Ground Motion Selection and Scaling in Practice

Abstract

IntroductionSeismic provisions in current building codes and standards include rules for design of structures using nonlinear response history analysis in some conditions. Due to the lack of recorded data for the design level earthquakes (which are usually rare events), it is critical to develop systematic methods and useful tools to select and modify from current ground motion databases to provide a group of earthquake motions that can realistically represent important aspects of the design motion controlling the nonlinear response of civil engineering facilities [1]. The best method for selecting and scaling ground motions will depend on the type of assessment being performed. ATC-58-1 identifies three types of performance assessment: intensity, scenario, and time-based. Intensity-based assessments are the most common of the three types and compute the response of a building and its components for a specified intensity of ground shaking (this approach is the focus of this paper). A scenario-based assessment computes the response of a building to a user specified earthquake event, which is typically defined by earthquake magnitude and the distance between the earthquake source and the building site. A risk-based (referred to as time-based assessment in ATC-58-1) assessment provides information on response over a period of time (e.g., annual rates). This is the most comprehensive type of assessment and involves a number of intensity-based assessments over the range of ground motion levels of interest [2]. Despite the scenario-based assessment which computes the response of a building based on a specific earthquake event, intensity and time-based assessments have been conducted subjecting to a group of records. Time-based assessment acquires information of all occurred earthquakes which have been utilized to adjust hazard curve of the assessed region; so, as much as records could be provided, the confidence level will promote, so many researchers attempts to enlarge records category to reduce record-by-record variations incorporated in this type of assessment. However, intensity-based assessment deal with number of records represented by intensity measures (IM), like peak ground acceleration, spectral acceleration on fundamental period of the model or etc., which are scaled associated to the intensity assumed target spectrum. Therefore, although enlarge-

Equation for achieving efficient length of link-beams in eccentrically braced frames and its reliability validation

“…How to choose the records are beyond the scope of this paper and for further detail the reader is referred to the paper [35]. Records were derived from PEER Strong Motion Database [36] and Iran Strong Motion Network Data Bank [37].…”

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“…However, the codes specify a number that should be used, though the number is different between the codes. Najafi et al [14] recommended selecting seven ground motions (based on the ASCE05-7 code recommendations) or eleven ground motions (based on the ATC recommendations). The codes UBC 1997, IBC 2000, FEMA-356, EC8, ASCE 2006 and ASCE 2007 recommend three or seven as a minimum number of ground motions to use the mean of the demand parameter in analysing the structure.…”

“…With regard to other parameters, such as event magnitude, peak ground acceleration, soil type and distance between the epicentre of the ground motion and the affected area, Najafi et al [14] summarised the process of ground motion selection based on these aspects. They then proposed approach of record selection (step-by-step), determined the primary list of records, chose a representative record for each earthquake event, selected the minimum number of records and explained and performed scaling of the ground motions.…”

Ground Motion Record Selection using Multi-objective Optimization Algorithms: A Comparative Study

“…Kayhan et al [8] proposed a harmony search based earthquake record selection and scaling solution in order to obtain ground motions which are compatible with the design spectrum. Najafi and Tehranizadeh [9] provided a very simple and practical procedure for selecting ground motions in addition to compare two common scaling methods based on the uniform hazard spec-trum (UHS) method and presents scale factors of the selected ground motions related with these methods. Macedo and Castro [10] described an advanced record selection and scaling utilizing Harmony search.…”