• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.33-38
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• 2022

As the intense heat continues, many cases of highway pavement blow up and bridge expansion joints damages have been inspected. Especially, Expansion joint closure of bridges is an important problem that can threat the safety of the bridge structure or reduce long-term durability. This paper proposed a structural analysis method for bridges having expansion joint closure and structural analysis was performed to verify the effects according to bridge types. Analysis bridges were divided into four types: concrete and steel bridges, shallow and piled foundations. To induce the situation of abutments and bridge decks are jammed, the following loads were additionally considered; lateral flow pressure, pavement expansion by alkali-aggregate reaction, creep settlement of backfill. The structural analysis method was verified by comparing the structural analysis results with the actually measured joint gap data. In addition, behavioral analysis due to joint closure was conducted to confirm the change in safety ratio by type of superstructure as the axial force increased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.597-604
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• 2006

Fiber Reinforced Polymer (FRP) is a relatively new material in the bridge construction. With high strength to weight ratios, excellent durability, and low life-cycle costs of FRP, FRP bridge decks can offer a low dead load, reduced maintenance, and long service life. Due to the lightweight of FRP, if existing concrete decks can be replaced with the FRP decks, the load carrying capacity of superstructure can be increased without strengthening of girders. In this study, we have conducted an experiment on 7 cases of connection conditions with steel girder by using bolts considering a rational and economical method of connection and compared with the results of FEM analysis. From the experimental result, if the bolts are strong enough to resist shear force between the FRP bridge deck and the steel girder, it will be structurally secure to use the zigzag method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.39-46
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• 2023

In this study, the dynamic behavior of friction bearings of PSC (Pre-Stressed Concrete) box train continuous bridge was numerically analyzed at 10 km/h intervals up to 600 km/h according to the increasing speed of the next-generation high-speed train. A frame model was generated targeting the 40-meter single-span and two-span continuous PSC box bridges in the Gyeongbu High-Speed Railway section. The interaction forces including the inertial mass vehicle model with 38 degrees of freedom and the irregularities of the bridge and track were considered. It was calculated the longitudinal displacement, cumulative sliding distance and displacement speed of the bridge bearings at each running speed so that compared with the dynamic behavior trend analysis of the bridge. In addition, long-term friction test standards were applied to evaluate the durability of friction plates.

• Steel and Composite Structures
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• v.51 no.5
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• pp.509-527
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• 2024

Bonding carbon fiber-reinforced polymer (CFRP) laminates have been extensively employed in the restoration of steel constructions. In addition to the mechanical properties of the CFRP, the bond strength (P_U) between the CFRP and steel is often important in the eventual strengthened performance. Nonetheless, the bond behavior of the CFRP-steel (CS) interface is exceedingly complicated, with multiple failure causes, giving the P_U challenging to forecast, and the CFRP-enhanced steel structure is unsteady. In just this case, appropriate methods were established by hybridized Random Forests (RF) and support vector regression (SVR) approaches on assembled CS single-shear experiment data to foresee the P_U of CS, in which a recently established optimization algorithm named Aquila optimizer (AO) was used to tune the RF and SVR hyperparameters. In summary, the practical novelty of the article lies in its development of a reliable and efficient method for predicting bond strength at the CS interface, which has significant implications for structural rehabilitation, design optimization, risk mitigation, cost savings, and decision support in engineering practice. Moreover, the Fourier Amplitude Sensitivity Test was performed to depict each parameter's impact on the target. The order of parameter importance was t_c> L_c > E_A > t_A > E_c > b_c > f_c > f_A from largest to smallest by 0.9345 > 0.8562 > 0.79354 > 0.7289 > 0.6531 > 0.5718 > 0.4307 > 0.3657. In three training, testing, and all data phases, the superiority of AO - RF with respect to AO - SVR and MARS was obvious. In the training stage, the values of R² and VAF were slightly similar with a tiny superiority of AO - RF compared to AO - SVR with R² equal to 0.9977 and VAF equal to 99.772, but large differences with results of MARS.

• Journal of the Korea Institute of Building Construction
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• v.24 no.4
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• pp.425-436
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• 2024

Modular apartment houses are a relatively new approach to public housing in South Korea. While promising in terms of efficiency and potential cost benefits, initial occupancy and maintenance data highlight areas for improvement in quality control. Analysis of defects reported during occupancy and maintenance stages revealed a high prevalence of issues with wallpaper and flooring. This suggests a need for stricter quality control measures during the production and installation of these building components. Furthermore, maintenance data identified shortcomings in the waterproofing methods employed for roofs, as well as in the design and construction management of connections between the low-rise concrete frames and the modular units themselves, including balconies. These findings point towards the importance of meticulous design and rigorous construction management practices to ensure the long-term durability of these critical building elements. Finally, the research suggests that unifying responsibility for construction management by awarding contracts for both the frame and the modular units to a single company could improve overall quality control. This approach could potentially mitigate issues arising from divided responsibility and streamline communication channels. By addressing these quality control concerns, modular construction has the potential to become a more widely adopted and successful method for delivering public housing in South Korea.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.3
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• pp.93-100
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• 2008

The use of fiber reinforced polymer (FRP) composites is significantly growing in construction and infrastructure applications where durability under harsh environmental conditions is of great concern. In order to examine the applicability of FRP rebar as a reinforcement in flexural member, flexural tests were conducted. 12 beams with different FRP materials such as CFRP, GFRP and Hybrid FRP and reinforcement ratio were tested and analyzed in terms of failure mode, moment-deflection, flexural capacity, ductility index and sectional strain distribution. The test results were also compared with the theoretical model represented in ACI 440.1R06. Test results indicate that the flexural capacity of the beams reinforced by FRP bars can be accurately predicted using the ultimate design theory. They also show that the current ACI model for computing the deflection overestimates the actual deflection of GFRP series and underestimates the deflection of CFRP series.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.623-630
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• 2007

Grouting materials are used for the unification of superstructural and substructural body like bridge seat (shoe) or machinery pedestal and e.t.c by filling their intercalary voids. Accordingly, grouting materials have been developed and used mainly with products of high strength because those materials are constructed specially in a part receiving large or impact load. In this situation, the structural body constructed by grouting materials with high stiffness-centered (caused by high strength) products is apt to cause brittle failure when receiving over a limit stress and to cause cracks according to cumulative fatigue by continuous and cyclic load. In addition, grouting materials are apt to cause cracks by using too much rapid hardening agents that give rise to high heat of hydration to maintain high strength at early age. In this study, to overcome these problems, cement type grouting materials including powder of waste tire and resin as elastic materials which aim to be more stable construction and to be improvement of mother-body's unification are developed and endowed with properties of high toughness and high durability add to existing properties of high flowability, non-shrinkage and high strength. Besides, this study contribute to of for green construction materials for being possible recycling industrial waste like waste tire and flyash. On the whole, seven type mixing conditions are tested and investigated to choose the best mixing condition.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.705-712
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• 2009

HPFRCCs (high-performance fiber reinforced cementitious composites), which is relatively more ductile and has the characteristic of high toughness with high fiber volume fractions, can be used in structures subjected to extreme loads and exposed to durability problems. In the case of PVA (polyvinyl alcohol) fiber, it is noted by former studies that around 2% fiber volume fractions contributes to the most effective performance at HPFRCCs. In this study, flexural tests were carried out to evaluate the flexural behavior of HPFRCCs and to optimize mix proportions. Two sets of hybrid fiber reinforced high performance specimens with total fiber volume fraction of 2 % were tested: the first set prepared by addition of short and long PVA fibers at different combination of fiber volume fractions, and the second set by addition of steel. In addition, in order to assess the performances of the HPFRCCs against to high strain rates, drop weight tests were conducted. Lastly, the sprayed FRP was applied on the bottom surface of specimens to compare their impact responses with non-reinforcing specimens. The experimental results showed that the specimen prepared with 1.6% short fibers (REC 15) and 0.4% long fiber (RF4000) outperformed the other specimens under flexure, and impact loading.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.473-476
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• 2008

Due to the pursuit of high function and international price increase in the field of construction, the application of the secondary product using cement is on the increase gradually in the construction industry in the pursuit of economic cost reduction by the shortening of the construction time like Expediting and the dry construction method at the same time. However, it is in very urgent situation of measures to improve the structural performance or durable performance because it is limited for use in terms of panel in interior exterior building or functional repair reinforce as yet. Accordingly, this study is to investigate applicability of permanent Formwork like mould with the structural performance or excellent durable performance in the field of construction, and to derive optimum mixture in the performance and quality of manufacture. As a result of analysis comparison with the dynamic and durable properties of vacuum extrusion molding high toughness cement panel according to the mixture of four conditions, this study has found that the test body of mixing ECC-DP3 using small filler and large granulated blast furnace slag and powder flame retardant had excellent relative hardness and bending stress strain. The durable performance has shown excellent tendency by the decrease of porosity and enhancement of water-tightness.

• Journal of the Korean GEO-environmental Society
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• v.3 no.2
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• pp.35-47
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• 2002

Soil and rock were yielded during construction of subway in Taegu. Produced rock is a kind of a sedimentary rock with low strength and low durability of shrinkage. So it is difficult using for resources engineering. But in our country, it is very important to use material resources due to lack of natural resources. In this study, after cracking sedimentary rock like black shale and red shale, they are compared with granite which usually used road constriction field to investigate property of use for road construction. Consequently, the engineering character of origin rock is satisfactory, but the soundness test, black shale and red shale are less than KS 12.9%, 37.5% respectively. The result of concrete freezing-thawing test shows that the strength among three materials is not a wide difference but red shale has relatively low strength. The result of asphalt freezing-thawing test with 50 cycles indicates that the stability of red shale in lower than KS 484~561kg on base course, 336~375kg on surface course respectively. A further research should be needed for propriety to the material of shale.