• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.145-150
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• 2008

This study proposes an improved AR-model based structural joint integrity monitoring method and a new damage sensitive feature using RMS values of impulse responses. The proposed methods were applied for joint integrity monitoring of a model scale 2-bay and 4-story steel frame structure and it was found that the AR coefficients could be more consistently estimated by adopting the band-pass filter and cross-correlation function to the raw acceleration signals and the joint damages could be successfully monitored by the proposed methods.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.6 s.99
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• pp.712-717
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• 2005

This paper presents a system identification method for multi-input, multi-output (MIMO) systems, by which a rational polynomial transfer function model is identified from experimentally determined frequency response function data. Analytically determined information is incorporated in this method to obtain a more reliable model, even in the frequency range where the excitation energy is limited. To verify the suggested method, shaking table test for an actively controlled two-story, bench-scale building employing an active mass damper is conducted. The results show that the proposed method is quite effective and robust for system identification of MIMO systems.

• Structural Monitoring and Maintenance
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• v.5 no.2
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• pp.189-204
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• 2018

This paper examines the seismic responses of a reinforced concrete (RC) frame core-tube building with pre-pressed spring self-centering energy dissipation (PS-SCED) braces. The PS-SCED brace system consists of friction devices for energy dissipation, pre-pressed combination disc springs for self-centering and tube members as guiding elements. A constitutive model of self-centering flag-shaped hysteresis for PS-SCED brace is developed to better simulate the seismic responses of the RC frame core-tube building with PS-SCED braces, which is also verified by the tests of two braces under low cyclic reversed loading. Results indicate that the self-centering and energy dissipation capabilities are well predicted by the proposed constitutive model of the PS-SCED brace. The structure with PS-SCED braces presents similar peak story drift ratio, smaller peak acceleration, smaller base shear force and much smaller residual deformations as compared to the RC frame core-tube building with bucking-restrained braces (BRBs).

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.278-286
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• 2001

The purpose of this paper is to suggest an analytical technique for time history analysis of R/C frame structure using high-strength concrete under seismic loading. Current researches in hysteretic model of structral elements using high-strength concrete are not enough. It is the cause of error that apply hysteretic model of element using normal-strength concrete to the inelastic analysis of high-strength concrete R/C frame structures. In this paper time history analysis using IDARC and DRAIN programs was performed for a 2-bay, 20-story R/C frame structures. Particularly nonlinear dynamic analysis was performed by IDARC program that was applied hysteretic model of structural element using high-strength concrete. centro earthquake 1940 NS waves was used in the analysis and its peak ground accelerations are changed to be 0.12g, 0.25g

• Steel and Composite Structures
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• v.16 no.1
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• pp.1-21
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• 2014

Knee Braced Frame (KBF) is a special form of ductile eccentrically braced frame having a diagonal brace connected to a knee element, as a hysteretic damper, instead of beam-column joint. This paper first presents an experimental investigation on cyclic performance of two knee braced single span one-story frame specimens. The general test arrangement, specimen details, and most relevant results (failure modes and hysteretic curves) are explained. Some indexes to assess the seismic performance of KBFs, including ductility; response reduction factor and energy dissipation capabilities are also subsequently discussed. Experimental results indicate that the maximum equivalent damping ratios achieved by test frames are 21.8 and 23% for the specimens, prior to failure. Finally, a simplified analytical model is derived to predict the bilinear behavior of the KBFs. Acceptable conformity between analytical and experimental results proves the accuracy of the proposed model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.571-575
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• 2000

The physical properties of the spatial model, mass, stiffness and damping matrix, can be defined by a specific natural frequency, damping ratio and mode shape. These modal parameters can be determined from a set of frequency response function(FRF) measured by exciting the structure and measuring the responses at various points around the structure. In this paper, The Transfer Matrix is obtained by experimental modal analysis for the 3-story scaled building model which TMD is installed on top and the physical properties of the spatial model is determined using the residue matrix and the location of poles from FRF measurement using polynomial curve fitting methods.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.1
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• pp.1-7
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• 2005

This paper describes the lightning surge analysis model of extra high voltage GIS using EMTP. Various lightning current parameters were investigated in order to confirm the impact on the lightning surge analysis such as lightning current amplitude, waveform, size of GIS, tower footing resistance and surge arresters. The multi-story tower model and EMTP/TACS model were introduced for the simulation of dynamic arc characteristics. The margin between the maximum overvoltage and BIL of the GIS was about 10 percent and the margin between the maximum overvoltage and BIL of the transformer was 21 percent.

• Steel and Composite Structures
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• v.43 no.2
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• pp.153-164
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• 2022

In this study, a series of cyclic loading tests were performed on viscoelastic dampers (VED) composed of viscoelastic polymer composite material and thin steel plates to observe the variation of the mechanical properties under different loading conditions. A mathematical model was developed based on the Kelvin-Voigt and Bouc-Wen models to formulate the nonlinear force-displacement relationship of the viscoelastic damper. The accuracy of the proposed mathematical model was verified using the data obtained from the tests. The mathematical model was applied to analyze a reinforced concrete framed structure retrofitted with viscoelastic dampers. Nonlinear dynamic analysis results showed that the average maximum inter-story drift ratios of the retrofitted structure met the target limit state after installing the VED. In addition, both the maximum and residual displacements were significantly reduced after the installation of the VED.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.170-177
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• 2000

Recently many high-rise apartment buildings are constructed using the box system which is composed only of concrete walls and slabs. Commercial softwares such as ETABS used for the analysis of high-rise apartment buildings are employing the rigid diaphragm assumption for simplicity in the analysis procedure. In general the flexural stiffness of floor slabs are ignored in the analysis, This assumption may be reasonable for the estimation of seismic response of framed structures. But in the case of the box system used in the apartment buildings floor slabs has major effects on the lateral stiffness of the structure. So if the flexural stiffness of slabs in the box system is ignored the lateral stiffness may be significantly underestimated, For these reasons it is recommended to use plate elements to represent the floor slabs. In the study A typical frame structure and a box system structure are chosen as the example structure. When a 20 story frame structure is subjected to the static lateral loads the displacements of the roof are 15.33cm and 17.52cm for the cases with and without the flexural stiffness of the floor slabs. And in case of box system the roof displacement was reduced from 16.18cm to 8.61cm The model without the flexural stiffness of floor slabs turned out to elongate the natural periods of vibration accordingly.

• Smart Structures and Systems
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• v.18 no.6
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• pp.1251-1267
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• 2016

In this paper, Simple Adaptive Control (SAC) is used to enhance the seismic response of nonlinear tall buildings based on acceleration feedback. Semi-active MR dampers are employed as control actuator due to their reliability and well-known dynamic models. Acceleration feedback is used because of availability, cost-efficiency and reliable measurements of acceleration sensors. However, using acceleration feedback in the control loop causes the structure not to apparently meet some requirements of the SAC algorithm. In addition to defining an appropriate SAC reference model and using inherently stable MR dampers, a modification in the original structure of the SAC is proposed in order to improve its adaptability to the situation in which the plant does not satisfy the algorithm's stability requirements. To investigate the performance of the developed control system, a numerical study is conducted on the benchmark 20-story nonlinear building and the responses of the SAC-controlled structure are compared to an $H_2/LQG$ clipped-optimal controller under the effect of different seismic excitations. As indicated by the results, SAC controller effectively reduces the story drifts and hence the seismically-induced damage throughout the structural members despite its simplicity, independence of structural parameters and while using fewer number of dampers in contrast with the $H_2/LQG$ clipped-optimal controller.