• Magazine of the Korea Concrete Institute
• /
• v.6 no.4
• /
• pp.92-101
• /
• 1994

A new analytical model is proposed to better understand the transfer bond performance in a prestressed pretensioned concrete beam. The transfer length is divided into an elastic and a plas tic zones in this model. The bond stress is assumed t.o increase proportionally with the slip t.o the lirnit of maximum bond stress within the elastic zone and remains at a constant maximum value wthin the plastic zone. Four main stress patterns: bond stress, slip, steel stress, and concrete stress distributions within the transfer length are obtained precisely. The total transfer length al\ulcornerd free-end slip obtained here give a close comparison to the test results by Cousins et al.

• International Journal of Concrete Structures and Materials
• /
• v.3 no.1
• /
• pp.33-37
• /
• 2009

Fiber Bragg grating (FBG) sensors already have been the focus for structural health monitoring (SHM) due to their distinguishing advantages. However, as bare optical fiber is very fragile, bare FBG strain sensor without encapsulation can not properly be applied in practical infrastructures. Therefore encapsulation techniques for making encapsulated FBG strain sensor show very important in pushing forward the application of FBG strain sensors in SHM. In this paper, a simplified approximate method to analyze the stress transferring rules for embedded FBG strain sensors in concrete monitoring is put forward according to mechanics of composite materials. Shear lag theory is applied to analyze the stress transferring rule of embedded FBG strain sensor in measured host material at the first time. The measured host objects (concrete) and the encapsulated FBG strain sensor are regarded as a composite, and then the stress transfer formula and stress transfer coefficient of encapsulated FBG strain sensor are obtained.

• KCI Concrete Journal
• /
• v.12 no.2
• /
• pp.31-43
• /
• 2000

The extensive usage of pretensioned prestressed concrete component in modem construe- tion as structural members mandates precise understanding of its mechanism. Especially, an adequate transfer of prestressing force from steel tendons to concrete around the end regions of the member is a critical issue. Due to the importance of the topic, several investigators have formulated equations modeling the transfer bond length based on various bonding mechanism between steel and concrete. However, the existing models are still inadequate in predicting the bond development in pretensioned prestressed concrete members. Therefore, this study presents a model of transfer bond length based on rational theory that can simulate experimental results. The model is developed into solid mechanics based structural analysis computer program. The program is validated by comparing the analysis results with experimental results of bond stress distribution, concrete strain profiles, and transfer length in pretensioned prestressed concrete members. The proposed analytical procedure in this study can be utilized as a useful tool for realistic evaluation of transfer length in pretensioned prestressed concrete members.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.6 no.4
• /
• pp.336-341
• /
• 2018

The prestressing force introduced to the tendon in pretensioned concrete members is transferred by direct bond between tendon and concrete, which requires a proper estimation of stress transfer length. The use of pretensiond and/or precast members with UHPC (Ultra High Performance Concrete) may give many advantages in quality control. This paper presents an experiment to estimate the stress transfer length of UHPC for various compressive strength levels of UHPC, cover depths, diameters of tendons and tensioning forces. According to the result of this experiment, the stress transfer length of UHPC member is much reduced comparing that of normal strength concrete. The reduction in stress transfer length of UHPC may come from the high bond strength capacity of UHPC. The transfer lengths obtained from this experiment are compared to those in current design code and a new formula is proposed.

• Magazine of the Korea Concrete Institute
• /
• v.6 no.1
• /
• pp.89-100
• /
• 1994

The current test procedure for transfer length, which determine transfer length by measuring concrete strain, has an actual bond stress state in the prestressed pretensioned member : however, it is difficult to determine the bond properties of maximum bond stress and bond stiffness with this method. It is also difficult for design engineer to understand and select a correct safety criterion from the widely distributed results of such a ransfer test alone. An alternative testing procedure is provided here to determine the bond properties without measuring the concrete strain. In this test the bond stress is measured directly by creating a similar boundary condition within the transfer length in a real beam during the transfer of prestressing force. The prestressing force was released step by step by step from the unloading side. The release of force induces a swelling of the strand at the unloading side of concrete block, bonding force in the block, and a bond slip of the strand toward the other side of the block. Two center-hole load cells are used to record the end loads until the point of general bond slip(maximum bond stress). It is suggested that this test procedure be performed with the ordinary transfer test when determining the transfer length in a prestressed, pretensioned concrete beam.

• Journal of the Korean Society of Safety
• /
• v.28 no.3
• /
• pp.80-87
• /
• 2013

Heat transfer analysis and thermal stress analysis for the concrete bridge was performed in order to investigate the damage of the concrete bridge by the fire of the vehicle. Changes in material properties, such as thermal conductivity, specific heat, density, elasticity, caused by temperature rise were considered. Heat transfer analysis and thermal stress analysis were performed according to the various location of the fire by ABAQUS. From the comparison of the numerical results, the degree of structural damage for the concrete bridge was investigated and considerations for the design of a concrete bridge against fire were identified.

• Magazine of the Korea Concrete Institute
• /
• v.7 no.3
• /
• pp.137-148
• /
• 1995

In this study, a program for evaluation of heat transfer and thermal stress of mass concrete is developed and verified by 2-experiments (internally and externally restricted). Furthermore, the result of the program is compared with those of ADINA-T and ADINA. As a result of the comparison, the proposed method produces comparable results with those from the popular programs (ADIIVA-T and ADINA) and shows the usefulness of the developed program for the evaluation of thermal stresses of mass concrete in both internally and externally restricted structures.

• Steel and Composite Structures
• /
• v.22 no.1
• /
• pp.63-77
• /
• 2016

Top-down construction is a construction technique in which pit excavation and structure construction are conducted simultaneously. Reducing construction time and minimizing noise and vibration which affect neighboring structures, the technique is widely employed in constructing downtown structures. While H-steel columns have been commonly used as core columns, concrete filled steel tube (CFT) columns are at the center of attention because the latter have less axial directionality and greater cross-sectional efficiency than the former. When compared with circular CFT columns, square CFT columns are more easily connected to the floor structure and the area of percussion rotary drilling (PRD) is smaller. For this reason, square CFT columns are used as core columns of concrete encased and filled square (CET) columns in underground floors. However, studies on the structural behavior and concrete stress transfer of CET columns have not been conducted. Since concrete is cast according to construction sequence, checking the stress of concrete inside the core columns and the stress of covering concrete is essential. This paper presents the results of structural tests and analyses conducted to evaluate the usability and safety of CET columns in top-down construction where CFT columns are used as core columns. Parameters in the tests are loading condition, concrete strength and covering depth. The compressive load capacity and failure behavior of specimens are evaluated. In addition, 2 cases of field application of CET columns in underground floors are analyzed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1990.04a
• /
• pp.122-127
• /
• 1990

The transfer of forces across the interface by bond between concrete and steel is of fundamental importance to many aspects of reinforced concrete behavior. Bond stress - slip relationships were studied using a symmetrical tension test specimen. This type of test is intented to simulate conditions in the tension zone of a concrete beam between primary cracks and below the neutral axis. These relationships between local bond stress and local slip are quite different at different locations along the bar. The present study allows more accurate analysis of reinforced concrete structures by employing more realistic bond stress-slip relations.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1997.04a
• /
• pp.515-520
• /
• 1997

This research is aimed at the development of the composite beam-column connection system by which the steel beam can be connected to the R/C column with smooth stress transfer. As the first step of the structural performance tests of the system, bearing resistance test has been carried out for actual size specimen. From the test, the connection system has been proved to take good bonding and stress transfer to the surrounding concrete with negligible relative displacements.