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CONTENTS
Volume 56, Number 1, October10 2015
 

Abstract
The main goal of this study was to develop a convenient strengthening technique for retrofitting of reinforced concrete members. For this purpose a new retrofitting material so-called prefabricated-HSPRCC (high performance steel plate reinforced cementitious composite) panel was developed by using high performance concrete and perforated steel plate. Prefabricated-HSPRCC composes advantages of steel and high performance concrete. The prefabricated-HSPRCC panels were either only bonded on the specimens using epoxy mortar or anchored to the specimen by steel bolts as well as bonding. Effect of different variations such as prefabricated-HSPRCC panel thicknesses, steel plate thicknesses, puncture orientation of perforated steel plate, existence of anchorage etc. were studied through a simple experimental work. The behaviour of the specimens under vertical point load was also studied by using simple mechanics. The retrofitted specimens were found to exhibit much better performance both in terms of strength and deformation capability. The anchorage application was found to positively affect this improved performance. Furthermore, as a result of the tests the best parameters of prefabricated-HSPRCC plate for improving strength and deformation capacities were determined.

Key Words
cement; concrete panel; confinement; ductility; steel plate reinforced cementitious composite; HSPRCC; retrofitting; shear

Address
Idris Bedirhanoglu: Department of Civil Engineering, Dicle University, 21280, Diyarbakir, Turkey

Abstract
In this study, the accuracy and reliability of fully nonlinear method against equivalent linear method for dynamic analysis of soil-structure interaction is investigated comparing the predicted results of both numerical procedures with the results of experimental shaking table tests. An enhanced numerical soilstructure model has been developed which treats the behaviour of the soil and the structure with equal rigour. The soil-structural model comprises a 15 storey structural model resting on a soft soil inside a laminar soil container. The structural model was analysed under three different conditions: (i) fixed base model performing conventional time history dynamic analysis, (ii) flexible base model (considering full soilstructure interaction) conducting equivalent linear dynamic analysis, and (iii) flexible base model performing fully nonlinear dynamic analysis. The results of the above mentioned three cases in terms of lateral storey deflections and inter-storey drifts are determined and compared with the experimental results of shaking table tests. Comparing the experimental results with the numerical analysis predictions, it is noted that equivalent linear method of dynamic analysis underestimates the inelastic seismic response of mid-rise moment resisting building frames resting on soft soils in comparison to the fully nonlinear dynamic analysis method. Thus, inelastic design procedure, using equivalent linear method, cannot adequately guarantee the structural safety for mid-rise building frames resting on soft soils. However, results obtained from the fully nonlinear method of analysis fit the experimental results reasonably well. Therefore, this method is recommended to be used by practicing engineers.

Key Words
soil-structure interaction; shaking table test; inelastic seismic response; equivalent linear method; fully nonlinear method; inelastic design procedure

Address
Hamid Reza Tabatabaiefar: School of Engineering and Information Technology, Federation University Australia, Australia
Behzad Fatahi: Centre for Built Infrastructure Research, School of Civil and Environmental Engineering, University of Technology Sydney (UTS), Australia
Kazem Ghabraie: School of Civil Engineering and Surveying, University of Southern Queensland, Australia
Wan-Huan Zhou: Department of Civil and Environmental Engineering, University of Macau, Macau, China

Abstract
Dynamic compaction (DC) is a useful method for improvement of granular soils. The method is based on falling a tamper (weighting 5 to 40 ton) from the height of 15 to 30 meters on loose soil that results in stress distribution, vibration of soil particles and desirable compaction of the soil. Propagation of the waves during tamping affects adjacent structures and causes structural damage or loss of performance. Therefore, determination of the safe or critical distance from tamping point to prevent structural hazards is necessary. According to FHWA, the critical distance is defined as the limit of a particle velocity of 76 mm/s. In present study, the ABAQUS software was used for numerical modeling of DC process and determination of the safe distance based on particle velocity criterion. Different variables like alluvium depth, relative density, and impact energy were considered in finite element modeling. It was concluded that for alluvium depths less than 10 m, reflection of the body waves from lower boundaries back to the soil and resonance phenomenon increases the critical distance. However, the critical distance decreases for alluvium depths more than 10 m. Moreover, it was observed that relative density of the alluvium does not significantly influence the critical distance value.

Key Words
dynamic compaction; numerical modeling; ABAQUS; cap plasticity model; critical distance; fourier amplitude; spectral acceleration

Address
Majid Pourjenabi and Amir Hamidi: School of Engineering, Kharazmi University, Tehran, Iran

Abstract
The load transfer mechanism and load-bearing capacity of cast steel joints for H-shaped beam to square tube column connection are studied based on the deformation compatibility theory. Then the monotonic tensile experiments are conducted for 12 specimens about the cast steel joints for H-shaped beam to square tube column connection. The findings are that the tensile bearing capacity of the cast steel joints for beam-column connection depends on the ring of cast steel stiffener. The tensile fracture happens at the ring of the cast steel stiffener when the joint fails. The thickness of square tube column has little influence on the bearing capacity of the joint. The square tube column buckles while the joint without concrete filled, but the strength failure happens for the joint with concrete filled column. And the length of welding connection between square tube column and cast steel stiffener has little influence on the load-bearing capacity of the cast steel joint. Finally it is shown that the load-bearing capacity of the joints for H-shaped beam to concrete filled square tube column connection is larger than that of the joints for H-shaped beam to square tube column connection by 10% to 15%.

Key Words
square tube column; cast steel joints; monotonic tensile experiment; load transfer mechanism; load-bearing capacity

Address
Qinghua Han and Yan Lu: School of Civil Engineering, Tianjin University, Tianjin 300072, China; Key Laboratory of Coast Civil Structure Safety of China Ministry of Education, Tianjin University, Tianjin 300072, China
Mingjie Liu: School of Civil Engineering, Tianjin University, Tianjin 300072, China

Abstract
Postbuckling of thick plates made of functionally graded material (FGM) subjected to in-plane compressive, thermal and thermomechanical loads is investigated in this work. It is assumed that the plate is in contact with a Pasternak-type elastic foundation during deformation. Thermomechanical nonhomogeneous properties are considered to be temperature independent, and graded smoothly by the distribution of power law across the thickness in the thickness in terms of the volume fractions of constituents. By employing the higher order shear deformation plate theory together the non-linear von- Karman strain-displacement relations, the equilibrium and compatibility equations of imperfect FGM plates are derived. The Galerkin technique is used to determine the buckling loads and postbuckling equilibrium paths for simply supported plates. Numerical examples are presented to show the influences of power law index, foundation stiffness and imperfection on the buckling and postbuckling loading capacity of the plates.

Key Words
functionally graded materials; postbuckling; higher order shear deformation theory; elastic foundation; imperfection

Address
Ahmed Bakora: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
Abdelouahed Tounsi: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Laboratoire des Structures et Materiaux Avances dans le Genie Civil et Travaux Publics, Universite de Sidi Bel Abbes, Faculte de Technologie, Departement de Genie Civil, Algeria; Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria

Abstract
The main objective of this research is to present the procedures of combining topology, shape & sizing optimization for truss structure by employing strain energy as objective function under the constraints of volume fractions which yield more general solution than that of total weight approach. Genetic Algorithm (GA) is used as searching engine for the convergence solution. A number of algorithms from previous research are used for evaluating the feasibility and stability of candidate to accelerate convergence and reduce the computational effort. It is followed by solving problem for topology & shape optimization and topology, shape & sizing optimization of truss structure to illustrate the feasibility of applying the objective function of strain energy throughout optimization stages.

Key Words
truss optimization; topology optimization; strain energy; Kinematic stability; genetic algorithm

Address
Xuan-Hoang Nguyen and Jaehong Lee: Department of Architectural Engineering, Sejong University, 98 Gunja Dong, Gwangjin Gu, Seoul 143-747, Republic of Korea

Abstract
The proposed techniques to repair concrete members such as steel plates, fiber-reinforced polymers or concrete have important deficiencies in adherence and durability. The use of ultra high performance fiber concrete (UHPFC) can overtake effectively these problems. In this paper, the possibility of using UHPFC to strengthen reinforced concrete beams under torsion is investigated. Seven specimens of concrete beams reinforced with longitudinal and transverse reinforcements. One of these beams consider as control specimen while the others was strengthened by UHPFC on four, three, and two sides. This study includes experimental results of all beams with different types of configurations and thickness of UHPFC. As well as, finite element analysis was conducted in tandem with experimental test. Results reveal the effectiveness of the proposed technique at cracking and ultimate torque for different beam strengthening configurations, torque - twist graphs and crack patterns. The UHPFC can generally be used as an effective external torsional reinforcement for RC beams. It was noted that the behavior of the beams strengthen with UHPFC are better than the control beams. This increase was proportional to the retrofitted beam sides. The use of UHPFC had effect in delaying the growth of crack formation. The finite element analysis is reasonably agreement with the experimental data.

Key Words
torsion; beam; strengthening; UHPFC; finite element analysis

Address
Thaer Jasim Mohammed: School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Pulau Pinang, Malaysia; Middle Technical University, Institute of Technology, Baghdad, Iraq
B.H. Abu Bakar and N. Muhamad Bunnori: School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Pulau Pinang, Malaysia

Abstract
In this paper, an analytical solution of displacement, strain and stress field for rotating thickwalled cylinder made of functionally graded material subjected to the uniform external magnetic field and thermal field in plane strain state has been studied. Stress, strain and displacement field as a function of radial coordinates considering magneto-thermo-elasticity are derived analytically. According to the Maxwell electro-dynamic equations, Lorentz force in term of displacement is obtained in cylindrical coordinates. Also, symmetric temperature distribution along the thickness of hollow cylinder is obtained by solving Fourier heat transfer equation in cylindrical coordinates. Using equation of equilibrium and thermomechanical constitutive equations associated with Lorentz force, a second-order inhomogeneous differential equation in term of displacement is obtained and will be solved analytically. Except Poisson\'s ratio, other mechanical properties such as elasticity modulus, density, magnetic permeability coefficient, heat conduction coefficient and thermal expansion coefficient are assumed to vary through the thickness according to a power law. In results analysis, non-homogeneity parameter has been chosen arbitrary and inner and outer surface of cylinder are assumed to be rich metal and rich ceramic, respectively. The effect of rotation, thermal, magnetic field and non-homogeneity parameter of functionally graded material which indicates percentages of cylinder\'s constituents are studied on displacement, Von Mises equivalent stress and Von Mises equivalent strain fields.

Key Words
analytical solution; functionally graded material; Magneto-thermo-elasticity; rotating thickwalled cylinder

Address
Mohammad Hosseini and Ali Dini: Department of Mechanical Engineering, Sirjan University of Technology, 78137-33385 Sirjan, I.R. Iran


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