Abstract
In the current article, the dual phase lag theory is used to discussed the waves propagations in poroelastic nanoscale
materials by the finite element method. Using the FEM to get the solutions of the complex formulation of the problem
numerically. The numerical accuracy is further improved by the implementation of quadratic interpolation functions. The
impacts of the thermal delay time and the porosity in a porothermal and elastic mediums are studied. The numerical outcomes for the components of displacement, the temperatures and the components of stress for the solid and liquid are represented graphically. Three theories of thermoelasticity viz. the Classical dynamical coupled (CT), Lord and Shulman (LS), and dualphase-lag (DPL) thermoelasticity theories are considered in this problem. the present analysis may have significant application
and contribution in areas utilizing the non-simples porothermoelastic with various phases in details.
Key Words
dual-phase-lag model; finite element method; poro-thermo-elastic medium
Address
Tareq Saeed: Nonlinear Analysis and Applied Mathematics Research Group (NAAM), Mathematics Department, King Abdulaziz University, Jeddah, Saudi Arabia
Ibrahim Abbas: Department of Mathematics, Faculty of Science, Sohag University, Sohag, Egypt
Abstract
Response surface (RS) methods, a combination of mathematical and statistical techniques, have been widely used in design optimization, response prediction, and model validation in structural engineering systems. However, its usage in structural damage identification, especially for historic structures has not been quite common. For this purpose, this study attempts to investigate damage detection in a masonry arch bridge. Within the scope of this, a reduced-scale model of a one span historical masonry arch bridge was built in a laboratory environment. To determine the modal parameters of the reduced-scaled
bridge model, operational modal analysis (OMA) was performed under ambient vibrations. Signals originated by sensitive accelerometers were collected to quantify the vibratory response of the reduced-scaled model bridge. The experimental natural frequencies, mode shapes, and damping ratios resulting from these measurements were figured out by using the Enhanced Frequency Domain Decomposition (EFDD) technique. The three-dimensional model of the reduced-scale bridge was created in the ANSYS finite element (FE) software program to expose the analytical dynamic characteristics of the bridge model. The results obtained in the experimental application were compared with those of the finite-element analysis of the bridge model. The calibration of the numeric model was utilized depending on the experimental modal analysis results of the reduced-scale
bridge by using the RS method. Design of experiments was constructed by using central composite design, and the RS models were generated by performing the genetic aggregation approach. The optimum results between the experimental and numerical analyses were found by using the RS optimization. Then, regional damages created on the scaled model and the changes of dynamic properties of the damaged case were evaluated. The damage location was approximately identified by using the RS method in the calibrated finite-element model. The results demonstrated that the RS-based FE updating approach is an effective way for damage detection and localization in masonry type structures.
Key Words
damage detection; enhanced frequency domain decomposition; finite element model updating; historical bridges; operational modal analysis; response surface method
Abstract
This study presents a comprehensive numerical dynamic finite element analysis to investigate the dynamic behavior and induced stresses of axially functionally graded rotating beam, for the first time. The material properties of the rotating beam are assumed to continuously vary nonlinearly along the longitudinal direction according to the power law. Based on Timoshenko beam theory (TBT), the Hamiltonian principle is applied to derive governing equations of motion. The dynamic finite element equation of motion for axially functionally straight rotating cantilever beam is derived. Both stress and vibration responses are detected and analyzed. The proposed computational procedure is verified by comparing the obtained results with the corresponding results in the literature and good agreement is observed. Effects of the material gradation index and the rotating speed on the dynamic behavior of functionally graded rotating cantilever are investigated and analyzed. The obtained results show the significant effect of the material gradation index and the rotating speed on the dynamic behavior of axially functionally graded beams. The proposed model can be used effectively in design of wind turbine, rotation shafts and turbomachinery systems.
Key Words
axially functionally graded; dynamic behavior; dynamic finite element; rotating cantilever; stress and vibration responses
Address
Khalid H. Almitani: Mechanical Engineering Department, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah, Saudi Arabia
M.A. Eltaher: Mechanical Engineering Department, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah, Saudi Arabia; Techanical Design & Production Department, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt
Alaa. A. Abdelrahman: Mechanical Design & Production Department, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt
Hanaa E. Abd-El-Mottaleb: Structural Engineering Department, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt
Abstract
In this research, an optimum equation is proposed for displacement estimation at the key point and key zone of powerhouse cavern sidewall in elasto-plastic condition based on the numerical experiments. Moreover, a new predictive equation is suggested to predict occurred displacement at the key point using the gene expression programming (GEP). Based on the numerical analyses (NA), the location of key point on the reciprocal longitudinal walls of the powerhouse cavern is studied. It was specified that for cavern with 33x52 m cross section, key point might be placed on the rock sidewall (left wall) or on the pillar side (right wall) of cavern. On the other hand, for cavern with 18x30 m cross section in various geo-engineering conditions, the key point was located on the rock sidewall. Verification of the proposed equations (from NA and GEP) were conducted using some case studies measurements which proved a good agreement of the new equations with the real values and showed the higher accuracy compared to the similar available equation. Finally, using warning levels of tunnel stability loss proposed by Sakurai, a new a system classification scheme is proposed for key point surrounding the powerhouse cavern based on the critical displacement.
Key Words
displacement; GEP; numerical analysis; powerhouse cavern; stability analysis
Address
Morteza Rajabi, Reza Rahmannejad: Department of Mining Engineering, Shahid Bahonar University of Kerman, Kerman, Iran
Mohammad Rezaei: Department of Mining Engineering, Faculty of Engineering, University of Kurdistan, Sanandaj, Iran
Abstract
In this paper, a multi-objective optimization of mixed convection air-cooling of two identical discrete heat sources mounted in an inclined channel is conducted to obtain the optimal design parameters, using Response Surface Methodology (RSM) and desirability function approach. Reynolds number (Re), inclination of the channel (r) and the width of the discrete heat source (b) are selected as the input parameters. The computational simulations are done for different Reynolds numbers (25-Re-250), inclination angles of the channel (0o-r-360o) and the width of the heat source (5-b-10 mm). A central composite design (CCD), which comes under the RSM approach, with design parameters was used for analysis of variance (ANOVA). A second-order regression models were developed to correlate the design parameters (Re, r and b) with mean Nusselt number (Nu) and maximum temperature (TMax). The optimum values of design parameters produce the lowest value of maximum temperature (TMax) with a higher mean Nusselt number (Nu) are Reynolds number (Re)=209.94, inclination angle of the channel (r)=330o and heat source width (b)=5.13 mm.
Key Words
air cooling; heat sources; mixed convection; multi-objective optimization; numerical simulation; RSM
Address
Moumtez Bensouici: Department of Science and Technology, Institute of Sciences and Technology, University Center of Mila, Mila 43000, Algeria; Laboratory of Applied Energetics and Pollution (LAEP), University of Constantine 1, Road of Ain El. Bey, Constantine 25000, Algeria
Mohamed Walid Azizi: Department of Science and Technology, Institute of Sciences and Technology, University Center of Mila, Mila 43000, Algeria; Advanced Technologies in Mechanical Production Research Laboratory (LRTAPM), BadjiMokhtar - Annaba University, P.O Box 12, 23000 Annaba, Algeria
Fatima Zohra Bensouici: Faculty of Pharmaceutical Process Engineering, University of Constantine 3, UVN05, Ali Mendjeli N V, Khroub, Constantine 25000, Algeria
Abstract
This study proposes DSTK, a new incompatible triangular element formulated from a combination of discrete shear
constraints, independent transverse shear strains and a free formulation approach. DSTK takes into account transverse shear effects and is valid for thin and thick plates. Furthermore, this element has 3 nodes and 3 DOFs per node (transverse displacement w and rotations Bx and By). The couple between lower order and higher order bending energy is assumed to be zero to fulfil the constant bending patch test. Unifying and integrating kinematic relationship, constitutive law, and equilibrium equations contribute to the independent transverse shear strain expression, which comprises merely the second derivatives of the rotations. The study performs validation based on individual element tests, patch tests, and convergence tests. This study shows that the DSTK element yields good results of various classical benchmark tests for thin to thick plates.
Abstract
Experimental and numerical studies have concluded that two of the main phenomena that govern the static response of damaged ropes and strands are the strain localization and asymmetry in damage distribution. In this paper, the dependency of the damage-tolerance properties and the accumulated damage level experienced up to the onset of failure on these two phenomena is investigated. To this end, a nonlinear model that couples the effects of these two phenomena is utilized to study the static response of damaged polyester ropes and metallic (steel and aluminium) strands. In particular, the residual stiffness, the residual strength, the reduction in the deformation capacity, and the accumulated damage, based on residual toughness values, are computed for a wide range of initial damage levels exerted on the ropes and strands. Experimental static tensile test data are used to validate the predictions provided by the nonlinear model in which initial damage levels and specimens diameters vary from 5% to 55% and 6mm to 166 mm respectively. Results indicate that the nonlinear model is capable of establishing the main phenomena that rules specimens response providing an accurate prediction of the damage tolerance-parameters and the damage level accumulated at the onset of specimens failure.
Key Words
asymmetry in damage distribution; damage-tolerance properties; nonlinear model; strain localization
Address
Juan F. Beltran and Tomas P. Bravo: Department of Civil Engineering, University of Chile, Blanco Encalada 2002, Santiago, Chile
Abstract
This study presents an optimal topology material distribution method in the framework of minimum compliance with a constraint on the total amount of multi-material using constant strain triangle (CST) elements and Moved and Regularized Heaviside Function (MRHF) filters. The sensitivity formulations for objective function and sensitivity for structures are derived in terms of multiphase design variables through triangle elements. Mathematical formulations of topology optimization problem solving the minimum compliance by using multiple materials are an alternating active-phase algorithm with a Gauss-Seidel version as an optimization model of optimality criteria. Moreover, MRHF that has the role of a filter in multiple materials is considered to produce obvious material distributions and improve the convergence of objective values. Some optimal topology results under the influence of rmin and filter are also investigated and verify the CST element-based multi-material topology optimization is appropriate to the use of MRHF and produces reasonable optimal results.
Key Words
constant strain triangle element (CST); finite element method; moved and regularized Heaviside function filter (MRHF); multiple materials; topology optimization
Address
Xuan Q. Nguyen, Thanh T. Banh and Dongkyu Lee: Department of Architectural Engineering, Sejong University, Seoul 05006, Republic of Korea
Abstract
The optimization conditions of the embedded nanocomposite multi-layer beams reinforced by ZnO nanoparticles are evaluated using a sinusoidal shear deformation theory. The adaptive improved harmony search (AIHS) optimization method is used as optimizer. Based on numerical method of differential quadrature, the buckling load is obtained. The optimum designs for nanocomposite reinforced sinusoidal multi-layer beams are evaluated using proposed AIHS based on the axial forces, applied voltage, volume fraction of ZnO nanoparticles, boundary conditions and geometrical parameters. The results demonstrated that optimum design conditions for a nanocomposite multi-layer beam under 50 GPa buckling constraint force are obtained as the length and thickness of multi-layer beam are 3.3326 m and 29.1125 cm. The applied voltage is the effective variables on the buckling of nanocomposite multi-layer beams.
Address
Bin Wang: Civil Engineering and Transportation Engineering, Yellow River Conservancy Technical Institute, Kaifeng 475004, Henan, China
Gongxing Yan: Scientific Research and Technical Service Office, Chongqing Vocational Institute of Engineering, Chongqing 402260, China
Seyedmahmoodreza Allahyari: Department of Mechanical Engineering, Dariun Branch, Islamic Azad University, Dariun, Iran
Abstract
The shear connector is the most important part of a composite beam and promotes a composite action between a steel beam and concrete slab. This paper presents the experiment results of three large-scale composite beams with a newly puzzle shaped crestbond rib shear connector. The behavior of this shear connector was investigated and the results were correlated with those obtained from the push-out-test specimens. Four-point-bending load testing was carried out on steelconcrete composite beam models to consider the effects of the concrete strength, number of transverse rebars in the crestbond and the width of the concrete slab. The results of large scale experimental test include of: the deflection, ultimate load, strains of the concrete, steel beam and Perfobond connectors; the relative slip between the steel beam and the concrete slab at the end of the beams; and the relative failure mechanism. The results showed that the general behavior of a steel-concrete composite beam using Perfobond shear connectors was similar to that of a steel-concrete composite beam using conventional shear connectors such as head stud shear connector. The newly puzzle shaped crestbond shear connectors showed satisfactory performance and could be considered for application in composite structures.
Key Words
composite behavior; crestbond rib shear connector; loading test; opposite steel beam; shear resistance formula
Address
Duy Kien Dao: Department of Civil Engineering, Ho Chi Minh City University of Technology and Education, 01 Vo Van Ngan street, Thu Duc District, Ho Chi Minh City, Vietnam
In-Tae Kim: School of Urban, Architecture and Civil Engineering, Pusan National University, 30 Jangjoen-dong, Geumjeong-gu, Busan 609-735, Korea
Haidang Phan: Institute of Theoretical and Applied Research, Duy Tan University, Hanoi 100000, Vietnam; Faculty of Civil Engineering, Duy Tan University, Danang 550000, Vietnam
