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CONTENTS
Volume 57, Number 4, February25 2016
 

Abstract
In structural reliability analysis, the response surface method is widely adopted because of its numerical efficiency. It should be understood that the response function must approximate the actual limit state function accurately in the main region influencing failure probability where it is evaluated. However, the size of main region influencing failure probability was not defined clearly in current response surface methods. In this study, the concept of sub-region of interest is constructed, and an improved response surface method is proposed based on the sub-region of interest. The sub-region of interest can clearly define the size of main region influencing failure probability, so that the accuracy of the evaluation of failure probability is increased. Some examples are introduced to demonstrate the efficiency and the accuracy of the proposed method for both numerical and implicit limit state functions.

Key Words
structural reliability; response surface; sub-region of interest; failure probability

Address
Weitao Zhao, Xueyan Shi and Kai Tang: Key Laboratory of Liaoning Province for Composite Structural Analysis of Aerocraft and Simulation, Shenyang Aerospace University, Shenyang, 110-136, China

Abstract
In this study, a convenient formulation for the bending of laminated composite plates that hold non-homogeneous properties is examined. The constitutive equations of first order shear deformation plate theory are obtained using Hamilton Principle. The effect of non-homogeneity, lamination schemes and aspect ratio on the deflections and stresses is analysed. It is understood from the study that economical and optimum designs for laminated composite plates can be achieved by changing lamination scheme and by considering non-homogeneity response of composite plate.

Key Words
First Order Shear Deformation Theory (FSDT); laminated composite plate; non-homogeneous plates; non-homogeneity effect

Address
Zihni Zerina, Ferruh Turan and Muhammed Fatih Başoğlu: Department of Civil Engineering, Ondokuz Mayis University, 55139 Atakum, Samsun, Turkey

Abstract
In this work, an analytical formulation based on both hyperbolic shear deformation theory and stress function, is presented to study the nonlinear post-buckling response of symmetric functionally graded plates supported by elastic foundations and subjected to in-plane compressive, thermal and thermo-mechanical loads. Elastic properties of material are based on sigmoid power law and varying across the thickness of the plate (S-FGM). In the present formulation, Von Karman nonlinearity and initial geometrical imperfection of plate are also taken into account. By utilizing Galerkin procedure, closed-form expressions of buckling loads and post-buckling equilibrium paths for simply supported plates are obtained. The effects of different parameters such as material and geometrical characteristics, temperature, boundary conditions, foundation stiffness and imperfection on the mechanical and thermal buckling and post-buckling loading capacity of the S-FGM plates are investigated.

Key Words
functionally graded materials; post-buckling; hyperbolic shear deformation theory; elastic foundation; imperfection

Address
Abdelbaki Chikh: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
Ahmed Bakora: 1Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
Houari Heireche: Laboratoire de Modélisation et Simulation Multi-échelle, Université de Sidi Bel Abbés, Algeria
Mohammed Sid Ahmed Houari: 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; Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria
Abdelouahed Tounsi: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria ; Laboratoire de Modélisation et Simulation Multi-échelle, Université de Sidi Bel Abbés, Algeria; 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 ; Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria
E.A. Adda Bedia: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria

Abstract
Reinforced concrete frame buildings with masonry infill walls are one of the most popular structural systems in the world. In most cases, the effects of masonry infill walls are not considered in structural models. The results of earthquakes show that infill walls have a significant effect on the seismic response of buildings. In some cases, the buildings collapsed as a result of the formation of a soft story. This study developed a simple method, called corner opening, by replacing the corner of infill walls with a very flexible material to enhance the structural behavior of walls. To evaluate the proposed method a series of experiments were conducted on masonry infill wall and reinforced concrete frames with and without corner openings. Two 1:4 scale masonry infill walls with and without corner openings were tested under diagonal tension or shear strength and two RC frames with full infill walls and with corner opening infill walls were tested under monotonic horizontal loading up to a drift level of 2.5%. The experimental results revealed that the proposed method reduced the strength of infill wall specimens but considerably enhanced the ductility of infill wall specimens in the diagonal tension test. Moreover, the corner opening in infill walls prevented the slid shear failure of the infill wall in RC frames with infill walls.

Key Words
masonry infill wall; corner opening; reinforcement concrete frames; monotonic lateral load; experimental methods; earthquake engineering

Address
Hamid Reza Khoshnoud; Department of Civil Engineering, Islamic Azad University, Langroud Branch, Langroud, Iran
Kadir Marsono; Faculty of Civil Engineering, University of Technology of Malaysia, Skudai, Johor, Malaysia

Abstract
Reinforced concrete (RC) deep beams are structural members that predominantly fail in shear. Therefore, determining the shear strength of these types of beams is very important. The strut-and-tie method is commonly used to design deep beams, and this method has been adopted in many building codes (ACI318-14, Eurocode 2-2004, CSA A23.3-2004). In this study, the efficiency of artificial neural networks (ANNs) in predicting the shear strength of RC deep beams is investigated as a different approach to the strut-and-tie method. An ANN model was developed using experimental data for 214 normal and high-strength concrete deep beams from an existing literature database. Seven different input parameters affecting the shear strength of the RC deep beams were selected to create the ANN structure. Each parameter was arranged as an input vector and a corresponding output vector that includes the shear strength of the RC deep beam. The ANN model was trained and tested using a multi-layered back-propagation method. The most convenient ANN algorithm was determined as trainGDX. Additionally, the results in the existing literature and the accuracy of the strut-and-tie model in ACI318-14 in predicting the shear strength of the RC deep beams were investigated using the same test data. The study shows that the ANN model provides acceptable predictions of the ultimate shear strength of RC deep beams (maximum R2≈0.97). Additionally, the ANN model is shown to provide more accurate predictions of the shear capacity than all the other computed methods in this study. The ACI318-14-STM method was very conservative, as expected. Moreover, the study shows that the proposed ANN model predicts the shear strengths of RC deep beams better than does the strut-and-tie model approaches.

Key Words
artificial neural network; deep beam; shear strength; strut-and-tie model; reinforced concrete

Address
Engineering Faculty, Department of Civil Engineering, Selcuk University, Konya, Turkey

Abstract
This paper presents an experimental study of six steel reinforced high strength concrete T-shaped short-limb shear walls configured with T-shaped steel truss under low cyclic reversed loading. Considering different categories of ratios of wall limb height to thickness, shear/span ratios, axial compression ratios and stirrup reinforcement ratios were selected to investigate the seismic behavior (strength, stiffness, energy dissipation capacity, ductility and deformation characteristics) of all the specimens. Two different failure modes were observed during the tests, including the flexural-shear failure for specimens with large shear/span ratio and the shear-diagonal compressive failure for specimens with small shear/span ratio. On the basis of requirement of Chinese seismic code, the deformation performance for all the specimens could not meet the level of \"three\" fortification goals. Recommendations for improving the structural deformation capacity of T-shaped steel reinforced high strength concrete short-limb shear wall were proposed. Based on the experimental observations, the mechanical analysis models for concrete cracking strength and shear strength were derived using the equivalence principle and superposition theory, respectively. As a result, the proposed method in this paper was verified by the test results, and the experimental results agreed well with the proposed model.

Key Words
steel reinforced concrete (SRC); high strength concrete; short-limb shear wall; T-shaped wall; seismic behavior; deformation; cracking strength; shear strength

Address
Zongping Chen; College of Civil Engineering and Architecture, Guangxi University, Nanning, 530004, P.R. China; Key Laboratory of Disaster Prevention and Structural Safety of Chinese Education Ministry, Guangxi University, Nanning, 530004, P.R. China
Jinjun Xu; College of Civil Engineering and Architecture, Guangxi University, Nanning, 530004, P.R. China
Yuliang Chen; College of Civil Engineering and Architecture, Guangxi University, Nanning, 530004, P.R. China
Yisheng Su; College of Civil Engineering and Architecture, Guangxi University, Nanning, 530004, P.R. China

Abstract
In this paper, we have investigated shear horizontal wave propagation in a layered structure, consisting of granular macromorphic rock (Dionysos Marble) substrate underlying a viscoelastic layer of finite thickness. SH waves characteristics are affected by the material properties of both substrate and the coating. The effects of microstructural parameter \"characteristic length\" of the substrate, along with heterogeneity, internal friction and thickness of viscoelastic layer are studied on the dispersion curves. Dispersion equation for SH wave is derived. Real and damping phase velocities of SH waves are studied against dimensionless wave number, for different combinations of various parameters involved in the problem.

Key Words
SH waves; viscoelastic; couple stress; heterogeneity; characteristic length

Address
Vikas Sharma; Department of Mathematics, Lovely Professional University, Phagwara, Punjab, 144411, India
Satish Kumar: School of Mathematics, Thapar University, Patiala, Punjab, 147004, India



Abstract
In orthopedic surgery and more especially in total arthroplastie of hip, the fixing of the implants generally takes place essentially by means of constituted surgical polymer cement. The damage of this materiel led to the fatal rupture and thus loosening of the prosthesis in total hip, the effect of over loading as the case of tripping of the patient during walking is one of the parameters that led to the damage of this binder. From this phenomenon we supposed that a remain of bone is included in the cement implantation. The object of this work is to study the effect of this bony inclusion in the zones where the outside conditions (loads and geometric shapes) can provoke the fracture of the cement and therefore the aseptic lousing of the prosthesis. In this study it was assumed the presence of two bones –type inclusions in this material, one after we analyzed the effect of interaction between these two inclusions damage of damage to this material. One have modeled the damage in the cement around this bone inclusion and estimate the crack length from the damaged cement zone in the acetabulum using the finite element method, for every position of the implant under the extreme effort undergone by the prosthesis. We noted that the most intense stress position is around the sharp corner of the bone fragment and the higher level of damage leads directly the fracture of the total prosthesis of the hip.

Key Words
finite element method; bone cement; biomechanics; bony inclusion; damage parameter (length and area)

Address
Cherfi Mohamed, Benbarek Smail, Bachir Bouiadjra and B. Serier: Department of Mechanical Engineering, University of Sidi Bel Abbes, BP 89, cite Ben M\'hidi, Sidi Bel Abbes, 22000, Algeria

Abstract
Based on a reduced displacement field, a layer-wise (LW) formulation is developed for analysis of thick shell panels which is subjected to axial tension. Employing the principle of minimum total potential energy, the local governing equations of thick panel which is subjected to axial extension are obtained. An analytical method is developed for solution of the governing equations for various edge conditions. The governing equations are solved for free and simply supported edge conditions. The interlaminar stresses in the panel are investigated by means of Hooke\'s law and also by means of integration of the equilibrium equations of elasticity. Dependency of the result upon the number of numerical layers in the layerwise theory (LWT) is studied. The accuracy of the numerical results is validated by comparison with the results of the finite element method and with other available results in the open literature and good agreement is seen between the results. Numerical results are then presented for the distribution of interlaminar normal and shear stresses within the symmetric and un-symmetric cross-ply thick panels with free and simply supported boundaries. The effects of the geometrical parameters such as radius to thickness and width to thickness ratio are investigated on the distribution of the interlaminar stresses in thick panels.

Key Words
thick shell panel; interlaminar stresses; layerwise theory; cross-ply laminate; free edge; simply supported edge

Address
Advanced Materials and Computational Mechanics Lab.Department of Mechanical Engineering, University of Zanjan, P.O. Box: 45371-38791, Zanjan, Iran


Abstract
A methodology based on Teaching Learning-Based Optimization (TLBO) algorithm is proposed for optimum design of reinforced concrete retaining walls. The objective function is to minimize total material cost including concrete and steel per unit length of the retaining walls. The requirements of the American Concrete Institute (ACI 318-05-Building code requirements for structural concrete) are considered for reinforced concrete (RC) design. During the optimization process, totally twenty-nine design constraints composed from stability, flexural moment capacity, shear strength capacity and RC design requirements such as minimum and maximum reinforcement ratio, development length of reinforcement are checked. Comparing to other nature-inspired algorithm, TLBO is a simple algorithm without parameters entered by users and self-adjusting ranges without intervention of users. In numerical examples, a retaining wall taken from the documented researches is optimized and the several effects (backfill slope angle, internal friction angle of retaining soil and surcharge load) on the optimum results are also investigated in the study. As a conclusion, TLBO based methods are feasible.

Key Words
cantilever retaining wall; reinforced concrete structures; Teaching-Learning Based Optimization (TLBO); optimum design

Address
Rasim Temür and Gebrail Bekdaş: Department of Civil Engineering, Istanbul University, 34320 Istanbul, Turkey


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