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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Computers and Concrete
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Volume & Issues
Volume 16, Issue 6 - Dec 2015
Volume 16, Issue 5 - Nov 2015
Volume 16, Issue 4 - Oct 2015
Volume 16, Issue 3 - Sep 2015
Volume 16, Issue 2 - Aug 2015
Volume 16, Issue 1 - Jul 2015
Volume 15, Issue 6 - Jun 2015
Volume 15, Issue 5 - May 2015
Volume 15, Issue 4 - Apr 2015
Volume 15, Issue 3 - Mar 2015
Volume 15, Issue 2 - Feb 2015
Volume 15, Issue 1 - Jan 2015
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A damage model formulation: unilateral effect and RC structures analysis
Pituba, Jose J.C. ;
Computers and Concrete, volume 15, issue 5, 2015, Pages 709~733
DOI : 10.12989/cac.2015.15.5.709
This work deals with a damage model formulation taking into account the unilateral effect of the mechanical behaviour of brittle materials such as concrete. The material is assumed as an initial elastic isotropic medium presenting anisotropy, permanent strains and bimodularity induced by damage evolution. Two damage tensors governing the stiffness in tension or compression regimes are introduced. A new damage tensor in tension regimes is proposed in order to model the diffuse damage originated in prevails compression regimes. Accordingly with micromechanical theory, the constitutive model is validate when dealing with unilateral effect of brittle materials, Finally, the proposed model is applied in the analyses of reinforced concrete framed structures submitted to reversal loading. The numerical results have shown the good performance of the modelling and its potentialities to simulate practical problems in structural engineering.
Modeling of unilateral effect in brittle materials by a mesoscopic scale approach
Pituba, Jose J.C. ; Neto, Eduardo A. Souza ;
Computers and Concrete, volume 15, issue 5, 2015, Pages 735~758
DOI : 10.12989/cac.2015.15.5.735
This work deals with unilateral effect of quasi-brittle materials, such as concrete. For this propose, a two-dimensional meso-scale model is presented. The material is considered as a three-phase material consisting of interface zone, matrix and inclusions - each constituent modeled by an appropriate constitutive model. The Representative Volume Element (RVE) consists of inclusions idealized as circular shapes randomly placed into the specimen. The interface zone is modeled by means of cohesive contact finite elements developed here in order to capture the effects of phase debonding and interface crack closure/opening. As an initial approximation, the inclusion is modeled as linear elastic as well as the matrix. Our main goal here is to show a computational homogenization-based approach as an alternative to complex macroscopic constitutive models for the mechanical behavior of the quasi-brittle materials using a finite element procedure within a purely kinematical multi-scale framework. A set of numerical examples, involving the microcracking processes, is provided. It illustrates the performance of the proposed model. In summary, the proposed homogenization-based model is found to be a suitable tool for the identification of macroscopic mechanical behavior of quasi-brittle materials dealing with unilateral effect.
Predicting the compressive strength of cement mortars containing FA and SF by MLPNN
Kocak, Yilmaz ; Gulbandilar, Eyyup ; Akcay, Muammer ;
Computers and Concrete, volume 15, issue 5, 2015, Pages 759~770
DOI : 10.12989/cac.2015.15.5.759
In this study, a multi-layer perceptron neural network (MLPNN) prediction model for compressive strength of the cement mortars has been developed. For purpose of constructing this model, 8 different mixes with 240 specimens of the 2, 7, 28, 56 and 90 days compressive strength experimental results of cement mortars containing fly ash (FA), silica fume (SF) and FA+SF used in training and testing for MLPNN system was gathered from the standard cement tests. The data used in the MLPNN model are arranged in a format of four input parameters that cover the FA, SF, FA+SF and age of samples and an output parameter which is compressive strength of cement mortars. In the model, the training and testing results have shown that MLPNN system has strong potential as a feasible tool for predicting 2, 7, 28, 56 and 90 days compressive strength of cement mortars.
Selection of measurement sets in static structural identification of bridges using observability trees
Lozano-Galant, Jose Antonio ; Nogal, Maria ; Turmo, Jose ; Castillo, Enrique ;
Computers and Concrete, volume 15, issue 5, 2015, Pages 771~794
DOI : 10.12989/cac.2015.15.5.771
This paper proposes an innovative method for selection of measurement sets in static parameter identification of concrete or steel bridges. This method is proved as a systematic tool to address the first steps of Structural System Identification procedures by observability techniques: the selection of adequate measurement sets. The observability trees show graphically how the unknown estimates are successively calculated throughout the recursive process of the observability analysis. The observability trees can be proved as an intuitive and powerful tool for measurement selection in beam bridges that can also be applied in complex structures, such as cable-stayed bridges. Nevertheless, in these structures, the strong link among structural parameters advises to assume a set of simplifications to increase the tree intuitiveness. In addition, a set of guidelines are provided to facilitate the representation of the observability trees in this kind of structures. These guidelines are applied in bridges of growing complexity to explain how the characteristics of the geometry of the structure (e.g. deck inclination, type of pylon-deck connection, or the existence of stay cables) affect the observability trees. The importance of the observability trees is justified by a statistical analysis of measurement sets randomly selected. This study shows that, in the analyzed structure, the probability of selecting an adequate measurement set with a minimum number of measurements at random is practically negligible. Furthermore, even bigger measurement sets might not provide adequate SSI of the unknown parameters. Finally, to show the potential of the observability trees, a large-scale concrete cable-stayed bridge is also analyzed. The comparison with the number of measurements required in the literature shows again the advantages of using the proposed method.
A study on dynamic modulus of self-consolidating rubberized concrete
Emiroglu, Mehmet ; Yildiz, Servet ; Kelestemur, M. Halidun ;
Computers and Concrete, volume 15, issue 5, 2015, Pages 795~805
DOI : 10.12989/cac.2015.15.5.795
In this study, dynamic modulus of elasticity of self-consolidating rubberized concrete is evaluated by using results of ultrasonic pulse velocity and resonance frequency tests. Additionally, correlation between dynamic modulus of elasticity and compressive strength results is compared. For evaluating the dynamic modulus of elasticity of self-consolidating rubberized concrete, prismatic specimens having
mm dimensions are prepared. Dynamic modulus of elasticity values obtained by non-destructive measurements techniques are well agreed with those given in the literature.
Improved strut-and-tie method for 2D RC beam-column joints under monotonic loading
Long, Xu ; Lee, Chi King ;
Computers and Concrete, volume 15, issue 5, 2015, Pages 807~831
DOI : 10.12989/cac.2015.15.5.807
In the previous analytical studies on 2D reinforced concrete (RC) beam-column joints, the modified compression field theory (MCFT) and the strut-and-tie method (STM) are usually employed. In this paper, the limitations of these analytical models for RC joint applications are reviewed. Essentially for predictions of RC joint shear behaviour, the MCFT is not applicable, while the STM can only predict the ultimate shear strength. To eliminate these limitations, an improved STM is derived and applied to some commonly encountered 2D joints, viz., interior and exterior joints, subjected to monotonic loading. Compared with the other STMs, the most attracting novelty of the proposed improved STM is that all critical stages of the shear stress-strain relationships for RC joints can be predicted, which cover the stages characterized by concrete cracking, transverse reinforcement yielding and concrete strut crushing. For validation and demonstration of superiority, the shear stress-strain relationships of interior and exterior RC beam-column joints from published experimental studies are employed and compared with the predictions by the proposed improved STM and other widely-used analytical models, such as the MCFT and STM.
Permeability features of concretes produced with aggregates coated with colemanite
Bideci, Ozlem Salli ; Bideci, Alper ; Oymael, Sabit ; Gultekin, Ali Haydar ; Yildirim, Hasan ;
Computers and Concrete, volume 15, issue 5, 2015, Pages 833~845
DOI : 10.12989/cac.2015.15.5.833
In the world total boron reserve rating, Turkey is taken place on the first rank, meeting the demand of refined mineral and main boron chemicals. Development of the new boron products and production technologies, spreading the using area of the boron are the study topics which must be finically discussed. In this study, with the help of colemanite taken in ratio as (0%, 7.5%, 12.5%, and 17.5%) by being mixed by the cement, surfaces of the pumice aggregates have been covered. Permeability of the samples has been investigated by producing lightweight concrete with 400 dose with the help of aggregates covered with colemanite. For this, the experiments of water absorption, capillary water absorption, depth of penetration of water under pressure and rapid chloride permeability have been performed. In addition, analyses of the thin section of covered and uncovered pumice aggregates and SEM (Scanning Electron Microscope) have been investigated. When the control samples produced with the covered aggregates and concretes produced with colemanite covered aggregates are compared each other, it has been determined that special lightweight concretes whose values of capillary water absorption experiment, depth of penetration of water under pressure experiment and rapid chloride permeability are low can be produced.
A reaction-diffusion modeling of carbonation process in self-compacting concrete
Fu, Chuanqing ; Ye, Hailong ; Jin, Xianyu ; Jin, Nanguo ; Gong, Lingli ;
Computers and Concrete, volume 15, issue 5, 2015, Pages 847~864
DOI : 10.12989/cac.2015.15.5.847
In this paper, a reaction-diffusion model of carbonation process in self-compacting concrete (SCC) was realized with a consideration of multi-field couplings. Various effects from environmental conditions, e.g. ambient temperature, relative humidity, carbonation reaction, were incorporated into a numerical simulation proposed by ANSYS. In addition, the carbonation process of SCC was experimentally investigated and compared with a conventionally vibrated concrete (CVC). It is found that SCC has a higher carbonation resistance than CVC with a comparable compressive strength. The numerical solution analysis agrees well with the test results, indicating that the proposed model is appropriate to calculate and predict the carbonation process in SCC. The parameters sensitivity analysis also shows that the carbon dioxide diffusion coefficient and moisture field are essentially crucial to the carbonation process in SCC.