• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.25-28
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• 2006

In general, post-installed dowel bars are used as a shear connector to ensure the composite actions between new slabs and existing slabs in an apartment remodelling constructions expecially for enlarging the interior space outward the existing buildings. But, it has not been checked that the connection performance between existing and new slab is satisfactory not only for the structural safety condition but also the for serviceability and dwelling requirements. In this research, an experimental works were presented to evaluate the load transfer capacity for the planar joints between existing and new slab. The existing slabs were obtained from the existing apartment housing which will be demolished, and were retrofitted with carbon fiber plate. Test results showed that the planar joints with post-installed dowel bars behaved in full composite modes until ultimate capacity of test specimens, so sufficient ultimate and serviceability performance are confirmed.

• Smart Structures and Systems
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• v.33 no.4
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• pp.301-311
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• 2024

This paper proposes a deep convolutional long short-term memory (ConvLSTM)-based crack growth prediction technique for predictive maintenance of structures. Since cracks are one of the critical damage types in a structure, their regular inspection has been mandatory for structural safety and serviceability. To effectively establish the structural maintenance plan using the inspection results, crack propagation or growth prediction is essential. However, conventional crack prediction techniques based on mathematical models are not typically suitable for tracking complex nonlinear crack propagation mechanism on civil structures under harsh environmental conditions. To address the technical issue, a field data-driven crack growth prediction technique using ConvLSTM is newly proposed in this study. The proposed technique consists of the four steps: (1) time-series crack image acquisition, (2) target image stabilization, (3) deep learning-based crack detection and quantification and (4) crack growth prediction. The performance of the proposed technique is experimentally validated using a concrete mock-up specimen by applying step-wise bending loads to generate crack growth. The validation test results reveal the prediction accuracy of 94% on average compared with the ground truth obtained by field measurement.

• Structural Engineering and Mechanics
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• v.17 no.5
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• pp.707-725
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• 2004

An optimal design method with nonlinear elastic analysis is presented. The proposed nonlinear elastic method overcomes the drawback of the conventional LRFD method that accounts for nonlinear effect by using the moment amplification factors of $B_1$ and $B_2$. The genetic algorithm used is a procedure based on Darwinian notions of survival of the fittest, where selection, crossover, and mutation operators are employed to look for high performance ones among sections in the database. They are satisfied with the constraint functions and give the lightest weight to the structure. The objective function taken is the total weight of the steel structure and the constraint functions are strength, serviceability, and ductility requirement. Case studies of a planar portal frame, a space two-story frame, and a three-dimensional steel arch bridge are presented.

• Advances in concrete construction
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• v.3 no.2
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• pp.113-126
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• 2015

Holed-Incrementally Prestressed Concrete (H-IPC) girders are designed using the following new design concepts. At first, web openings reduce the self-weight of the girder, and also diffuse prestressing tendon anchorages. The reduced end anchoring forces decrease the web thickness of the end sections. Additionally, precast technology help to improve the quality of concrete and to reduce the construction period at the site. For experimentally verification, two 50 m full-scale H-IPC girders are manufactured with different concrete strength of 55 MPa and 80 MPa. The safety, stiffness, ductility, serviceability and crack development of H-IPC girder are measured and compared with each other for different strengths. Both girders show enough strength to carry live load and good stiffness to satisfy the design criteria. The experimental result shows the advantages of using high strength concrete and adopting precast girder. The test data can be used as a criterion for safety control and maintenance of the H-IPC girder.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.04a
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• pp.113-119
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• 1994

Vibration control of offshore structures subjected to wave loads is studied. The reduction of the dynamic responses of offshore towers subjected to wind generated random ocean waves is an important issue in the aspect of serviceability, fatigue life and safety of the structure. In this thesis, the effectiveness of the active tuned mass damper(ATMD) compared with the tuned mass damper(TMD) is mainly considered. Instantaneous optimal control scheme is employed for the active vibration control and Kalman filtering technique is used for the estimation of unmeasured response of structures. In practice, displacements and velocities could not be measured as easily as accelerations. So the state estimation methods like Kalman filter is very important. Numerical simulation is conducted for guarantee the effectiveness of ATMD for offshore structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.4
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• pp.147-155
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• 2002

To find the safety and serviceability of bridges, it must consider the behaviour of structural member and evaluation of the exact resistance of the member subjected to external loads. To evaluate the behaviour and the resistance of the structural member, it must measure the strains and displacements of the structures. Usually we use the strain gauge to measure the strains. When, the bridge is long span and high pier, the setting of strain gauge is very difficult and not economic. It is not recommendable for the use of strain gauge, when the structural member has many cracks and moisture. Thus, to make up for this demerits, the algorithm of strain analysis by measured displacements data is proposed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.247-254
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• 2010

Due to lightweight and high durability of glass-fiber reinforced polyester (GFRP) materials, they are promising alternatives to conventional construction materials such as steel, concrete and wood. As good application examples of GFRP materials, several types of temporary arch bridges were suggested and verified by finite element analyses in our previous study where snap-fit GFRP decks were applied. In this paper, we conduct a structural performance test to verify safety and serviceability of the temporary arch bridge, where snap-fit GFRP decks are assembled by bolts. The structural problems occurred in this test are also discussed and improvement of temporary arch bridges is suggested to resolve the occurred structural problems.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.1 s.53
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• pp.145-151
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• 2009

The span deflection among the monitoring items of bridge measurement system in real time is representative behaviour and important index of superstructure condition. the limit of span deflection in Standard Specifications for Highway Bridge in Korea has been applied to the method that is making the management-criteria for span deflection in bridge measurement system. But the limit concern mainly serviceability of divers. So it is difficult to find the safety factor of the limit from the viewpoint of bridge safety. This study estimated the safety factor of the limit of span-deflection in Standard Specifications for Highway Bridge in Korea from the viewpoint of bridge safety by the indoor structural test.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.385-392
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• 2001

The stiffness of pavement is scarcely considered in structural analysis of the superstructure bridge. It will be reasonable in the case of asphalt concrete pavement over concrete deck plate because stiffness of the pavement compared with concrete deck plate can be ignored. Additionally, it is considered correct to do a design with a safety. However, various pavement materials which have even value reaching to the elastic modulus of concrete are applied to the orthotropic steel deck plate which has a relatively less stiffness comparing with the concrete deck plate. In this paper, the steel plate deck of the bridge of real project was modeled considering the pavement stiffness for the FEM analysis and the linear elastic analysis was performed. It was assumed to be perfectly bonded between the steel plate deck and the pavement and the temperature effect was ignored. It was analyzed on the vertical deflection of steel deck plate influencing to the serviceability of pavement and the bending stress of steel deck plate related to the fatigue life. As a result, It was indicated that the structural behavior of the orthotropic steel deck plate could be affected by the stiffness of pavement in some cases.

• Journal of The Korea Institute of Healthcare Architecture
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• v.18 no.3
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• pp.51-59
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• 2012

Over a past century, the continuity in post-earthquake serviceability of medical facilities has been demonstrated to be essential for sustaining a society and/or a nation stable. However, not many countries including Korea have paid appropriate attention to such a lesson learned from the previous experiences of the countries located in high seismicity for various reasons, one of which may be the lack of social consensus in allocating a portion of the resources to the earthquake preparedness. As a result, an earthquake-related policy might have been pushed away out of the list of priority in the government agenda. Therefore, the present paper attempts to persuade the public general, experts and government officials together to seek a way to upgrade the seismic safety of the country a step forward by enhancing the seismic performance of medical facilities. For this the framework of seismic design codes and standards for medical facilities, and Californian experience in managing the seismic performance enhancement program and U.S.-Italian collaborative study to improve the seismic safety of Italian hospitals are reviewed. Finally, a list of further researches and practices to perform for seismic enhancement of medical facilities in Korea are suggested.