• Computers and Concrete
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• v.16 no.4
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• pp.643-667
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• 2015

3-dimentional precast recycled aggregate concrete (RAC) finite element models were developed by means of the platform OpenSees to implement sophisticated nonlinear model subjected to seismic loads. Efforts were devoted to the dynamic responses (including dynamic characteristics, acceleration amplifications, displacements, story drifts) and capacity curve. In addition, this study extended the prediction on dynamic response of precast RAC model by parametric study of material properties that represent the replacement percentage of recycled coarse aggregate (RCA). Principles and assumptions that represent characteristics of precast structure and influence of the interface between head of column and cast-in-place (CIP) joint on the stiffness of the joints was put forward and validated by test results. The comparison between simulated and tested results of the precast RAC frame shows a good correlation with most of the relative errors about 25% in general. Therefore, the adopted assumptions and the platform OpenSees are a viable approach to simulate the dynamic response of precast frames made of RAC.

• Steel and Composite Structures
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• v.51 no.2
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• pp.127-138
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• 2024

In this paper, structural behavior under fire conditions is comprehensively examined, and a novel software interface for testing interfaces efficiently is developed and validated. In order to accurately assess the response of structures to fire scenarios, advanced simulation techniques and modeling approaches are incorporated into the study. This interface enables accurate heat transfer analysis and thermo-mechanical simulations by integrating software tools such as CSI ETABS, CSI SAP2000, and OpenSees. Heat transfer models can be automatically generated, simulation outputs processed, and structural responses interpreted under a variety of fire scenarios using the proposed technique. As a result of rigorous testing and validation against established methods, including Cardington tests on scales and hybrid simulation approaches, the software interface has been proven to be effective and accurate. The analysis process is streamlined by this interface, providing engineers and researchers with a robust tool for assessing structural performance under fire conditions.

• Steel and Composite Structures
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• v.18 no.5
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• pp.1083-1101
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• 2015

Previous theoretical equations for the shear capacity of steel beam to concrete filled steel tube (CFT) column connections vary in the assumptions for the shear deformation mechanisms and adopt different equations for calculating shear strength of each component (steel tube webs, steel tube flanges, diaphragms, and concrete etc.); thus result in different equations for calculating shear strength of the joint. Besides, shear force-deformation relations of the joint, needed for estimating building drift, are not well developed at the present. This paper compares previously proposed equations for joint shear capacity, discusses the shear deformation mechanism of the joint, and suggests recommendations for obtaining more accurate predictions. Finite element analyses of internal diaphragm connections to CFT columns were carried out in ABAQUS. ABAQUS results and theoretical estimations of the shear capacities were then used to calibrate rotational springs in joint elements in OpenSEES simulating the shear deformation behavior of the joint. The ABAQUS and OpenSEES results were validated with experimental results available. Results show that: (1) shear deformation of the steel tube dominates the deformation of the joint; while the thickness of the diaphragms has a negligible effect; (2) in OpenSEES simulation, the joint behavior is highly dependent on the yielding strength given to the rotational spring; and (3) axial force ratio has a significant effect on the joint deformation of the specimen analyzed. Finally, modified joint shear force-deformation relations are proposed based on previous theory.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.417-423
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• 2019

In this investigation, a set of seismic fragility curves for RC bridges in Korea is derived by considering variations of the representative analytical model. The dimensions and specifications of the model are determined, based on statistical analysis of the inventory of RC bridges in Korea. Variations of important modeling parameters such as material properties, size of structural members, and dimension of the bridge are defined based on statistical studies of the bridges. The OpenSees program is utilized for the analysis to represent the inelastic behavior of RC members. A systematic approach is developed to perform a large volume of inelastic dynamic analysis, in which continuous variation of the modeling parameters are programmed to appropriately represent the characteristics of RC bridges in Korea.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.61-69
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• 2010

Unbonded precast concrete piers have better seismic performances than conventional reinforced concrete piers. In this research, seismic performances of unbonded precast prestressed concrete piers are analyzed using OpenSEES. Main parameters of analysis are concrete strength, jacking force ratio, ratio of tendon, and size of precast segment. In results, as the ratio of tendon and jacking force ratio increase, the flexural strength increases at softening state and ultimate state. Concrete strength and size of precast segment are negligible. But initial jacking force ratio leads to early yielding of prestressing tendon. Since compressive strain in core concrete is much less than ultimate strain, it can be expected that the amount of transverse steel reinforcement is to be reduced in comparison with conventional reinforced concrete column.

• Journal of The Korean Astronomical Society
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• v.35 no.3
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• pp.131-141
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• 2002

We present Near-IR photometry of the Arches cluster, a young and massive stellar cluster near the Galactic center. We have analyzed the high resolution (FWHM $\~$ 0.2") Hand K' band images in the Galactic Center Demonstration Science Data Set, which were obtained with the Gemini/Hokupa's adaptive optics (AO) system. We present the color-magnitude diagram, the luminosity function and the initial mass function (IMF) of the stars in the Arches cluster in comparison with the HST/NICMOS data. The IMF slope for the range of 1.0 < log (M/M$\bigodot$) < 2.1 is estimated to be ${\Gamma} = -0.79 {\pm} 0.16$, in good agreements with the earlier result based on the HST/NICMOS data [Figer et al. 1999, ApJ, 525, 750]. These results strengthen the evidence that the IMF of the bright. stars close to the Galactic center is much flatter than that for the solar neighborhood. This is also consistent with a recent finding that the IMFs of the bright stars in young clusters in M33 get flatter as the galactocentric distance decreases [Lee et al. 2001, astro-ph 0109258]. It is found that the power of the Gemini/ AO system is comparable, with some limits, to that of the HST/NICMOS.

• Journal of The Korean Astronomical Society
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• v.38 no.4
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• pp.429-435
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• 2005

We present BV CCD photometry for the open clusters Czernik 24 and Czernik 27. These clusters have never been studied before, and we provide, for the first time, the cluster parameters; reddening, distance, metallicity and age. Czernik 24 is an old open cluster with age $1.8{\pm}0.2Gyr$, metallicity $[Fe/H]=-0.41{\pm}0.15dex$, distance modulus $(m-M)_0=13.1{\pm}0.3mag$ ($d=4.1{\pm}0.5kpc$), and reddening $E(B-V)=0.54{\pm}0.12mag$. The parameters for Czernik 27 are estimated to be $age=0.63{\pm}0.07Gyr$, $[Fe/H]=-0.02{\pm}0.10dex$, $(m-M)_0=13.8{\pm}0.2mag$ ($d=5.8{\pm}0.5kpc$), and $E(B-V)=0.15{\pm}0.05mag$. The metallicity and distance values for Czernik 24 are consistent with the relation between the metallicity and the Galactocentric distance of other old open clusters. We find the metallicity gradient of 51 old open clusters including Czernik 24 to be ${\Delta}[Fe/H]/{\Delta}R_{gc}=-0.064 {\pm}0.009dex\;kpc^{-1}$.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.219-222
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• 2005

Many RC building structures of multiple uses constructed in Korea have the irregularities of torsion and soft story at bottom stories. A typical irregular building was selected as prototype and shaking table tests were performed to investigate the seismic performance of this building. The objective of this study is to evaluate the correlation between the experimental and analytical responses of this irregular building structure subjected to the earthquake excitation by using OpenSees(Open System for Earthquake Engineering Simulation). The results of analyses simulate well the behavior of the building having torsional irregularity and weak stories.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1557-1568
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• 2015

The nonlinear static analysis of structure, which is under the effect of lateral loads and provides the capacity curve of the structure, is defined as a push-over analysis. Ordinarily, by using base shear and the lateral displacement of target point, the capacity curve is obtained. The speed and ease of results interpretation in this method is more than that of the NRHA responses. In this study, the nonlinear static analysis is applied on the semi-rigid steel gabled frames. It should be noted that the members of this structure are analyzed as a prismatic beam-column element in two states of semi-rigid connections and supports. The gabled frame is modeled in the OpenSees software and analyzed based on the displacement control at the target point. The lateral displacement results, calculated in the top level of columns, are reported. Furthermore, responses of the structure are obtained for various support conditions and the rigidity of nodal connections. Ultimately, the effect of semi-rigid connections and supports on the capacity and the performance point of the structure are presented in separated graphs.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.5
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• pp.229-238
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• 2015

For small-size reinforce-concrete buildings, Midas Gen, OpenSees, and Perform-3D, which are structural analysis programs that are most popularly used at present, were applied for nonlinear static pushover analysis, and then difference between those programs was analyzed. Example buildings were limited to 2-story frames with irregular shaped walls. Analysis result showed that there were more differences than for frames only and frames with rectangular walls, but it was not so significant. Nevertheless, the capacity curve were different in some buildings, which is attributed to shape and location of walls, and feature of the analysis program. Especially, selection of automatic or manual input in Midas Gen, or nonlinear wall elements in Perform3D can affect the capacity curve and performance of the buildings. Therefore, the program users should understand the feature of the program well, and then conduct performance assessment. The result of this study is limited to low-story buildings so that it should be noted that it is possible to get different results for mid- to high-rise buildings.