• Earthquakes and Structures
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• v.20 no.2
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• pp.133-148
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• 2021

The paper presents a simplified force-based seismic design procedure for the preliminary design of steel haunch retrofitting for the seismic upgrade of deficient RC frames. The procedure involved constructing a site-specific seismic design spectrum for the site, which is transformed into seismic base shear coefficient demand, using an applicable response modification factor, that defines base shear force for seismic analysis of the structure. Recent experimental campaign; involving shake table testing of ten (10), and quasi-static cyclic testing of two (02), 1:3 reduced scale RC frame models, carried out for the seismic performance assessment of both deficient and retrofitted structures has provided the basis to calculate retrofit-specific response modification factor Rretrofitted. The haunch retrofitting technique enhanced the structural stiffness, strength, and ductility, hence, increased the structural response modification factor, which is mainly dependent on the applied retrofit scheme. An additional retrofit effectiveness factor (ΩR) is proposed for the deficient structure's response modification factor Rdeficient, representing the retrofit effectiveness (ΩR=Rretrofitted /Rdeficient), to calculate components' moment and shear demands for the retrofitted structure. The experimental campaign revealed that regardless of the deficient structures' characteristics, the ΩR factor remains fairly the unchanged, which is encouraging to generalize the design procedure. Haunch configuration is finalized that avoid brittle hinging of beam-column joints and ensure ductile beam yielding. Example case study for the seismic retrofit designs of RC frames are presented, which were validated through equivalent lateral load analysis using elastic model and response history analysis of finite-element based inelastic model, showing reasonable performance of the proposed design procedure. The proposed design has the advantage to provide a seismic zone-specific design solution, and also, to suggest if any additional measure is required to enhance the strength/deformability of beams and columns.

• Journal of Korean Society of Steel Construction
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• v.18 no.5
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• pp.553-562
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• 2006

Lateral loading due to wind or earthquake is a major factor that affects the design of high-rise buildings. This paper highlights the problems associated with the seismic design of high-rise buildings in regions of strong wind and moderate seismicity. Seismic response analysis and performance evaluation were conducted for wind-designed concentrically braced steel high-rise buildings in order to check the feasibility of designing them per elastic seismic design criterion (or strength and stiffness solution) in such regions. Review of wind design and pushover analysis results indicated that wind-designed high-rise buildings possess significantly increased elastic seismic capacity due to the overstrength resulting from the wind serviceability criterion. The strength demand-to-capacity study showed that, due to the wind design overstrength, high-rise buildings with a slenderness ratio of larger than four or five can elastically withstand even the maximum considered earthquake (MCE) with the seismic performance level of immediate occupancy under the limited conditions of this study. A step-by-step seismic design procedure per the elastic criterion that is directly usable for practicing design engineers is also recommended.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.04a
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• pp.160-166
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• 1997

Current Seismic Design Procedure has been developed and improved mostly based on the experiences of the past earthquakes. Many engineers and researchers believe that the seismic codes and provisions are adequate for the basic objective of the code which is "life-safe". However they doubt the performance of the structure during the earthquake. The seismic code seems the black box for the designers which means it is not transparent since the designer can not predict the level of the damage of the structure under future earthquakes. This purpose of this study is to check the validity of the current seismic design procedures. Two structures with different heights are designed and their seismic performances are evaluated for this purpose. Both structures are assumed to be located at the same strong seismic zone.

• Computers and Concrete
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• v.20 no.4
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• pp.419-427
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• 2017

A methodology, based on fragility functions, is proposed to evaluate the seismic performance of seismic isolated $45^{\circ}$ skewed concrete bridge: 1) twelve types of seismic isolation devices are considered based on two different design parameters 2) fragility functions of a three-span bridge with and without seismic isolation devices are analytically evaluated based on 3D nonlinear incremental dynamic analyses which seismic input consists of 20 selected ground motions. The optimum combinations of isolation device design parameters are identified comparing, for different limit states, the performance of 1) the Seismic Isolated Bridges (SIB) and 2) Not Seismic Isolated Bridge (NSIB) designed according to the AASHTO standards.

• Steel and Composite Structures
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• v.50 no.3
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• pp.337-345
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• 2024

This research proposed a particle swarm optimization (PSO) based seismic retrofit design of moment frame structures using a steel frame assembly. Two full scale specimens of the steel frame assembly with different corner details were attached to one-story RC frames for seismic retrofit, and the lateral load resisting capacities of the retrofitted frames subjected to cyclic loads were compared with those of a bare RC frame. The open source software framework Opensees was used to develop an analytical model for validating the experimental results. The developed analytical model and the optimization scheme were applied to a case study structure for economic seismic retrofit design, and its seismic performance was assessed before and after the retrofit. The results show that the developed steel frame assembly was effective in increasing seismic load resisting capability of the structure, and the PSO algorithm could be applied as convenient optimization tool for seismic retrofit design of structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.173-181
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• 2006

Many isolated bridges are designed and constructed after the introduction of the seismic design. However those bridges designed in engineering fields have unnecessarily high serviceability limit and brittle failure mechanism, which do not satisfy the seismic design concept. Such design results are due to the excessive substructure stiffness of the conventional design method as well as the misunderstanding of the seismic design method. In this study an isolated bridge designed with the conventional design method is selected and the same bridge with steel bearings is modelled for the comparative seismic design. From the comparison, the seismic design procedures satisfying the required performance levels are provided for the two bridges. It is confirmed that the isolated bridge requires more complicated design procedure with trial and error methods and reanalyses but provides higher serviceability limit compared to the bridge with steel bearings. However, because the required serviceability limit can also be obtained by adjusting substructure stiffness, it is a resonable seismic design process that an isolated bridge is to be considered as an alternative design when the ductile failure mechanism is not obtained with a bridge with steel bearings.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.276-283
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• 2006

Korea is considered to be immune from the earthquake hazard because it is located far away from the active fault. However, recent earthquake caused a loss of lives and economical loss worldwide. Hence there has been raised an importance of the earthquake resistant design for various infrastructures. In this research, the seismic design and evaluation criterion for RC bridge pier were proposed from the experimental results of 82 circular RC bridge piers tested in domestic and aboard. New seismic criterion was introduced the limited ductile design provision suitable to Korean peninsula, which would be classified as a low or moderate seismic region. In addition, further important topic for the seismic safety of RC bridge piers in Korea is the seismic performance enhancement of RC bridge piers, which were designed and constructed before the 1992 seismic design provision. Therefore, the proposed seismic performance evaluation criterion could be very useful to judge seismic retrofit need or not according to the residual seismic performance of the RC bridge piers. Also, it could reduce an uncertainty for the safety of the infrastructure under earthquakes.

• Journal of the Earthquake Engineering Society of Korea
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• v.18 no.2
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• pp.105-115
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• 2014

This paper is the sequel of a companion paper (I. Performance Evaluation) evaluating the relation between the seismic performance of steel intermediate moment frames (IMFs) and the rotation capacity of connections. The evaluation revealed that the seismic performance of IMFs having the required minimum rotation capacity suggested in the current standards did not meet the seismic performance criteria presented in FEMA 695. Therefore, thepresent study evaluates the causes of the vulnerable seismic performance for steel IMFs and proposes alternatives to satisfy the seismic performance suggested in FEMA 695. To that goal, the results of nonlinear analysis, which are the pushover analysis and the incremental dynamic analysis, are examined and evaluated. As a result, high-rise IMF systems are seen to have the lower collapse margin ratio after connection fracture than row-rise IMF systems and, the actual response isfound to compared tothedesign drift ratio acting on design load design. Finally, the minimum design load values are proposed to meet the seismic performance suggested in FEMA 695 for IMF systems having vulnerable seismic performance.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.867-872
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• 2002

The seismic design from the underground structures with the ground structures differently relative acceleration of ground and structure for, that period ci it was a condition where the recognition against the seismic design of the underground structure is insufficient because the decease damage does not very to that extent. Analysis result, earthquake hour section power increase one that price smiles from one part and when it applies a regular design hour safety rate 20%, seismic efficiency level satisfaction is it becomes feed with the fact that it will be able to augment the efficient characteristic of design.

• Earthquakes and Structures
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• v.13 no.4
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• pp.421-427
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• 2017

Seismic safety evaluation of weir structure is significant considering the catastrophic economical consequence of operational disruption. In recent years, the seismic probabilistic risk assessment (SPRA) has been issued as a key area of research for the hydraulic system to mitigate and manage the risk. The aim of this paper is to assess the seismic probabilistic risk of weir structures employing the seismic hazard and the structural fragility in Korea. At the first stage, probabilistic seismic hazard analysis (PSHA) approach is performed to extract the hazard curve at the weir site using the seismic and geological data. Thereafter, the seismic fragility that defines the probability of structural collapse is evaluated by using the incremental dynamic analysis (IDA) method in accordance with the four different design limit states as failure identification criteria. Consequently, by combining the seismic hazard and fragility results, the seismic risk curves are developed that contain helpful information for risk management of hydraulic structures. The tensile stress of the mass concrete is found to be more vulnerable than other design criteria. The hazard deaggregation illustrates that moderate size and far source earthquakes are the most likely scenario for the site. In addition, the annual loss curves for two different hazard source models corresponding to design limit states are extracted.