Selecting Real Seismic Records and Scaling it to Fit the Syrian Design Spectra using Genetic Algorithm

In this study, basic methodologies of the GA and the scaling procedures are summarized, the scaling criteria of real time history records to satisfy the Syrian design code are discussed. The traditional time domain scaling procedures and the scaling procedures using GA are utilized to scale a number of the available real records to match the Syrian design spectra. The resulting time histories of the procedures are investigated and compared in terms of meeting criteria.

Nonlinear Dynamic Analysis of Structures Located in Lattakia City using Real Seismic Records Compatible with Syrian Design Spectra

: Nonlinear response history evaluation is becoming a practical tool due to availability of high performance computing and recommendations of the new seismic guidelines, and due to the increase of available strong ground motion database. When testing the selected and scaled ground motions, it’s a standard procedure to use the time history analysis to validate the results in terms of structural responses and their variation. this proves the efficiency of the presented procedure. In this study the selection and scaling criteria of real time history records to satisfy the Syrian design code are discussed. Ten set of records have been selected and scaled, every set consists of seven records of available real records, to match the Syrian design spectra. The resulting time histories are investigated and compared in terms of suitability as input to time history analysis of civil engineering structures, by mean of time history analyses of SDOF systems which are conducted to examine the efficiency of the scaling method in reducing the scatter in structural response. The nonlinear response of SDOF systems is represented by bilinear hysteretic model. Assuming 5 different Periods, α=3% post-yield stiffness, a number of 700 runs of analysis are conducted. And a number of 280 runs of analysis are conducted for MDOF systems.

Validation of Real Seismic Records Sets for Nonlinear Dynamic Analysis of Structures Located in Lattakia City - Syria

Structural design for seismic loading, which is traditionally done for most types of common structures by the means of equivalent lateral static loading or modal spectrum analysis, is no longer a preferred methodology for design of modern structures with complex topology and functionality under extreme loading scenarios. Nonlinear response history evaluation, on the other hand, is becoming a practical tool due to availability of high performance computing and recommendations of the new seismic guidelines, and due to the increase of available strong ground motion database. Therefor using and scaling real recorded accelerograms is becoming one of the most contemporary research issues in this field. Seismological characteristics of the records, such as earthquake magnitude, epicentral distance and site classification are usually considered in the selection of real records, as they influence the shape of the response spectrum, the energy content and duration of strong ground shaking, and therefore the expected demand on structures. After real seismic records selection it is necessary to scale these records to match the intensity of the earthquake expected for the site. Generally, scaling can be made by ground motions uniform scaling in time domain which is simply scaled up or down the ground motions uniformly to best match (in average) the target spectrum within a period range of interest. It’s an engineer’s job to find the best scaling factors to best match the target spectrum, which is a complex task, so we employed the Genetic Algorithm (GA) in finding them to achieve the best results. When testing the selected and scaled ground motions, it’s a standard procedure to use the nonlinear time history analysis to validate the results in terms of structural responses and their variation. this proves the efficiency of the presented procedure. In this study, basic methodologies for selecting and scaling strong ground motion time histories are summarized, the selection and scaling criteria of real time history records to satisfy the Syrian design code are discussed. The GA scaling procedures are utilized to scale 10 set of records, every set consists of seven records of available real records to match the Syrian design spectra. The resulting time histories are investigated and compared in terms of suitability as input to time history analysis of civil engineering structures, by mean of time history analyses of SDOF systems which are conducted to examine the efficiency of the scaling method in reducing the scatter in structural response. The nonlinear response of SDOF systems is represented by bilinear hysteretic model. Assuming 5 different Periods, yield strength reduction factor, R= 4.5, α=3% post-yield stiffness, a number of 700 runs of analysis are conducted. The results are described for elastic displacement D.

Spectral Matching by Wavelets vs. ASCE Ground Motion Uniform Scaling in Time Domain

Design ground motions are typically prescribed by smooth response spectra. Engineers often prefer to use a time history that matches the target design spectrum rather than evaluate a structure for a sit of time histories that are representative of the target spectrum in an ensemble average. Generally, scaling actual time histories to match a given design spectrum can be made by two preferred methods: First, ground motions uniform scaling in time domain which is simply scaled up or down the ground motion uniformly to best match the target spectrum within a period range of interest, without changing the frequency content. Second, spectral matching in time domain which produces only localized perturbations on both the time history and the its response spectrum, where small adjustments can be made to a time history to change its response spectrum from jagged to smooth, if done properly the resulting time history can be “realistic”. The realistic nature of a time history should be judged in the time domain in terms of the non stationary character of acceleration, velocity and displacement, for that the effectiveness of the two methods is examined by applying them to adjust actual earthquake time histories to much the design spectra while minimizing perturbations on their characteristics. The procedures are utilized to scale 15 set of records, every set consists of seven records of available real records to match the Syrian design spectra. The resulting time histories are investigated and compared in terms of suitability as input to time history analysis of civil engineering structures

Comparison study of total displacements of multi-story buildings subjected to earthquake using synthetic timehistory records compatible with Syrian code

Response spectrum analysis and equivalent static analysis is widely used by engineers and engineering offices to estimate buildings and structures response to earthquakes. But performance based procedures to evaluate buildings and new designs according to Syrian code and other international codes require response analysis using smallest of earthquake records, where we can estimate engineeringdemandparameters(EDPs)— floordisplacements,storydrifts,memberforces,memberdeformations,etc.— ofbuildingsandspecialstructuressubjectedtogroundmotions, consecutively to verify required performance criteria. Theserecordsshouldbeproperlyselectedandscaledincompliancewithsitespecifichazardconditionstoestimate (EDPs) and ensure that they verify ―expected‖ median demands. In this study, background, selection procedures compatible with Syrian code, and review of most scaling methods were introduced. The structural response was studied by comparing displacements due to response spectrum analysis, scaled records using PGA, and synthetic time histories records in time domain and frequency domain (generated according to Syrian response spectrum). Tow three-dimensional models of real buildings in Lattakia city were used as study cases, the results obtained by 20 analysis processes. The results show that analysis using synthetic records compatible with Syrian code give noticeably less displacements estimates comparing with response spectrum analysis and analysis using records scaled by PGA scaling.