• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1440-1448
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• 2014

Co(II)-tetrasulfonated phthalocyanine (CoTSP) is known to be aggregated to dimer at high concentration levels in water. A study on the aggregation of CoTSP using multivariate curve resolution analysis of the visible absorbance spectra over a concentration range of 30, 40 and 50 ${\mu}M$ in the presence of dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), acetonitrile (AN) and ethanol (EtOH) in the concentration range of 0 to 3.57 M is conducted. A hard modeling-based multivariate curve resolution method was applied to determine the dissociation constants of the CoTSP aggregates at various temperatures ranging from 25, 45 and $65^{\circ}C$ and in the presence of various co-solvents. Dissociation constant for aggregation was increased and then decrease by temperature and concentration of phthalocyanine, respectively. Utilizing the vant Hoff relation, the enthalpy and entropy of the dissociation equilibriums were calculated. For the dissociation of both aggregates, the enthalpy and entropy changes were positive and negative, respectively. Molecular dynamics simulation of cosolvent effect on CoTSP aggregation was done to confirm spectroscopy results. Results of radial distribution function (RDF), root mean square deviation (RMSD) and distance curves confirmed more effect of polar solvent to decrease monomer formation.

• Steel and Composite Structures
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• v.52 no.1
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• pp.57-76
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• 2024

The management of waste tire rubber has become a pressing environmental and health issue, requiring sustainable solutions to mitigate fire hazards and conserve natural resources. The performance of waste materials in structural components needs to be investigated to fabricate sustainable structures. This study aims to investigate the behavior of glass fiber reinforced polymer (GFRP) reinforced rubberized concrete (GRRC) compressive components under compressive loads. Nine GRRC circular compressive components, varying in longitudinal and transverse reinforcement ratios, were constructed. A 3D nonlinear finite element model (FEM) was proposed by means of the ABAQUS software to simulate the behavior of the GRRC compressive components. A comprehensive parametric analysis was conducted to assess the impact of different parameters on the performance of GRRC compressive components. The experimental findings demonstrated that reducing the spacing of GFRP stirrups enhanced the ductility of GRRC compressive components, while the addition of rubberized concrete further improved their ductility. Failure in GRRC compressive components occurred in a compressive columnar manner, characterized by vertical cracks and increased deformability. The finite element simulations closely matched the experimental results. The proposed empirical model, based on 600 test samples and considering the lateral confinement effect of FRP stirrups, demonstrated higher accuracy (R² = 0.835, MSE = 171.296, MAE = 203.549, RMSE = 195.438) than previous models.

• Coupled systems mechanics
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• v.7 no.5
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• pp.509-524
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• 2018

A hierarchical multi-scale modeling strategy devoted to the study of a Bitumen-Bound Gravel (BBG) is presented in this paper. More precisely, the paper investigates the temperature-dependent linear viscoelastic of the material when submitted to low deformations levels and moderate number of cycles. In such a hierarchical approach, 3D digital Representative Elementary Volumes are built and the outcomes at a scale (here, the sub-mesoscale) are used as input data at the next higher scale (here, the mesoscale). The viscoelastic behavior of the bituminous phases at each scale is taken into account by means of a generalized Maxwell model: the bulk part of the behavior is separated from the deviatoric one and bulk and shear moduli are expanded into Prony series. Furthermore, the viscoelastic phases are considered to be thermorheologically simple: time and temperature are not independent. This behavior is reproduced by the Williams-Landel-Ferry law. By means of the FE simulations of stress relaxation tests, the parameters of the various features of this temperature-dependent viscoelastic behavior are identified.

• Explosives and Blasting
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• v.23 no.1
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• pp.47-54
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• 2005

An explosion modeling technique was developed by using the spherical discrete element code, $PFC^{3D}$, which can be used to model the dynamic stress wave propagation phenomenon. The modeling technique is simply based on an idea that the explosion pressure should be applied to a $PFC^{3D}$ particle assembly not in the form of an external force (body force), but in the form of a contact force (surface force). A test blast was conducted for a RC column, whose dimension was $600\times300\times1800$ in millimeters. The initial velocities of the surface movements were measured to be in the range of $14\~18\;m/s$ with the initiation times of $1.5\~2.0m$. Then the blasting procedure was simulated by using the modeling technique. The particle assembly representing the concrete was made of cement mortar and coarse aggregates, whose mirco-properties were obtained from the calibration processes. As a result, the modeling technique developed in this study made it possible for the burden to move with the velocity of $17\~24\;m/s$, which are slightly higher values compared to those of the test blast.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.04a
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• pp.35-41
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• 1995

Fracture Mechanics does work for concrete, provided that a finite nonlinear zone at fracture front is being considered. The development of model for fracture process zone is most important to describe fracture phenomena in concrete. The fracture process zone is a region ahead of a traction-free crack, in which two major mechanisms, microcracking and bridging, play important rules. The toughness due to bridging is dominant compared to toughness induced by microcracking, so that the bridging is dominant mechanism governing the fracture process of concrete. In this paper the bridging zone, which is a part of extended macrocrack with stresses transmitted by aggregates in concrete, is model led by a Dugdale-Barenblatt type model with linear tension-softening curve. Two finite element techniques are shown for the model of fracture process zone in concrete.

• Structural Engineering and Mechanics
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• v.38 no.4
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• pp.503-516
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• 2011

Uncertainty in concrete properties, including concrete modulus of elasticity and modulus of rupture, are predicted by developing a microstructural homogenization model. The homogenization model is developed by analyzing a concrete representative volume element (RVE) using the finite element (FE) method. The concrete RVE considers concrete as a three phase composite material including: cement paste, aggregate and interfacial transition zone (ITZ). The homogenization model allows for considering two sources of variability in concrete, randomly dispersed aggregates in the concrete matrix and uncertain mechanical properties of composite phases of concrete. Using the proposed homogenization technique, the uncertainty in concrete modulus of elasticity and modulus of rupture (described by numerical cumulative probability density function) are determined. Deflection uncertainty of reinforced concrete (RC) beams, propagated from uncertainties in concrete properties, is quantified using Monte Carlo (MC) simulation. Cracked plane frame analysis is used to account for tension stiffening in concrete. Concrete homogenization enables a unique opportunity to bridge the gap between concrete materials and structural modeling, which is necessary for realistic serviceability prediction.

• Interaction and multiscale mechanics
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• v.2 no.1
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• pp.15-30
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• 2009

The theoretical framework of the interaction fields for multiple scales based on field theory is applied to one-dimensional problem mimicking dislocation substructure sensitive intra-granular inhomogeneity evolution under fatigue of Cu-added steels. Three distinct scale levels corresponding respectively to the orders of (A)dislocation substructures, (B)grain size and (C)grain aggregates are set-up based on FE-RKPM (reproducing kernel particle method) based interpolated strain distribution to obtain the incompatibility term in the interaction field. Comparisons between analytical conditions with and without the interaction, and that among different cell size in the scale A are simulated. The effect of interaction field on the B-scale field evolution is extensively examined. Finer and larger fluctuation is demonstrated to be obtained by taking account of the field interactions. Finer cell size exhibits larger field fluctuation whereas the coarse cell size yields negligible interaction effects.

• International Journal of CAD/CAM
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• v.6 no.1
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• pp.125-137
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• 2006

Nowadays, many commercial CAD systems support history-based, constraint-based and feature-based modeling. Unfortunately, most systems fail during the re-evaluation phase when various kind of topological changes occur. This issue is known as "persistent naming" which refers to the problem of identifying entities in an initial parametric model and matching them in the re-evaluated model. Most works in this domain focus on the persistent naming of atomic entities such as vertices, edges or faces. But very few of them consider the persistent naming of aggregates like shells (any set of faces). We propose in this paper a complete framework for identifying and matching any kind of entities based on their underlying topology, and particularly shells. The identifying method is based on the invariant structure of each class of form features (a hierarchical structure of shells) and on its topological evolution (an historical structure of faces). The matching method compares the initial and the re-evaluated topological histories, and computes two measures of topological similarity between any couple of entities occurring in both models. The naming and matching method has been implemented and integrated in a prototype of commercial CAD Software (Topsolid).

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.155-158
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• 2005

Precipitates, present in most commercial alloys, can have a strong influence on strength and hardening behavior of a single crystal. The effect of thin precipitates on the anisotropy of initial slip resistance and hardening behavior of crystals is modeled in this article. For the convenience of the computational derivation and implementation, the material formulation is given in the unrelated intermediate configuration mapped by the plastic part of the deformation gradient. Material descriptions for the considered two phased aggregates consisting in lattice hardening as well as isotropic hardening and kinematic hardening are suggested. Numerical simulations of various loading cases are presented to discuss and assess the performance of the suggested model.

• Computers and Concrete
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• v.16 no.4
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• pp.545-568
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• 2015

High Performance Fiber Reinforced Cementitious Composites which are called HPFRCC, include cement matrices with strain hardening response under tension loading. In these composites, the cement mortar with fine aggregates, is reinforced by continuous or random distributed fibers and could be used for various applications including structural fuses and retrofitting of reinforced concrete members etc. In this paper, mechanical properties of HPFRCC materials are reviewed briefly. Moreover, a reinforced concrete beam (experimentally tested by Maalej et al.) is chosen and in different specimens, lower or upper or both parts of that beam are replaced with HPFRCC layers. After modeling of specimens in ABAQUS and calibration of those, mechanical properties of these specimens are investigated with different thicknesses, tensile strengths, tensile strains and compressive bars. Analytical results which are obtained by nonlinear finite analyses show that using HPFRCC layers with different parameters, increase loading capacity and ultimate displacement of these beams compare to RC specimens.