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CONTENTS
Volume 15, Number 3, March 2015
 

Abstract
To be able to understand the behavior of reinforced concrete (RC) members, cross sectional behavior should be known well. Cross sectional behavior can be best evaluated by moment-curvature relationship. On a reinforced concrete cross section moment-curvature relationship can be best determined by both experimentally or numerically with some complicated iteration methods. Making these experiments or iterations manually is very difficult and not practical. The aim of this study is to research the efficiency of Neural Networks (NN) as a more secure and robust method to obtain the moment-curvature relationship of circular RC columns. It is demonstrated that the NN based model is highly successful to determine the moment-curvature relationship of circular reinforced concrete columns.

Key Words
moment-curvature; circular RC column; neural networks; column behavior; confinement

Address
Naci Caglar, Aydin Demir and Hakan Ozturk: Department of Civil Engineering, Engineering Faculty, Sakarya University, 54187 Sakarya, Turkey

Abdulhalim Akkaya: Department of Civil Engineering, Technology Faculty, Sakarya University, 54187 Sakarya, Turkey

Abstract
In this scientific work, an improved analytical solution for adhesive stresses in a concrete beam bonded with the FRP plate is developed by including the effect of the adherend shear deformations. The analysis is based on the deformation compatibility approach where both the shear and normal stresses are assumed to be invariant across the adhesive layer thickness. The shear stress distribution is supposed to be parabolic across the depth of the adherends in computing the adhesive shear stress and Timoshenko\'s s beam theory is employed in predicting adhesive normal stress to consider the shear deformation. Numerical results from the present analysis are presented both to demonstrate the advantages of the present solution over existing ones and to illustrate the main characteristics of adhesive stress distributions.

Key Words
plated concrete beams; adhesive stress; shear deformation; FRP composites

Address
Mahmoud Touati and Abdelouahed Tounsi: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria

Abdelouahed Tounsi: Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics,
Université de Sidi Bel Abbes, Faculté de Technologie, Département de génie civil, Algeria

Mohamed Benguediab: Département de Mécanique, Faculté de Technologie, Université de Sidi Bel Abbes, Algeria

Abstract
This study reports the test results of twelve reinforced concrete deep beams. The deep beams were tested with loads applied through and supported by columns. The main variables studied were the shear span-to-depth ratios, and the horizontal and vertical stirrups. The shear strengths can be effectively enhanced for deep beams reinforced with both horizontal and vertical stirrups. The test results indicate the shear strengths of deep beams increase with the decrease of the shear span-to-depth ratios. The normalized shear strengths of the deep beams did not increase proportionally with an increase in effective depth. An analytical method for predicting the shear strengths of deep beams is proposed in this study. The shear strengths predicted by the proposed method and the strut-and-tie model of the ACI Code are compared with available test results. The comparison shows the proposed method can predict the shear strengths of reinforced concrete deep beams more accurately than the strut-and-tie model of the ACI Code.

Key Words
deep beams; shear strength; strut-and-tie

Address
Wen-Yao Lu, Chun-Liang Chen, Shu-Min Huang and Ming-Che Lin: Department of Interior Design, China University of Technology, Taipei 11695, Taiwan, R.O.C.


Hsin-Tai Hsiao: Department of Civil Engineering, China University of Technology, Taipei 11695, Taiwan, R.O.C.

Abstract
The development of a finite element model for the geometric and material nonlinear analysis of bonded prestressed concrete continuous beams is presented. The nonlinear geometric effect is introduced by the coupling of axial and flexural fields. A layered approach is applied so as to consider different material properties across the depth of a cross section. The proposed method of analysis is formulated based on the Euler-Bernoulli beam theory. According to the total Lagrangian description, the constructed stiffness matrix consists of three components, namely, the material stiffness matrix reflecting the nonlinear material effect, the geometric stiffness matrix reflecting the nonlinear geometric effect and the large displacement stiffness matrix reflecting the large displacement effect. The analysis is capable of predicting the nonlinear behaviour of bonded prestressed concrete continuous beams over the entire loading stage up to failure. Some numerical examples are presented to demonstrate the validity and applicability of the proposed model.

Key Words
prestressed concrete beams; finite element; material nonlinearity; geometric nonlinearity; behaviour

Address
Tiejiong Lou and Sergio M.R. Lopes: CEMUC, Department of Civil Engineering, University of Coimbra, Coimbra 3030-788, Portugal

Adelino V. Lopes: Department of Civil Engineering, University of Coimbra, Coimbra 3030-788, Portugal

Abstract
One of the most common applications of ferrocement is the manufacturing of thin stiffened plates which are prone to buckling. This study focuses on the investigation of the behavior of a ferrocement plate, stiffened in both directions by means of an appropriate grid of ribs. In the present paper detailed three-dimensional numerical Finite Element models are formulated for the simulation of the behavior of the structure under study, which are able to take into account both the geometric and material non-linearities that are present in the subject at hand (plasticity, cracking, large displacements). The difference among the formulated models lies on the use of different types of finite elements. The numerical results obtained by each model are compared and the most efficient model is determined. Finally, this model is in the sequel used for the further investigation of the effect of different parameters on the ultimate load capacity, such as the initial out-of-plane imperfection of the plate and the interaction between the axial loads in both directions.

Key Words
computational mechanics; construction materials; ferrocement; finite elements method; non-linear analysis

Address
Apostolos Koukouselis and Euripidis Mistakidis: Laboratory of Structural Analysis and Design, Department of Civil Engineering, University of Thessaly,
Pedion Areos, GR-38334 Volos, Greece

Abstract
In this work, a comprehensive approach to model the structural behaviour of Reinforced Concrete (RC) beams subjected to reinforcement corrosion is proposed. The coupled environmental – mechanical damage model developed by some of the authors is enhanced for considering the main effects of corrosion on concrete, on composite interaction between reinforcement bars and concrete and on steel reinforcement. This approach is adopted for reproducing a set of experimental tests on RC beams with different corrosion degrees. After the simulation of the sound beams, the main parameters involved in the relationships characterizing the effects of corrosion are calibrated and tested, referring to one degraded beam. Then, in order to validate the proposed approach and to assess its ability to predict the structural response of deteriorated elements, several corroded beams are analyzed. The numerical results show a good agreement with the experimental ones: in particular, the proposed model properly predicts the structural response in terms of both failure mode and load-deflection curves, with increasing corrosion level.

Key Words
damage model; non-linear analysis; reinforcement corrosion; cracked concrete cover

Address
Department of Architecture Construction and Conservation
University IUAV of Venezia, Dorsoduro 2206 - Venezia, 30123, Italy

Abstract
An experimental investigation on the behaviour of geopolymer composite concrete beams reinforced with conventional steel bars and various types of fibres namely steel, polypropylene and glass in different volume fractions under flexural loading is presented in this paper. The cross sectional dimensions and the span of the beams were same for all the beams. The first crack load, ultimate load and the load-deflection response at various stages of loading were evaluated experimentally. The details of the finite element analysis using \"ANSYS 10.0\" program to predict the load-deflection behavior of geopolymer composite reinforced concrete beams on significant stages of loading are also presented. Nonlinear finite element analysis has been performed and a comparison between the results obtained from finite element analysis (FEA) and experiments were made. Analytical results obtained using ANSYS were also compared with the calculations based on theory and presented.

Key Words
geopolymer; steel fibre; polyproylene fibre; glass fibre; volume fraction; ultimate load; finite element analysis.

Address
Vijai K and Kumutha R.: Department of Civil Engineering, Sethu Institute of Technology, Kariapatti, Tamilnadu, India

Vishnuram B.G.: P.S.R. Engineering College, Sivakasi, Tamilnadu, India

Abstract
The permeability is the most direct indicator to reflect the durability of concrete, and the testing methods based on external electric field can be used to evaluate concrete permeability rapidly. This study aims to use an experiment method to accurately predict the permeability of concrete box beam during service. The ion migration experiments and concrete surface resistivity are measured to evaluate permeability of five concrete box beams, and the relations between these results in service concrete and electric flux after 6 hours by ASTM C1202 in the laboratory are analyzed. The chloride diffusion coefficient of concrete, concrete surface resistivity and concrete 6 hours charge have good correlation relationship, which denote that the chloride diffusion coefficient and the surface resistivity of concrete are effective for evaluating the durability of concrete structures. The chloride diffusion coefficient of concrete is directly evaluated permeability of concrete box beam in service and may be used to predict the service life, which is fit to engineering applications and the concrete box beam is non-destructive. The concrete surface resistivity is easier available than the chloride diffusion coefficient, but it is directly not used to calculate the service life. Therefore the mathematical relation of the concrete surface resistivity and the concrete chloride diffusion coefficient need to be found, which the service life of reinforced concrete is obtained by the concrete surface resistivity.

Key Words
permeability; concrete beam; surface resistivity; chloride diffusion coefficient; in service

Address
Jia chun Wang: Department of Civil Engineering, Xiamen University of technology, Xiamen, 361024, China

Abstract
In this study, the availability of Schmidt hammer has been investigated as a reliable method to determine the quality of concrete in irrigation networks. For this purpose, the 28-day compressive strength of concrete material used in the construction irrigation channel of Bafra lowland, which is one of the most fertile plains in Turkey was examined by means of concrete compression and as well as concrete Schmidt hammer in laboratory conditions. This study was carried out on cylindrical samples to represent the everyday concrete party (150 m3) produced by contractor firm as 3 replications. The statistical analysis of experimental data showed that the correlations between the values of 28-day compressive strength of Schmidt hammer and the rebound number was found to be 0.98. Differences of the compressive strength between compression testing and Schmidt hammer were statistically significant at P<0.01. In this context, it was found that the reliability of compressive strength of the concrete compression test are excellent, also the reliability of compressive strength of Schmidt hammer are fair in assessing the quality of concrete irrigation channels.

Key Words
Irrigation channel; compressive strength; impact rebound hammer (IRH); non-destructive testing (NDT)

Address
Hakan Kibar: Department of Seed Science and Technology, Faculty of Agriculture and Natural Sciences,
Abant Izzet Baysal University, Bolu, Turkey

Turgut Öztürk: Department of Agricultural Structures and Irrigation, Faculty of Agriculture, Ondokuz Mayis University, Samsun, Turkey

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