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CONTENTS
Volume 7, Number 6, December 2010
 

Abstract
This work deals with the determination of crack openings in 2D reinforced concrete structures using the Finite Element Method with a smeared rotating crack model or an embedded crack model. In the smeared crack model, the strong discontinuity associated with the crack is spread throughout the finite element. As is well known, the continuity of the displacement field assumed for these models is incompatible with the actual discontinuity. However, this type of model has been used extensively due to the relative computational simplicity it provides by treating cracks in a continuum framework, as well as the reportedly good predictions of reinforced concrete members

Key Words
finite elements, fracture mechanics, smeared crack model, embedded crack model.

Address
Andre Luis Gamino: University of Campinas, 13083-852, Campinas, Brazil
Osvaldo Luis Manzoli: UNESP - Univ Estadual Paulista, 17030-360, Bauru, Brazil
Jose Luiz Antunes de Oliveira e Sousa: University of Campinas, 13083-852, Campinas, Brazil
Tulio Nogueira Bittencourt: University of Sao Paulo, 05508-900, Sao Paulo, Brazil

Abstract
For better estimation of elastic property of concrete composites, the effect of Interfacial Transition Zone (ITZ) has been found to be significant. Numerical concrete composites models have been introduced using Finite Element Method (FEM), where ITZ is modeled as a thin shell surrounding aggregate. Therefore, difficulties arise from the mesh generation. In this study, a numerical concrete composites model in 3D based on FEM and random unit cell method is proposed to calculate elastic modulus of concrete composites with ITZ. The validity of the model has been verified by comparing the calculated elastic modulus with those obtained from other analytical and numerical models.

Key Words
elastic modulus; ITZ; numerical concrete composites model; finite element method; random unit cell; composite materials.

Address
Said Abdelmoumen and Emmanuel Bellenger: LTI EA-3899, Universite de Picardie Jules Verne, IUT de l\'Aisne, 48 rue d\'Ostende, 02100 Saint-Quentin, France
Brandon Lynge: University of Tulsa, Mechanical Engineering Department, 600 South College Ave. Room L185 Keplinger Hall, Tulsa OK 74104-3189, USA
Michele Queneudec-t\'Kint: LTI EA-3899, Universite de Picardie Jules Verne, IUT de l\'Aisne, 48 rue d\'Ostende, 02100 Saint-Quentin, France

Abstract
A color based segmentation procedure and a modified signature technique have been applied to the detection and analyses of complicated void shapes in cemented materials. The gray-scale segmentation and available signature methods were found to be inefficient especially for the analyses of complicated void shapes. The applicability of the developed methodology has been demonstrated on artificially prepared cemented materials made of self compacted concrete material. In order to characterize the void shapes in the investigated sample images, two new shape parameters called as coefficients of inclusion and exclusion have been proposed. When compared with the traditional use of the signature method, it was found that the methodology followed herein would better characterize complicated void shapes. The methodology followed in this study may be applied to the analysis of complicated void shapes that are often encountered in other cementitious materials such as clays and rocks.

Key Words
void shape; color segmentation; image analysis; coefficients of inclusion and exclusion.

Address
Okan Onal, Gurkan Ozden and Burak Felekoglu: Dept. of Civil Engineering, Kaynaklar Yerleskesi, Buca-Izmir 35160, Turkey

Abstract
If an infill wall in a reinforced concrete frame is shorter than the column height and there is no initial gap between the column and the infill wall, the short column effect can occur during an earthquake shaking. This form of damage is frequently observed in many earthquake-damaged buildings all around the world and especially in Turkey. In this study, an effective method, which consists of placing additional infill wall segments surrounding the short column, to prevent this type of failure is examined. The influence of adding infill wall in the reduction of the shear force in the short column is also investigated. A parametric study is carried out for one-storey infilled frames with one to five bays using the percentage of the additional infill wall surrounding the short column and the number of spans as the parameters. Then the investigation is extended to a case of a multistorey building damaged due to short column effect during the 1998 Adana-Ceyhan earthquake in Turkey. The results show that the addition of the infill walls around the potential short columns is an effective way to significantly reduce the shear force.

Key Words
short column effect; dynamic analysis; earthquake damage; infill wall.

Address
Ismail H. Cagatay: Cukurova University, Civil Engineering Department, Adana, Turkey
Caner Beklen: Adana, Turkey
Khalid M. Mosalam: Dept. of Civil and Environmental Engineering, 733 Davis Hall, University of California, Berkeley, CA 94720-1710, USA

Abstract
Recent developments in concrete mixing made possible the production of concretes with high compressive strength showing, simultaneously, high workability. These concretes also present high strengths at young ages, allowing the application of loads sooner. It is of fundamental importance to verify if creep models developed for current concrete still apply to these new concretes. First, a FEM-based software was adopted to test available creep models, most used for normal strength concrete, considering examples with known analytical results. Several limitations were registered, resulting in an incorrect simulation of threedimensional creep. Afterwards, it was implemented a Kelvin-chain algorithm allowing the use of a chosen number of elements, which adequately simulated the adopted examples. From the comparison between numerical and experimental results, it was concluded that the adopted algorithm can be used to model creep of high strength concrete, if the material properties are previously experimentally assessed.

Key Words
high strength concrete; creep; numerical modeling; kelvin-chain.

Address
D. Dias-da-Costa and E.N.B.S. Julio: ISISE, Department of Civil Engineering, University of Coimbra, Rua Luis Reis Santos, Universidade de Coimbra - Polo II, 3030-290 Coimbra, Portugal

Abstract
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Key Words
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Address
In Tai Kim: Dept. of Transportation Engineering, Myungji University, San 38-2 Namdong, Yongin, 449-728, Korea
Chang Joon Lee: BK21 Research Division, School of Architecture and Civil Engineering, Kyungpook National University, 1370 Sangyuk-Dong, 702-701 Daegu, Korea
Cheolwoo Park: Dept. of Civil Engineering, Kangwon National University, 1 Choongang-ro, Samcheok, 245-711 Korea


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