spectral acceleration
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Author(s):  
Yeudy F. Vargas-Alzate ◽  
Jorge E. Hurtado ◽  
Luis G. Pujades

AbstractThis paper focuses on the probabilistic analysis of Intensity Measures (IMs) and Engineering Demand Parameters (EDPs) in the context of earthquake-induced ground motions. Several statistical properties, which are desirable in IMs when they are used to predict EDPs, have been analysed. Specifically, efficiency, sufficiency and steadfastness have been quantified for a set of IMs with respect to two EDPs: the maximum inter-storey drift ratio, MIDR, and the maximum floor acceleration, MFA. Steadfastness is a new statistical property proposed in this article, which is related to the ability of IMs to forecast EDPs for large building suites. In other words, this means that efficiency does not significantly vary when different types of buildings are simultanously considered in the statistical analyses. This property allows reducing the number of calculations when performing seismic risk estimations at urban level since, for instance, a large variety of fragility curves, representing specific building typologies, can be grouped together within a more generic one. The main sources of uncertainty involved in the calculation of the seismic risk have been considered in the analysis. To do so, the nonlinear dynamic responses of probabilistic multi-degree-of-freedom building models, subjected to a large data set of ground motion records, have been calculated. These models have been generated to simulate the dynamic behavior of reinforced concrete buildings whose number of stories vary from 3 to 13. 18 spectrum-, energy- and direct-accelerogram-based IMs have been considered herein. Then, from clouds of IM-EDP points, efficiency, sufficiency and steadfastness have been quantified. For MIDR, results show that IMs based on spectral velocity are more efficient and steadfast than the ones based on spectral acceleration; spectral velocity averaged in a range of periods, AvSv, has shown to be the most efficient IM with an adequate level of steadfastness. For MFA, spectral acceleration-based-IMs are more efficient than velocity-based ones. A comparison is also presented on the use of linear vs quadratic regression models, and their implications on the derivation of fragility functions. Concerning sufficiency, most of the 18 IMs analysed do not have this property. Nonetheless, multi-regression models have been employed to address this lack of sufficiency allowing to obtain a so-called ‘ideal’ IM.


2021 ◽  
Author(s):  
Muhammad Waseem ◽  
Mustafa Erdik

Abstract Probabilistic seismic hazard assessment of Pakistan is carried out to compute hazard in terms of peak ground acceleration (PGA) and spectral acceleration (SA) for 975 and 2475 years return periods. A composite earthquake catalogue consisting of 32,700 events has been compiled having a magnitude range of Mw 4.0-8.2 in this study and used in the analysis to make computations at a rectangular grid of 5 km in the OpenQuake plateform. Ground motion values have been obtained for flat rock reference seismic site conditions with shear wave velocity of 760 m/s. The epistemic uncertainties inherent in ground motion prediction equations and maximum magnitude potential of seismic sources are taken into account through logic tree. Ground motion prediction equations are assigned equal weights in the logic tree while different various weight are assigned to the maximum magnitude potential models. Results of the study are expressed as ground motion contour maps, mean uniform hazard spectra for important cities in Pakistan. PGA ranges from 0.16 to 0.54g for 10 % of probability of exceedance, 0.23 to 0.72g of probability of exceedance 0.32 to 1.02 g for 2 % of probability of exceedance in 50 years. Spectral acceleration at 0.2 s range from 0.67 to 2.19g for 2% chance of exceedance in 50 years, respectively. While spectral acceleration at 1.0 s values range from 0.09 to 0.52g 2% chance of exceedance in 50 years. Comparison of results of this study with other well regarded references of suggest that results of the study are rational and are reliable.


2021 ◽  
pp. 875529302110582
Author(s):  
Ioanna Kavvada ◽  
Scott Moura ◽  
Arpad Horvath ◽  
Norman Abrahamson

Regional seismic hazard analyses are necessary to assess the infrastructure performance within a region and ensure that mitigation funds are utilized effectively by probabilistically considering the suite of potential earthquake events. This research aims to efficiently represent the regional seismic hazard through a compact set of seismic inputs in the form of spectral acceleration (SA) maps by considering the spatial cross-correlation of SA at a wide period range. The SA maps can then be used to probabilistically estimate the performance of a portfolio of spatially distributed structures with different fundamental periods. Efficient representation reduces the number of required SA maps to decrease the computational demands of the infrastructure performance analysis in the subsequent steps. The added dimension of the between-period spatial SA correlation exacerbates the challenge of effectively simulating and selecting a set of SA maps to reproduce the hazard curves particularly at long return periods. Two approaches are proposed to generate an optimal set of SA maps: (a) a simulation-based methodology that uses state-of-the-art variance reduction methods and (b) a simplified methodology that aims to increase the ease of use and reduce the computational demands of the simulation. The two approaches are implemented and compared using the city of San Francisco as a case study to illustrate their feasibility. The simplified approach increases the scalability of the methodology to larger study areas at the expense of reduced accuracy in terms of seismic hazard curve and SA correlation errors.


2021 ◽  
Vol 933 (1) ◽  
pp. 012031
Author(s):  
Y Muntafi ◽  
N Nojima

Abstract The M6.1 earthquake which hit Malang and its surroundings in 2021 resulted in fatalities and over 10,400 damaged houses. Several seismicity studies have been carried out for Malang region, but no specific studies have implied the M6.1 Malang earthquake yet. This study addresses such gap by investigating the Spatio-temporal b-value of Gutenberg-Richter Law and generating the microzonation maps of spectral acceleration by considering the effects of the M6.1 Malang earthquake. The earthquake data compiled from the national and international earthquake catalogs were homogenized into a moment magnitude scale. The b-value analysis was calculated using the Maximum Likelihood method and spatio-temporal mapping. Several ground motion prediction equations (GMPEs) were selected for subduction and shallow crustal earthquake sources to generate probabilistic seismic hazard analysis (PSHA). PSHA was conducted using the 2% probability of exceedance in 50 years. The results show that the b-value after the M6.1 Malang earthquake still tends to decrease, indicating a relatively-high stress level which accommodates the potential for large earthquakes in the future. The microzonation maps for Malang region show that the southern part of Malang has a higher spectral acceleration value than the others. Therefore, these findings can be considered in the future disaster mitigation plan.


Author(s):  
Utkarsh Mishra

Abstract: In this paper we study certain modelling techniques by which the concept of soil structure interaction can be simulated in engineering problems and become fruitful for modern construction methods. For practical examination, a baseline model is prepared and put in comparison with an isolated base model which conforms to a rigid bathtub model with spring arrangement. Soil flexibility is taken into consideration during modeling. These modelling techniques are analysed using response spectrum analysis to get the maximum response of seismic parameters like storey forces and spectral acceleration. The study showed that the isolated base model had a superior seismic response and may be used in a variety of engineering applications, such as the design of new infrastructure, such as structures for storing water or other types of sediment, geotechnical modelling. Keywords: Baseline Model, Storey Forces, Spectral Acceleration, Soil Flexibility Rigid Bathtub Model


2021 ◽  
pp. 875529302110438
Author(s):  
Chenying Liu ◽  
Jorge Macedo

The PEER NGA-Sub ground-motion intensity measure database is used to develop new conditional ground-motion models (CGMMs), a set of scenario-based models, and non-conditional models to estimate the cumulative absolute velocity ([Formula: see text]) of ground motions from subduction zone earthquakes. In the CGMMs, the median estimate of [Formula: see text] is conditioned on the estimated peak ground acceleration ([Formula: see text]), the time-averaged shear-wave velocity in the top 30 m of the soil ([Formula: see text]), the earthquake magnitude ([Formula: see text]), and the spectral acceleration at the period of 1 s ([Formula: see text]). Multiple scenario-based [Formula: see text] models are developed by combining the CGMMs with pseudo-spectral acceleration ([Formula: see text]) ground-motion models (GMMs) for [Formula: see text] and [Formula: see text] to directly estimate [Formula: see text] given an earthquake scenario and site conditions. Scenario-based [Formula: see text] models are capable of capturing the complex ground-motion effects (e.g. soil non-linearity and regionalization effects) included in their underlying [Formula: see text]/[Formula: see text] GMMs. This approach also ensures the consistency of the [Formula: see text] estimates with a [Formula: see text] design spectrum. In addition, two non-conditional [Formula: see text] GMMs are developed using Bayesian hierarchical regressions. Finally, we present comparisons between the developed models. The comparisons show that if non-conditional GMMs are properly constrained, they are consistent with scenario-based GMMs. The [Formula: see text] GMMs developed in this study advance the performance-based earthquake engineering practice in areas affected by subduction zone earthquakes.


2021 ◽  
Author(s):  
Rahman Tauhidur ◽  
Ricky L Chhangte

Abstract This article presented ground motion model (GMM) for vertical peak ground acceleration (PGA) and pseudo spectral acceleration (Sa) at 5 % damping for North-east India (NEI) and adjacent regions at a time period of 0.01 to 5 s, and hypocentral distance 40 to 300 km. We used combined point source (4.5 ≤ Mw ≤ 6.5) and finite fault model (6.5 < Mw ≤ 9.5) (refer as combined model) to develop GMM for vertical component of ground motion (VCGM) for the region. The vertical GMM obtained is validated with the available recorded events in NEI and adjacent regions for the interface subduction zone earthquakes. It is observed that peak ground accelerations and spectral accelerations are 55 to 65% lesser than the horizontal components of ground motions. VCGM parameters obtained in this study play an important role in designing low rise buildings and linear superstructures such as bridges, silos and chimneys.


2021 ◽  
Author(s):  
Yeudy Felipe Vargas-Alzate ◽  
Jorge E. Hurtado ◽  
Lluis G. Pujades

Abstract This paper focuses on the probabilistic analysis of Intensity Measures (IMs) and Engineering Demand Parameters (EDPs) for earthquake excitations. Several statistical properties, which are desirable in IMs when they are used to predict EDPs, have been analyzed. The main sources of uncertainty involved in the calculation of the seismic risk have been considered in the analysis. Efficiency, sufficiency and steadfastness have been quantified for a set of IMs with respect to two EDPs: the maximum inter-storey drift ratio, MIDR, and the maximum floor acceleration, MFA. Steadfastness is a new statistical property proposed in this article. It is related to the ability of IMs to forecast EDPs for big building suites. This also means that efficiency does not significantly vary when different types of buildings are included in the statistical analyses. This property allows reducing the number of calculations when performing seismic risk estimations at urban level since, for instance, a large variety of fragility curves of specific buildings can be grouped together within an only one, but more generic, fragility function. The nonlinear dynamic response of probabilistic multi-degree-of-freedom buildings’ models, subjected to a large data set of ground motion records, have been considered to perform the statistical analysis. Specifically, reinforced concrete buildings whose number of stories vary from 3 to 13 stories have been analysed. 18 spectrum-, energy- and direct-accelerogram-based IMs have been considered harein. From the statistical properties of the generated clouds of IM-EDP points, efficiency and sufficiency properties have been quantified. For MIDR, results show that IMs based on spectral velocity are more efficient and steadfast than the ones based on spectral acceleration; spectral velocity averaged in a range of periods, AvSv, has shown to be the most efficient and steadfast IM. The opposite happens for MFA, that is, spectral acceleration-based-IMs are more efficient than the velocity-based ones. A comparison on the use of linear vs quadratic regression models, and their implications on the derivation of fragility functions, is presented as well. Concerning sufficiency, most of the 18 basic IMs analyzed herein do not have this property. However, multi-regression models have been employed to address this lack of sufficiency allowing to obtain a so-called ‘ideal’ IM.


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