• Journal of the Korea Concrete Institute
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• v.22 no.6
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• pp.761-768
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• 2010

When cracks occur in reinforced concrete structures, a steel carries all tensile force at crack section, while the concrete between cracks carries a part of the tensile force due to bond, so that the steel is less elongated. This is called the tension-stiffening effect, that plays an important role in verification of a serviceability limit state. But it is a complicated work to use a complex strain distribution between cracks, therefore an average strain is used to calculate deflection and crack width. In Eurocode 2, tension-stiffening effect expressed in the first order form or the second order form is used in calculating an average curvature for deflection. In this study for a flexural member deflection and crack width are calculated using various models for the tension-stiffening effect and the results are compared with the values of Eurocode 2 and KCI provisions. As results, the predicted values using the second order form are appeared to be well agreed with the experimental values and it could secure more analytical consistency.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.105-117
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• 2015

The purpose of this study is to develop a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were experimentally performed on one unreinforced beam-column specimen and two reinforced specimens with L-type precast wall panels. The results were analyzed to find that the specimen with anchored connection experienced shear failure, while the other specimen with steel plate connection principally manifested flexural failure. The ultimate strength of the specimens was determined to be the weaker of the shear strength of top connection and flexural strength at the critical section of precast panel. In this setup of L-type panel specimens, if a push loading is applied to the reinforced concrete column on one side and push the precast concrete panel, a pull loading from upper shear connection is to be applied to the other side of the top shear connection of precast panel. Since the composite flexural behavior of the two members govern the total behavior during the push loading process, the ultimate horizontal resistance of this specimen was not directly influenced by shear strength at the top connection of precast panel. However, the RC column and PC wall panel member mainly exhibited non-composite behavior during the pull loading process. The ultimate horizontal resistance was directly influenced by the shear strength of top connection because the pull loading from the beam applied directly to the upper shear connection. The analytical result for the internal shear resistance at the connection pursuant to the anchor shear design of ACI 318M-11 Appendix-D except for the equation to predict the concrete breakout failure strength at the concrete side, principally agreed with the experimental result based on the elastic analysis of Midas-Zen by using the largest loading from experiment.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.153-159
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• 2018

Many researches have been carried out on carbonation, a representative deterioration in underground structure. The carbonation of RC (Reinforced Concrete) structure can cause steel corrosion through pH drop in concrete pore water. However extension of service life in RC structures can be obtained through simple surface protection. Unlike the conventional deterministic maintenance technique, probabilistic technique can consider a variation of service life but it deals with only normal distributions. In the work, life time-probability distributions considering not only normal but also log distributions are induced, and repair cost estimation technique is proposed based on the induced model. The proposed technique can evaluate the repair cost through probabilistic manner regardless of normal or log distribution from initial service life and extended service life with repair. When the extended service life through repair has log distribution, repair cost is effectively reduced. The more reasonable maintenance strategy can be set up though actual determination of life-probability distribution based on long term tests and field investigations.

• Steel and Composite Structures
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• v.49 no.3
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• pp.257-270
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• 2023

In this study, the feasibility and applicability of a friction damper with a vertical installation scheme are investigated. This device is composed of a steel section and two friction hinges at both ends which dissipate seismic energy. Due to its small width and vertical installation scheme, the proposed damper can minimize the interference with architectural functions. To evaluate the performance of the proposed damper, its mechanical behavior is theoretically evaluated and the required formulas for the yield strength and elastic stiffness are derived. The theoretical formulas are verified by establishing the analytical model of the damper in the SAP2000 software and comparing their results. To further investigate the performance of the developed damper, the provided analytical model is applied to a 4-story reinforced concrete (RC) structure and its performance is evaluated before and after retrofit under the Maximum Considered Earthquake (MCE) hazard level. The seismic performance is thoroughly evaluated in terms of maximum interstory drift ratio, displacement time history, residual displacement, and energy dissipation. The results show that the proposed damper can be efficiently used to protect the structure against seismic loads.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.231-238
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• 2004

This paper presents the tensile behavior of the stud connection between reinforced concrete(RC) and steel members. Hanger reinforcements are placed around the studs to transfer the tensile and flexural loads to the opposite side of the concrete member. Eight specimens for the tensile tests are tested with variables, which are the arrangement details of hanger reinforcements, the reinforcing bars, and the embedment length of stud. The results of the tensile tests show that hanger reinforcements are effective to increase tensile strength for stud connections. Hangers and reinforcing bars near stud bolts contributed to the reduction of brittle failure. From the evaluation on the tensile strength by previous design guidelines, it was shown that CCD (Concrete Capacity Design) method was more suitable for estimation of test strength.

• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.149-160
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• 1999

This paper is a part of a research aimed at the verification of basic design rules of high-strength concrete columns. A total of 32 column specimens were tested to investigate structural behavior and strength of eccentrically loaded reinforced concrete tied columns. Main variables included in this test program were concrete compressive strength. steel amount, eccentricity, and slenderness ratio. The concrete compressive strength varied from 356 kg/$cm^2$ to 951 kg/$cm^2$ and the longitudinal steel ratios were between 1.13 % and 5.51 %. Test results of column sectional strength are compared with the results of analyses by ACI rectangular stress block, trapezoidal stress block, and modified rectangular stress block. Axial force-moment-curvature analysis is also performed for predicting axial load-moment strength and compared with the test results. The ACI rectangular stress block provides over-estimated column strengths for the lightly reinforced high strength column specimens. The calculated strengths by moment-curvature analyses are highly affected by $k_3$ values of the concrete stress-strain curve. Observed failure mode. concrete ultimate strain, and stress block parameters are discussed.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.5
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• pp.41-53
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• 2012

The objective of this study is to evaluate the seismic capacity of RC piers with small aspect ratios. Test specimens were selected from the prototype piers among existing national roadway bridges which are expected to fail in shear and/or complex shear-flexural mode. Two groups of full scale RC pier models were constructed with aspect ratios of 2.25 and 2.67. Quasi-static tests have been implemented to investigate the failure behavior of the RC piers in terms of the lap-spliced longitudinal reinforcing steel and the aspect ratio. It is confirmed that regarding its shear-flexural behavior, the pier is very sensitive to the aspect ratio or details. In the case of a test pier with highly lap-spliced longitudinal bars, the bond failure of lap-splice steels was the dominant cause of failure before the occurrence of flexure or shear-flexural failure, despite a slight change in the aspect ratio. Finally, based on the test results and analysis, this paper proposes formulas for the yielding and ultimate displacements of circular reinforced concrete bridge piers without seismic details. These formulas will be useful for the investigation and upgrade of the seismic capacity of bridge piers without seismic details.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.11a
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• pp.115-118
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• 2011

본 연구에서는 현재 법정내화구조로 규정되어 있는 철근콘크리트(RC: Reinforced concrete)조 및 철골철망모르타르(SWM: Steel & Wire Mortar)조 슬래브에 대하여 재하조건에서 구조별 내화성능을 검토하고, 철골철망모르타르조 슬래브에 대해서는 피복두께별 내화성능을 검토하고자 표준화재조건에서 내화실험을 실시하였다. 실험결과 동일피복 두께일 경우 철근콘크리트조 슬래브가 내화성능이 우수한 것으로 나타났으며, 철골철망 모르타르조 슬래브의 경우 피복두께가 10mm 증가 시 7%의 내화성능이 향상되는 것으로 나타났다. 가열 이면온도는 슬래브의 두께가 늘어날수록 낮은 것으로 나타났다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.190-197
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• 2000

A moment-curvature relationship to simulate the behavior of reinforced concrete beam under cyclic loading is introduced. Unlike previous moment-curvature models and the layered section approach, the proposed model takes into consideration the bond-slip effect by using monotonic moment-curvature relationship constructed on the basis of the bond-slip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stress-strain relation of steel gives more exact numerical result. The advantages of the proposed model, comparing to layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures. The modification of the moment-curvature relation to reflect the fixed-end rotation and pinching effect is also introduced. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed model.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.313-324
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• 2010

There are many problems in application of FRP reinforcing bars as shear reinforcement, since bending of FRP bars is not a feasible process on construction site. Even though FRP bars can be manufactured in bent shape, they have lower strength at bent location. However, there are no serious problems to use FRP bars as flexural reinforcement. Plates or slabs like bridge decks, in general, do not need shear reinforcements. These types of members with FRP flexural reinforcement have lower shear strength than those with conventional steel flexural reinforcement. However, reliable process or equation for shear strength estimation of FRP reinforced concrete without shear reinforcement are not established, yet. In this study, predicted shear strength obtained from available design equations and assessment equations are compared with 211 experimental results. The results showed that among the current design codes, the Architectural Institute of Japan (AIJ) and the Institution of Structural Engineers (ISE) provided the best estimation. ACI 440.1R-06 provided conservative results with degree of dispersion similar to that of ISE. In addition, regression analysis on the collected experimental results was conducted to develop regression models. As a result, a new reliable shear strength equation was proposed.