Which Spectral Acceleration are you Using?

2006 ◽  
Vol 22 (2) ◽  
pp. 293-312 ◽  
Author(s):  
Jack W. Baker ◽  
C. Allin Cornell
Keyword(s):  
Seismic Risk ◽  
Hazard Analysis ◽  
Ground Motions ◽  
Geometric Mean ◽  
Response Analysis ◽  
Spectral Acceleration ◽  
Intensity Measure ◽  
Structure Response ◽  
Future Earthquake ◽  
Structural Engineers

Analysis of the seismic risk to a structure requires assessment of both the rate of occurrence of future earthquake ground motions (hazard) and the effect of these ground motions on the structure (response). These two pieces are often linked using an intensity measure such as spectral acceleration. However, earth scientists typically use the geometric mean of the spectral accelerations of the two horizontal components of ground motion as the intensity measure for hazard analysis, while structural engineers often use spectral acceleration of a single horizontal component as the intensity measure for response analysis. This inconsistency in definitions is typically not recognized when the two assessments are combined, resulting in unconservative conclusions about the seismic risk to the structure. The source and impact of the problem is examined in this paper, and several potential resolutions are proposed. This discussion is directly applicable to probabilistic analyses, but also has implications for deterministic seismic evaluations.

A spectral-acceleration-based combination-type earthquake intensity measure for high-rise stack-like structures

2019 ◽  
Vol 23 (7) ◽  
pp. 1350-1366 ◽  
Author(s):  
Yikun Qiu ◽  
Changdong Zhou ◽  
Siha A ◽  
Guangwei Zhang
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Spectral Acceleration ◽  
Intensity Measure ◽  
Earthquake Intensity ◽  
Intensity Measures ◽  
Higher Modes ◽  
High Rise ◽  
Near Fault ◽  
Period Elongation

Ground motion intensity measures are of great importance for the seismic design of structures. A well-chosen intensity measure will reduce the detailed ground motion record selection effort for the nonlinear dynamic structural analyses. In this article, a spectral-acceleration-based combination-type earthquake intensity measure is presented. This intensity measure considers the higher modes effect and period elongation effect due to nonlinear deformation at the same time. The modal mass participation factors are determined to take weighting coefficients and the product of elastic first-mode period T1 and a constant C is expressed to represent the elongated period. Therefore, the proposed intensity measure is a combination of earthquake ground motion characteristics, elastic structural responses, higher modes participation, and the period elongation effect due to inelastic structural behaviors. Four three-dimensional models of reinforced concrete stack-like structures including a 240 m-high chimney, a 180 m-high chimney, a 120 m-high chimney, and a 42.3 m-high water tower are established and analyzed in ABAQUS to investigate the correlation between the intensity measure and the maximum curvatures under 44 far-field ground motions and 28 near-fault ground motions with a pulse-like effect. With the optimal vibration modes and the proper period elongation coefficient, the efficiency of the introduced intensity measure is compared with the other 15 intensity measures. The results indicate that the proposed intensity measure is believed to be a good choice for high-rise stack-like structures, especially under the near-fault ground motions with pulse-like effect.

Istanbul at the Threshold: An Evaluation of the Seismic Risk in Istanbul

2007 ◽  
Vol 23 (1) ◽  
pp. 63-75 ◽  
Author(s):  
Jacob H. Pyper Griffiths ◽  
Ayhan Irfanoglu ◽  
Santiago Pujol
Keyword(s):  
Ground Motion ◽  
Emergency Response ◽  
Seismic Risk ◽  
Ground Motions ◽  
Convincing Evidence ◽  
Severe Damage ◽  
Future Earthquake ◽  
The City ◽  
Better Than

There is no convincing evidence indicating that future ground motion in at least two-thirds of Istanbul, Turkey, shall be less demanding than the ground motions that devastated the city of Düzce, Turkey, in 1999. Comparison of vulnerability indices calibrated for Turkish construction indicates that the structures of the buildings in Istanbul are no better than the structures of buildings in Düzce. On the basis of these arguments, we project that a future earthquake near Istanbul may cause severe damage or collapse approximately quarter of a million buildings. Leaving the vulnerable buildings as they are and organizing for emergency response is not an option for Istanbul.

Ground Motion Selection in the Near-Fault Region considering Directivity-Induced Pulse Effects

2019 ◽  
Vol 35 (2) ◽  
pp. 759-786 ◽  
Author(s):  
Karim Tarbali ◽  
Brendon A. Bradley ◽  
Jack W. Baker
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Hazard Analysis ◽  
Ground Motions ◽  
Seismic Hazard Analysis ◽  
Response Analysis ◽  
Seismic Demand ◽  
Ground Motion Selection ◽  
Near Fault ◽  
Fault Region

This paper focuses on the selection of ground motions for seismic response analysis in the near-fault region, where directivity effects are significant. An approach is presented to consider forward directivity velocity pulse effects in seismic hazard analysis without separate hazard calculations for ‘pulse-like’ and ‘non-pulse-like’ ground motions, resulting in a single target hazard (at the site of interest) for ground motion selection. The ability of ground motion selection methods to appropriately select records that exhibit pulse-like ground motions in the near-fault region is then examined. Applications for scenario and probabilistic seismic hazard analysis cases are examined through the computation of conditional seismic demand distributions and the seismic demand hazard. It is shown that ground motion selection based on an appropriate set of intensity measures (IMs) will lead to ground motion ensembles with an appropriate representation of the directivity-included target hazard in terms of IMs, which are themselves affected by directivity pulse effects. This alleviates the need to specify the proportion of pulse-like motions and their pulse periods a priori as strict criteria for ground motion selection.

Intensity Measure Correlations Observed in the NGA-West2 Database, and Dependence of Correlations on Rupture and Site Parameters

2017 ◽  
Vol 33 (1) ◽  
pp. 145-156 ◽  
Author(s):  
Jack W. Baker ◽  
Brendon A. Bradley
Keyword(s):  
Geometric Mean ◽  
Condition Dependence ◽  
Peak Ground Velocity ◽  
Spectral Acceleration ◽  
Intensity Measure ◽  
Ground Acceleration ◽  
Correlation Models ◽  
Continued Use ◽  
S Peak ◽  
Ground Motion Intensity Measure

This manuscript reports ground motion intensity measure ( IM) correlations for a number of IM types, as measured from the NGA-West2 database. IMs considered are Spectral Accelerations with periods from 0.01 s to 10 s, Peak Ground Acceleration, Peak Ground Velocity, and Significant Duration (for 5–75% and 5–95% definitions). Results are shown for correlations of both maximum-direction and geometric mean spectral acceleration values, given the need for such maximum-direction correlations in a new ASCE 7-16 procedure. Additionally, the potential magnitude-, distance- and site-condition-dependence of IM correlations are evaluated. The results are practically important as IM correlations are increasingly used in a range of engineering and seismic hazard calculations. We find that maximum-direction spectral correlations are comparable to correlations for other spectral acceleration definitions, and that the correlations have no practically significant dependence on magnitude, distance or site conditions. These results support the collective understanding that IM correlations are stable across a range of conditions, and as a result, that existing correlation models are generally appropriate for continued use in engineering calculations.

scholarly journals DEVELOPMENT OF SEISMIC MICROZONATION MAPS OF SEMARANG, INDONESIA

2015 ◽  
Vol 77 (11) ◽  
Author(s):  
Windu Partono ◽  
Sri Prabandiyani Retno Wardani ◽  
Masyhur Irsyam ◽  
Syamsul Maarif
Keyword(s):  
Seismic Risk ◽  
Response Analysis ◽  
Spectral Acceleration ◽  
Ground Response Analysis ◽  
Ground Acceleration ◽  
Local Site Effects ◽  
Geotechnical Parameters ◽  
Local Site ◽  
Single Station ◽  
Fault Interpretation

The new Indonesian Code for seismic resistance design for building has been issued recently. It follows the concept of Risk-Targeted Maximum Considered Earthquake (MCER). Seismic risk microzonation of Semarang is analyzed using the new concept.  Seismic risk microzonation study for hazard mitigation is also performed for the whole city based on deterministic approach, considering the closes distance fault (Lasem Fault). Interpretation of local site effects is performed by carrying one-dimensional ground response analysis. Depth of bedrock is estimated based on single station feedback seismometer measurement. Geotechnical parameters are interpreted from recent and previous measurements. The result of deterministic microzonation study includes the distribution of surface peak ground acceleration (PGA) and spectral acceleration due to Lasem Fault. The obtained results are compared with the distribution of surface PGA and spectral acceleration obtained through new code. 

scholarly journals Representative ground-motion ensembles for several major earthquake scenarios in New Zealand

2014 ◽  
Vol 47 (4) ◽  
pp. 231-252 ◽  
Author(s):  
Karim Tarbali ◽  
Brendon A. Bradley
Keyword(s):  
New Zealand ◽  
Ground Motion ◽  
Hazard Analysis ◽  
Ground Motions ◽  
Conditional Intensity ◽  
Intensity Measure ◽  
Earthquake Scenarios ◽  
Major Earthquake ◽  
The Mean ◽  
Representative Ground

In this paper, representative ground motion ensembles for several major earthquake scenarios in New Zealand are developed. Cases considered include representative ground motions for the occurrence of Alpine, Hope and Porters Pass earthquakes in Christchurch city, and the occurrence of Wellington, Wairarapa and Ohariu fault ruptures in Wellington city. For each considered scenario rupture, ensembles of 20 and 7 ground motions are selected using the generalized conditional intensity measure (GCIM) approach, ensuring that the ground motion ensembles represent both the mean and distribution of ground motion intensity which such scenarios could impose. These scenario-based ground motion sets can be used to complement ground motions which are often selected in conjunction with probabilistic seismic hazard analysis, in order to understand the performance of structures for the question “what if this fault ruptures?”

Seismic Risk Assessment of Structures Using Multiple Stripe Analysis

2012 ◽  
Vol 226-228 ◽  
pp. 897-900
Author(s):  
Peng Peng Ni ◽  
Shu Hong Wang ◽  
Lei Jiang ◽  
Run Qiu Huang
Keyword(s):  
Risk Assessment ◽  
Seismic Risk ◽  
Hazard Analysis ◽  
Ground Motions ◽  
Point Of View ◽  
Seismic Risk Assessment ◽  
Existing Structures ◽  
Fragility Function ◽  
Hazard Curve ◽  
Assessment Procedures

The implementation of seismic risk assessment of existing structures is necessitated for practical engineers to select the retrofitting strategies. The reliability based approaches are proposed to investigate the behaviour of structures subjected to ground excitation and encouraging evaluation results of various typologies of structures have been obtained exploiting such methodologies. The decision regarding the retrofitting strategies that will rehabilitate the flaws of the structure under prescribed ground motions that have high probability of occurrences at the scenario can be made. This paper addresses the generation of hazard curve by probabilistic seismic hazard analysis from the seismological point of view. The multiple stripe analysis, as one of typical probabilistic based assessment procedures, will be utilized to evaluate the structural seismic fragility. The seismic risk can be estimated based on the numerically integrating the fragility function with the hazard curve.

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