Representation of Bidirectional Ground Motions for Design Spectra in Building Codes

2011 ◽  
Vol 27 (3) ◽  
pp. 927-937 ◽  
Author(s):  
Jonathan P. Stewart ◽  
Norman A. Abrahamson ◽  
Gail M. Atkinson ◽  
Jack W. Baker ◽  
David M. Boore ◽  
...  
Keyword(s):  
Ground Motion ◽  
Dynamic Properties ◽  
Ground Motions ◽  
Geometric Mean ◽  
Structural Response ◽  
Risk Level ◽  
Lower Probability ◽  
Lumped Mass ◽  
Risk Levels ◽  
Design Spectra

The 2009 NEHRP Provisions modified the definition of horizontal ground motion from the geometric mean of spectral accelerations for two components to the peak response of a single lumped mass oscillator regardless of direction. These maximum-direction (MD) ground motions operate under the assumption that the dynamic properties of the structure (e.g., stiffness, strength) are identical in all directions. This assumption may be true for some in-plan symmetric structures, however, the response of most structures is dominated by modes of vibration along specific axes (e.g., longitudinal and transverse axes in a building), and often the dynamic properties (especially stiffness) along those axes are distinct. In order to achieve structural designs consistent with the collapse risk level given in the NEHRP documents, we argue that design spectra should be compatible with expected levels of ground motion along those principal response axes. The use of MD ground motions effectively assumes that the azimuth of maximum ground motion coincides with the directions of principal structural response. Because this is unlikely, design ground motions have lower probability of occurrence than intended, with significant societal costs. We recommend adjustments to make design ground motions compatible with target risk levels.

Pounding between Inelastic Three-Storey Buildings under Seismic Excitations

2015 ◽  
Vol 665 ◽  
pp. 121-124 ◽  
Author(s):  
Robert Jankowski
Keyword(s):  
Numerical Analysis ◽  
Numerical Models ◽  
Ground Motions ◽  
Permanent Deformation ◽  
Structural Response ◽  
The Other ◽  
Lumped Mass ◽  
Seismic Excitations ◽  
Structural Interactions ◽  
Inelastic Behaviour

Structural interactions between adjacent, insufficiently separated buildings have been repeatedly observed during damaging ground motions. This phenomenon, known as the structural pounding, may result in substantial damage or even total collapse of structures. The aim of the present paper is to show the results of the nonlinear numerical analysis focused on pounding between inelastic three-storey buildings under seismic excitations. The discrete lumped-mass numerical models of two building have been used in the analysis. The results of the study indicate that the response of the lighter and more flexible inelastic building can be substantially influenced by structural interactions, and collisions may even lead to the permanent deformation of the structure. On the other hand, the behaviour of the heavier and stiffer building does not really change considerably during the earthquake. The results of the study also indicate that incorporation of the inelastic behaviour of colliding buildings with different dynamic characteristics is very important for the purposes of accurate numerical modelling of pounding-involved structural response under damaging seismic excitations.

Relations between MaxRotD50 and Some Horizontal Components of Ground-Motion Intensity Used in Practice

2021 ◽  
Author(s):  
Alan Poulos ◽  
Eduardo Miranda
Keyword(s):  
Ground Motion ◽  
Earthquake Engineering ◽  
Ground Motions ◽  
Geometric Mean ◽  
The Other ◽  
Horizontal Projection ◽  
Site Class ◽  
Engineering Research ◽  
Natural Logarithm ◽  
Horizontal Ground Motion

ABSTRACT The most commonly used intensity measure of ground motion in earthquake engineering is the 5% damped spectral ordinate, which varies in different directions. Several different measures have been proposed over the years to combine the intensity of the two horizontal recorded ground motions to derive ground-motion models as well as for design purposes. This study provides the relation to seven previously used measures of horizontal ground motion with respect to a recently proposed orientation-independent measure of horizontal ground-motion intensity referred to as MaxRotD50. This new measure of horizontal intensity is defined as the median value of the maximum spectral ordinate of two orthogonal directions computed for all possible nonredundant orientations. The relations are computed using 5065 pairs of horizontal ground motions taken from the database of ground motions recorded in shallow crustal earthquakes in active tectonic regions developed as part of the Pacific Earthquake Engineering Research Center’s Next Generation Attenuation-West2 project. Empirically derived period-dependent relations are presented for three quantities that permit transforming any of the seven other definitions of horizontal ground-motion intensity to MaxRotD50, namely, (1) geometric mean of the ratio of MaxRotD50 to any of the seven other measures of intensities, (2) standard deviation of the natural logarithm of the ratio of MaxRotD50 to any of the seven other measures of intensities, and (3) the correlation between the natural logarithm of the ratio of MaxRotD50 to the other measures of intensities and the natural logarithm of the other measure of intensity. In addition, the influence of site class at the recording station, earthquake magnitude, and distance to the horizontal projection of the rupture is examined on the geometric mean of the ratio of MaxRotD50 to the median intensity of all nonredundant orientations (i.e., RotD50), showing negligible influence of site class and only a relatively small influence of magnitude and distance.

Investigation on Damage-Involved Structural Response of Colliding Steel Structures during Ground Motions

2016 ◽  
Vol 713 ◽  
pp. 26-29 ◽  
Author(s):  
Barbara Sołtysik ◽  
Tomasz Falborski ◽  
Robert Jankowski
Keyword(s):  
Dynamic Properties ◽  
Ground Motions ◽  
Structural Response ◽  
Steel Structures ◽  
Separation Distance ◽  
Shaking Table ◽  
Engineering Structures ◽  
Positive Role ◽  
Acceleration Time Histories ◽  
Adjacent Structures

Earthquakes are the most unpredictable damaging loads which can affect civil engineering structures. Due to insufficient separation distance between adjacent structures with different dynamic properties, structural collisions may occur during ground motions. Although the research on structural pounding has recently been much advanced, the studies have mainly been conducted for concrete structures. The aim of this paper is to show the results of experimental investigation, focused on dynamic behaviour of closely-separated three models of steel structures which have been subjected to damaging earthquake excitations. The study was performed using three models of steel towers with different dynamic parameters and various distances between the structures. The acceleration time histories of the Kobe and the Northridge earthquakes were applied as the seismic excitation. The unidirectional shaking table, located at the Gdansk University of Technology (Poland), was used in the experimental study. The results have confirmed that collisions may lead to the increase in the structural response, although they may also play a positive role, depending on the size of the separation gap between the structures.

Time Series Modeling of Earthquake Ground Motions Using ARMA-GARCH Models

2013 ◽  
Vol 470 ◽  
pp. 240-243 ◽  
Author(s):  
Jeng Hsiang Lin
Keyword(s):  
Ground Motion ◽  
Moving Average ◽  
Ground Motions ◽  
Structural Response ◽  
Earthquake Ground Motion ◽  
Response Analysis ◽  
Practical Implementation ◽  
Autoregressive Moving Average ◽  
Arma Models ◽  
Earthquake Models

Engineers are well aware that, due to the stochastic nature of earthquake ground motion, the information obtained from structural response analysis using scant records is quite unreliable. Thus, providing earthquake models for specific sites or areas of research and practical implementation is essential. This paper presents a procedure for the modeling strong earthquake ground motion based on autoregressive moving average (ARMA) models. The Generalized autoregressive conditional heteroskedasticity (GARCH) model is used to simulate the time-varying characteristics of earthquakes.

Influence of ground motion duration on the dynamic deformation capacity of reinforced concrete frame structures

2021 ◽  
pp. 875529302110338
Author(s):  
Vishvendra Bhanu ◽  
Reagan Chandramohan ◽  
Timothy J Sullivan
Keyword(s):  
Reinforced Concrete ◽  
Ground Motion ◽  
Dynamic Deformation ◽  
Ground Motions ◽  
Geometric Mean ◽  
Deformation Capacity ◽  
Reinforced Concrete Frame ◽  
Moment Frame ◽  
Concrete Frame ◽  
Reinforced Concrete Frame Structures

This study investigates the influence of ground motion duration on the dynamic deformation capacity of a suite of 10 modern reinforced concrete moment frame buildings. A robust numerical algorithm is proposed to estimate the dynamic deformation capacity of a structure by conducting incremental dynamic analysis. The geometric mean dynamic deformation capacity of the considered buildings was, on average, found to be 26% lower under long duration ground motions, compared to spectrally equivalent short duration ground motions. A consistent effect of duration on dynamic deformation capacity was observed over a broad range of structural periods considered in this study. Response spectral shape, however, was found to not significantly influence dynamic deformation capacity. These results indicate that the effect of duration could be explicitly considered in seismic design codes by modifying the deformation capacities of structures.

scholarly journals A Computationally Efficient Ground-Motion Selection Algorithm for Matching a Target Response Spectrum Mean and Variance

2011 ◽  
Vol 27 (3) ◽  
pp. 797-815 ◽  
Author(s):  
Nirmal Jayaram ◽  
Ting Lin ◽  
Jack W. Baker
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Ground Motions ◽  
Structural Response ◽  
Response Spectra ◽  
Selection Algorithm ◽  
Target Response ◽  
Computationally Efficient ◽  
Mean And Variance ◽  
The Impact

Dynamic structural analysis often requires the selection of input ground motions with a target mean response spectrum. The variance of the target response spectrum is usually ignored or accounted for in an ad hoc manner, which can bias the structural response estimates. This manuscript proposes a computationally efficient and theoretically consistent algorithm to select ground motions that match the target response spectrum mean and variance. The selection algorithm probabilistically generates multiple response spectra from a target distribution, and then selects recorded ground motions whose response spectra individually match the simulated response spectra. A greedy optimization technique further improves the match between the target and the sample means and variances. The proposed algorithm is used to select ground motions for the analysis of sample structures in order to assess the impact of considering ground-motion variance on the structural response estimates. The implications for code-based design and performance-based earthquake engineering are discussed.

The prospects of occupational risk management during reforms of regulatory legislation basis

2019 ◽  
pp. 39-44 ◽  
Author(s):  
Vadim B. Alekseev ◽  
Nina V. Zaitseva ◽  
Pavel Z. Shur
Keyword(s):  
Risk Assessment ◽  
Risk Management ◽  
Social Insurance ◽  
Well Being ◽  
Occupational Risk ◽  
Risk Level ◽  
Federal Law ◽  
Work Safety ◽  
Risk Levels ◽  
Legal Principles

Despite wide legislation basis of regulating relations in work safety and workers’ health, one third of workplaces demonstrate exceeded allowable normal levels of workers’ exposure to occupational hazards and present occupational risk for health disorders.In accordance to national legislation acts, evaluation should cover factors of occupational environment and working process, and occupational risk is understood in context of mandatory social insurance. This approach has been formed due to mostly compensatory trend in legal principles of work safety in Russia by now. Implementation of new preventive concept of work safety, based on idea of risk management for workers, necessitates development of legal acts that regulate requirements to evaluation of occupational risk and its reports with consideration of changes in Federal Law on 30 March 1999 №52 FZ “On sanitary epidemiologic well-being of population”.Those acts can include Sanitary Rules and Regulations “Evaluation of occupational risk for workers’ health”, that will contain main principles of risk assessment, requirements to risk assessment, including its characteristics which can serve as a basis of categorizing the risk levels with acceptability.To standardize requirements for informing a worker on the occupational risk, the expediency is specification of sanitary rules “Notifying a worker on occupational risk”. These rules should contain requirements: to a source of data on occupational risk level at workplace, to informational content and to ways of notifying the worker. Specification and implementation of the stated documents enable to fulfil legal requirements completely on work safety — that will provide preservation and increase of efficiency in using work resources.

A subset of CyberShake ground-motion time series for response-history analysis

2021 ◽  
pp. 875529302098197
Author(s):  
Jack W Baker ◽  
Sanaz Rezaeian ◽  
Christine A Goulet ◽  
Nicolas Luco ◽  
Ganyu Teng
Keyword(s):  
Time Series ◽  
Los Angeles ◽  
Seismic Hazard ◽  
Ground Motion ◽  
Ground Motions ◽  
Response Spectra ◽  
Motion Time ◽  
History Analysis ◽  
Response History Analysis ◽  
Simulated Ground Motions

This manuscript describes a subset of CyberShake numerically simulated ground motions that were selected and vetted for use in engineering response-history analyses. Ground motions were selected that have seismological properties and response spectra representative of conditions in the Los Angeles area, based on disaggregation of seismic hazard. Ground motions were selected from millions of available time series and were reviewed to confirm their suitability for response-history analysis. The processes used to select the time series, the characteristics of the resulting data, and the provided documentation are described in this article. The resulting data and documentation are available electronically.

Ground-motion model for subduction earthquakes in northern South America

2021 ◽  
pp. 875529302110275
Author(s):  
Carlos A Arteta ◽  
Cesar A Pajaro ◽  
Vicente Mercado ◽  
Julián Montejo ◽  
Mónica Arcila ◽  
...  
Keyword(s):  
South America ◽  
Ground Motion ◽  
Ground Motions ◽  
Strong Motion ◽  
Motion Prediction ◽  
Depth Range ◽  
Ground Motion Prediction ◽  
Natural Period ◽  
Nazca Plate ◽  
Northern South America

Subduction ground motions in northern South America are about a factor of 2 smaller than the ground motions for similar events in other regions. Nevertheless, historical and recent large-interface and intermediate-depth slab earthquakes of moment magnitudes Mw = 7.8 (Ecuador, 2016) and 7.2 (Colombia, 2012) evidenced the vast potential damage that vulnerable populations close to earthquake epicenters could experience. This article proposes a new empirical ground-motion prediction model for subduction events in northern South America, a regionalization of the global AG2020 ground-motion prediction equations. An updated ground-motion database curated by the Colombian Geological Survey is employed. It comprises recordings from earthquakes associated with the subduction of the Nazca plate gathered by the National Strong Motion Network in Colombia and by the Institute of Geophysics at Escuela Politécnica Nacional in Ecuador. The regional terms of our model are estimated with 539 records from 60 subduction events in Colombia and Ecuador with epicenters in the range of −0.6° to 7.6°N and 75.5° to 79.6°W, with Mw≥4.5, hypocentral depth range of 4 ≤  Zhypo ≤ 210 km, for distances up to 350 km. The model includes forearc and backarc terms to account for larger attenuation at backarc sites for slab events and site categorization based on natural period. The proposed model corrects the median AG2020 global model to better account for the larger attenuation of local ground motions and includes a partially non-ergodic variance model.

Applying the risk principle to optimize accuracy and equity in correctional risk assessment: Results From a Simulation

2021 ◽  
pp. 0306624X2098652
Author(s):  
Grant Duwe
Keyword(s):  
Risk Assessment ◽  
Predictive Accuracy ◽  
Ethnic Disparities ◽  
Simulated Data ◽  
Risk Assessments ◽  
Risk Level ◽  
Risk Levels ◽  
Risk Principle ◽  
Changes In Risk ◽  
The Impact

As the use of risk assessments for correctional populations has grown, so has concern that these instruments exacerbate existing racial and ethnic disparities. While much of the attention arising from this concern has focused on how algorithms are designed, relatively little consideration has been given to how risk assessments are used. To this end, the present study tests whether application of the risk principle would help preserve predictive accuracy while, at the same time, mitigate disparities. Using a sample of 9,529 inmates released from Minnesota prisons who had been assessed multiple times during their confinement on a fully-automated risk assessment, this study relies on both actual and simulated data to examine the impact of program assignment decisions on changes in risk level from intake to release. The findings showed that while the risk principle was used in practice to some extent, the simulated results showed that greater adherence to the risk principle would increase reductions in risk levels and minimize the disparities observed at intake. The simulated data further revealed the most favorable outcomes would be achieved by not only applying the risk principle, but also by expanding program capacity for the higher-risk inmates in order to adequately reduce their risk.

Sign in / Sign up

Export Citation Format

Share Document