Using Spectral Acceleration Area as an Intensity Measure Parameter for Accurate Estimation of Seismic Demand

2015 ◽  
Keyword(s):  
Accurate Estimation ◽  
Seismic Demand ◽  
Spectral Acceleration ◽  
Intensity Measure

Conditional Ground-Motion Model for Damaging Characteristics of Near-Fault Ground Motions Based on Instantaneous Power

2020 ◽  
Vol 110 (6) ◽  
pp. 2828-2842
Author(s):  
Esra Zengin ◽  
Norman Abrahamson
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Accurate Estimation ◽  
Spectral Acceleration ◽  
Motion Model ◽  
Velocity Pulse ◽  
Near Fault ◽  
Instantaneous Power ◽  
Ground Motion Model ◽  
Short Time

ABSTRACT The velocity pulse in near-fault ground motions has been used as a key characteristic of damaging ground motions. Characterization of the velocity pulse involves three parameters: presence of the pulse, period of the pulse, and amplitude of the pulse. The basic concept behind the velocity pulse is that a large amount of seismic energy is packed into a short time, leading to larger demands on the structure. An intensity measure for near-fault ground motions, which is a direct measure of the amount of energy arriving in short time, called instantaneous power (IP (T1)), is defined as the maximum power of the bandpass-filtered velocity time series measured over a time interval of 0.5T1, in which T1 is the fundamental period of the structure. The records are bandpass filtered in the period band (0.2T1−3T1) to remove the frequencies that are not expected to excite the structure. Zengin and Abrahamson (2020) showed that the drift is better correlated with the IP (T1) than with the velocity pulse parameters for records scaled to the same spectral acceleration at T1. A conditional ground-motion model (GMM) for the IP is developed based on the 5%-damped spectral acceleration at T1, the earthquake magnitude, and the rupture distance. This conditional GMM can be used for record selection for near-fault ground motions that captures the key features of velocity pulses and can lead to a better representation of the median and variability of the maximum interstory drift. The conditional GMM can also be used in a vector hazard analysis for spectral acceleration (T1) and IP (T1) that can be used for more accurate estimation of drift hazard and seismic risk.

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.

Seismic design spectra for different soil classes

2013 ◽  
Vol 46 (2) ◽  
pp. 79-87 ◽  
Author(s):  
Rajesh P. Dhakal ◽  
Sheng-Lin Lin ◽  
Alexander K. Loye ◽  
Scott J. Evans
Keyword(s):  
Seismic Design ◽  
Soft Soil ◽  
Response Analysis ◽  
Seismic Demand ◽  
Analysis Tool ◽  
Spectral Acceleration ◽  
Acceleration Response ◽  
Design Spectra ◽  
Nonlinear Site Response ◽  
Short Period

This paper investigates the validity of the soil class dependent spectral shape factors used to calculate seismic design actions in the New Zealand seismic design standard NZS1170.5, which currently specifies seismic design spectra corresponding to five different soil classes. According to the current provisions stipulated in NZS1170.5, for all natural periods, the seismic demand for structures on soft soil is either equal to or greater than that for structures on hard soil. This is opposite to the basic structural dynamics theory which suggests that an increase in stiffness of a system results in an increase in the acceleration response. In this pretext, a numerical parametric study is undertaken using a nonlinear site response analysis tool in order to capture the effect of soil characteristics on structural seismic demand and to scrutinize the validity of the current site specific seismic design spectra. It is identified that the level of input ground motion intensity and shear stiffness of the soil deposit (represented by its shear wave velocity Vs) greatly affect the maximum acceleration and frequency content of the surface motion. The study found some shortfalls in the way the current code defines seismic design demand, in particular the hierarchy of soil stiffness at low structural periods. It was found that stiff soils generally tend to have a higher spectral acceleration response in comparison to soft soils although this trend is less prominent for high intensity bed rock motions. It was also found that for medium to hard soils the spectral acceleration response at short period is grossly underestimated by the current NZS1170.5 provisions. Based on the outcomes of the parametric numerical analyses, a revised strategy to determine structural seismic demand for different soil classes is proposed and its application is demonstrated through an example.

Improved intensity measures for probabilistic seismic demand analysis. Part 2: application of the improved intensity measures

2011 ◽  
Vol 38 (1) ◽  
pp. 89-99 ◽  
Author(s):  
Lan Lin ◽  
Nove Naumoski ◽  
Murat Saatcioglu ◽  
Simon Foo
Keyword(s):  
Demand Analysis ◽  
Seismic Demand ◽  
Intensity Measure ◽  
Reinforced Concrete Frame ◽  
Intensity Measures ◽  
Seismic Demands ◽  
Concrete Frame ◽  
Probabilistic Seismic Demand Analysis ◽  
Frame Buildings ◽  
Probabilistic Seismic Demand

This is the second of two companion papers on improved intensity measures of strong seismic ground motions for use in probabilistic seismic demand analysis of reinforced concrete frame buildings. The first paper discusses the development of improved intensity measures. This paper describes the application of the developed intensity measures in probabilistic seismic demand analysis. The application is illustrated on the three reinforced concrete frame buildings (4, 10, and 16-storey high) that were used in the first paper. This involved computations of the seismic responses of the structures and the seismic hazard using the improved intensity measures. The response and the hazard results were then combined by means of probabilistic seismic demand analysis to determine the mean annual frequencies of exceeding specified response levels due to future earthquakes (i.e., the probabilistic seismic demands). For the purpose of comparison, probabilistic seismic demand analyses were also conducted by employing the spectral acceleration at the fundamental structural periods (Sa(T1)) as an intensity measure, which is currently the most used in practice. It was found that the use of the improved intensity measures results in significantly lower seismic demands relative to those corresponding to the intensity measure represented by Sa(T1), especially for long period structures.

Average spectral acceleration as an intensity measure for collapse risk assessment

2015 ◽  
Vol 44 (12) ◽  
pp. 2057-2073 ◽  
Author(s):  
Laura Eads ◽  
Eduardo Miranda ◽  
Dimitrios G. Lignos
Keyword(s):  
Risk Assessment ◽  
Spectral Acceleration ◽  
Intensity Measure

scholarly journals Fragility Analyses of Bridge Structures Using the Logarithmic Piecewise Function-Based Probabilistic Seismic Demand Model

2021 ◽  
Vol 13 (14) ◽  
pp. 7814
Author(s):  
Yinghao Zhao ◽  
Hesong Hu ◽  
Lunhua Bai ◽  
Mengxiong Tang ◽  
Hang Chen ◽  
...  
Keyword(s):  
Fragility Curves ◽  
Statistical Significance ◽  
Seismic Intensity ◽  
Fragility Analysis ◽  
Seismic Demand ◽  
Demand Model ◽  
Intensity Measure ◽  
System Fragility ◽  
Probabilistic Seismic Demand ◽  
Seismic Demand Model

Seismic fragility analysis is an efficient method to evaluate the structural failure probability during earthquake events. Among the existing fragility analysis methods, the probabilistic seismic demand model (PSDM) and the joint probabilistic seismic demand model (JPSDM) are generally used to compute the component and system fragility, respectively. However, the statistical significance behind the parameters related to the current PSDM and JPSDM are not comparable. Aside from that, when calculating the system fragility, the Monte Carlo sampling (MCS) method is time-consuming. To solve the two flaws, in this paper, the logarithm piecewise functions were used to generate the PSDM and the JPSDM, and the MCS was replaced by the univariate conditioning approximation (UCA) method. The concepts and application procedures of the proposed fragility analysis methods were elaborated first. Then, the UCA method was illustrated in detail. Finally, fragility curves of a steel arch truss case study bridge were generated by the proposed method. The research results indicate the following: (1) the proposed methods unify the data sources and statistical significance of the parameters used in the PSDM and the JPSDM; (2) the logarithmic piecewise function-based PSDM sensitively reflects the changing trend of the component’s demand with the fluctuation of the seismic intensity measure; (3) under transverse seismic waves, major injuries happen on the side bearings of the bridge, while slight damage may occur on each pier, and as the seismic intensity measure increases, the side bearings are more likely to be damaged; (4) for the severe damage and the absolute damage of the studied bridge, the system fragility curves are closer to the upper failure bounds; and (5) compared with the MSC method, the accuracy of the UCA method can be guaranteed with less calculation time.

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