• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.4
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• pp.13-18
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• 2007

The research was performed to review the design factors which affect the durability of structures. For the study, domestic and foreign literature review were performed on various design criteria. Based on Korean standard specifications, the results showed that the durability of structure as the diameter of reinforcing steel bar becomes smaller and the distance between reinforcing bar is closer than the normal gap. The results were also presented that the minimum required bar cover is 6.6cm to obtain the durability index value. In addition, the maximum limited bar cover was 12cm considering the durability index and the change of increasing value of durability index. In case that there is no specified regulation for the bar cover thickness change, the durability life by neutralization is proportional to the thickness of bar cover.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.66-71
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• 2018

In general, when an existing pier is enlarged and reinforced using a small diameter pile, bonded anchor with deformed reinforcing bars is used to maintain the integrity of the joint. However, in the case of bonded anchors, the performance depends largely on the type of joint material. Nevertheless, unlike mechanical anchors, there is no standard method for designing appropriate design methods and proper performance evaluation. Therefore, in this study, the performance of the anchoring anchor was evaluated by performing a model experiment using the reinforcing bars and anchor reinforcing bars. Experimental results show that the structural performance of the unbonded specimen is the best, and the failure mode is the punching shear failure. The deflection of the end of the member is smaller than that of the unconnected member, The deflection of the connected member is larger than the deflection of the small connected member. As the load increases, the possibility of slippage of the anchor steel or fold connection rebar is high.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.430-439
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• 2002

The development of reinforcing steel is required in reinforced concrete structures. The standard hooks that have been widely used for the tensile development in the beam-column joints tend to create difficulties of construction such as steel congestion as the member cross sections are becoming smaller due to the use of higher strength concrete and higher grade steel. Using the reinforcing bars with end mechanical anchoring device (headed reinforcement) provides potential economies in construction such as reduction in development lengths, simplified details, and improved responses to cyclic loadings. In this paper, the pullout strengths and behaviors of the headed reinforcement were experimentally studied. In 33 pullout tests performed using D25 deformed reinforcing bars, the test parameters were embedment depth, edge distance, head size, and the use of transverse reinforcement. The pullout strengths determined from tests closely agreed with the pullout strengths predicted using the CCD method. The pullout strengths increased with increasing embedment depths nd edge distances. The strengths tend to increase with the use of larger heads. From the experimental program where the effect of the transverse reinforcement was examined, a modification factor to the CCD was suggested to represent the effect of such reinforcement that is installed across the concrete failure plane on the pullout strengths.

• Land and Housing Review
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• v.7 no.1
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• pp.31-41
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• 2016

In this paper, we propose experimental results, which target the major variables that influence the structural performance of a wall, as well as the resulting seismic and hysteretic behavior. Results also provide the basis for the application of performance based design by identifying the nonlinear hysteretic behavior of the wall with boundary element details recently proposed in previous study by Chun et al(2011). From the experimental results, the crack and fracture patterns of a specimen, which adopt the proposed boundary element details, showed similar tendencies regardless of whether axial force or high performance steel bars is applied. Furthermore, results show that the maximum strength of the specimen can be predicted accurately based on the design equation proposed by the standard. In addition, with a higher axial force, there is a tendency that both the initial load and maximum strength increase as deformation capacity reduces, requiring consideration of the reduced deformation capacity due to a high axial force. For walls under such high axial forces, using high performance steel bars is a very effective manner of enhancing deformation capacity. Therefore, reinforcing the plastic hinge region with boundary elements using high performance steel bars is preferable.

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.323-333
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• 2007

This paper presents a study that attempted to improve the site applicability of profile sheets and check the effects of bending reinforcement in composite profiled beams, and consequently, to suggest an improved modular-type CB2 and two types of bending reinforcement methods. As a result of the reinforcing and reforming modular profiled beam experiment conducted, CBIIshowed an adequate deformation capacity as well as a sufficient plastic plateau at the maximum load and thereafter. For all the specimens, an insignificant modular slip occurred while linear relations were kept constant, at up to approximately 50% of the maximum load and at constant linear relations. The experimental values were very low. Probably, due to the small-scale experiment, the area of the concrete for the concrete filling and covering might have been insufficient, which might have led to the failure to improve the strength. Comparing the results with the standard design stress, all the specimens-except for T16 and B16-indicated more than 0.9. Based on the standard design stress, the reinforced modular profiled beam was consideredto have positive applicability.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.167-179
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• 1999

The thin web panels of plate girders often need to be reinforced with transverse stiffeners to increase the shear strength. Since early 1960s, extensive researches have been conducted on the ultimate shear strength of plate girder webs with transverse stiffeners. These results have been first adopted into AASHTO(1970) and British Standard(1983) Specifications for the determination of the ultimate shear strength of transversely stiffened web panels. Although the main purposes of reinforcing web panels with longitudinal stiffeners are to increase the buckling strength and to control the lateral deflections due to bending, it has been reported that the longitudinal stiffeners increase the shear strength. However lack of studies has kept the effects of the longitudinal stiffeners on the ultimate shear strength from the design of plate girder web panels. In the present study an experimental investigation is carried out in order to assess the increment of the ultimate shear strength of shear web panels due to the longitudinal stiffeners and the results are compared with the existing failure theories.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.1
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• pp.51-60
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• 2010

Recently, a new type of polyolefin fiber having a good mechanical properties is being developed, and it is necessary to examine a possibility for the new fiber together to be used as a reinforcing fiber with other types of fiber or by itself. The objective of this study is to find flexural toughness and tensile strength of concrete reinforced with steel and polyolefin fibers. Four point beam tests were performed with 324 specimens following two standard tests methods: KS F 2566 and ASTM C 1399-02. From the test results, the effects of volume fraction of fibers, and aspect ratio of steel fiber on the toughness and tensile strength were investigated, and the optimal ratio of steel fiber to polyolefin fiber was suggested.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.76-83
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• 2021

This study examines the bending behavior of lap-spliced ultra-high-strength fiber-reinforced concrete members and evaluates the safety of the design codes for ultra-high-strength fiber-reinforced concrete structures. An experiment on a total of six beams was performed. The main variables were the fiber-inclusion and the lap-spliced length at the center of the beams. The steel fibers in a volume fraction of 2% were used, and the lap-splice lengths were determined to be 8db and 16db. As a result of the test, the specimens not reinforced with fiber lost abrupt load-bearing capacity at the lap region and did not experience yielding of the reinforcing bar. In the case of fiber-reinforced concrete, if a lap-splice length of 16db is secured, the yielding of the main reinforcing bar can be experienced, and appropriate flexural strength can be expressed. Based on the experimental results of this study, as a result of reviewing the lap-splice length calculation formulas of the current design standards and the ultra-high-strength concrete structural design recommendations, it was found that all of them were evaluated conservatively.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.603-611
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• 2005

For the establishment of rational seismic design code for RC (reinforced concrete) bridge pier, this paper has analyzed the seismic code of RC bridge pier specified in )veil-known codes such as KHBDS (Korea Highway Bridge Design Specification), AASHTO Standard, ATC-32, Eurocode 8, NZS 3101, etc. So as to secure aseismic ductility of RC pier, transverse confinement steel ratios of those codes have been examined together with other design parameters such as strength of concrete and reinforcing steel, axial force ratio, aspect ratio, longitudinal steel ratio, etc. However, there has been arisen a doubt for the validity of those parameters. Thus, the objective of this study is to quantitatively evaluate the validity of design parameter of each code on the experimental seismic ductility for about 80 test specimens. It was concluded from this study that the axial force ratio is a dominant factor for the seismic displacement ductility. Therefore, it Is desirable that the axial force ratio be further taken into account in the corresponding seismic design formula of RC bridge pier in current KHBDS.

• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.44-51
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• 2018

As the LNG storage tank is aged, if there is a crack in the outer wall concrete or corrosion of the reinforcing steel, there is a risk of a major accident such as collapse of the structure depending on the type and degree of damage. Since 2014, LNG storage tanks have undergone precise safety diagnosis and safety inspection has been carried out. The condition evaluation criteria for each component have been revised and applied in January 2016. The condition evaluation standard is to evaluate the status of storage tanks based on the appearance survey and material test results of LNG storage tanks and it is important for maintenance. In addition, the representative condition evaluation standard that shows the comprehensive state of each LNG storage tank is important in maintenance, but the related standard for LNG storage tank outer concrete is not available in Korea and abroad, and development of the condition evaluation standard is necessary. In this paper, we examined the structural characteristics of LNG storage tanks, analyzed the status of the condition evaluation criteria for each member, and developed a comprehensive status rating system by weighting the members. We used the AHP(Analytic Hierarchy Process) technique and developed a representative conditon evaluation criteria through surveys of professional organizations.