• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.61-69
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• 2010

Unbonded precast concrete piers have better seismic performances than conventional reinforced concrete piers. In this research, seismic performances of unbonded precast prestressed concrete piers are analyzed using OpenSEES. Main parameters of analysis are concrete strength, jacking force ratio, ratio of tendon, and size of precast segment. In results, as the ratio of tendon and jacking force ratio increase, the flexural strength increases at softening state and ultimate state. Concrete strength and size of precast segment are negligible. But initial jacking force ratio leads to early yielding of prestressing tendon. Since compressive strain in core concrete is much less than ultimate strain, it can be expected that the amount of transverse steel reinforcement is to be reduced in comparison with conventional reinforced concrete column.

• Advances in concrete construction
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• v.16 no.4
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• pp.177-188
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• 2023

In the context of the shortage of river sand, two types of manufactured sand (MS) were used to partially replace river sand (RS) to design manufactured sand concrete (MSC). A total of 81 specimens were designed for uniaxial compression test and beam flexure test. Two parameters were considered in the tests, including the types of MS (i.e. limestone manufactured sand (LMS), pebble manufactured sand (PMS)) and the MS replacement percentage (i.e., 0%, 25%, 50%, 75%, 100%). The stress-strain curves of MSC were obtained. The effects of these parameters on the compressive strength, elastic modulus, peak strain, toughness and flexural strength were discussed. Additionally, the sensitivity of particle size distributions to the performance of MSC was evaluated based on the grey correlation analysis. The results showed that compared with river sand concrete (RSC), the rising slope of the stress-strain curves of limestone manufactured sand concrete (LMSC) and pebble manufactured sand concrete (PMSC) were higher, the descending phrase of LMSC were gentle but that of PMSC showed an opposite trend. The physical and mechanical properties of MSC were affected by the MS replacement percentage except the compressive strength of PMSC. When the replacement percentage of LMS and PMS were 50% and 25% respectively, the corresponding performances of LMSC and PMSC were better. In generally, when the replacement percentage of LMS and PMS were same, the comprehensive performance of LMSC were better than that of PMSC. The constitutive model and the equations for mechanical properties were proposed. The influence of particle ranging from 0.15 mm to 0 mm on the performance of MSC was lower than particle ranging from 4.75 mm to 0.15 mm but this influence should not be ignored.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.5
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• pp.455-463
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• 2010

This is a basic experimental study to apply FRP modular box member to a variety of construction structures exposed to flexural strength, such as a slab and a girder. Tests were conducted under various conditions in order to analyze jointing performance features of the developed FRP modular box member as a large section. For the methods of jointing FRP modular box member, chemical connection, mechanical connection, and a combination of both were used to test both vertical and horizontal jointing. As a result of the test, using urethane+two bolts+sheets was the most efficient method of connecting FRP modular box member, and confirmed the efficient behavior by a finite element analysis.

• Journal of Korean Society of Steel Construction
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• v.12 no.1 s.44
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• pp.29-43
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• 2000

In this study, the computationally efficient inelastic buckling analysis program is developed to be used as the research tool in finding buckling strength of inelastic members. The program can determine buckling loads and buckled shapes of elastic and inelastic members which failed by flexural, lateral-torsional and/or local buckling. It can analyze singly and doubly symmetric I-shape members. In the program, the web of the member is modeled using the plate element and the flanges are modeled by beam elements. Multilinear isotropic hardening rule and the incremental theory of plasticity are used to simulate the inelastic stress-strain relationship from material tests. The program is verified using theoretical solutions and experimental results. The results from the program show good agreement with those from experiments and theory.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.169-172
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• 2008

Longitudinal elongation develops in reinforced concrete beams that exhibit flexural yielding during cyclic loading. The longitudinal elongation can decrease the shear strength and deformation capacity of the beams. In the present study, nonlinear truss model analysis was performed to study the elongation mechanism of reinforced concrete beams. The results showed that residual tensile plastic strain of the longitudinal reinforcing bar in the plastic hinge is the primary factor causing the member elongation, and that the shear-force transfer mechanism of diagonal concrete struts has a substantial effect on the magnitude of the elongation. Based on the analysis results, a simplified method for evaluating member elongation was developed. The proposed method was applied to test specimens with various design parameters and loading conditions..

• Steel and Composite Structures
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• v.8 no.6
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• pp.457-473
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• 2008

Yielding of the internal steel reinforcement is an important mechanism that influences the Intermediate Crack-induced debonding (IC debonding) behavior in FRP-strengthened RC members since the FRP is required to carry additional forces beyond the condition of steel yielding. However, rational design practice dictates an appropriate limit state is defined when steel yielding is assured prior to FRP debonding. This paper proposes a criterion which correlates the occurrence of IC debonding to the formulation of a critical steel yielding length. Once this length is exceeded the average bond stress in the FRP/concrete interface exceeds its threshold value, which proves to correlate with the average bond resistance in an FRP/concrete joint under simple shear loading. This proposed IC debonding concept is based on traditional sections analysis which is conventionally applied in design practice. Hence complex bond stress-slip analyses are avoided. Furthermore, the proposed model incorporates not only the bond properties of FRP/concrete interface but also the beam geometry, and properties of steel and FRP reinforcement in the analysis of IC debonding strength. Based upon a solid database, the validity of the proposed simple IC debonding criterion is demonstrated.

• Computers and Concrete
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• v.1 no.2
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• pp.211-226
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• 2004

A relatively simple multiple-vertical-line-element macro model has been incorporated into a standard computer code DRAIN-2D. It was used in blind predictions of seismic response of cantilever RC walls subjected to a series of consequent earthquakes on a shaking table. The model was able to predict predominantly flexural response with relative success. It was able to predict the stiffness and the strength of the pre-cracked specimen and time-history response of the highly nonlinear wall as well as to simulate the shift of the neutral axis and corresponding varying axial force in the cantilever wall. However, failing to identify the rupture of some brittle reinforcement in the third test, the model was not able to predict post-critical, near collapse behaviour during the subsequent response to two stronger earthquakes. The analysed macro model seems to be appropriate for global analyses of complex building structures with RC structural walls subjected to moderate/strong earthquakes. However, it cannot, by definition, be used in refined research analyses monitoring local behaviour in the post critical region.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.4
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• pp.185-195
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• 2001

Latex Modified Concrete(LMC) has been widely used for the pavement of highway bridges over the past 35years around the world since it is more resistant to the intrusion of chloride ions, has higher tensile, compressive, and flexural strength, and has greater freeze-thaw resistance. However, in Korea, it has not been introduced to fields due to higher initial construction cost for its overlay compared with that of conventional pavement materials. Due to durable characteristics, it should be noted that the LMC may be more cost-effective than conventional pavements such as asphalt pavement, when life-cycle cost(LCC) concept is considered. The objective of this study is intended to suggest a practical LCC analysis model for pavement projects and to demonstrate relative cost-effectiveness of the LMC overlays in comparison with conventional pavement techniques. It may be stated that the procedure proposed in this study may be utilized for making optimal decision on cost-effective pavement design.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1289-1290
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• 2007

The composites were fabricated 61Vo.% ${\beta}$-SiC and 39Vol.% $TiB_2$ powders with the liquid forming additives of 12wt% $Al_{2}O_{3}+Y_{2}O_{3}$ as a sintering aid by pressure or pressureless annealing at $1650^{\circ}C$ for 4 hours. The present study investigated the influence of annealed sintering on the microstructure and mechanical of SiC-$TiB_2$ electroconductmive ceramic composites. Reactions between SiC and transition metal $TiB_2$ were not observed in the microstructure and the phase analysis of the SiC-$TiB_2$ electroconductive ceramic composites. Phase analysis of SiC-$TiB_2$ composites by XRD revealed mostly of ${\alpha}$-SiC(6H), $TiB_2$, and In Situ YAG($Al_{5}Y_{3}O_{12}$). The relative density, the flexural strength, the Young's modulus showed the highest value of 86.69[%], 136.43[MPa], 52.82[GPa] for pressure annealed SiC-$TiB_2$ ceramic composites.

• Structural Engineering and Mechanics
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• v.77 no.5
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• pp.691-703
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• 2021

Reinforced concrete (RC) beams can be subjected to a complex combination of shear forces (V), torsional moments (T), flexural moments (M) and axial loads (N). This paper proposes a unified approach for the analysis of these elements. An existing model for the analysis of orthogonally reinforced concrete membrane elements subjected to in-plane shear and normal stresses is generalized to apply to the case of beams subjected to the complex loading. The combination of V and T can be critical. Torsion is modelled using the hollow-tube analogy. A direct equation for the calculation of the thickness of the equivalent hollow tube is proposed, and the shear stresses caused by V and T are combined using a simple approach. The development and the evaluation of the model are described. The calculations of the model are compared to experimental data from 350 beams subjected to various combinations of stress-resultants and to the calculations of the ACI and the CSA codes. The proposed model provides the most favorable results. It is also shown that it can accurately model the interaction between V and T. The proposed model provides a unified treatment of shear in beams subjected to complex stress-resultants and in thin membrane elements subjected to in-plane stresses.