• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.5
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• pp.455-468
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• 2013

In recent, various types of steel pipe-roof methods, which is reinforced by mortar after propulsion of steel pipe into the ground, have been used for the construction of trenchless underpass. Integrated steel pipe-roof has flexural stiffness and can resist against overburden load and reduce the stress acting on the concrete underpass structures. Due to arching effect, vertical and horizontal stress distribution around the steel pipe-roof is changing. In this study, therefore, the characteristic of stress distribution around the underpass induced by the construction of integrated steel pipe-roof is investigated by using numerical method. To examine the soil-structure interaction, interface element is introduced. Results show that vertical stress acting on the concrete structure placing inside the steel pipe-roof is significantly reduced due to arching effect and flexural stiffness of integrated steel pipe-roof. Design load can be reduced and effective design of underpass will be available if the earth pressure reduction due to arching effect is considered in the design stage.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.289-292
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• 2008

This paper studied experimentally on the structural performance and serviceability of RC beams with high-strength reinforcing bars. Following to the previous research, high-strength reinforcing bars have an negative effect on the deflection and crack depth. But, there are advantages about reducing amount of reinforcement than normal-strength reinforcing bars. So, the purpose of this paper is to analyze the effect of flexural performance on the beams with high-strength reinforcing bars. Three specimens were tested, and the main variable was the yield strength of the reinforcements; SD400, SD600 and SD700. Experimental results shows that the stiffness of members reduced when apply to high-strength reinforcement and equal reinforcement ratio. But the flexural strength of members increased to proportion to the strength and amount of reinforcement. Also, when high-strength reinforcement used, serviceability aspect do not appear to be affected because there is no change for crack number and maximum crack width.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.16-25
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• 2018

Concrete is a suitable construction material for long-term structure, however, it is needed to understand the calcium leaching damage caused by exposure to underground pure water for a long time. In this paper, it is experimentally investigated that the characteristics of flexural behavior in RC member damaged by calcium leaching degradation. From the test results, when calcium leaching is happened, yielding load and flexural rigidity is reduced, neutral axis depth and displacement is increased. That is, calcium leaching degradation adversely affects RC member performance. And, when the mineral admixture is used in the calcium leaching environment, it is considered that the optimal replacement ratio should be prepared according to the type of mineral admixture.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.559-566
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• 2012

In this study, fiber elements and a spring are used to build a reinforced concrete shear wall model. The fiber elements and the spring reflect flexural and shear behaviors of the shear wall, respectively. The fiber elements are built by inputting section data and material properties. The spring parameters representing strength and stiffness degradation, pinching, and slip were determined by comparing behaviors of fiber element and VecTor2 results. 'Pinching4' model in OpenSees is used for shear spring. The parameter selecting process for shear spring is a complicated and time consuming process. To study the applicability of the fiber element, reinforced concrete buildings containing a shear wall are evaluated using nonlinear dynamic analysis with various wall aspect ratio (H/L), various beam heights, and stiffness and flexural strength of beam and wall ratios. The aspect ratio of the wall showed distinct difference in IDR (interstory drift ratio) of the models with and without spring. On the other hand, the height of beam and ratio of stiffness and flexural strength of beam and wall did not show clear relation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.30-39
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• 2016

An experimental study was performed to investigate flexural performance and bond characteristics of RC beams strengthened using ductile polyethylene terephthalate(PET) with low elastic modulus. Bond tests were planned and completed following CSA S806. Test variables were fiber type and fiber amount. Also, total of 8 RC beams was tested. Major test variables of the beam tests included section ductility(${\mu}=3.4$, 7.0), fiber type(CF, GF, PET) and amount of fiber strengthening. Moment-curvature analyses of the beam sections were also performed. In bond tests, the bond stress distribution as well as the maximum bond stress increased with increasing amount of PET. In case of 10 layers of PET, the effective bond length was 60 mm with the maximum and the average bond stress of 2.33 and 2.10 MPa, respectively. RC beam test results revealed that the moment capacity of the RC beams strengthened using PET 10 and 20 layers increased over the control beam with little reduction in ductility by fiber strengthening. All beams strengthened using PET resulted in ductile flexural failure without any sign of fiber debonding or fiber rupture. It was important to include the mechanical properties of adhesive in the moment-curvature analysis of PET-strengthened beam sections.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.4
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• pp.123-132
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• 1990

This paper deals with the influences on the wall movements and earth pressure distribution for strutted diaphragm wall of various design depth ration and pre-displacement at strutted point. The numerical method is adopted for the study. The conclusions derived from the study were summarized as followes: 1. The elasto-plastic depth ratio in the passive region is found to decrease as such parameters as wall stiffness, soil density and penetration depth ratio decrease. 2. Values of maxium bending moments of the walls decrease with the increase of soil density, and the influence to the wall stiffness increases in proportion to the penetration depth. 3. Maximum strut reaction is found to be inversely proportional to the soil density. 4. Pre-displacement at the point of strut installation must be brougt into consideration on account of its active influence to the deflection of wall bodies.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.3
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• pp.12-17
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• 2011

This paper presents the flexural behavior of a hybrid Glass Fiber-Reinforced Polymer(GFRP)-steel decks for use in deteriorated bridge decks replacement. Static load tests were conducted to investigate the structural characteristics of the hybrid FRP-steel deck. The tested deck panel satisfied the design criteria. The failure mode of the hybrid deck was demonstrated ductility with deformation beyond initial yielding. The responses were compared with the ANSYS finite element predictions. It was found that the presented hybrid deck was efficient for use in bridges. The thickness of the hybrid deck may be decreased when compared to that of the all FRP deck with similar flexural rigidity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.59-66
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• 2020

Two octagonal RC bridge columns of small scale model were tested under cyclic lateral load with constant axial load. One in two specimens was solid cross section, the other was hollow cross section. The volumetric ratio of transverse spiral hoop of all specimens is 0.00206. The columns showed flexure-shear failure. Failure behavior and seismic performance were investigated. The test results showed that the structural performance of the hollow specimen such as initial crack pattern, initial stiffness, and energy dissipation performance was comparable to that of the solid specimen, but the lateral strength, ultimate displacement, energy dissipation performance of hollow specimen noticeably decreased after drift ratio of 3%.

• Journal of the Society of Disaster Information
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• v.14 no.3
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• pp.343-351
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• 2018

Purpose: Recently, As the size of the structure increased, the necessity of reducing its weight was raised. To reduce weight In concrete structures, a hollow slab is proposed as an alternative for weight reduction effect. Method: It is difficult to construct the hollow body due to buoyancy, and the shear performance is insufficient due to the decreased cross section. Slabs were fabricated using unidirectional hollow bodies such as PVC pipes, and experiments were conducted about construction performance and structural performance. Results: The buoyancy preventive device has been improved the construction performance by preventing floating hollow body, it has been confirmed that it has adequate performance to be used as a hollow slab system because it has enough expected shear performance. Coclusion: Hollow ratio has a little connection with bending performance, but after the yielding load, it is necessary to consider the secondary stiffness of structure, and is is supposed that the decrease of shear performance with the increase of hollow core ratio can be complemented with shear reinforcement.

• Journal of the Korea Concrete Institute
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• v.20 no.3
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• pp.393-404
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• 2008

The approaches in many design codes for the estimation of the deflection of flexural reinforced concrete (RC) members utilize the concept of the effective moment of inertia which considers the reduction of flexural rigidity of RC beams after cracking. However, the effective moment of inertia in design codes are primarily based on the ratio of maximum moment and cracking moment of beam subjected to loading without proper consideration on many other possible influencing factors such as span length, member end condition, sectional size, loading geometry, materials, sectional properties, amount of cracks and its distribution, and etc. In this study, therefore, an experimental investigation was conducted to provide fundamental test data on the effective moment of inertia of RC beams for the evaluation of flexural deflection, and to develop a modified method on the estimation of the effective moment of inertia based on test results. 14 specimens were fabricated with the primary test parameters of concrete strength, cover thickness, reinforcement ratio, and bar diameters, and the effective moments of inertia obtained from the test results were compared with those by design codes, existing equations, and the modified equation proposed in this study. The proposed method considered the effect of the length of cracking region, reinforcement ratio, and the effective concrete area per bar on the effective moment of inertia, which estimated the effective moment of inertia more close to the test results compared to other approaches.