Abstract
The current paper discusses the dynamic and stability responses of cross-ply composite laminated plates by
employing a refined quasi-3D trigonometric shear deformation theory. The proposed theory takes into consideration shear
deformation and thickness stretching by a trigonometric variation of in-plane and transverse displacements through the plate thickness and assures the vanished shear stresses conditions on the upper and lower surfaces of the plate. The strong point of the new formulation is that the displacements field contains only 4 unknowns, which is less than the other shear deformation theories. In addition, the present model considers the thickness extension effects (ez=/0). The presence of the Winkler-Pasternak elastic base is included in the mathematical formulation. The Hamilton's principle is utilized in order to derive the four differentials' equations of motion, which are solved via Navier's technique of simply supported structures. The accuracy of the present 3-D theory is demonstrated by comparing fundamental frequencies and critical buckling loads numerical results with those provided using other models available in the open literature.
Key Words
buckling; dynamic response; Hamilton
Address
Nasrine Belbachir: Civil Engineering Department, Faculty of Science and Technology, Abdelhamid Ibn Badis University, Mostaganem, Algeria; Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Fouad Bourada: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria; Science and Technology Department, Faculty of Science and Technology, Tissemsilt University, Algeria
Abdelmoumen Anis Bousahla: Laboratoire de Modélisation et Simulation Multi-Échelle, Université de Sidi Bel Abbés, Algeria
Abdelouahed Tounsi: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria; YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia; Interdisciplinary Research Center for Construction and Building Materials, KFUPM,31261 Dhahran, Saudi Arabia
Mohamed A. Al-Osta: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia; Interdisciplinary Research Center for Construction and Building Materials, KFUPM,31261 Dhahran, Saudi Arabia
Mofareh Hassan Ghazwani: Department of Mechanical Engineering, Faculty of Engineering, Jazan University, P.O Box 45124, Jazan, Kingdom of Saudia Arabia
Ali Alnujaie: Department of Mechanical Engineering, Faculty of Engineering, Jazan University, P.O Box 45124, Jazan, Kingdom of Saudia Arabia
Abdeldjebbar Tounsi: Industrial Engineering and Sustainable Development Laboratory, Faculty of Science & Technology, Mechanical Engineering Department, University of Relizane, Algeria
Abstract
The current investigation is the first endeavor to apply the full layerwise finite element method (FEM) in free vibration analysis of functionally graded (FG) composite plates reinforced with graphene nanoplatelets (GPLs) in thermal environment. Unlike the equivalent single-layer (ESL) theories, the layerwise FEM focuses on all three-dimensional (3D) effects. The GPLs weight fraction is presumed invariable in each layer but varies through the plate thickness in a layerwise model. The modified Halpin-Tsai model is employed to acquire the effective Young's modulus. The rule of mixtures is applied to specify the effective Poisson's ratio and mass density. First, the current method is validated by comparing the numerical results with those stated in the available works. Next, a thorough numerical study is performed to examine the influence of various factors involving the pattern of distribution, weight fraction, geometry, and size of GPLs, together with the thickness-tospan ratio, thermal environment, and boundary conditions of the plate, on its free vibration behaviors. Numerical results demonstrate that employing a small percentage of GPL as reinforcement considerably grows the natural frequencies of the pure epoxy. Also, distributing more square-shaped GPLs, involving a smaller amount of graphene layers, and vicinity to the upper and lower surfaces make it the most efficient method to enhance the free vibration behaviors of the plate.
Key Words
boundary conditions; finite element approach; full layerwise theory; functionally graded composite plate; graphene nanoplatelets; natural frequency
Address
Mohammad Sadegh Tayebi: Department of Mechanical Engineering, West Tehran Branch, Islamic Azad University, Tehran, Iran
Sattar Jedari Salami: Department of Biomedical Engineering, Central Tehran Branch, Islamic Azad University, Tehran, Iran
Majid Tavakolian: Department of Mechanical Engineering, West Tehran Branch, Islamic Azad University, Tehran, Iran
Abstract
Edible coatings are one of the most innovative methods to preserve the quality and increase the shelf life of fresh
fruits and vegetables. A successful edible coating should have a barrier against gases, especially oxygen and water vapor, and have good surface characteristics. Today, chitosan coating is widely used due to its properties, such as non-toxic, biodegradable, and biocompatibility. Is. Coating the surface of fruits and vegetables with chitosan increases shelf life due to reducing weight loss and reducing respiration rate and also reduces decay due to its antimicrobial and anti-fungal effect. This work discusses the effect of using chitosan coating containing chamomile extract to increase fresh vegetables' shelf life. In addition to increasing the shelf life of vegetables, this method can be used as a solution for the economic management of human resources. The results of this method confirm the successful synthesis of these nanoparticles, and the results of applying this food coating on vegetables have been successful. They have increased the shelf life of vegetables such as basil and spinach.
Key Words
economic management; human businesses; life span; vegetables
Address
Honglei Zhu: College of Economics and Management, Northeast Agricultural University, Harbin 150030, Heilongjiang, China
Duo Li: Institute of Education Sciences, Heilongjiang University, Harbin 150080, Heilongjiang, China
Abstract
A deep recursive bidirectional Cuda Deep Neural Network Long Short Term Memory (Bi-CuDNNLSTM) layer is recruited in this paper to predict the entire force time histories, and the corresponding hysteresis and backbone curves of reinforced concrete (RC) bridge piers using experimental fast and slow cyclic tests. The proposed stacked Bi-CuDNNLSTM layers involve multiple uncertain input variables, including horizontal actuator displacements, vertical actuators axial loads, the effective height of the bridge pier, the moment of inertia, and mass. The functional application programming interface in the Keras Python library is utilized to develop a deep learning model considering all the above various input attributes. To have a robust and reliable prediction, the dataset for both the fast and slow cyclic tests is split into three mutually exclusive subsets of training, validation, and testing (unseen). The whole datasets include 17 RC bridge piers tested experimentally ten for fast and seven for slow cyclic tests. The results bring to light that the mean absolute error, as a loss function, is monotonically decreased to zero for both the training and validation datasets after 5000 epochs, and a high level of correlation is observed between the predicted and the experimentally measured values of the force time histories for all the datasets, more than 90%. It can be concluded that the maximum mean of the normalized error, obtained through Box-Whisker plot and Gaussian distribution of normalized error, associated with unseen data is about 10% and 3% for the fast and slow cyclic tests, respectively. In recapitulation, it brings to an end that the stacked Bi-CuDNNLSTM layer implemented in this study has a myriad of benefits in reducing the time and experimental costs for conducting new fast and slow cyclic tests in the future and results in a fast and accurate insight into hysteretic behavior of bridge piers.
Key Words
bridge piers; fast and slow cyclic tests; NVIDIA CuDNN library; predicted backbone curves; predicted force time histories; predicted hysteresis curves; stacked bidirectional LSTM
Address
Omid Yazdanpanah, Minwoo Chang, Minseok Park: Department of Civil and Environmental Engineering, Myongji University, Yongin-si, Republic of Korea
Yunbyeong Chae: Department of Civil and Environmental Engineering, Seoul National University, Seoul, Republic of Korea
Abstract
The non-linear static analysis of reinforced concrete (RC) structures using the three-dimensional (3D) finite element
method is a time-consuming and challenging task. Moreover, this type of analysis encounters numerical problems such as the lack of convergence of results in the stages of growth and propagation of cracks in the structure. The time integration analysis along with the mass scaling (MS) technique is usually used to overcome these limitations. Despite the use of this method in the 3D finite element analysis of RC structures, a comprehensive study has not been conducted so far to assess the effects of the MS
method on the accuracy of results. This study aims to evaluate the accuracy of the MS method in the non-linear quasi-static finite element analysis of RC structures. To this aim, different types of RC structures were simulated using the finite element approach based on the implicit time integration method and the mass scaling technique. The influences of effective parameters of the MS method (i.e., the allowable values of increase in the mass of the RC structure, the relationship between the duration of the
applied load and fundamental vibration period of the RC structure, and the pattern of applied loads) on the accuracy of the simulated results were investigated. The accuracy of numerical simulation results has been evaluated through comparison with existing experimental data. The results of this study show that the achievement of accurate structural responses in the implicit time integration analyses using the MS method involves the appropriate selection of the effective parameters of the MS method.
Key Words
implicit time integration analysis; mass scaling; non-linear finite element; RC structures
Address
A. Yeganeh-Salman and M. Lezgy-Nazargah: Faculty of Engineering, Department of Civil Engineering, Hakim Sabzevari University, Sabzevar 9617976487-397, Iran
Abstract
Horizontally polarized shear waves (SH) have numerous applications in various scientific, engineering, and medical fields. The study deals with an investigation of SH-waves in a thin microstructural plate. The plate has been mathematically modelled by employing size dependent consistent couple stress theory, which involves a length parameter, known as characteristic length. Characteristic length is assumed to be of the order of internal microstructures of the material. Dispersion relations have been calculated for the propagation of SH-waves using different set of boundary conditions. Group velocity of the SH-waves has been calculated by using an analytical approach. The mathematical results obtained in the problem are discussed in detail and the impacts of characteristic length parameter and thickness of plate are presented on phase velocity of SH-waves through graphical illustrations.
Key Words
characteristic length; consistent couple stress theory; group velocity; plate waves; SH-waves
Address
Vikas Sharma: Department of Mathematics, Lovely Professional University, Phagwara, Punjab, India
Satish Kumar: School of Mathematics, Thapar Institute of Engineering and Technology, Patiala, Punjab, India
Abstract
This paper aims to better understand the bonding behavior in Reinforced Concrete beams strengthened with an Ultra-
High Performance Fiber Reinforced Concrete (RCUHPFRC) layer on the compression side using experimental tests and
numerical analyses. The UHPFRC mix design was obtained through an optimization procedure, and the characterization of the materials included compression and slant shear tests. Flexural tests were carried out in RC beams and RC-UHPFRC beams. The tests demonstrated a debonding of the UHPFRC layer. In addition, 3D finite element analyses were carried out in the Abaqus CAE program, in which the interface is modeled considering a zero-thickness cohesive-contact approach. The cohesive parameters are investigated, aiming to calibrate the numerical models, and a sensitivity analysis is performed to check the reliability of the assumed cohesive parameters and the mesh size. Finally, the experimental and numerical values are compared, showing a good approximation for both the RC beams and the RC strengthened beams.
Key Words
cohesive-contact modeling; debonding; experimental tests; numerical analysis; UHPFRC
Address
Thomaz E.T. Buttignol: Department of Structures, University of Campinas, Rua Saturnino de Brito, 224, Cidade Universitária Zeferino Vaz, Campinas, São Paulo, Brazil
Eduardo C. Granato, Túlio N. Bittencourt, Luís A.G. Bitencourt Jr.: Department of Structural and Geotechnical Engineering, Polytechnic School at the University of São Paulo, Av. Prof. Almeida Prado, Trav. do Biênio, 83, Universidade de São Paulo, USP, 05508-070, São Paulo, SP, Brazil
Abstract
The existing concrete bridges are time-varying working systems, where the maintenance strategy should be planned
according to the time-varying performance of the bridge. This work proposes a time-dependent residual capacity assessment procedure, which considers the non-stationary bridge load effects under growing traffic and non-stationary structural deterioration owing to material degradations. Lifetime bridge load effects under traffic growth are predicated by the nonstationary peaks-over-threshold (POT) method using time-dependent generalized Pareto distribution (GPD) models. The nonstationary structural resistance owing to material degradation is modeled by incorporating the Gamma deterioration process and field inspection data. A three-span continuous box-girder bridge is illustrated as an example to demonstrate the application of the proposed procedure, and the time-varying reliability indexes of the bridge girder are calculated. The accuracy of the proposed
non-stationary POT method is verified through numerical examples, where the shape parameter of the time-varying GPD model is constant but the threshold and scale parameters are polynomial functions increasing with time. The case study illustrates that the residual flexural capacities show a degradation trend from a slow decrease to an accelerated decrease under traffic growth and material degradation. The reliability index for the mid-span cross-section reduces from 4.91 to 4.55 after being in service for 100 years, and the value is from 4.96 to 4.75 for the mid-support cross-section. The studied bridge shows no safety risk under
traffic growth and structural deterioration owing to its high design safety reserve. However, applying the proposed numerical approach to analyze the degradation of residual bearing capacity for bridge structures with low safety reserves is of great significance for management and maintenance.
Address
Yuanyuan Liu: School of Civil Engineering, Guangzhou University, 230 West Waihuan Road, Guangzhou, Guangdong 510006, China; Research Centre for Wind Engineering and Engineering Vibration, Guangzhou University, 230 West Waihuan Road, Guangzhou, Guangdong 510006, China
Junyong Zhou: School of Civil Engineering, Guangzhou University, 230 West Waihuan Road, Guangzhou, Guangdong 510006, China
Jianxu Su, Junping Zhang: Earthquake Engineering Research & Test Center, Guangzhou University, 230 West Waihuan Road, Guangzhou, Guangdong 510006, China
Abstract
In this work, superharmonic and subharmonic resonance of rotating stiffened FGM truncated conical shells exposed to harmonic excitation in a thermal environment is investigated. Utilizing classical shell theory considering Coriolis acceleration and the centrifugal force, the governing equations are extracted. Non-linear model is formulated employing the von Kármán non-linear relations. In this study, to model the stiffener effects the smeared stiffened technique is utilized. The non-linear partial differential equations are discretized into non-linear ordinary differential equations by applying Galerkin's method. The method of multiple scales is utilized to examine the non-linear superharmonic and subharmonic resonances behavior of the conical shells. In this regard, the effects of the rotating speed of the shell on the frequency response plot are investigated. Also, the effects of different semi-vertex angles, force amplitude, volume-fraction index, and temperature variations on the frequencyresponse graph are examined for different rotating speeds of the stiffened FGM truncated conical shells.
Key Words
non-linear vibration; rotating shells; semi-analytical method; stiffened truncated conical shell; superharmonic and subharmonic resonance
Address
Hamid Aris and Habib Ahmadi: Faculty of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran
Abstract
Girdling underpinning joints are key areas of concern for the pier-cutting bridge-lifting process. In this study, five specimens of an underpinning joint were prepared by varying the cross-sectional shape of the respective column, the process used to treat the beam-column interface (BCI), and the casting process. These specimens were subsequently analyzed through static failure tests. The BCI was found to be the weakest area of the joint, and the specimens containing a BCI underwent punching shear failure. The top of the girdling beam (GB) was subjected to a circumferential tensile force during slippage failure. Compared to the specimens with a smooth BCI, the specimens subjected to chiseling exhibited more pronounced circumferential compression at the BCI, which in turn considerably increased the shear capacity of the BCI and the ductility of the structure. The GB for the specimens containing a column with a circular cross-section exhibited better shear mechanical properties than the GB of other specimens. The BCI in specimens containing a column with a circular cross-section was more ductile during failure than that in specimens containing a column with a square cross-section.
Key Words
beam-column interface (BCI); casting process; field static test; girdling beam (GB); mechanical performance
Address
Fangyuan Li, Wenhao Li and Peifeng Wu: Department of Bridge Engineering, Tongji University, Shanghai 200092, China
