• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.439-446
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• 1998

One of the most important roles in the nonlinear dynamic structural analysis is to select a proper ground excitation, which dominates the response of a structure. Because of the lack of recorded accelerograms in Korea, a stochastic model of ground excitation with various dynamic properties rather than recorded accelerograms is necessarily required. If all information is not available at site, the information from other sites with similar features can be used by the procedure of seismic hazard analysis. Eliopoulos and Wen identified the parameters of the ground motion model by the empirical relations or expressions developed by Trifunac and Lee. Because the relations used in the parameter identification are largely empirical, it is required to apply the artificial neural networks instead of the empirical model. Additionally, neural networks have the advantage of the empirical model that it can continuously re-train the new recorded data, so that it can adapt to the change of the enormous data. Based on the redefined traditional processes, three neural-networks-based models (FAS_NN, PSD_NN and INT_NN) are proposed to individually substitute the Fourier amplitude spectrum, the parameter identification of power spectral density function and intensity function. The paper describes the first half of the research for the development of Neural-Networks-based model for the generation of an Artificial earthquake and a Response Spectrum(NNARS).

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.28-35
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• 2002

The probabilistic seismic hazard analysis for engineering needs several active fault parameters as input data. Fault slip rates, the segmentation model for each fault, and the date of the most recent large earthquake in seismic hazard analysis are the critical pieces of information required to characterize behavior of the faults. Slip rates provide a basis for calculating earthquake recurrence intervals. Segmentation models define potential rupture lengths and are inputs to earthquake magnitude. The most recent event is used in time-dependent probability calculations. These data were assembled by expert source-characterization groups consisting of geologists, geophysicists, and seismologists evaluating the information available for earth fault. The procedures to prepare inputs for seismic hazard are illustrated with possible segmentation scenarios of capable fault models and the seismic hazards are evaluated to see the implication of considering capable faults models.

• Earthquakes and Structures
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• v.20 no.3
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• pp.337-351
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• 2021

On September 12, 2016, the Gyeongju earthquake occurred in the south-eastern region of the Korean peninsula. The event was ranked as the largest magnitude earthquake (=5.8) since instrumental recording was started by the Korean Metrological Administration (KMA) in 1978. The objective of this study is to provide information obtained from the 2016 Gyeongju earthquake and to propose a procedure estimating seismic risk of a typical old RC building for past and potential earthquakes. Ground motions are simulated using the point source model at 4941 grid locations in the Korean peninsula that resulted from the Gyeongju earthquake and from potential future earthquakes with the same hypocenter considering different soil conditions. Nonlinear response history analyses are conducted for each grid location using a three-story gravity-designed reinforced concrete (RC) frame that most closely represents conventional old school and public buildings. Then, contour maps are constructed to present the seismic risk associated with this building for the Gyeongju earthquake and potential future scenario earthquakes. These contour maps can be useful in the development of a mitigation plan for potential earthquake damage to school and public buildings at all grid locations on the Korean peninsula.

• Structural Engineering and Mechanics
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• v.29 no.2
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• pp.171-186
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• 2008

The seismic response analysis of an existing bridge needs a mathematical model that can be calibrated with measured dynamic characteristics. These characteristics are the periods and the associated mode shapes of vibration and the modal damping coefficients. This paper deals with the measurements and the interpretation of the results of ambient vibration tests done on a newly erected cable stayed bridge across the Oued Dib River at Mila city in Algeria. The signal analysis of ambient vibration records will permit to determine the dynamic characteristics of the bridge. On the other hand, a 3-D model of the bridge is developed in order to assess the frequencies and the associated modes of vibration. This information will be necessary in the planning of the test on the site (locations of the sensors, frequencies to be measured and the associated mode shapes of vibration). The frequencies predicted by the finite element model are compared with those measured during full-scale ambient vibration measurements of the bridge. In the same way, the modal damping coefficients obtained by the random decrement method are compared to those of similar bridges.

• Journal of the Korea Society of Computer and Information
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• v.26 no.5
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• pp.95-101
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• 2021

In this study, we present how to improve the current seismic disaster information service by utilizing Shake, which can express the effects of earthquakes in the form of isolines. Using ShakeMap software provided by the U.S. Geological Survey, an automated rapid ShakeMap generation system was implemented, and based on this, an earthquake disaster information service improvement model was presented to identify earthquake risk in the form of intensity or peak ground acceleration. In order to verify the feasibility and effectiveness of the improved model, the seismic disaster information service app. was developed and operated on a trial basis in Pohang, Gyeongsangbuk-do. As a result of the operation, it was found that more detailed seismic risk information could be provided by providing information using rapid ShakeMap to induce users' safety behavior more effectively.

• Structural Engineering and Mechanics
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• v.23 no.2
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• pp.177-193
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• 2006

Determining the hysteretic energy demand and dissipation capacity and level of damage of the structure to a predefined earthquake ground motion is a highly non-linear problem and is one of the questions involved in predicting the structure's response for low-performance levels (life safe, near collapse, collapse) in performance-based earthquake resistant design. Neural Network (NN) analysis offers an alternative approach for investigation of non-linear relationships in engineering problems. The results of NN yield a more realistic and accurate prediction. A NN model can help the engineer to predict the seismic performance of the structure and to design the structural elements, even when there is not adequate information at the early stages of the design process. The principal aim of this study is to develop and test multi-layered feedforward NNs trained with the back-propagation algorithm to model the non-linear relationship between the structural and ground motion parameters and the hysteretic energy demand in steel moment resisting frames. The approach adapted in this study was shown to be capable of providing accurate estimates of hysteretic energy demand by using the six design parameters.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.223-230
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• 1999

The seismic damage assessment to the postulated earthquake is attempted for the buildings in the model district of Seoul City. The capacity spectrum method is employed in which the vulnerability functions are expressed as functions of the spectral displacement. the database of the building stock is constructed and managed using Geographic Information System software. The model district is selected to represent the typical structural and residential characteristics of Seoul City The structural properties were collected from the design documents. The field inspections were carried out to find out the current status of the building. They are classified into 11 structural types. The fragility curves in HazUS are employed, The ground motions from the postulated earthquakes are simulated using the Boor's methods, The surface soil in the district is classified into 3 profiles using the depth as the parameter. The one-dimensional wave propagation method is used to calculate he filtered ground motion through surface soil layer. The average spectrum of this sample time histories is used as the demand curves. The calculated results are expressed in maps using GIS software ArcView 3.0a

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.36-41
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• 2002

In this study we produced 1-dimensional p wave velocity structure of the crust using 449 P arrivals of 35 stations and we analysed hypocenters of the southeastern Korean peninsula area. A initial velocity model was selected from the priori studies and 30 different initial models were generated using random number generation from it. Using the veriest program 30 different velocity structures were calculated and the result show that velocities are 5.8 - 6.4 km/sec within 6 - 16 km depth and 7 $\pm$ 0.2 km/sec within 20 - 30 km with resonable resolution. Hypocenters were relocated by using resulted 1-dimensional velocity model as a initial model. Recalculated hypocenters'depth are shallower than initial data and epicenters show a little better lineality around study area but more much earthquake information are needed fur the determination of relation between epicenter distribution and geological tectonic structures.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.123-130
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• 1998

The probability of unseating failure of the bridge spans under earthquakes is investigated. Seismic excitations are simulated as nonstationary processes by combining a stationary process and an intensity function. For computational convenience, a simplified single-degree-of-freedom model is adopted, which retains the dynamic characteristics of the original brige motion in concern. The time history analysis for the developed single degree-of-freedom model are carried out to evaluate the response processes, and the probabilistic characteristics of response displacements are evaluated. The reliability analysis of the bridge against the unseating failure is performed with the statistical information of the maximum displacements of responses.

• Smart Structures and Systems
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• v.23 no.2
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• pp.107-122
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• 2019

As one of the most important parameters in structural health monitoring, structural frequency has many advantages, such as convenient to be measured, high precision, and insensitive to noise. In addition, frequency-change-ratio based method had been validated to have the ability to identify the damage occurrence and location. However, building a precise enough finite elemental model (FEM) for the test structure is still a huge challenge for this frequency-change-ratio based damage detection technique. In order to overcome this disadvantage and extend the application for frequencies in structural health monitoring area, a novel method was developed in this paper by combining the cross-model cross-mode (CMCM) model updating algorithm with the frequency-change-ratio based method. At first, assuming the physical parameters, including the element mass and stiffness, of the test structure had been known with a certain value, then an initial to-be-updated model with these assumed parameters was constructed according to the typical mass and stiffness distribution characteristic of shear buildings. After that, this to-be-updated model was updated using CMCM algorithm by combining with the measured frequencies of the actual structure when no damage was introduced. Thus, this updated model was regarded as a representation of the FEM model of actual structure, because their modal information were almost the same. Finally, based on this updated model, the frequency-change-ratio based method can be further proceed to realize the damage detection and localization. In order to verify the effectiveness of the developed method, a four-level shear building was numerically simulated and two actual shear structures, including a three-level shear model and an eight-story frame, were experimentally test in laboratory, and all the test results demonstrate that the developed method can identify the structural damage occurrence and location effectively, even only very limited modal frequencies of the test structure were provided.