Application of hybrid‐simulation to fragility assessment of the telescoping self‐centering energy dissipative bracing system          下载免费PDF全文

Viswanath Kammula  Jeffrey Erochko  Oh‐Sung Kwon  Constantin Christopoulos 《地震工程与结构动力学》2014,43(6):811-830

Substructure hybrid simulation has been the subject of numerous investigations in recent years. The simulation method allows for the assessment of the seismic performance of structures by representing critical components with physical specimens and the rest of the structure with numerical models. In this study the system level performance of a six‐storey structure with telescoping self‐centering energy dissipative (T‐SCED) braces is validated through pseudo‐dynamic (PsD) hybrid simulation. Fragility curves are derived for the T‐SCED system. This paper presents the configuration of the hybrid simulation, the newly developed control software for PsD hybrid simulation, which can integrate generic hydraulic actuators into PsD hybrid simulation, and the seismic performance of a structure equipped with T‐SCED braces. The experimental results show that the six‐storey structure with T‐SCED braces satisfies performance limits specified in ASCE 41. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Potential increase of flood hazards in Korea due to global warming from a high-resolution regional climate simulation   总被引：1，自引：0，他引：1  

Eun-Soon Im  Byong-Ju Lee  Ji-Hye Kwon  So-Ra In  Sang-Ok Han 《Asia-Pacific Journal of Atmospheric Sciences》2012,48(1):107-113

Because of the importance of the changes in the hydrologic cycle, accurate assessment of precipitation characteristics is essential to understand the impact of climate change due to global warming. This study investigates the changes in extreme precipitation with sub-daily and daily temporal scales. For a fine-scale climate change projection focusing on the Korean peninsula (20 km), we performed the dynamical downscaling of the global climate scenario covering the period 1971?C2100 (130-year) simulated by the Max-Planck-Institute global climate model, ECHAM5, using the latest version of the International Centre for Theoretical Physics (ICTP) regional climate model, RegCM3. While annual mean precipitation exhibits a pronounced interannual and interdecadal variability, with the increasing or decreasing trend repeated during a certain period, extreme precipitation with sub-daily and daily temporal scales estimated from the generalized extreme value distribution shows consistently increasing pattern. The return period of extreme precipitation is significantly reduced despite the decreased annual mean precipitation at the end of 21^st century. The decreased relatively weak precipitation is responsible for the decreased total precipitation, so that the decreased total precipitation does not necessarily mean less heavy precipitation. Climate change projection based on the ECHAM5-RegCM3 model chain clearly shows the effect of global warming in increasing the intensity and frequency of extreme precipitation, even without significantly increased total precipitation, which implies an increased risk for flood hazards.  相似文献   

Effects of freshwater runoff on a tropical pacific climate in the HadGEM2     

Suryun Ham  Song-You Hong  Yign Noh  Soon-Il An  Young-Hwa Byun  Hyun-Suk Kang  Johan Lee  Won-Tae Kwon 《Asia-Pacific Journal of Atmospheric Sciences》2012,48(4):457-463

This paper investigates the effects of river discharge on simulated climatology from 1979 to 1988 using the Hadley Centre Global Environmental Model version 2. Two experiments are performed with and without the inclusion of Total Runoff Integrating Pathways. The results show that the inclusion of flow routing can lead to the decrease of salinity over the coastal region due to freshwater. This reduction results in a shallower mixed layer depth, which in turn leads to the weakening of trade winds and a decrease in vertical mixing in the ocean. The enhanced sensible and latent heat fluxes over warmed SST improve the simulated precipitation and thermodynamic circulation. As a result, the experiment with flow routing is capable of improving the large-scale climate feature with an increase in precipitation over the eastern tropical equatorial Pacific region.  相似文献   

A land data assimilation system using the MODIS-derived land data and its application to numerical weather prediction in East Asia   总被引：1，自引：0，他引：1  

Yoon-Jin Lim  Kun-Young Byun  Tae-Young Lee  Hyojung Kwon  Jinkyu Hong  Joon Kim 《Asia-Pacific Journal of Atmospheric Sciences》2012,48(1):83-95

Land Data Assimilation Systems have been developed to generate the surface initial conditions such as soil moisture and temperature for better prediction of weather and climate. We have constructed Korea Land Data Assimilation System (KLDAS) based on an uncoupled land surface modeling framework that integrates high-resolution in-situ observation, satellite data, land surface information from the WRF Preprocessing System (WPS) and the MODIS land products over the East Asia. To present better surface conditions, the KLDAS is driven by atmospheric forcing data from the in-situ rainfall gauges and satellite. In this study, we 1) briefly introduce the KLDAS, 2) evaluate the meteorological states near the surface and the surface fluxes reproduced by the KLDAS against the in-situ observation, and then 3) examine the performance of the mesoscale model initialized by the KLDAS. We have generated a 5-year, 10 km, hourly atmospheric forcing dataset for use in KLDAS operating across East Asia. The KLDAS has effectively reproduced the observed patterns of soil moisture, soil temperature, and surface fluxes. Further scrutiny reveals that the numerical simulations incorporating the KLDAS outputs show better agreement in both the simulated near-surface conditions and rainfall distribution over the Korean Peninsula, compared to those without the KLDAS.  相似文献   

Static pullout resistance of anchor chains in cohesionless soil—laboratory testing     

Byeongwan Kim  Osoon Kwon  BooHyun Nam 《Marine Georesources & Geotechnology》2017,35(6):780-787

This paper investigates the static pullout resistance of anchor chains embedded into cohesionless soil. The anchor chains, which are made of steel, were buried into Jumunjin sand whose relative density was set to approximately 60%. The anchor chains were horizontally pulled out through a displacement of 70?mm in laboratory model tests. Three different embedment depths and seven different numbers of chain links were adopted. The pullout resistance of the anchor chains was found to increase with increasing embedment depth and the number of anchor chain links. The measured resistance was significantly higher than the calculated frictional resistance, implying that the passive resistance at the front of the anchor chain significantly contributes to the pullout resistance. The contribution of the passive resistance tends to decrease with increasing number of chain links.  相似文献   

A time‐domain seismic SSI analysis method for inelastic bridge structures through the use of a frequency‐dependent lumped parameter model          下载免费PDF全文

Nikolaos Lesgidis  Oh‐Sung Kwon  Anastasios Sextos 《地震工程与结构动力学》2015,44(13):2137-2156

It is highlighted in the past that the soil–structure interaction phenomenon can produce a significant alteration on the response of a bridge structure. A variety of approaches has been developed in the past, which is capable of tackling the soil–structure interaction problem from different perspectives. The popular approach of a discretized truncated finite element model of the soil domain is not always a numerically viable solution, especially for computationally demanding simulations such as the probabilistic fragility analysis of a bridge structure or the real time hybrid simulation. This paper aims to develop a complete modeling procedure that is capable of coping with the soil–structure interaction problem of inelastic bridge structures through the use of a frequency dependent lumped parameter assembly. The proposed procedure encounters accuracy and global stability issues observed on past methods while maintaining the broad applicability of the method by any commercial FEM software. A case study of an overpass bridge structure under earthquake excitations is illustrated in order to verify the proposed method. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

PAHs contamination and bacterial communities in mangrove surface sediments of the Jiulong River Estuary, China   总被引：2，自引：0，他引：2  

Tian Y  Liu HJ  Zheng TL  Kwon KK  Kim SJ  Yan CL 《Marine pollution bulletin》2008,57(6-12):707-715

Sixteen sediment samples collected from eight transects in a mangrove swamp of the Jiulong River Estuary, Fujian, China were investigated for their content of polycyclic aromatic hydrocarbons (PAHs) and the biodegradation potential of the indigenous microorganisms. The bacterial community structures in the mangrove sediments and in enrichment cultures were also investigated. The results showed that the total PAHs concentration of mangrove sediments ranged from 280 to 1074 ng g(-1) dry weight, that the PAHs composition pattern in the mangrove sediments was dominated by high molecular weight PAH components (4-6 rings), and that Benzo[ghi]perylene and Indeno[1,2,3-cd]pyrene were the most dominant at different stations. Abundant PAH-degrading bacteria were found in all the stations, the values of phenanthrene-degrading bacteria ranged from 5.85 x 10(4) to 7.80 x 10(5) CFU g(-1) dry weight, fluoranthene-degrading bacteria ranged from 5.25 x 10(4) to 5.79 x 10(5) CFU g(-1) dry weight, pyrene-degrading bacteria ranged from 3.10 x 10(4) to 6.97 x 10(5) CFU g(-1) dry weight and the benzo(a)pyrene-degrading bacteria ranged from 5.25 x 10(4) to 7.26 x 10(5) CFU g(-1) dry weight. DGGE analysis of PCR-amplified 16S rDNA gene fragments confirmed that there was a remarkable shift in the composition of the bacterial community due to the addition of the different model PAH compound phenanthrene (three ring PAH), fluoranthene(four ring PAH), pyrene(four ring PAH) and benzo(a)pyrene(five ring PAH) during enrichment batch culture. Eleven strains were obtained with different morphology and different degradation ability. The presence of common bands for microbial species in the cultures and in the native mangrove sediment DNA indicated that these strains could be potential in situ PAH-degraders.  相似文献   

Microbial Diversity of Deep-sea Sediments from Three Newly Discovered Hydrothermal Vent Fields in the Central Indian Ridge     

Namirimu  Teddy  Park  Mi-Jeong  Kim  Yun Jae  Lim  Dhongil  Lee  Jung-Hyun  Shin  Ayoung  Kim  Dongsung  Kwon  Kae Kyoung 《Ocean Science Journal》2023,58(2):1-15

Since the discovery of hydrothermal vents in the late 1970s, deep-sea hydrothermal vent fields have attracted great attention as biological hotspots. However, compared with other ocean ridges, the structure and function of microbial communities inhabiting vent fields in the Central Indian ridge (CIR) remain understudied. Here, we provide for the first time 16S rRNA gene-based comparative metagenomic analysis of the sediment-associated microbial communities from three newly discovered vent fields in the CIR. Sediment samples collected in the Invent B, Invent E and Onnuri vent fields varied in geochemical properties, elemental concentrations and associated microbial communities. Proteobacteria (Gammaproteobacteria) was the dominant phylum in Invent B and Onnuri vent fields. In contrast, Invent E mainly consisted of Chloroflexi and Euryarchaeota. Predicted functional profiling revealed that the microbial communities in the three vents are dominated by chemoheterotrophic functions. In addition, microbial communities capable of respiration of sulfur compounds, nitrification, nitrite oxidation, methylotrophy, and methanotropy were found to be the main chemolithoautotrophs. Compared to other vent fields, Invent E showed a predominance of archaeal methanogens suggesting it exhibits slightly different geochemistry. Multivariate analysis indicated that the biogeochemical and trace metal differences are reflected in the sediment microbial compositions of the three vent fields. This study expands our current understanding of the microbial community structure and potential ecological functions of the newly discovered hydrothermal vent fields in the CIR.

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A frequency‐dependent and intensity‐dependent macroelement for reduced order seismic analysis of soil‐structure interacting systems          下载免费PDF全文

Nikolaos Lesgidis  Anastasios Sextos  Oh‐Sung Kwon 《地震工程与结构动力学》2018,47(11):2172-2194

The computational demand of the soil‐structure interaction analysis for the design and assessment of structures, as well as for the evaluation of their life‐cycle cost and risk exposure, has led the civil engineering community to the development of a variety of methods toward the model order reduction of the coupled soil‐structure dynamic system in earthquake regions. Different approaches have been proposed in the past as computationally efficient alternatives to the conventional finite element model simulation of the complete soil‐structure domain, such as the nonlinear lumped spring, the macroelement method, and the substructure partition method. Yet no approach was capable of capturing simultaneously the frequency‐dependent dynamic properties along with the nonlinear behavior of the condensed segment of the overall soil‐structure system under strong earthquake ground motion, thus generating an imbalance between the modeling refinement achieved for the soil and the structure. To this end, a dual frequency‐dependent and intensity‐dependent expansion of the lumped parameter modeling method is proposed in the current paper, materialized through a multiobjective algorithm, capable of closely approximating the behavior of the nonlinear dynamic system of the condensed segment. This is essentially the extension of an established methodology, also developed by the authors, in the inelastic domain. The efficiency of the proposed methodology is validated for the case of a bridge foundation system, wherein the seismic response is comparatively assessed for both the proposed method and the detailed finite element model. The above expansion is deemed a computationally efficient and reliable method for simultaneously considering the frequency and amplitude dependence of soil‐foundation systems in the framework of nonlinear seismic analysis of soil‐structure interaction systems.  相似文献   

Small-scale multi-axial hybrid simulation of a shear-critical reinforced concrete frame     

Vahid Sadeghian  Oh-Sung Kwon  Frank Vecchio 《地震工程与工程振动(英文版)》2017,16(4):727-743

This study presents a numerical multi-scale simulation framework which is extended to accommodate hybrid simulation (numerical-experimental integration). The framework is enhanced with a standardized data exchange format and connected to a generalized controller interface program which facilitates communication with various types of laboratory equipment and testing configurations. A small-scale experimental program was conducted using a six degree-of-freedom hydraulic testing equipment to verify the proposed framework and provide additional data for small-scale testing of shearcritical reinforced concrete structures. The specimens were tested in a multi-axial hybrid simulation manner under a reversed cyclic loading condition simulating earthquake forces. The physical models were 1/3.23-scale representations of a beam and two columns. A mixed-type modelling technique was employed to analyze the remainder of the structures. The hybrid simulation results were compared against those obtained from a large-scale test and finite element analyses. The study found that if precautions are taken in preparing model materials and if the shear-related mechanisms are accurately considered in the numerical model, small-scale hybrid simulations can adequately simulate the behaviour of shear-critical structures. Although the findings of the study are promising, to draw general conclusions additional test data are required.  相似文献