• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.4
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• pp.1-8
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• 2013

Constitutive modeling of constituent materials is very important for reinforced concrete (RC) frames. Cyclic constitutive behavior of unconfined concrete, confined concrete and reinforcing steel should be well defined in fiber-based discretization of RC sections. This study performs nonlinear dynamic analyses of RC frame structures to investigate the sensitivity of seismic behavior of such frames to different constitutive models of constituent materials. The study specifically attempts to examine confinement effects in concrete modeling and degrading effects in steel modeling, which substantially affects the monotonic, cyclic and seismic responses of RC members and frames. Based on the system level analysis, it is shown that the response of non-ductile frames is less sensitive to confined concrete models while the modeling of reinforcing steel is quite influential to the inelastic response of both non-ductile and ductile frames.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.4
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• pp.29-36
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• 2010

To investigate the cyclic characteristics of exterior joints in RC frame buildings which are typically used after 1988, 70% scaled T-shaped beam-column subassemblies were designed and tested with a displacement control that is composed of 9 steps, until 3.5% story drift was reached. Axial forces are applied to columns during the experiment to simulate a real situation. The results show that the non-seismic detailed specimens failed before reaching 0.85% story drift, and their strengths are less than 0.85 times the nominal flexural strength which beam or columns should reach. The relationship of principal stress and story drift of exterior joints is similar to the one that Priestly proposed.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.4
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• pp.63-69
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• 2003

In this study seismic design procedure for buckling-restrained braced frame systems was proposed using hysteretic energy spectrum and accumulated ductility spectrum constructed from single degree of freedom systems. The hysteretic energy spectra and accumulated ductility spectra corresponding to target ductility ratio were constructed first. The cross-sectional area of braces required to meet a given target displacement was obtained by equating the hysteretic energy demand to the accumulated plastic energy dissipated by braces. Twenty earthquake records were utilized to construct the spectra and to verify the validity of the design procedure. According to analysis results of three- and eight-story buckling-restrained braced frame structures designed using the proposed method, the mean values for the top story displacement correspond well with the given performance target displacements. Also, the inter-story drifts turned out to be relatively uniform over the structure height, which is desirable because uniform inter-story drifts indicate uniform damage distribution. Therefore if was concluded that the proposed energy-based method could be a reliable alternative to conventional strength-based design procedure for structures with buckling-restrained braces.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.513-523
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• 2012

The objective of this research is to examine how the lateral resisting system of selected prototypes are affected by seismic zone effect and shape irregularity on its seismic performance. The lateral resisting systems are divided into the three types, diagrid, braced tube, and outrigger system. The prototype models were assumed to be located in LA, a high-seismicity region, and in Boston, a low-seismicity region. The shape irregularity was classified with rotated angle of plane, $0^{\circ}$, $1^{\circ}$, $2^{\circ}$. This study performed two parts of analyses, Linear Response and Non-Linear Response History(NLRH) analysis. The Linear Response analysis was used to check the displacement at the top and natural period of models. NLRH analysis was conducted to invest base shear and story drift ratio of buildings. As results, the displacement of roof and natural period of three structural systems increase as the building stiffness reduces due to the changes in rotation angle of the plane. Also, the base shear is diminished by the same reason. The result of NLRH, the story drift ratio, that was subject to Maximum Considered Earthquake(MCE) satisfied 0.045, a recommended limit according to Tall Building Initiative(TBI).

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.1
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• pp.55-62
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• 2002

The upper wall-lower frame structures(mixed building structures) are usually composed of shear wall structure in the upper part of structure which is used as residential space and frame structure in the lower part of structure which is used as commercial space centering around the transfer system in the lower part of structure. These structures are characteristics of stiffness irregularity, mass irregularity, and vertical geometric irregularity. The purpose of this study is to investigate the nonlinear response characteristics and the seismic capacity of mixed building structures when the number of stories in the lower frame is varied. The conclusions of this study are following. 1) As the result of push-over analysis of structure such as roof drift(i.e. roof displacement/structural height) and base shear coefficient, when the stories of lower frame system are increased, base shear coefficient is decreased, but roof drift is increased. 2) According to an increase in stories of the lower fame, story drift and ductility ratio of upper wall system are decreased and behavior of upper wall system is closed to elastic. 3) When the stories of lower frame system are increased, the excessive story drift is concentrated on the lower frame system.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.2
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• pp.29-37
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• 2002

The purpose of this study is to provide a fundamental data of earthquake resistant design through the estimation of the response modification factor and nonlinear displacement for moment resisting reinforced concrete frames by linear and nonlinear static analysis. The analysis models are designed in accordance with AIK code and then, estimated the response modification factor and nonlinear displacement of the buildings. The parameters such as story numbers(10, 20, 30), plan ratios(1:1, 1:2) and analysis types(2D, 3D) of building structure are chosen for use in this study. After comparing the results of linear and nonlinear static analysis, the response modification factor is obtained as the product of four factors: ductility factor, strength factor, damping factor and redundancy factor. The response modification factor are close to 3.5 in case of 2 span, 4.3 in case of 3 span and 5.0 in case 4 or more span models regardless number of stories and plan ratios. The nonlinear displacement is evaluated from the ratio of story drift angle(nonlinear drift/linear drift). The ratio of story drift angle increases as story numbers increase and the value varies from 5.85 to 9.34.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.1
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• pp.47-51
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• 2015

In this paper, feasibility of dynamic characteristics recovery of delaminated composite structure is numerically studied by using active control algorithm and piezoelectric actuator. Macro-fiber composite(MFC), which has great flexibility and high actuating force, is considered as an actuator in this work. After construction of finite element model for delaminated composite structure based on improved layerwise theory, modal characteristics are investigated and changes of natural frequencies and mode shapes, caused by delamination, are observed. Then, active control algorithm is realized and implemented to system model and control performances are numerically evaluated. Dynamic characteristics of delaminated composite structure are effectively recovered to those of healthy composite structure.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.639-647
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• 2002

A simplified analytical procedure is presented to estimate the reduction of elastic lateral stiffness of steel moment frames arising from the radius-cut dogbone weakening. With the original radius-cut dogbone shape, it is almost impossible or too complicated to integrate analytically the mathematical expressions encountered when applying the conjugate beam method to compute the beam deflection component. In this study, the problem is circumvented by replacing the original radius-cut dogbone with an equivalent dogbone of constant width. The equivalence between the two is established by imposing an equal dogbone elongation criterion. This approach is justified by using a calibrated finite clement analysis. Then, the elastic lateral deflection components from the column, panel zone, and beam are derived for a typical beam-column subassembly. The derived results can be used to evaluate the reduction of the frame lateral stiffness. Case studies conducted within some practical ranges of frame configurations show that the reduction in frame lateral stiffness due to the presence of dogbone cut is on the order of 1 to 2 percent and is reasonably negligible in practical sense.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.171-180
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• 2005

In this study the seismic performance of a three-story knee-braced moment-resisting frame (KBMRF), which is typically employed to support pipelines for oil or gas, was investigated. Nonlinear static pushover analyses were performed first to observe the force-displacement relationship of KBMRF under increasing seismic load. The results show that, when the maximum inter-story drift reached 1.5% of the story height, the main structural members, such as beams and columns, still remained elastic. Then nonlinear dynamic time-history analyses were carried out using eight earthquake ground motion time-histories scaled to at the design spectrum of UBC-97. It turned out that the maximum inter-story drift was smaller than the drift limit of 1.5 % of the structure height, and that the columns remained elastic. Based on these analytical results, it can be concluded that the seismic performance of the structure satisfies all the requirements regulated in the seismic code.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.205-206
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• 2009

This study deals with the viscoelastic damper system with displacement-amplification unit (DAU) which can maximize the effectiveness of a damper system in controlling seismic response of a building by amplifying story drift induced to damper. DAUs in this study were analyzed to be able to amplify the displacement 2 to 4 times greater than the original story drift. The efficiency of each DAU was expressed by $\beta$ (DAU ratio) and examined in this analytical study.