• Computers and Concrete
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• v.21 no.2
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• pp.157-166
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• 2018

This article presents the flexural behaviour of reinforced fly ash (FA)-based geopolymer concrete (GPC) beams with partial replacement of FA for about 10% by weight with paper sludge ash (PSA). The beams were made of M35 grade concrete and cured under three curing conditions for comparison viz., ambient curing, external exposure curing, and oven curing at $60^{\circ}C$. The beams were experimentally tested at the 28th day of casting after curing by conducting two-point loading flexural test. Performance aspects such as load carrying capacity, first crack load, load-deflection and moment-curvature behaviours of both types of beams were experimentally studied and their results were compared under different curing conditions. To verify the response of reinforced GPC beams numerically, an ANSYS 13.0 finite element program was also used. The result shows that there is a good agreement between computer model failure behaviour with the experimental failure behaviour.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.399-404
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• 1998

Analysis of partially prestressed beams in which cracking under service loads is allowed requires a knowledge of geometric cross section properties such as neutral axis, centroid, area and moment of initia of this cracked transformed section. Especially an exact calculation for the stresses of steel and concrete and the width of crack and the amount of deflection can be obtained with accrurate prediction of neutral of centroidal axis location. In this paper, the procedures for predicting the centroidal axis location of partially cracked prestressed concrete members, using the compatibility of deformation of concrete and steel are formulated and compared with Dilger`s computed results. And also the computed results according to this paper are compared with Branson`s experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.403-406
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• 1999

Although infilled wall considered as a non-structural element, the infilled applied in reinforced concrete frame structural systems represents an important element influencing the behaviour and the stability of a structure under seismic effect. This research is performed an experimental investigation of gravity-load designed single-stroy, single-bay, low-rise nonseismic moment-resisting reinforced concrete frame 2 dimension specimens to evaluate the effect of seismic capacity. For pseudo static test, it was manufactured one half scale specimens of two types (Bare Frame, Infilled Frame) based on typical building. The results of these experiments provided regarding the global as well as the local responses of 1) Crack pattern and failure modes, 2) Stiffness, strength.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.481-486
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• 1998

In this paper, elastic and inelastic behavior of exterior joint of moment-resisting R.C frame with non-seismic detail subjected to reversed cyclic lateral load such as earthquake excitations was investigated. 1/2-scals subassemblage exterior beam-column joint including slab was manufactured based on similitude law. Then, pseudo static test under the displacement control was performed. The results of 1)crack pattern and failure mode, 2)degradation stiffness and strength, energy dissipation capacity from load-displacement hysteresis curve, 3)strain of steel were analysed.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.553-558
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• 1998

Two-way slab-column specimens were tested under monotonic loading increased up to punching shear failure to investigate the beneficial effects of fiber-reinforced concrete. The parameters for experiments are the placement of fibers within the immediate column region, the placement on the entire surface of the slab, and no placement of fibers. The effects of these parameters on the punching shear capacity, negative moment cracking. and stiffness of the two-way slab specimens were studied. According to the results the addition of steel fibers in the slab around the column results in a significant improvement in the performance including the increase of punching shear resistance, greater post-cracking stiffness and smaller crack width at service load levels.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.543-555
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• 2018

Fiber Reinforced Polymer (FRP), which has a high strength to weight ratio, are now regularly used for strengthening of deficient reinforced concrete (RC) structures. While various researches have been conducted on FRP strengthening, an area that still requires attention is predicting the debonding failure load of prestressed FRP strengthened RC beams. Application of prestressing increases the capacity and reduces the premature failure of the beams largely, though not entirely. Few analytical methods are available to predict the failure loads under flexure failure. With this paucity, this research proposes a method for predicting debonding failure induced by intermediate crack (IC) for prestressed FRP-strengthened beams. The method consists of a numerical study on beams retrofitted with prestressed FRP in the tension side of the beam. The method applies modified Branson moment-curvature analysis together with the global energy balance approach in combination with fracture mechanics criteria to predict failure load for complicated IC-induced failure. The numerically simulated results were compared with published experimental data and the average of theoretical to experimental debonding failure load is found to be 0.93 with a standard deviation of 0.09.

• Magazine of the Korea Concrete Institute
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• v.5 no.1
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• pp.145-155
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• 1993

본 연구에서는 표면부를 에폭시 폴리머 모르터로 하고 , 중심부를 발포 폴리스티렌으로 하는샌드위치 패널을 제조하여, 표면부를 용접철강으로 보강한 경우와 보강하지 않은 경우에 대하여 4강 단순지지 조건에서의 정적 차 통해 하중-처짐, 휨모멘트-변형률, 파괴양상 등을 구명하였다. 단위중량, 극한가중, 휨모멘트는 중심부의 두께보다 표면부 두께에 더 큰 영향을 받으며 극한처짐은 보강안된 경우 표면부 보다 중심부 두께의 영향이 월등히 컸으마 보당된 경우는 표면부나 중심부 두께의 영향이 비슷하였다. 그러나 용접철망의 보강은 샌드위치 패널의 처짐억제 보다 인성증가에 기여도가 높은 것으로 나타났다. 샌드위치 패널의 파괴양상은 보강하지 않은 경우 선형파괴가 일어난데 비해 보강한 경우에는 방사상의 파괴가 일어났다.

• Advances in concrete construction
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• v.4 no.3
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• pp.161-172
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• 2016

An experimental investigation was carried out on the strength and behavior plain and fiber reinforced geopolymer concrete beam column joints and the results were compared with plain and steel fiber reinforced conventional concrete beam column joints. The volume fraction of fibers used was 0.5%. A total of six Geopolymer concrete joints and four conventional concrete joints were cast and tested under reversed cyclic loading to evaluate the performance of the joints. First crack load, ultimate load, energy absorption capacity, energy dissipation capacity stiffness degradation and moment-curvature relation were evaluated from the test results. The comparison of test results revealed that the strength and behavior of plain and fiber reinforced geopolymer concrete beam column joints are marginally better than corresponding conventional concrete beam column joints.

• Journal of Magnetics
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• v.6 no.1
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• pp.1-4
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• 2001

We have used acetic acids ethanol and distilled water as a solvent to synthesize $La_{2/3}Sr_{1/3}Mn_{0.99}{^{57}}Fe_{0.01}O_3$(LSMFO) precursor. Crack-free LSMFO granular polycrystalline thin films have been deposited on thermally oxidized silicon substrates by spin coaling. The dependence of crystallization, surface morphology, magnetic and transport properties on annealing temperature was investigated. With increasing annealing temperature, the metal-semiconductor (insulator) transition temperature and the magnetic moment decrease while the resistivity increases. The lattice constants remain almost unchanged. For LSMFO thin films, spin-dependent interfacial tunneling and/or scattering magnetoresistance were observed. Our results indicate that the annealing temperature is very important in determining the intrinsic and extrinsic magnetotransport properties.

• Journal of the Korea Concrete Institute
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• v.12 no.5
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• pp.13-23
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• 2000

In this study, an flexural test on half-scale spliced PSC-I girder was conducted to verify the efficiency of the long span spliced girder as suggested by the Korean Highway Design Specification. The experimental results showed that the specimens developed a complex failure mode due to flexural-compression and torsional stress. The cracking moment of each girder was higher the experiment than was calulated by the ACI and the ultimate strength were the almost same. To estimate the safety and the structural efficiency of the spliced girder, the proposed Yielding Resistance Index(YRI) and ductility index by American Concrete Institutes were used based on the energy concept. The proposed YRI defined the ratio of crack resisting energy and the total energy calculated from load-displacement relationship. Based on the analysis of YRI and ductility index, the flexural behavior of the spliced girder was found to be efficient. Through the experimental results, the structural behavior of proposed spliced PSC I-type girder for long span bridge was found to be more efficient than the exsisting PSC I-type girders.