• 한국방재학회:학술대회논문집
• /
• 2008.02a
• /
• pp.67-70
• /
• 2008

This study is to analyzes the global behavior of frame structures with local cracks in structural members by frame analysis, using the stiffness matrix of cracked frame element. This local compliance is utilized to derive the stiffness matrix of the cracked frame element and the effects of interaction among multiple cracks are also examined. The proposed technique is applied to frame structures with local cracks. Analysis results confirm the possibility of quantitative analysis of a structure damaged with local cracks and the feasibility of the technique as a tool for analyzing the global behavior of frame structures, reflecting effects of local cracks.

• Steel and Composite Structures
• /
• v.44 no.2
• /
• pp.283-294
• /
• 2022

In this study, a new seismic retrofit scheme of building structures is developed by combining a steel moment frame and steel slit plates to be installed inside of an existing reinforced concrete frame. This device has the energy dissipation capability of slit dampers with slight loss of stiffness compared to the conventional steel frame reinforcement method. In order to investigate the seismic performance of the retrofit system, it was installed inside of a reinforced concrete frame and tested under cyclic loading. Finite element analysis was carried out for validation of the test results, and it was observed that the analysis and the test results match well. An analytical model was developed to apply the retrofit system to a commercial software to be used for seismic retrofit design of an example structure. The effectiveness of the retrofit scheme was investigated through nonlinear time-history response analysis (NLTHA). The cyclic loading test showed that the steel frame with slit dampers provides significant increase in strength and ductility to the bare structure. According to the analysis results of a case study building, the proposed system turned out to be effective in decreasing the seismic response of the model structure below the given target limit state.

• Steel and Composite Structures
• /
• v.46 no.6
• /
• pp.857-865
• /
• 2023

This study aimed to develop a seismic retrofit technique using a steel frame which can be easily transported and assembled on site. This enables the retrofit steel frame to be easily attached to an existing structure minimizing the unwanted gap between the structure and the steel frame assembly. A one-story one-bay RC frame was tested with and without seismic retrofit using the proposed steel frame to verify the seismic retrofit effect of the proposed system, and an analysis model was developed in Opensees for seismic performance evaluation of a case study soft first-story model structure retrofitted with the developed steel frame assembly. Seismic performance of the model structure was also evaluated considering soil structure interaction effect. The experimental study confirmed that the proposed seismic retrofit system can be applied effectively to improve the seismic performance of framed structures. Time history analysis results of the model structure showed that the proposed steel frame assembly was effective in increasing the seismic load resisting capacity of the soft first-story structure. However more steel frame assemblies were required to satisfy the given performance limit state of the model structure located on weak soil due to the negative soil-structure interaction effect.

• Computers and Concrete
• /
• v.31 no.5
• /
• pp.419-432
• /
• 2023

Beam-column joints are a critical component of reinforced concrete frame structures. They are responsible for transferring forces between adjoining beams and columns while limiting story drifts and maintaining structural integrity. During severe loading, beam-column joints deform significantly, affecting, and sometimes governing, the overall response of frame structures. While most failure modes for beam and column elements are commonly considered in plastic-hinge-based global frame analyses, the beam-column joint failure modes, such as concrete shear and reinforcement bond slip, are frequently omitted. One reason for this is the dearth of published guidance on what type of hinges to use, how to derive the joint hinge properties, and where to place these hinges. Many beam-column joint models are available in literature but their adoption by practicing structural engineers has been limited due to their complex nature and lack of practical application tools. The objective of this study is to provide a comparative review of the available beam-column joint models and present a practical joint modeling approach for integration into commonly used global frame analysis software. The presented modeling approach uses rotational spring models and is capable of modeling both interior and exterior joints with or without transverse reinforcement. A spreadsheet tool is also developed to execute the mathematical calculations and derive the shear stress-strain and moment-rotation curves ready for inputting into the global frame analysis. The application of the approach is presented by modeling a beam column joint specimen which was tested experimentally. Important modeling considerations are also presented to assist practitioners in properly modeling beam-column joints in frame analyses.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.39 no.5
• /
• pp.313-319
• /
• 2021

The national geodetic reference frame of Korea was adopted in 2003, which is referenced to ITRF (International Terrestrial Reference Frame) 2000 at the epoch of January 1, 2002. For precise positioning based on the satellites, it should be thoroughly maintained to the newest global reference frame. Other than plate tectonic motion, there are significant events or changes such as earthquakes, antenna replacement, PSD (Post-Seismic Deformation), seasonal variation etc. We processed three years of GNSS (Global Navigation Satellite System) data(60 NGII CORS stations, 51 IGS core stations) to produce daily solutions minimally constrained to ITRF. From the time series of daily solutions, the sites with unexpected discontinuity were identified to set up an event(mostly antenna replacement). The combined solution with minimum constraints was estimated along with the velocity, the offsets, and the periodic signals. The residuals show that the surrounding environment also affects the time series to a certain degree, thus it should be improved eventually. The transformation parameters to ITRF2014 were calculated with stability and consistency, which means the national geodetic reference frame is properly aligned to the global reference frame.

• Steel and Composite Structures
• /
• v.50 no.5
• /
• pp.549-562
• /
• 2024

In this study a steel moment frame system to be installed on the exterior surface of an existing structure is proposed as a seismic retrofit device. The seismic performance of the retrofit system was investigated by installing it on the exterior of a single story single bay reinforced concrete frame and testing it under cyclic loading. The cyclic loading test results indicated that the steel frame significantly enhanced the strength and ductility of the bare structure. Finite element analysis was carried out to validate the test results, and it was observed that there was good agreement between the two results. An analytical model was developed in order to apply the retrofit system to an example structure subjected to seven mainshock-aftershock sequential earthquake records. It was observed that the model structure was severely damaged due to the mainshock earthquakes, and the seismic response of the model structure increased significantly due to the subsequent aftershock earthquakes. The seismic retrofit of the model structure using the proposed steel frame turned out to be effective in decreasing the seismic response below the given limit state.

• KCI Concrete Journal
• /
• v.12 no.1
• /
• pp.3-16
• /
• 2000

A series of dynamic and static tests were conducted to observe the actual responses of a 1:5 scale 3-story reinforced concrete(RC) frame which was designed only for gravity loads. One of the major objectives of these experiments is to provide the calibration to the available static and dynamic inelastic analysis techniques. In this study, the experimental results were simulated by using a nonlinear analysis program for reinforced concrete frame, IDARC-2D. The evaluation of the degree of the simulation leads to the conclusion that while the global behaviors such as story drifts and shears can be in general simulated with the limited accuracy in the dynamic nonlinear analysis, it is rather easy and simple to get the fairly high level of accuracy in the prediction of global and local behaviors in the static nonlinear analysis by using IDARC-2D.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.483-486
• /
• 1999

A series of dynamic and static tests were conducted to observe the actual responses of a 1:5 scale 3-story reinforced concrete (RC) frame which was designed only for gravity loads. One of the major objectives of these experiments are to provide the calibration to the available static and dynamic inelastic techniques. In this study, the experimental results were simulated by using a nonlinear analysis program for reinforced concrete frame, IDARC-2D. The evaluation of the degree of the simulation leads to the conclusion that while the global behaviors such as story drifts and shears can be in general simulated with the limited accuracy in the dynamic nonlinear analysis, it is rather easy and simple to get the fairly high level of accuracy in the prediction of global and local behaviors in the static nonlinear analysis by using IDARC-2D.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.25 no.2
• /
• pp.189-198
• /
• 2014

In this paper, we propose a SSD(Simultaneous Single band Duplex) system using turbo equalizer with frame structure for simultaneous full-duplex communication in single band. the proposed system uses frame structure for self-interference cancellation effectively. In this paper, performance of the proposed system with frame structure compares to performance of SSD system without frame structure to analysis performance of the proposed system with frame structure. Simulation results show that the performance of proposed system with frame structure is batter than performance of SSD system without frame structure when the number of global iterations of both system is same. Using proposed system with frame structure, we can verify that the performance like SSD system without frame structure by few global iteration of turbo equalizer.

• Computers and Concrete
• /
• v.21 no.6
• /
• pp.637-647
• /
• 2018

Numerical approach using finite element method has been used to evaluate the behaviour of reinforced concrete frame structure subjected to fire. The structure is previously designed in accordance with Eurocode standards for the design of structures for earthquake resistance, for the ductility class M. Thermal and structural response are obtained using a commercially available software ANSYS. Temperature-dependent nonlinear thermal and mechanical properties are adopted according to Eurocode standards, with the application of constitutive model for the triaxial behaviour of concrete with a smeared crack approach. Discrete modelling of concrete and reinforcement has enabled monitoring of the behaviour at a global, as well as at a local level, providing information on the level of damage occurring during fire. Critical regions in frame structures are identified and assessed, based on temperatures, displacements, variations of internal forces magnitudes and achieved plastic deformations of main reinforcement bars. Parametric analyses are conducted for different fire scenarios and different types of concrete aggregate to determine their effect on global deformations of frame structures. According to analyses results, the three-dimensional finite element model can be used to evaluate the insulation and mechanical resistance criteria of reinforced concrete frame structures subjected to nominal fire curves.