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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 8, Issue 6 - Dec 2011
Volume 8, Issue 5 - Oct 2011
Volume 8, Issue 4 - Aug 2011
Volume 8, Issue 3 - Jun 2011
Volume 8, Issue 2 - Apr 2011
Volume 8, Issue 1 - Feb 2011
Selecting the target year
Numerical analysis of Brazilian split test on concrete cylinder
Wosatko, Adam ; Winnicki, Andrzej ; Pamin, Jerzy ;
Computers and Concrete, volume 8, issue 3, 2011, Pages 243~278
DOI : 10.12989/cac.2011.8.3.243
The paper presents simulations of the Brazilian test using two numerical models. Both models are regularized in order to obtain results independent of discretization. The first one, called gradient damage, is refined by additional averaging equation which contains gradient terms and an internal length scale as localization limiter. In the second one, called viscoplastic consistency model, the yield function depends on the viscoplastic strain rate. In this model regularization properties are governed by the assumed strain rate. The two models are implemented in the FEAP finite element package and compared in this paper. Parameter studies of the split test are performed in order to point out the features of each model.
Modeling the effects of additives on rheological properties of fresh self-consolidating cement paste using artificial neural network
Mohebbi, Alireze ; Shekarchi, Mohammad ; Mahoutian, Mehrdad ; Mohebbi, Shima ;
Computers and Concrete, volume 8, issue 3, 2011, Pages 279~292
DOI : 10.12989/cac.2011.8.3.279
The main purpose of this study includes investigation of the rheological properties of fresh self consolidating cement paste containing chemical and mineral additives using Artificial Neural Network (ANN) model. In order to develop the model, 200 different mixes are cast in the laboratory as a part of an extensive experimental research program. The data used in the ANN model are arranged in a format of fourteen input parameters covering water-binder ratio, four different mineral additives (calcium carbonate, metakaolin, silica fume, and limestone), five different superplasticizers based on the poly carboxylate and naphthalene and four different Viscosity Modified Admixtures (VMAs). Two common output parameters including the mini slump value and flow cone time are chosen for measuring the rheological properties of fresh self consolidating cement paste. Having validated the model, the influence of effective parameters on the rheological properties of fresh self consolidating cement paste is investigated based on the ANN model outputs. The output results of the model are then compared with the results of previous studies performed by other researchers. Ultimately, the analysis of the model outputs determines the optimal percentage of additives which has a strong influence on the rheological properties of fresh self consolidating cement paste. The proposed ANN model shows that metakaolin and silica fume affect the rheological properties in the same manner. In addition, for providing the suitable rheological properties, the ANN model introduces the optimal percentage of metakaolin, silica fume, calcium carbonate and limestone as 15, 15, 20 and 20% by cement weight, respectively.
Modeling of temperature distribution in a reinforced concrete supertall structure based on structural health monitoring data
Ni, Y.Q. ; Ye, X.W. ; Lin, K.C. ; Liao, W.Y. ;
Computers and Concrete, volume 8, issue 3, 2011, Pages 293~309
DOI : 10.12989/cac.2011.8.3.293
A long-term structural health monitoring (SHM) system comprising over 700 sensors of sixteen types has been implemented on the Guangzhou Television and Sightseeing Tower (GTST) of 610 m high for real-time monitoring of the structure at both construction and service stages. As part of this sophisticated SHM system, 48 temperature sensors have been deployed at 12 cross-sections of the reinforced concrete inner structure of the GTST to provide on-line monitoring via a wireless data transmission system. In this paper, the differential temperature profiles in the reinforced concrete inner structure of the GTST, which are mainly caused by solar radiation, are recognized from the monitoring data with the purpose of understanding the temperature-induced structural internal forces and deformations. After a careful examination of the pre-classified temperature measurement data obtained under sunny days and non-sunny days, common characteristic of the daily temperature variation is observed from the data acquired in sunny days. Making use of 60-day temperature measurement data obtained in sunny days, statistical patterns of the daily rising temperature and daily descending temperature are synthesized, and temperature distribution models of the reinforced concrete inner structure of the GTST are formulated using linear regression analysis. The developed monitoring-based temperature distribution models will serve as a reliable input for numerical prediction of the temperature-induced deformations and provide a robust basis to facilitate the design and construction of similar structures in consideration of thermal effects.
Global seismic damage assessment of high-rise hybrid structures
Lu, Xilin ; Huang, Zhihua ; Zhou, Ying ;
Computers and Concrete, volume 8, issue 3, 2011, Pages 311~325
DOI : 10.12989/cac.2011.8.3.311
Nowadays, many engineers believe that hybrid structures with reinforced concrete central core walls and perimeter steel frames offer an economical method to develop the strength and stiffness required for seismic design. As a result, a variety of such structures have recently been applied in actual construction. However, the performance-based seismic design of such structures has not been investigated systematically. In the performance-based seismic design, quantifying the seismic damage of complete structures by damage indices is one of the fundamental issues. Four damage states and the final softening index at each state for high-rise hybrid structures are suggested firstly in this paper. Based on nonlinear dynamic analysis, the relation of the maximum inter-story drift, the main structural characteristics, and the final softening index is obtained. At the same time, the relation between the maximum inter-story drift and the maximum roof displacement over the height is also acquired. A double-variable index accounting for maximum deformation and cumulative energy is put forward based on the pushover analysis. Finally, a case study is conducted on a high-rise hybrid structure model tested on shaking table before to verify the suggested quantities of damage indices.
Three-dimensional numerical simulation and cracking analysis of fiber-reinforced cement-based composites
Huang, Jun ; Huang, Peiyan ;
Computers and Concrete, volume 8, issue 3, 2011, Pages 327~341
DOI : 10.12989/cac.2011.8.3.327
Three-dimensional graphic objects created by MATLAB are exported to the AUTOCAD program through the MATLAB handle functions. The imported SAT format files are used to produce the finite element mesh for MSC.PATRAN. Based on the Monte-Carlo random sample principle, the material heterogeneity of cement composites with randomly distributed fibers is described by the WEIBULL distribution function. In this paper, a concept called "soft region" including micro-defects, micro-voids, etc. is put forward for the simulation of crack propagation in fiber-reinforced cement composites. The performance of the numerical model is demonstrated by several examples involving crack initiation and growth in the composites under three-dimensional stress conditions: tensile loading; compressive loading and crack growth along a bimaterial interface.
Prediction of chloride diffusion coefficient of concrete under flexural cyclic load
Tran, Van Mien ; Stitmannaithum, Boonchai ; Nawa, Toyoharu ;
Computers and Concrete, volume 8, issue 3, 2011, Pages 343~355
DOI : 10.12989/cac.2011.8.3.343
This paper presented the model to predict the chloride diffusion coefficient in tension zone of plain concrete under flexural cyclic load. The fictitious crack based analytical model was used together with the stress degradation law in cracked zone to predict crack growth of plain concrete beams under flexural cyclic load. Then, under cyclic load, the chloride diffusion, in the steady state and one dimensional regime, through the tension zone of the plain concrete beam, in which microcracks were formed by a large number of cycles, was simulated with assumptions of continuously straight crack and uniform-size crack. The numerical analysis in terms of the chloride diffusion coefficient,
, crack width and crack length was issued as a function of the load cycle, N, and load level, SR. The nonlinear model as regarding with the chloride diffusion coefficient in tension zone and the load level was proposed. According to this model, the chloride diffusion increases with increasing load level. The predictions using model fit well with experimental data when we adopted suitable crack density and tortuosity parameter.
Modeling of concrete containing steel fibers: toughness and mechanical properties
Cagatay, Lsmail H. ; Dincer, Riza ;
Computers and Concrete, volume 8, issue 3, 2011, Pages 357~369
DOI : 10.12989/cac.2011.8.3.357
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 (
) 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.