• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.5
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• pp.29-37
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• 2008

Stress-strain relation and stress block parameters of polymer concrete flexural compression members were experimentally investigated. For these purposes, a series of C-shaped polymer concrete specimens subjected to axial compressive load was tested. Based on the test results, we proposed an equation by which the stress-strain relation of polymer concrete can be predicted. In this model, we took account the slope of descending branch beyond the peak stress point of single curve. The proposed equation was numerically integrated to compute the rectangular stress block parameters. Computed ${\beta}_1$ was greater than the values prescribed in ACI 318 Code for cement concrete, and $\gamma$ was about 0.85 that is similar to the value regulated in the ACI.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.557-562
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• 2007

In order to analyze the PSC box-girder bridge by the cantilever construction method, three dimensional analysis method using the PSC shell clement is suggested. The time dependent material functions are based on the ACI and CEB code. The time dependent concrete material properties considered are changes in strength, elastic modulus, creep and shrinkage. For the prestressing tendon, relaxation effects are considered. Anchorage and friction loses during tendon installations are also included. The ACI and CEB material models for creep and elastic modulus are also included.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.851-856
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• 2000

When subjected to the strong earthquake ground motion, upper-wall lower-frame structures have high possibility of the weak-story failure in the lower frame part. Sufficient strength, energy dissipation capacity and ductility should be provided at the joint between the deep beam and the lower column. In this study, a typical structure was selected for a prototype and four 1:2.5 scaled models, representing the subassemblage including the exterior column and the deep beam, were constructed. The transverse reinforcement was designed according to ACI procedure¹ and the procedure proposed by Sheikh². The inelastic behavior of the subassemblages subjected to the cyclic lateral displacement were evaluated through investigation of the ultimate strength, ductility, load-deformation characteristics. From the test of 4 specimens, it is concluded that the specimens designed according to Sheikh's procedure revealed higher ductility than that by ACI procedure.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.475-482
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• 1997

This study reports the results of flexural test on 6 specimens for maximum reinforcement ratio and 4 specimens for minmum reinforcement ratio with concrete compressive strength 1,000, 1,200 kg/$\textrm{cm}^2$ . The major test variables for the reinforcement ratio designed 0.55$\rho_b$, 0.65$\rho_b$, 0.75$\rho_b$ for maximurm reinforcement ratio test 14/fy $\sqrt[0.72]{\rho}\acute{f}_c$ / $f_y$ for minimum reinforcement ratio test. The test results were compared with ACI 318-95 Code. In the Ultra High Strength Concrete beam, the maximum reinforcement ration should be less than 0.6$\rho_b$ for ductile behavior and the existing minimum reinforcement ratio by ACI Building Code is Sufficiently safe.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.251-254
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• 2005

A number of studies have been conducted on FRP shear strengthening of RC beams during the past decade. The test results indicated. that the strengthened specimens failed predominantly by debonding of the FRP sheets before reaching the rupture strength of FRP sheets. For this reason, limits on the effective strain in FRP have been incorporated in ACI 440.2R recommendation considering debonding failure. This paper presents the test results of 7 small scale RC beams shear-strengthened with glass fiber sheets. Three types of FRP configurations, such as two sides bonded, U wrap and fiber shear-key embedded, were considered. GFRP sheet were bonded vertically to member axis along the shear span. From the test results, it was found that debonding strain of GFRP sheets at failure decreased with the number of layers. In addition, effective strain of FRP proposed by ACI 440.2R recommendation has been verified in this study.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.31-34
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• 2005

An experimental investigation was conducted to examine the hysteric behavior of Ultra-High strength concrete columns for the requirement of ACI provision. Seven 1/3 scaled columns were fabricated to simulate an 1/2 story of actual structural members with the cross section $300\times300mm$ and the shear span ratio 4. The main variables are axial load ratio, configuration and volumetric ratio of transverse reinforcement. It has been found that the behavior of columns was affected by axial load ratio rather than the amount and the configuration of transverse reinforcement. Consequently, to secure the ductile behavior of 100MPa Ultra-High strength concrete columns, ACI provision for the requirement of transverse steel may considered axial level and the detail of transverse reinforcement.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.179-182
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• 2005

Recently, many design codes including ACI 318-02 recommend the use of a strut-tie model approach for design of structural concrete with D-region(s). However, there are several unclear problems and shortcomings in the codes' strut-tie model approach. A grid strut-tie model approach was proposed to resolve these problems. In this study, the ultimate strengths of 17 deep beams, the most familiar type of D-regions, were evaluated for the validity check of the grid strut-tie model approach. The analytical results obtained by the approach are compared with those by the strut-tie model approach presented by CEB-FIP, AASHTO LRFD, and ACI 318-02.

• Computers and Concrete
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• v.3 no.5
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• pp.335-355
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• 2006

The application of radial basis function neural networks (RBFN) to predict the ultimate torsional strength of reinforced concrete (RC) beams is explored in this study. A database on torsional failure of RC beams with rectangular section subjected to pure torsion was retrieved from past experiments in the literature; several RBFN models are sequentially built, trained and tested. Then the ultimate torsional strength of each beam is determined from the developed RBFN models. In addition, the predictions of the RBFN models are also compared with those obtained using the ACI 318 Code equations. The study shows that the RBFN models give reasonable predictions of the ultimate torsional strength of RC beams. Moreover, the results also show that the RBFN models provide better accuracy than the existing ACI 318 equations for torsion, both in terms of root-mean-square error and coefficients of determination.

• Earthquakes and Structures
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• v.7 no.5
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• pp.861-875
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• 2014

This paper studies the response of seismic behavior of reinforced concrete exterior beam-column joints under reversal loading with different anchorages and joint core details. The joint core was detailed without much confinement (group-I) and/or with proposed X-cross bars in the core (group-II). The beam longitudinal reinforcement's anchorages were designed as per ACI 352 (headed bars), ACI 318 (conventional $90^{\circ}$ bent hooks) and IS 456 ($90^{\circ}$ bent hooks with extended tails). The nonlinear finite element analysis response of the beam-column joints was studied, along with initial and progressive cracks up to failure. The experimental and analytical results were compared and presented in this paper to make more scientific conclusions.

• ETRI Journal
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• v.37 no.4
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• pp.647-656
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• 2015

This paper proposes a single-RF MIMO receiver that adopts a beam-switching antenna (BSA) instead of a conventional array antenna. The beauty of the proposed single-RF MIMO receiver with BSA is that it can be deployed in a very small physical space while achieving a full spatial multiplexing gain. Our analysis has revealed that the use of a BSA inevitably results in the spectrum spreading effect at the RF output, which in turn causes an SNR decrease and adjacent channel interference (ACI). Two novel receiver techniques are proposed to mitigate the issues of redundant sub-band suppression and ACI avoidance. Numerical analysis results verify the performance improvement from the proposed receiver techniques.