Techno Press
Tp_Editing System.E (TES.E)
Login Search


cac
 
CONTENTS
Volume 5, Number 3, June 2008
 

Abstract
Increasingly numerical (finite element) modeling of concrete hinges on our ability to develop a representative volume element with all its heterogeneity properly discretized. Yet, despite all the sophistication of the ensuing numerical models, the initial discretization has been for the most part simplistic. Whenever the heterogeneity of the concrete is to be accounted for, a mesh is often manually crafted through the arbitrary inclusion of the particles (aggregates and/or voids) in an ad-hoc manner. This paper develops a mathematical strategy to precisely address this limitation. Algorithms for the random generation and placement of elliptical (2D) or ellipsoid (3D) inclusions, with possibly radiating cracks, in a virtual concrete model are presented. Collision detection algorithms are extensively used.

Key Words
composites; mesoconcrete; concrete; representative equivalent volume.

Address
W. Puatatsananon; Department of Civil Engineering, Ubon Ratchathani University, Thailand
V. Saouma; Department of Civil Engineering, University of Colorado at Boulder, USA
V. Slowik; Hochschule fur Technik, Wirtschaft and Kultur Leipzig (FH), Germany

Abstract
This paper presents a new hypoelasticity model which was implemented in a nonlinear finite element formulation to analyze reinforced concrete (RC) structures. The model includes a new hypoelasticity constitutive relationship utilizing the rotation of material axis through successive iterations. The model can account for high nonlinearity of the stress-strain behavior of the concrete in the pre-peak regime, the softening behavior of the concrete in the post-peak regime and the irrecoverable volume dilatation at high levels of compressive load. This research introduces the modified version of the common application orthotropic stress-strain relation developed by Darwin and Pecknold. It is endeavored not to violate the principal of \"simplicity\" by improvement of the \"capability\" The results of analyses of experimental reinforced concrete walls are presented to confirm the abilities of the proposed relationships.

Key Words
cracking; damage; smeared crack model; hypoelasticity; strength degradation; shear wall.

Address
Mohsen A. Shayanfar; Civil Engineering Department, Iran Univ. of Science and Technology, Narmak 16846, Tehran, Iran
Amir Safiey; Moshanir Power Engineering Consultants, Park Prince Buildings, Vanak, Tehran, Iran

Abstract
In this paper, a total strain-based hysteretic material model based on MCFT is proposed for non-linear finite element analysis of reinforced concrete structures. Although many concrete models have been proposed for simulating behavior of structures under cyclic loading conditions, accurate simulations remain challenging due to uncertainties in materials, pitfalls of crude assumptions of existing models, and limited understanding of failure mechanisms. The proposed model is equipped with a fully generalized hysteresis rule and is formulated for 2D plane stress non-linear finite element analysis. The proposed model has been formulated in a tangent stiffness-based finite element scheme so that it can be used for most general finite element analysis packages. Moreover, it eliminates the need to check that tensile stresses can be transmitted across a crack. The tension stiffening model is a function of the bar orientation and any orientation can be accommodated. The proposed model has been verified with a series of experimental results of 2D RC planar panels. This study also demonstrates how parameters of the proposed model associated with cyclic damage modeling influences the pinched cyclic shear behavior.

Key Words
hysteretic material constitutive model; reinforced concrete; non-linear finite element analysis; tangent stiffness-based formulation; hysteretic behavior; cyclic loading.

Address
Gun Jin Yun; Department of Civil Engineering, The University of Akron, Akron, OH, 44325-3905, USA
Thomas G. Harmon, Shirley J. Dyke and Migeum So; Dept. of Mechanical, Aerospace and Structural Engineering, Washington University in St. Louis, St. Louis, MO, 64130, USA

Abstract
The present article summarises the fundamental characteristics of concrete behaviour which underlie the formulation of an engineering finite element model capable of realistically predicting the behaviour of (plain or reinforced) concrete structural forms in a wide range of problems ranging from static to impact loading without the need of any kind of re-calibration. The already published evidence supporting the proposed formulation is complemented by four additional typical case studies presented herein; for each case, a comparative study is carried out between numerical predictions and the experimental data which reveals good agreement. Such evidence validates the material characteristics upon which the FE model

Key Words
brittle behaviour; concrete; constitutive law; static (monotonic and cyclic) and dynamic (earthquake and impact) loading; nonlinear finite element analysis; structural concrete.

Address
Michael D. Kotsovos; Laboratory of Concrete Structures, National Technical University of Athens, Greece
Milija N. Pavlovic and Demetrios M. Cotsovos; epartment of Civil Engineering, Imperial College, London, USA

Abstract
This paper presents methodologies for remaining life prediction of plain concrete structural components considering tension softening effect. Non-linear fracture mechanics principles (NLFM) have been used for crack growth analysis and remaining life prediction. Various tension softening models such as linear, bi-linear, tri-linear, exponential and power curve have been presented with appropriate expressions. A methodology to account for tension softening effects in the computation of SIF and remaining life prediction of concrete structural components has been presented. The tension softening effects has been represented by using any one of the models mentioned above. Numerical studies have been conducted on three point bending concrete structural component under constant amplitude loading. Remaining life has been predicted for different loading cases and for various tension softening models. The predicted values have been compared with the corresponding experimental observations. It is observed that the predicted life using bi-linear model and power curve model is in close agreement with the experimental values. Parametric studies on remaining life prediction have also been conducted by using modified bilinear model. A suitable value for constant

Key Words
concrete fracture; fatigue; tension softening; stress intensity factor; crack growth; remaining life.

Address
A. Rama Chandra Murthy*, G.S. Palani, Nagesh R. Iyer and Smitha Gopinath; Scientists, Structural Eng. Research Centre, CSIR Campus, Taramani, Chennai, India, 600-113


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com