• Journal of the Korea Concrete Institute
• /
• v.20 no.4
• /
• pp.423-430
• /
• 2008

VES-LMC (very-early strength latex-modified concrete) has been widely used as repair material for bridge deck overlay or rehabilitation, because the overlaid or repaired could be opened to the traffic after 3 hours of curing. Although the field performance of VES-LMC generally indicates that it has an excellent bonding to the substrate and shows a long term performance, little quantitative data or research results have been presented in the literature on structural studies. The purpose of this study was to investigate the flexural behavior, interfacial performance, crack propagation, and strengthen effect of RC beam overlaid or repaired by VES-LMC through the 4-point flexural loading test. Two different types of RC beam were fabricated for repair and rehabilitation types. The test result showed that the strengthen effect, in term of flexural stiffness, increases as the depth of repair or overlay increases. More than 40% of stiffness was improved when the depth of repair was up to steel position. However, there was a little difference between 80 mm and 120 mm repaired beam. This means the repair depth must be considered. The interfacial behavior data showed that the repaired or overlaid beams had a little relative displacement. This means that two materials behave comparatively acting together. However, there were two specimens which had large displacement at the interface, because of poor bond strength. This suggested that interface treatment is one of the most important jobs in composite beams.

• Journal of the Society of Disaster Information
• /
• v.19 no.1
• /
• pp.138-145
• /
• 2023

Purpose: In accordance with the increase in the number of buildings repaired and reinforced following deterioration from when a fire occurs in a previously reinforced building, the impact on the structure after the fire is analyzed to establish standards for repair and reinforcement measures. Method: After curing for 28 days, the process was to measure the compressive strength and induce destruction through a compressor, repair and reinforce it with epoxy, and conduct a re-compressive strength test on some specimens after curing for 3 days to understand the degree of strength restoration. The rest of the repaired and reinforced specimens as well as the unrepaired and unreinforced specimens were then put into an oven and heated according to the temporal and temperate conditions listed below, and then the compressive strength was tested to estimate the impact of fire. Result: After reinforcing the yielded specimen with epoxy, the process was to then put it in an oven and heat it at different temperatures over time. It was found that there was a decrease in the strength of the reinforcement more than that of the actual specimen. Conclusion: Based on this, it was found that a building repaired and reinforced with epoxy resin is actually more dangerous than a general unrepaired building when it is damaged by fire, and thus, that it must be prepared for fire vulnerabilities.

• Proceedings of the Korean Institute of Industrial Safety Conference
• /
• 2003.10a
• /
• pp.378-383
• /
• 2003

콘크리트 구조물은 여러 가지 원인에 의해 손상을 입거나 시간이 지남에 따라 노후화가 진행된다. 이와 같이 손상을 입거나 노후화가 진행된 구조물은 그 내구성능이 저하되어 계속 사용하기 위해서는 보수를 하거나 보강해야만 한다. 구조물을 보수하거나 보강하는 것은 구조물의 수명을 크게 연장하는 일로 여러 가지의 경제적인 효과가 있기 때문에 이에 대한 연구와 공법 개발 등이 활발히 이루어지고 있다.(중략)

• Magazine of the Korea Concrete Institute
• /
• v.7 no.6
• /
• pp.4-4
• /
• 1995

• Magazine of the Korea Concrete Institute
• /
• v.7 no.6
• /
• pp.74-91
• /
• 1995

• Journal of Korean Society of Steel Construction
• /
• v.16 no.5 s.72
• /
• pp.555-564
• /
• 2004

Steel materials, which are normally used in bridge structures, are prone to corrosion and have thin plate structures. Steel bridges that have been damaged through increased vehicle load and corrosion are frequently expected to be strengthened. Repair or strengthening methods generally include cutting, bolting, and welding. The basic characteristics of stress and deformation behavior generated by cutting and welding in the course of the repair work, however, are not yet understood. It is difficult to say whether the safety of the structure after welding conforms with existing safety evaluation methods.Therefore, to gain confidence in the material and to guarantee the safety of the structure after welding, the stress generated by heat, through welding and cutting, was generalized. The effect of additional loads with respect to stress generated by heat was also investigated.

• Journal of Korean Society of Steel Construction
• /
• v.9 no.3 s.32
• /
• pp.363-375
• /
• 1997

This study encompasses the performance of static and fatigue test for the 8 large scale test specimens to clarify the fatigue behavior of coped stringer and the effect of the repair and strengthening on the damaged stringer of the floor system in steel railway bridges. For the purpose of the research, the actual stress wave for the existing bridge was measured, the basic stress range frequency histogram was made and the equivalent stress range was calculated. Using the result from the equivalent stress range made by adjusting the stress range, the static and fatigue test was carried out by identifying the previous rehabilitation and after. As the result of the static tests, it was revealed that the level of local stress under the S1 specimen test of the real equivalent stress range was similar to tensile strength of the test material, and it was consistent with the requirement of the initiation condition of the fatigue crack. Through the various rehabilitation methods to the damaged specimens, the effects of the repair and reinforcement were analyzed. According to the results of the repair of effect, bolting the high tension bolt over the stop hole was confirmed to be more adequate method than drilling only stop hole to delay the fatigue crack growth. Futhermore, in case of the stringer subjected by bending moment, the reinforcement over the upper flange side was determined to be a useful strengthening method, and the reinforcement to the web of the stringer was not appropriate to accomodate as a adequate strengthening method. Also it was confirmed that the category of the fatigue design for the coped stringer met with the category E specified on the fatigue design criteria of the Highway Standard Specification in Korea.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.11
• /
• pp.128-134
• /
• 2016

Estimating the repair and reinforcement (R&R) costs for each bridge member is essential for managing the life cycle of a bridge using a bridge management system (BMS). Representative members of a bridge were defined in this study, and detailed and representative R&R methods for each one were drawn in order to develop a systematic maintenance cost model that is applicable to the BMS. The unit cost for each detailed R&R method was established using the standard of estimate and historical cost data, and a systematic procedure is presented using an integration program to enable easy renewal of the R&R unit cost. Also, the average unit cost of the representative R&R methods was calculated in the form of a weighted average by considering the unit cost and application frequency of each detained R&R method. The appropriateness of the drawn average unit cost was reviewed by comparing and verifying it with the previous historical unit cost. The suggested average R&R unit cost can be used to review the validity of the required budget or the appropriateness of the R&R performance cost in the stage to establish the bridge maintenance plan. The results of this study are expected to improve the reliability of maintenance cost information and the rationality of decision making.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.17 no.6
• /
• pp.145-152
• /
• 2013

As a typical construction material, concrete has been used in building all kinds of structures since the late $19^{th}$ century. Although it was recognized to secure durability as long as the regulations on design and construction have been reasonably complied, the trends of life-shortening and deterioration have frequently occurred due to all kinds of the external effects that have been experienced during the procedures of using the structures. To make matters even worse, deterioration of the concrete structures according to deterioration can not be controlled any more. Finally, the reality is that repair and maintenance are necessary in the maintenance aspect of the concrete structure. In this study, CRM(Chemical Resistance of Laminating Reinforcement Method), which had been developed to reinforce the surface of concrete and specially improve chemical resistance performance, has been applied to enhance the existing repairing and maintenance method. Therefore, the result has been drawn with comparison and analysis of the specimens applied with the general repairing and maintenance method and CRM through a variety of durability test in this study. With the result of the test, durability of the specimen applied with CRM has been more improved than the existing repairing and maintenance method, which is judged as because of the laminating effect due to reinforcement of epoxy impregnated of alkali-resistance fiber and double layered fiber reinforced seat.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.5A
• /
• pp.503-510
• /
• 2009

Latex modified concrete (LMC) is a successful polymer-portland cement concretes, which have been developed and used for many years, in overlaying bridge decks and resurfacing industrial floors. The excellent bond strength to substrate, easy application and high resistance to impact, abrasion, wear, aggressive chemicals and freeze-thaw deterioration have made this material used widely. The objective of this study was to determine experimentally the load-deflection response and ultimate strength of reinforced RC beams. The cracking patterns and the mode of failure were observed. Because of excellent bond strength and repairing effects, the RC beams repaired by LMC at compression or tension zone showed over 100% recovery from damaged structures. The RC beams overlaid by LMC showed significant improvement at load carrying capacity as overlay thickness increases. However, the beams repaired of tension zone without shear stirrups almost showed no strengthen effect, and indicated an interfacial failures. The interfacial behavior was estimated by numerical method adopting the concept of shear flow.