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CONTENTS
Volume 6, Number 2, April 2021
 


Abstract
This paper provides a numerical solution for null field complex variable boundary integral equation (CVBIE) in plane elasticity. All kernels in the null field CVBIE are regular function. An accurate shape function for the displacement and traction along the contour is suggested. With the usage of suggested shape function, a discretization for the boundary integral equation (BIE) is carried out. The Dirichlet and the Neumann boundary value problems (BVPs) for the interior region and the exterior region are studied. Two numerical examples are provided in the paper. It is shown that a higher accuracy has been achieved in the examples with the usage of the suggested shape function.

Key Words
null field formulation; complex variable boundary integral equation; interior BVP; exterior BVP; accurate shape function

Address
Y. Z. Chen:Division of Engineering Mechanics, Jiangsu University, Zhenjiang, Jiangsu, 212013 People's Republic of China

Abstract
Research is still ongoing to establish accurate models to predict the ultimate capacity of carbon fiber reinforced polymer (CFRP) repaired Reinforced Concrete (RC) beams, despite the numerous studies that have been conducted in this area. Previous studies suggested that more research is needed to better understand concrete behavior at flexural and shear, as well as the interaction between RC beams and externally bonded CFRP sheets. This study aims to experimentally validate the equations provided by the ACI 440.2 code for calculating the ultimate flexural and shear capacity of damaged RC beams repaired with CFRP sheets. The two design criteria for flexural capacity are the minimum and maximum steel ratios. Likewise, the two design criteria for shear capacity are having and not having shear stirrups. Moreover, two shear locations are investigated as the shear capacity at the quarter-span and shear capacity at 1.5d (d is the beam depth from supports). Finally, modified models are proposed to calculate the flexural and shear capacities, considering the contributions from other parameters to better correlate with the experimental results. The study concluded that the current ACI models result in differences from experimental results of up to 21%, 64% and 25% for flexural capacity, shear capacity at quarter-span and shear capacity at 1.5d, respectively. The modified models result in differences from experimental models of 6.9%, 2% and 7.3% for flexural capacity, shear capacity at quarter-span and shear capacity at 1.5d, respectively.

Key Words
CFRP repair; flexural capacity; shear capacity; contribution factors; concrete reduction factor; RC structures; design criteria; damage location

Address
Moatasem:
1) Engineering Services & Asset Management, John Holland Group, 2150 NSW, Australia
2) Department of Civil Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

Abstract
The use of externally bonded composite materials for strengthening reinforced concrete structures has received considerable attention in recent years. Since, concrete is a relatively fragile material and will fail when subject to the influence of many factors whose origins can be mechanical, physicochemical and accidental or related to the design and miscalculations. The bonding of FRP plate to reinforced concrete structure, appeared in the middle of the fourtwenties years, proves to be a promising and fully justified technique. In this paper, an analysis and modeling of the concentrations of interfacial stresses in a damaged reinforced concrete beam strengthening in bending by an imperfect FGM plate, was presented, based on a development of a mathematical formulation taking into account the theory of beams. The theoretical predictions are compared with other existing solutions. This research is helpful for the understanding on mechanical behaviour of the interface and design of the imperfect FGM – damaged RC hybrid structures.

Key Words
interfacial stresses; damaged RC beam; strengthening; imperfect FGM plate

Address
Rabahi Abderezak: Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria

Tahar Hassaine Daouadji:Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria

Benferhat Rabia:Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria

Abstract
Flow through the rectangular side weir is a spatially varied type flow with decreasing discharge and used as a flow diversion structure. They are mainly used in the field of hydraulic, irrigation, and environmental engineering for diverting and controlling the flow of water in irrigation–drainage systems, drainage canal systems, and wastewater channels. In this study, gene expression programming and group method of data handling were used to estimate the coefficient of discharge for rectangular side weir under subcritical flow condition. Based on dimensional analysis, the coefficient of the discharge depends on the ratio of the crest height to length, ratio of the width of channel to crest length, ratio of the upstream depth in the channel to crest length and the approach Froude number. The performance of the proposed GMDH and GEP model is based on the coefficient of correlation (0.91), mean absolute percentage error (3.54), average absolute deviation (3.3), root mean square error (0.027) and the coefficient of correlation (0.905), mean absolute percentage error (4.12) average absolute deviation (3.9), root mean square error (0.029), respectively. Finally, the results reveal that GMDH model could provide more satisfactorily estimations as compared to those obtained by traditional regression and GEP models.

Key Words
rectangular side weir; coefficient of discharge; froude number; GMDH; GEP

Address
Ajmal Hussain:Department of Civil Engineering, Zakir Hussain College of Engineering & Technology, Aligarh Muslim University, Aligarh-202002, India

Ali Shariq:Department of Civil Engineering, Zakir Hussain College of Engineering & Technology, Aligarh Muslim University, Aligarh-202002, India

Mohd Danish:Department of Civil Engineering, Zakir Hussain College of Engineering & Technology, Aligarh Muslim University, Aligarh-202002, India

Mujib A. Ansari:Civil Engineering Section, University Polytechnic, Aligarh Muslim University, Aligarh-202002, India

Abstract
The present paper is concerned with analysis of two longitudinal cracks in a viscoelastic inhomogeneous cantilever beam. The loading of the beam is applied by two stages. At the first stage, the strains increase with time at a constant speed up to a given magnitude. At the second stage, the strains remain constant with time. The viscoelastic behavior of the beam is described by using a viscoelastic model with a linear spring in series with a linear dashpot and a second linear dashpot connected parallel to the spring and the first dashpot. Stress-strain-time relationships of the viscoelastic model are derived for both stages (at increasing strain and at constant strain with time). Time-dependent strain energy release rates are obtained for both longitudinal cracks by analyzing the balance of the energy. Solutions to the time-dependent strain energy release rate are derived also by considering the time-dependent strain energy stored in the beam structure. The solutions are used to analyze the change of the strain energy release rate with time at both stages of loading.

Key Words
longitudinal crack; viscoelastic beam; inhomogeneous material; time-dependent strain; analytical study

Address
Victor I. Rizov: Department of Technical Mechanics, University of Architecture, Civil Engineering and Geodesy, 1 Chr. Smirnensky blvd., 1046 – Sofia, Bulgaria


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