• Earthquakes and Structures
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• v.20 no.3
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• pp.279-293
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• 2021

Most of the existing seismic codes for RC buildings consider only a scenario earthquake for analysis, often characterized by the response spectrum at the specified location. However, any real earthquake event often involves occurrences of multiple earthquakes within a few hours or days, possessing similar or even higher energy than the first earthquake. This critically impairs the rehabilitation measures thereby resulting in the accumulation of structural damages for subsequent earthquakes after the first earthquake. Also, the existing seismic provisions account for the non-linear response of an RC building frame implicitly by specifying a constant response modification factor (R) in a linear elastic design. However, the 'R' specified does not address the changes in structural configurations of RC moment-resisting frames (RC MRFs) viz., building height, number of bays present, bay width, irregularities arising out of mass and stiffness changes, etc. resulting in changed dynamic characteristics of the structural system. Hence, there is an imperative need to assess the seismic performance under sequential earthquake ground motions, considering the adequacy of code-specified 'R' in the representation of dynamic characteristics of RC buildings. Therefore, the present research is focused on the evaluation of the non-linear response of medium-rise 3D RC MRFs with and without vertical irregularities under bi-directional sequential earthquake ground motions using non-linear dynamic analysis. It is evident from the results that collapse probability increases, and 'R' reduces significantly for various RC MRFs subjected to sequential earthquakes, pronouncing the vulnerability and inadequacy of estimation of design base shear by code-specified 'R' under sequential earthquakes.

• KIEAE Journal
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• v.7 no.4
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• pp.147-152
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• 2007

Numerous non-destructive tests(NDT) to assess the safety of real structures have been developed. System identification(SI) techniques using dynamic responses and behaviors of structural systems become an outstanding issue of researchers. However the conventional SI techniques are identified to be non-practical to the complex and tall buildings, due to limitation of the availability of an accurate data that is magnitude or location of external loads. In most SI approaches, the information on input loading and output responses must be known. In many cases, measuring the input information may take most of the resources, and it is very difficult to accurately measure the input information during actual vibrations of practical importance, e.g., earthquakes, winds, micro seismic tremors, and mechanical vibration. However, the desirability and application potential of SI to real structures could be highly improved if an algorithm is available that can estimate structural parameters based on the response data alone without the input information. Thus a technique to estimate structural properties of building without input measurement data and using limited response is essential in structural health monitoring. In this study, shaking table tests on three-story plane frame steel structures were performed. Out-put only model analysis on the measured data was performed, and the dynamic properties were inverse analyzed using least square method in time domain. In results damage detection was performed in each member level, which was performed at story level in conventional SI techniques of frequency domain.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.6
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• pp.279-291
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• 2013

The seismic damage of non-structural components, such as communication facilities, causes direct economic losses as well as indirect losses which result from social chaos occurring with downtime of communication and financial management network systems. The current Korean seismic code, KBC2009, prescribes the design criteria and requirements of non-structural components based on their elastic response. However, it is difficult for KBC to reflect the dynamic characteristics of structures where non-structural components exist. In this study, both linear and nonlinear time history analyses of structures with various analysis parameters were carried out and floor acceleration spectra obtained from analyses were compared with both ground acceleration spectra used for input records of the analyses and the design floor acceleration spectrum proposed by National Radio Research Agency. Also, this study investigates to find out the influence of structural dynamic characteristics on the floor acceleration spectra. The analysis results show that the acceleration amplification is observed due to the resonance phenomenon and such amplification increases with the increase of building heights and with the decrease of structure's energy dissipation capacities.

• Wind and Structures
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• v.4 no.1
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• pp.31-44
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• 2001

Mean concentrations of ammonia gas released as a tracer from an isolated low-rise building have been measured and predicted. Predictions were calculated using computational fluid dynamics (CFD) and two dispersion models: a diffusion model and a Lagrangian particle tracking technique. Explicit account was taken of the natural variation of wind direction by a technique based on the weighted summation of individual steady state wind direction results according to the probability density function of the wind direction. The results indicated that at distances >3 building heights downstream the weighted predictions from either model are satisfactory but that in the near wake the diffusion model is less successful. Weighted solutions give significantly improved predictions over unweighted results. Lack of plume spread is identified as the main cause of inaccuracies in predictions and this is linked to inadequate resolution of flow features and mixing in the CFD model. Further work on non-steady state simulation of wake flows for dispersion studies is recommended.

• Earthquakes and Structures
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• v.4 no.3
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• pp.325-339
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• 2013

A number of structural and modal parameters are derived from the strong motion records of an instrumented G + 9 storeyed RC building during Bhuj earthquake, 26 Jan. 2001 in India. Some of the extracted parameters are peak floor accelerations, storey drift and modal characteristics. Modal parameters of the building are also compared with the values obtained from ambient vibration survey of the instrumented building after the occurrence of earthquake. These parameters are further used for calibrating the accuracy of fixed-base Finite Element (FE) models considering structural and non-structural elements. Some conclusions are drawn based on theoretical and experimental results obtained from strong motion records and time history analysis of FE models. An important outcome of the study is that strong motion peak acceleration profile in two horizontal directions is close to FE model in which masonry infill walls are modeled.

• Earthquakes and Structures
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• v.15 no.5
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• pp.565-581
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• 2018

This paper proposes a new analytical formulation for computing the seismic input at various levels of a structure in terms of floor response spectra. The approach, which neglects the dynamic interaction between primary structure and secondary element, is particularly useful for the seismic assessment of secondary and non-structural elements. The proposed formulation has a robust theoretical basis and it is based on few meaningful dynamic parameters of the main building. The method has been validated in the linear and nonlinear behavior of the main building through results coming from both experimental tests (available in literature) and parametric numerical analyses. The conditions, for which the Floor Spectrum Approach and its simplified assumptions are valid, have been derived in terms of specific interval ratios between the mass of the secondary element and the participant mass of the main structure. Finally, a practice-oriented formulation has been derived, which could be easily implementable also at code level.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.224-225
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• 2019

The purpose of this study was to develop a technology to prevent leakage of construction structures for the Chinese market. The first key development factor is to establish a joint quality standard that corresponds to all performance criteria set out in Chinese Standard JC / T 2428-2017. The second key development factor is to develop a product capable of exhibiting performance in a low temperature environment of $-30^{\circ}C$ and coping with 15mm structure behavior.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.85-86
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• 2020

In securing durability of underground structure non-exposed waterproof materials, the company aims to improve durability of waterproof materials by studying more realistic weather conditions than KS standards and developers' durability standards. Analyzing the actual climate data in Korea and the temperature of the basement layer, it is a waterproofing sheet method, a self-adhesive sheet method in which a film and a compound, which are currently widely used as underground water-proofing, and a self-adhesive waterproofing sheet method, etc. We would like to present the guidelines necessary to prevent the temperature situation and waterproof defects that are ideal for setting the endurance conditions later.

• Wind and Structures
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• v.20 no.3
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• pp.469-488
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• 2015

A full-scale instrumented low-rise building with gable roof was built at a coastal site with a high incidence of tropical cyclones for monitoring of wind effects on the building during windstorms. This paper presents the field measurements of the wind velocity field around and the wind-induced pressures on the low-rise building during the passage of severe tropical storm Soudelor. Near-ground wind characteristics such as wind speed, wind direction, turbulence intensity, gust factor, turbulence integral length scale and wind velocity spectra were investigated. The wind-induced pressures on the roof of the building were analyzed and discussed. The results revealed that the eave and ridge edges on the roof were subjected to the most severe suction pressures under quartering winds. These suction pressures showed obvious non-Gaussian behavior. The measured results were compared with the provisions of ASCE 7-10 to assess the suitability of the code of practice for the wind-resistant design of low-rise buildings under tropical cyclones. The field study aims to provide useful information that can enhance our understanding of the extreme wind effects on low-rise buildings in an effort to reduce tropical cyclone wind damages to residential buildings.

• Earthquakes and Structures
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• v.11 no.2
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• pp.371-386
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• 2016

During the last decades, many destructive earthquakes occurred in Algeria, particularly in the northern part of the country (Chlef (1980), Constantine (1985), Tipaza (1989), Mascara (1994), Ain-Benian (1996), Ain Temouchent (1999), Beni Ourtilane (2000), and recently $Boumerd{\acute{e}}s$ (2003), causing enormous losses in human lives, buildings and equipments. In order to reduce this risk and avoid serious damages to the strategic existing buildings, the authorities of the country, aware of this risk and in order to have the necessary elements that let them to know and estimate the potential losses in advance, with an acceptable error, and to take the necessary countermeasures, decided to invest into seismic upgrade, strengthening and retrofitting of those buildings. To do so, seismic vulnerability study of this category of buildings has been considered. Structural analysis is performed based on the site investigation (inspection of the building, collecting data, materials characteristics, general conditions of the building, etc.), and existing drawings (architectural plans, structural design, etc.). The aim of these seismic vulnerability studies is to develop guidelines and a methodology for rehabilitation of existing buildings. This paper presents the methodology, based on non linear and seismic analysis of existing buildings, followed in this study and summarizes the vulnerability assessment and strengthening of one of the strategic buildings according to the new Algerian code RPA 99/version 2003. As a direct application of this methodology, both, static equivalent method and non linear dynamic analysis, of composite concrete masonry existing building in the city of "CONSTANTINE", located in the east side of ALGERIA, are presented in this paper.