• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.10a
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• pp.97-102
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• 1992

To predict the shear strength of low - rise reinforced concrete shear walls with boundary elements, truss model theory considering the Vecchio - Collins stress - strain curve for softened concrete is applied. The model transforms cracked shear walls with a truss which consists of vertical bar. horizontal bar and diagonal concrete strut, and is based on equilibrium and compatibility conditions among three truss components, as well as stress - strain relationship considered for softening in diagonal concrete strut. In barbell specimens(M/VD = 0.75. fc = 420 kg/$\textrm{cm}^2$), the ratio of experimental to analytical maximum shear strength was within 0.83 ν$_{exp}$. / ν$_{cal}$. 1.25 with a relatively good agreement. As a result, the truss model was observed to be capable of predicting the maximum shear strength wi th a reasonable accuracy.acy.

• Computers and Concrete
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• v.27 no.4
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• pp.305-317
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• 2021

The bond between the concrete and bar is a main factor affecting the performance of the reinforced concrete (RC) members, and since the steel corrosion reduces the bond strength, studying the bond behavior of concrete and GFRP bars is quite necessary. In this research, a database including 112 concrete beam test specimens reinforced with spliced GFRP bars in the splitting failure mode has been collected and used to estimate the concrete-GFRP bar bond strength. This paper aims to accurately estimate the bond strength of spliced GFRP bars in concrete beams by applying three soft computing models including multivariate adaptive regression spline (MARS), Kriging, and M5 model tree. Since the selection of regularization parameters greatly affects the fitting of MARS, Kriging, and M5 models, the regularization parameters have been so optimized as to maximize the training data convergence coefficient. Three hybrid model coupling soft computing methods and genetic algorithm is proposed to automatically perform the trial and error process for finding appropriate modeling regularization parameters. Results have shown that proposed models have significantly increased the prediction accuracy compared to previous models. The proposed MARS, Kriging, and M5 models have improved the convergence coefficient by about 65, 63 and 49%, respectively, compared to the best previous model.

• Computers and Concrete
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• v.8 no.3
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• pp.357-369
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• 2011

In this study, effect of steel fibers on toughness and some mechanical properties of concrete were investigated. Hooked-end steel fibers were used in concrete samples with three volume fractions (${\nu}_f$) of 0.5%, 0.75% and 1% and for two aspect ratios (l/d) of 45 and 65. Compressive and flexural tensile strength and modulus of elasticity of concrete were determined for cylindrical, cubic and prismatic samples at the age of 7 and 28 days. The stress-strain curves of standard cylindrical specimens were studied to determine the effect of steel fibers on toughness of steel-fiber-reinforced concrete (SFRC). In addition, the relationship between compressive strength and the flexural tensile strength of SFRC were reported. Finally, a simple model was proposed to generate the stress-strain curves for SFRC based on strains corresponding to the peak compressive strength and 60% of peak compressive stress. The proposed model was shown to provide results in good correlation with the experimental results.

• Structural Engineering and Mechanics
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• v.45 no.6
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• pp.837-851
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• 2013

In construction industry, strength is a primary criterion in selecting a concrete for a particular application. The concrete used for construction gains strength over a long period of time after pouring the concrete. The characteristic strength of concrete is defined as the compressive strength of a sample that has been aged for 28 days. Neither waiting for 28 days for such a test would serve the rapidity of construction, nor would neglecting it serve the quality control process on concrete in large construction sites. Therefore, rapid and reliable prediction of the strength of concrete would be of great significance. On this backdrop, the method is proposed to establish a predictive relationship between properties and proportions of ingredients of concrete, compaction factor, weight of concrete cubes and strength of concrete whereby the strength of concrete can be predicted at early age. Multiple regression analysis was carried out for predicting the compressive strength of concrete containing Portland Pozolana cement using statistical analysis for the concrete data obtained from the experimental work done in this study. The multiple linear regression models yielded fairly good correlation coefficient for the prediction of compressive strength for 7, 28 and 40 days curing. The results indicate that the proposed regression models are effectively capable of evaluating the compressive strength of the concrete containing Portaland Pozolana Cement. The derived formulas are very simple, straightforward and provide an effective analysis tool accessible to practicing engineers.

• Computers and Concrete
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• v.9 no.3
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• pp.227-244
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• 2012

A theoretical model for shear strength evaluation of fibrous concrete beams reinforced with stirrups is proposed. The formulation is founded on the theory of plasticity and the stress field concepts, generalizing a known plastic model for calculating the bearing capacity of reinforced concrete beams, to the case of fibrous concrete. The beneficial effect of steel fibres is estimated taking into account the residual tensile strength of fibrous concrete, by modifying an analytical constitutive law which presents a plastic plateau as a post-peak branch. Around fifty results of experimental tests carried out on steel fibrous concrete beams available in the literature were collected, and a comparison of shear strength estimation provided by other semi-empirical models is performed, proving that the numerical values obtained with the proposed model are in very good agreement with the experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.375-379
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• 2003

In this paper, the linear and nonlinear strut-tie model approaches for the analysis and design of concrete structures are suggested. The validity of the approaches are examined through the strength analysis of four dapped-end beams tested to failure. According to the analysis results, the nonlinear strut-tie model approach which takes the various characteristics of nonlinear behaviors into account in the analysis and design of structural concrete and predicts the strength of structural concrete proven to be an effective method for structural analysis and design.

• Computers and Concrete
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• v.6 no.2
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• pp.155-165
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• 2009

Splitting tensile strength (STS) of high-performance concrete (HPC) is one of the important mechanical properties for structural design. This property is related to compressive strength (CS), water/binder (W/B) ratio and concrete age. This paper presents a clustering-based fuzzy model for the prediction of STS based on the CS and (W/B) at a fixed age (28 days). The data driven fuzzy model consists of three main steps: fuzzy clustering, inference system, and prediction. The system can be analyzed directly by the model from measured data. The performance evaluations showed that the fuzzy model is more accurate than the other prediction models concerned.

• Computers and Concrete
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• v.29 no.5
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• pp.285-301
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• 2022

This study aims at developing a torsional strength model based on a nonlinear analysis method presented in the previous studies. To this end, flexural neutral axis depth of a reinforced concrete section and effective thickness of an idealized thin-walled tube were formulated based on reasonable approximations. In addition, various sectional force components, such as shear, flexure, axial compression, and torsional moment, were considered in estimating torsional strength by addressing a simple and linear strain profile. Existing test results were collected from literature for verifications by comparing with those estimated from the proposed model. On this basis, it can be confirmed that the proposed model can evaluate the torsional strength of RC members subjected to combined loads with a good level of accuracy, and it also well captured inter-related mechanisms between shear, bending moment, axial compression, and torsion.

• Computers and Concrete
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• v.28 no.6
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• pp.621-634
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• 2021

For the reliable strut-and-tie model (STM) design of disturbed regions of concrete members, structural designers must accurately determine the strength of concrete struts to check the strength conditions of a selected STM el and the anchorage of reinforcing bars in nodal zones. In this study, the author proposed a consistent numerical method for strut strength, applicable to all two-dimensional STMs. The proposed method includes the effects of a biaxial stress state associated with tensile strains in reinforcing bars crossing a strut, deviation angle between strut orientation and compressive principal stress flow, and degree of confinement provided by reinforcement. The author examined the method's validity through the STM prediction of the ultimate strengths of 517 reinforced concrete (RC) deep beams, 24 RC panels, and 258 RC corbels, all tested to failure.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.565-570
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• 2000

The objective of this paper is to analyse the high-strength concrete columns subjected to reversed cyclic and axial loads by using nonlinear analysis model and compare the experimental results with analysis. The analytical parameters are the compressive strength of concrete, spacing of lateral reinforcement and lateral reinforcement ratio. In this study, the proposed analytical model takes ito account the influence of confined concrete, tension stiffening and strain hardening of steel. The high-strength concrete columns are used to model fiber section element. The analysis results are shown comparatively good prediction on envelope curve, accumulative dissipated energy, deformability and so on.