyses. First, the modal properties were validated. The differences between the numerical and the experimental natural frequencies, obtained using the operational modal analysis, were less than 10%. The comparison of the experimental and numerical mode shapes also proved a good agreement since the modal assurance criterion values were satisfactory for both structures. Secondly, nonuniform kinematic excitation was experimentally imposed using vibroseis tests. The apparent wave velocities, evaluated from the cross-correlation functions of the acceleration-time histories registered at two consecutive structures supports, equaled 203 and 214 m/s for both structures, respectively. Also, the coherence functions proved the similarity of the signals, especially for the frequency range 5 to 15 Hz. Then, artificial kinematic excitation was generated on the basis of the adopted model of nonuniform excitation. The obtained power spectral density functions of acceleration-time histories registered at all supports as well as the cross-spectral density functions between registered and artificial acceleration-time histories confirmed the strong similarity of the measured and artificial signals. Finally, the experimental and numerical assessments of the footbridges performance under the known dynamic excitation generated by the vibroseis were carried out. The FE models and procedures were positively validated by linking full-scale tests and numerical calculations. In the numerical part of the research, seismic analyses of the footbridges were conducted. The dynamic responses of structures to a representative seismic shock were calculated. Both the uniform and nonuniform models of excitation were applied to demonstrate and quantify the influence of SVEGM on the seismic assessment of footbridges. It occurred that SVEGM may generate non-conservative results in comparison with classic uniform seismic excitation. For the stiff steel frame footbridge the maximum dynamic response was obtained for the model of nonuniform excitation with the lowest wave velocity. Especially zones located closely to stiff frame nodes were significantly more disturbed. For the flexible cable-stayed footbridge, in case of nonuniform excitation, the dynamic response was enhanced only at the points located in the extreme spans and in the midspan closely to the pillars.

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.

scholarly journals Earthquake Ground Motion Matching on a Small Electric Shaking Table Using a Combined NN-PDFF Controller

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Selma H. Larbi ◽  
Nouredine Bourahla ◽  
Hacine Benchoubane ◽  
Khireddine Choutri ◽  
Mohammed Badaoui
Keyword(s):  
Control Function ◽  
Coupling Effect ◽  
Experimental Tests ◽  
Shaking Table ◽  
Earthquake Ground Motion ◽  
Feedback Signal ◽  
Linear Motors ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Acceleration Tracking

Replicating acceleration time histories with high accuracy on shaking table platforms is still a challenging task. The complex interference between the components of the system, the inherent nonlinearities, and the coupling effect between the specimen and the shaking table are among other reasons that most affect the control performance. In this paper, a neural network- (NN-) based controller has been developed and experimentally implemented to improve the acceleration tracking performance of an electric shaking table. The latter is a biaxial shaking table driven by linear motors and controlled by a proportional-derivative-feedforward (PDFF) controller that is very efficient in reproducing displacement waveforms on the detriment of the simulation of the prescribed acceleration ground motions. In order to bypass this shortcoming, a control scheme combining the PDFF as a basic control function with a NN controller which filters the shaking table feedback signal and acts on the drive signal by compensating for acceleration distortions is proposed in this study. Several experimental tests have been carried out to build a database for offline training, validating, and testing of the proposed NN control model. Subsequently, the well-trained NN is implemented in the inner control loop of the shaking table to compensate, in parallel with the PDFF controller, the distortions during the replication of acceleration signals. Results of tests using earthquake records showed an enhancement in signal matching when integrating the NN model for both bare and loaded conditions of the shaking table. The tracking errors, estimated using the relative root-mean-square error, between the measured and the desired signal, are significantly reduced in time and frequency domains with the additional NN online controller.

Inelastic Response of a Spectrum-Compatible Artificial Accelerogram

1989 ◽  
Vol 5 (3) ◽  
pp. 477-493 ◽  
Author(s):  
Michael E. Barenberg
Keyword(s):  
Response Spectrum ◽  
Ground Motions ◽  
Normalization Procedure ◽  
Target Response ◽  
Single Degree Of Freedom ◽  
Inelastic Response ◽  
Strong Ground Motions ◽  
Single Degree ◽  
Initial Frequency ◽  
Strong Ground

The validity of evaluating the inelastic response of a structure subjected to an artificial accelerogram in lieu of a suite of eight recorded ground motions is determined by analyzing the inelastic response of single-degree-of-freedom oscillators over a range of frequencies from 1.0 to 10.0 Hz. A normalization procedure to minimize the dispersion in the ductility response of the oscillators subjected to the recorded ground motions is investigated. The artificial accelerogram is derived by superimposing closely spaced sine waves in order to match a target response spectrum. The results show that the artificial accelerogram is expected to produce the same amount of damage as the average of the recorded strong ground motions for structures with an initial frequency of less than 5.0 Hz and close to the average for the entire suite of ground motions for structures with frequencies greater then 5.0 Hz.

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.

An Improved Stochastic Finite-Fault Method Based on Energy

2015 ◽  
Vol 744-746 ◽  
pp. 878-883
Author(s):  
Ju Fang Zhong ◽  
Jun Wei Liang ◽  
Zhi Peng Fan ◽  
Luo Long Zhan
Keyword(s):  
Ground Motion ◽  
Amplification Factor ◽  
Response Spectrum ◽  
Near Field ◽  
Energy Accumulation ◽  
Accumulation Curve ◽  
Finite Fault ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Finite Fault Method

Owing to the simulated ground motion energy distribution by stochastic finite-fault method is not reasonable, near-field bedrock strong ground motion acceleration time histories are used to study. Fourier transform is adapted to analysis the variation of the energy accumulation curve with frequency. The results show that the record energy accumulation curve is a steep rise curve, 80% of total energy of the vertical ground motion is concentrated on the 2.5-15Hz, while the horizontal is mainly concentrated on the 2-11Hz. An improved stochastic finite-fault method is proposed by multiplying an amplification factor in some frequency. The results show that multiplying an amplification factor, the simulated acceleration energy accumulation curve matches to the record acceleration energy accumulation curve, and the peak of simulated acceleration response spectrum tends to the record acceleration value.

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