• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.45-52
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• 2020

An open-spandrel arch bridges, which consists of slab deck, arch rib, and vertical members, shows a various level of moment and axial forces according to the supporting boundary condition of arch rib and vehicle speeds. Also, the definition of impact factor accepts any kind of response parameters, not only displacement response at slab deck. The present study considers concrete open-spandrel arch bridges constrained with fixed conditions at the ends of arch rib and investigates the impact factor variation due to moving load speeds, response parameters, measuring locations, and vertical member spacing ratio of the bridges. The results of Reference model show that the impact factor is biggest when the reactive moment resulted at the vehicle-inducing opposite end of the arch rib is applied. The peak impact factor is a similar level obtained for the middle of the span adjacent to the slab deck center, but it is 19% higher than the peak impact factor calculated using the axial force developed at the same location. Reducing the spacing ratio of the vertical members as half as the reference model whose ratio is 1/9.375 produces a similar level of the moment-based peak impact factor compared to the reference model. However, when the spacing ratio is doubled, the peak impact factor is 4.4 times greater than the reference model.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.93-101
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• 2022

RC Slab bridges in Korea account for more than 70% of the total bridges for more than 20 years of service. As the number of aging structures increases, the importance of safety diagnosis and maintenance of structures increases. For highway bridges, cracks are a main cause of deck deterioration, which is very closely related to the decrease in bridge durability and service life. In addition, the damage rate of expansion joints and bearings accounts for approximately 73% higher than that of major members. Therefore, this study defined damage scenarios combined with devices damages and deck deterioration. The stress distribution and maximum stress on the deck were then evaluated using design vehicle load and daily temperature gradient for single and combined damage scenarios. Furthermore, this study performed damage-spread analysis and predicted condition ratings according to a deck deterioration model generated from the inspection and diagnosis history data of cracks. The heterogeneous damages combined with the member damages of expansion joints and bearings increased the rate of crack area and damage spread, which accelerated the time to reach the condition rating of C. Therefore, damage to bridge members requires proper and prompt repair and replacement, and otherwise it can cause the damage to bridge deck and the spread of the damage.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.152-160
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• 2008

Since wall system apartment used the shear wall as main lateral resistance member, installation of openings which causing section loss of walls may cause significant problem to structure. Also, there are few studies for inducing coupling beam or slabs which are occurred by installing openings. Therefore, this study planned isolated 2-story shear walls which are reduced three half-scale specimen to find out walls behavior characteristic. The test results showed that strength reduction caused by loss of effective section of walls and different result of stiffness and energy dissipation regarding to the coupling beam and coupling slabs.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.3
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• pp.103-112
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• 1998

In this study, database schema which is capable of maintaining various design-knowledge and applicable to the structural designs has been presented. Futhermore, by utilizing the database system, RECODSS (REinforced COncrete Design Support System) was developed as well. Knowledge-base that were formulated from the document is constructed by applying the concrete standard specifications of Korea from 1989. The basic drawing was prepared by $AutoCAD^TM$. As an inference in the preliminary design, the certainty function and the interpolation function were presented. The certainty function is made by assuming linear relations between each data while referencing $MYCIN^TM$ (expert systems). Nevertheless, the interpolation function was made by utilizing the linear Lagrange interpolation. For the search of the design-knowledge, fast search algorithm and full-text search algorithm were used, however, the design engine was programmed with C language. RECODSS was applied for designing a slab and a beam member. And the results were compared with the existing results. In conclusion, RECODSS was able to efficiently manage various design knowledge and to introduce stable design results.

• Korean Journal of Construction Engineering and Management
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• v.4 no.1 s.13
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• pp.114-121
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• 2003

The precise quantity of materials is not yet taken off by the CAD system although it has Influenced in design productivity and automatic estimate. And various estimate systems developed so far deal with the quantity take-off of building members separately, which caused to over-estimate the part of each member. Therefore, the purpose of this paper is to develop algorithms of more precise estimate than that of current estimate by solving boundary conditions of the connection parts of building members, such as column, girder, beam, wall and slab. The algorithms are proposed to take off the quantity of concrete and form work and they will be used for the estimate of building structure more precisely and automatically than ever.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.8
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• pp.131-138
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• 2019

Since concrete has a low tensile strength compared to the compressive strength, reinforced concrete flexural members represent easy crack occurance under a small load. In order to overcome this problem, steel fiber reinforced concrete has been developed to compensate the tensile strength and brittleness of members. However, in the design formula of the domestic building code, it is not specified in the design formula reflecting the material characteristics. Therefore, the field application of the steel fiber reinforced concrete have had many restrictions. In this study, a flexural tensile strength model of steel fiber reinforced concrete is proposed by collecting and analyzing the material properties of material test results conducted by various researchers, and verified by the test results of cracking and stiffness evaluation of flexural members based on the proposed model. As a result of this study, the flexural tensile strength model of steel fiber reinforced concrete which can reflect the mixing ratio and aspect ratio of the steel fiber was proposed and the validity of the proposed material model equation was evaluated from the load-deflection relationship in the flexural test of the slab member.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.53-62
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• 2018

Follofwing the accelerating speed-up of trains and rising demand for large-volume transfer capacity, not only in Korea, but also around the world, track structures for trains have been improving consistently. Precast concrete slab track (PST), a concrete structure track, was developed as a system that can fulfil new safety and economic requirements for railroad traffic. The purpose of this study is to provide the information required for the development and design of the system in the future, by analyzing the behavior of each structural member of the PST system. The stress distribution result for different combinations of appropriate loads according to the KRL-2012 train load and KRC code was analyzed by conducting a three-dimensional finite element analysis, while the result for different thicknesses of the grouting layer is also presented. Among the structural members, the largest stress took place on the grouting layer. The stress changed sensitively following the thickness and the combination of loads. When compared with a case of applying only a vertical KRL-2012 load, the stress increased by 3.3 times and 14.1 times on a concrete panel and HSB, respectively, from the starting load and temperature load. When the thickness of the grouting layer increased from 20 mm to 80 mm, the stress generated on the concrete panel decreased by 4%, while the stress increased by 24% on the grouting layer. As for the cracking condition, tension cracking was caused locally on the grouting layer. Such a result indicates that more attention should be paid to the flexure and tension behavior from horizontal loads rather than from vertical loads when developing PST systems. In addition, the safety of each structural member must be ensured by maintaining the thickness of the grouting layer at 40 mm or more.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.293-303
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• 2012

Recently, as construction technology improved, concrete structures not only became larger, taller and longer but were able to perform various functions. However, if extreme loads such as impact, blast, and fire are applied to those structures, it would cause severe property damages and human casualties. Especially, the structural responses from extreme loading are totally different than that from quasi-static loading, because large pressure is applied to structures from mass acceleration effect of impact and blast loads. Therefore, the strain rate effect and damage levels should be considered when concrete structure is designed. In this study, the low velocity impact loading test of steel fiber reinforced concrete (SFRC) slabs including 0%~1.5% (by volume) of steel fibers, and strengthened with two types of FRP sheets was performed to develop an impact resistant structural member. From the test results, the maximum impact load, dissipated energy and the number of drop to failure increased, whereas the maximum displacement and support rotation were reduced by strengthening SFRC slab with FRP sheets in tensile zone. The test results showed that the impact resistance of concrete slab can be substantially improved by externally strengthening using FRP sheets. This result can be used in designing of primary facilities exposed to such extreme loads. The dynamic responses of SFRC slab strengthened with FRP sheets under low velocity impact load were also analyzed using LS-DYNA, a finite element analysis program with an explicit time integration scheme. The comparison of test and analytical results showed that they were within 5% of error with respect to maximum displacements.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.4
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• pp.371-381
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• 2020

The failure mode of concrete reinforced with FRP is defined as the concrete crushing and the fiber rupture and the definition of limit state is a slightly different according to the design methods. It is relatively difficult to predict of FRP reinforced concrete because the mechanical properties of fibers are quite depending on its of fibers. The design code by ACI440 committee, which has been developed mainly on GFRP having low modulus of elasticity, is widely used, but the applicability on other FRPs of this code has not been sufficiently verified. In addition, the ultimate and serviceability limit state based on the ACI440 are comparatively difficult to predict the behavior of member with the 0.8~1.2 𝜌_b because crushing and rupturing failure can be occurred simultaneously is in this region of reinforcement ratio, and predicted deflection is too sensitive according to the loading condition. Therefore, in this study, reliability and convenience of the prediction of structural performance by design methods such as ACI440 and MC90 concept, respectively, were examined through the experimental results and literature review of the beam and slab with the reinforcement ratio of 0.8 ~ 1.4. As a result of the analysis, it can be applied to the FRP reinforced structure in the case of the simple moment-curvature formula (LIM-MC) of Model Code, and the limit state design method based on the EC2 is more reliable than the ultimate strength design method.

• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.105-116
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• 2009

Reinforced concrete (RC) structures have been most widely used because of their good economic efficiency. However, it is very weak in tensile stresses and difficult to control deflection due to the heavy self-weight of concrete. On the other hand, it is generally known that prestressed concrete structures can be the most effective to overcome the demerits of RC structures by using various tendon lay-out and its amount. In the prestressed concrete members, the inflection points of tendons should be placed effectively for the deflection control and the moment reduction. Therefore, in this study, the equations of tendon profiles are derived in terms of polynomials that satisfy essential conditions of tendon geometries such as inflection points and natural curved shapes of tendons placed in continuous members, from which vertical components of prestressing forces can be also calculated. The derived high order polynomial expression for the distributed shape of the upward and downward forces was transformed to an simplified equivalent uniform vertical force in order to improve the applicability in the calculation of member deflection. The influences of vertical forces by tendons to deflection and moment in a continuous slab were also considered depending on the distance from column face to the location of tendons. The applicability of the proposed method was examined by an example of deflection calculation for the cases of slabs with and without tendons, and the efficiency of deflection control by tendons was also quantitatively estimated.