• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.1
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• pp.13-25
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• 2012

The purpose of this study was to investigate the seismic behavior of hollow circular reinforced concrete bridge columns with confinement steel, and to develop improved seismic design criteria. Three hollow circular columns were tested under a constant axial load and a quasi-static, cyclically reversed horizontal load. The accuracy and objectivity of the assessment process can be enhanced by using a sophisticated nonlinear finite element analysis program. The numerical method used gives a realistic prediction of the seismic performance throughout the loading cycles for the several test specimens investigated. Based on the experimental and analytical results, design recommendations are presented to improve current practice in the design and construction of hollow circular reinforced concrete bridge columns.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.113-114
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• 2010

In this study, the earthquake damage evaluation of a R/C frame building is carried out based on the method proposed in Part I. Using the proposed method, the earthquake damage of building system based on non-linear required strength spectrum can be effectively evaluated without using the detailed seismic evaluation methods, including non-linear dynamic analyses, capacity spectrum method, etc.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.6
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• pp.75-84
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• 2010

In current seismic design provisions, a reduced beam section with bolted web (RBS-B) connections is only permitted for intermediate moment frames (IMF). This study evaluated the seismic performance of steel moment resisting frame systems having RBS-B connections designed according to current seismic design provisions. For this purpose, 12 archetypal IMF systems having two different span lengths (9m, 6m) were designed considering two design load levels (SDC $C_{max}$, SDC $C_{min}$). A nonlinear analytical model that can simulate hysteretic behavior of an RBS-B connection was also developed in this study. The procedures specified in ATC 63 are used to conduct a seismic performance evaluation. Moreover, this study conducts the seismic performance evaluation of IMF systems designed according to a new design method proposed by the authors in the previous study. It was observed that several model frames designed according to current seismic design provisions did not provide satisfactory collapse margin ratios (ACMR). This study also showed that the model frames designed according to the new design procedures had a sufficient ACMR.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.3
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• pp.97-103
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• 2004

Most of the columns in centrally braced steel frame buildings are usually designed as the gravity columns to reduce connection cost. For a rational seismic performance evaluation of centrally braced steel frame buildings, it is important to properly incorporate in the analysis  the P-${\Delta}$ effects arising from the gravity columns. An effective scheme for the P-${\Delta}$ effects modeling due to the gravity columns was illustrated based on the concept of fictitious leaning column. Seismic performance evaluation of inverted V braced steel frames with or without P-${\Delta}$ effects modeling was conducted by following the FEMA 273 NSP (Nonlinear Static Procedure). The problem in estimating dynamic P-${\Delta}$ modification factor (C3) in FEMA 273 was discussed. The results of this study indicated that the P-${\Delta}$ effects should be included in the seismic performance evaluation of centrally braced steel frames. This study also showed that the inverted V braced frames, retrofitted by applying the tie bars to redistribute the inelastic demand over the height of the building, exhibit significantly improved seismic performance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.9-20
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• 2014

Steel intermediate moment frames (IMFs) have been generally used as seismic load resisting systems (SLRSs) of a building to provide resistances against strong ground shaking. However, most of low and mid-rise steel buildings in Korea were constructed during pre-seismic code era or before the introduction of well-organized current seismic codes. It has been recognized that the seismic performance of these steel IMFs is still questionable. In order to respond to such a question, this study quantitatively investigates the seismic capacities of steel IMFs. Prototype models are built according to the number of stories, the levels of elastic seismic design base shear and the ductilities of structural components. Also, the other prototype models employing hysteretic energy dissipating devices (HEDDs) are considered. The collapse mechanism and the seismic performance of the prototype models are then described based on the results obtained from nonlinear-static and incremental-dynamic analyses. The seismic performance of the prototype models is assessed from collapse margin ratio (CMR) and collapse probability. From the assessment, the prototype model representing new steel IMFs has enough seismic capacities while, the prototype models representing existing steel IMFs provide higher collapse probabilities. From the analytic results of the prototype models retrofitted with HEDDs, the HEDDs enhance the seismic performance and collapse capacity of the existing steel IMFs. This is due to the energy dissipating capacity of the HEDDs and the redistribution of plastic hinges.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.2
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• pp.75-84
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• 2003

Most structures are expected to deform beyond the limit of linearly elastic behavior when subjected to strong ground motion. Seismic evaluation of structure requires an estimation of the structural performance in terms of displacement demand imposed by earthquakes on the structure. The nonlinear response history analysis(NRHA) among various nonlinear analysis methods is the most accurate to compute seismic performance of structures, but it is time-consuming and necessitate more efforts. The nonlinear approximate methods, which is more practical and reliable tools for predicting seismic behavior of structures, are extensively studied. Among them, the capacity spectrum method(CSM) is conceptually simple, but the iterative procedure is time-consuming and may sometimes lead to no solution or multiple solutions. This paper considers a nonlinear direct spectrum method(NDSM) to evaluate seismic performance of mixed building structures without iterative computations, given dynamic property T from stiffness skeleton curve and nonlinear pseudo acceleration $A_{y}$/g and/or ductility ratio $\mu$ from response spectrum. The nonlinear response history analysis has been performed and analyzed with various earthquakes for estimation of reliability and practicality of NDSM with mixed building structures.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.41-51
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• 2010

For safe seismic evaluation and design, it is necessary to predict the plastic deformation demands of members. In the present study, a quick and reasonable method for the evaluation of member plastic deformations of dual systems was developed on the basis of results of elastic analysis, without using nonlinear analysis. Plastic deformations of beams, columns, and walls are functions of member stiffness, story drift ratio, and moment redistribution determined from elastic analysis. For dual systems with rigid connections between walls and beams, an increase in the plastic deformations of beams due to the rocking effect was considered. The proposed method was applied to 8-story dual systems and the predicted plastic deformations were compared with the results of nonlinear analysis. The results showed that the proposed method accurately predicted the member plastic deformations with simple calculations, but that for the accurate evaluation of member plastic deformations, the inelastic story drift ratio must also be predicted with accuracy. The proposed method can be applied to both the performance-based seismic design of new structures and the seismic evaluation of existing structures.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.491-497
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• 2007

In the current research, the scheme of displacement-based seismic design for seismic retrofit of concrete structures using FRP composite materials has been proposed. An algorithm of the nonlinear flexural analysis of FRP composite concrete members has been presented under multiaxial constitutive laws of concrete and composite materials. An algorithm for performance-based seismic retrofit design of reinforced concrete columns with FRP jacket has been newly introduced to modify the displacement coefficient method used in reinforced concrete structures. From applications of retrofit design, the method are easy to apply in the practice of retrofit design and give practical prediction of nonlinear seismic performance evaluation of retrofitted structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.127-128
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• 2010

The purpose of this study is to evaluate the seismic performance of gravity-designed post tensioned (PT) flat plate frames with and without slab bottom reinforcement passing through the column. For the PT flat plate frames, the slab bottom reinforcement is often omitted since the requirement for the slab bottom reinforcement for PT flat plates is not clearly specified in ACI 318-08. This study evaluates the seismic performance of the model frames was evaluated by conducting nonlinear time history analysis. The seismic performance of PT flat plate frames is significantly improved by placing slab bottom reinforcement passing through the column.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.6
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• pp.455-462
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• 2013

The effects of earthquakes can be devastating especially to existing structures that are not based on earthquake resistant design. This study proposes a steel grid shear wall that can provide a sufficient lateral resistance and can be used as a seismic retrofit method. The pushover analysis was performed on RC structure with and without the proposed steel grid shear wall. Obtain the performance point that the target structure for seismic loads applied to evaluate the response and performance levels. The capacity spectrum at performance point is nearly elastic range, so satisfied the performance objectives(LS level). And response modification factor(R factor) were calculated from the pushover analysis. The R factor approach is currently implemented to reflect inelastic ductile behavior of the structures and to reduce elastic spectral demands from earthquakes to the design level. The R factor increases from 2.17 to 3.25 was higher than the design criteria. As a result, according to reinforcement by steel grid shear wall, strength, stiffness, and ductility of the low-rise RC structure has been appropriately improved.