Abstract
In this paper, a quasi-3D hyperbolic shear deformation theory for the bending responses of a functionally graded
(FG) porous micro-beam is based on a modified couple stress theory requiring only one material length scale parameter that can capture the size influence. The model proposed accounts for both shear and normal deformation effects through an illustrative variation of all displacements across the thickness and satisfies the zero traction boundary conditions on the top and bottom surfaces of the micro-beam. The effective material properties of the functionally graded micro-beam are assumed to vary in the
thickness direction and are estimated using the homogenization method of power law distribution, which is modified to approximate the porous material properties with even and uneven distributions of porosity phases. The equilibrium equations are obtained using the virtual work principle and solved using Navier's technique. The validity of the derived formulation is established by comparing it with the ones available in the literature. Numerical examples are presented to investigate the influences of the power law index, material length scale parameter, beam thickness, and shear and normal deformation effects on
the mechanical characteristics of the FG micro-beam. The results demonstrate that the inclusion of the size effects increases the microbeams stiffness, which consequently leads to a reduction in deflections. In contrast, the shear and normal deformation effects are just the opposite.
Key Words
functionally graded micro-beam; material length scale parameter; modified couple stress theory; porosity;
shear and normal deformation effects
Address
Lemya Hanifi Hachemi Amar: Ecole Nationale Supérieure d'Ingénieurs de Bretagne Sud, Institut de Recherche Dupuy de Lôme (IRDL), UMR CNRS 6027, Centre de Recherche, Rue de Saint Maudé-BP 92116, 56321 Lorient Cedex, France; Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Sidi Bel Abbes, Algeria
Abdelhakim Kaci: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Sidi Bel Abbes, Algeria; Faculté de Technologie, Département de Génie Civil et Hydraulique, Université de Saida Dr. Tahar Moulay, BP 138 Cité En-Nasr 20000 Saida, Algérie
Aicha Bessaim: Laboratoire d'Etude des Structures et de Mécanique des Matériaux, Département de Génie Civil, Faculté des Sciences et de la Technologie, Université Mustapha Stambouli, Mascara 29000, Algérie
Mohammed Sid Ahmed Houari: Laboratoire d'Etude des Structures et de Mécanique des Matériaux, Département de Génie Civil, Faculté des Sciences et de la Technologie, Université Mustapha Stambouli, Mascara 29000, Algérie
Abdelouahed Tounsi: Faculté de Technologie, Département de Génie Civil et Hydraulique, Université de Saida Dr. Tahar Moulay, BP 138 Cité En-Nasr 20000 Saida, Algérie; YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea; Department of Civil and Environmental Engineering, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Eastern Province, Saudi Arabia
Abstract
Steel plate shear walls (SPSWs) are classified as lateral load-resisting systems. The feasibility of openings in the steel plate is a characteristic of SPSWs. The use of openings in SPSWs can lower the load capacity, stiffness, and energy dissipation. This study proposes a novel form of SPSWs that provides convenient access through openings by combining steel plates and eccentrically braced frames (EBFs). The proposed system also avoids a substantial reduction in the strength and stiffness. Hence, various geometric forms were analyzed through two different structural approaches. Groups 1, 2, and 3 included a steel EBF with a steel plate between the column and EBF in order to improve system performance. In Group 4, the proposed system was evaluated within an SPSW with openings and an EBF on the opening edge. To evaluate the performance of the proposed systems, the nonlinear finite element method (NL-FEM) was employed under cyclic loading. The hysteresis (load-drift) curve, stress contour, stiffness, and damping were evaluated as the structural outputs. The numerical models indicated that local buckling within the middle plate-EBF connection prevented a diagonal tension field. Moreover, in group 4, the EBF and stiffeners on the opening edge enhanced the structural response by approximately 7.5% in comparison with the base SPSW system.
Key Words
cyclic load; damping; eccentrically braced frame; finite element analysis; steel infill panel
Address
Reza Khalili Sarbangoli, Ahmad Maleki: Department of Civil Engineering, Maragheh Branch, Islamic Azad University, Maragheh, Iran
Ramin K. Badri: Department of Civil Engineering, Azarshahr Branch, Islamic Azad University, Azarshahr, Iran
Abstract
Slope stability is generally paid more attention to in slope protection works, especially for slope containing weak
layers. Two indexes of safety factor and failure model are selected to perform slope stability. Moreover, the finite element limit analysis method comprehensively combines the advantage of the limit analysis method and the finite element method obtaining the upper and lower bounds of the safety factor and the failure mode under the slope stability limit state. In this study, taking a waste dump containing a weak layer as an engineering background, the finite element limit analysis method is adopted to explore the potential failure mode. Meanwhile, the sensitivity analysis of slope stability is performed on geometrical and geotechnical parameters of the waste dump. The results show that the failure mode of the waste dump slope is two wedges if the
weak layer is located on the ground surface (Model A), while the slope can be observed as three wedges failure if the weak layer is below the ground surface (Model B). In addition, both failure modes are highly sensitive to the friction angle of the weak layer and the shear strength of waste disposal, and moderately sensitive to the heap height, the dip angle and cohesion of the weak layer, while the toe cutting has limited effect on the slope stability. Moreover, the sensitivity to the excavation of the ground depends on the location of the weak layer and failure mode.
Key Words
failure mode; finite element limit analysis; sensitivity analysis; slope stability of waste dump; weak layer
Address
Chong Chen: Ansteel Beijing Research Institute Co. Ltd., Beijing 102209, China
Huayong Lv: School of Architecture and Engineering, Shangqiu Normal University, Shangqiu 476000, China
Jianjian Zhao: Sinosteel Co. Ltd., Beijing 100080, China
Zhanbo Cheng: School of Engineering, University of Warwick, Coventry, CV47AL, UK
Huaiyuan Wang: Ansteel Beijing Research Institute Co. Ltd., Beijing 102209, China
Gao Xu: Railway Engineering Research Institute, China Academy of Railway Sciences Co. Ltd., Beijing 100081, China
Abstract
The sound radiation responses of multi-layer composite plates subjected to harmonic mechanical excitation in
hygrothermal environment is numerically investigated. A homogenized micromechanical finite element (FE) based on the
higher-order mid-plane kinematics replicating quadratic function as well as the through the thickness stretching effect together with the indirect boundary element (IBE) scheme has been first time employed. The isoparametric Lagrangian element (ten degrees of freedom per node) is used for discretization to attain the hygro-thermo-elastic natural frequencies and the modes of the plate via Hamilton's principle. The effective material properties under combined hygrothermal loading are considered via a
micromechanical model. An IBE method is then implemented to attain structure-surrounding coupling and the Helmholtz wave
equation is solved to compute the sound radiation responses. The effectiveness of the model is tested by converging it with the similar analytical/numerical results as well as the experimentally acquired data. The present scheme is further hold out for solving diverse numerical illustrations. The results revealed the relevance of the current higher-order FE-IBE micromechanical model in realistic estimation of hygro-thermo-acoustic responses. The geometrical parameters, volume fraction of fiber, layup, and support conditions alongside the hygrothermal load is found to have significant influence on the vibroacoustic characteristics.
Address
Binita Dash, Trupti R Mahapatra, Debadutta Mishra: Department of Production Engineering, Veer Surendra University of Technology, Burla, 768018, India
Punyapriya Mishra: Department of Mechanical Engineering, Veer Surendra University of Technology, Burla, 768018, India
Abstract
Machine learning (ML) models based on artificial neural network (ANN) and decision tree (DT) were developed for estimation of axial capacity of concrete columns reinforced with fiber reinforced polymer (FRP) bars. Between the design codes, the Canadian code provides better formulation compared to the Australian or American code. For empirical models based on elastic modulus of FRP, Hadhood et al. (2017) model performed best. Whereas for empirical models based on tensile strength of FRP, as well as all empirical models, Raza et al. (2021) was adjudged superior. However, compared to the empirical models, all ML models exhibited superior performance according to all five performance metrics considered. The performance of ANN and DT models were comparable in general. Under the present setup, inclusion of the transverse reinforcement information did not improve the accuracy of estimation with either ANN or DT. With selective use of inputs, and a much simpler ANN architecture (4-3-1) compared to that reported in literature (Raza et al. 2020: 6-11-11-1), marginal improvement in correlation could be achieved. The metrics for the best model from the study was a correlation of 0.94, absolute errors between 420 kN to 530 kN, and the range being 0.39 to 0.51 for relative errors. Though much superior performance could be obtained using ANN/DT models over empirical models, further work towards improving accuracy of the estimation is indicated before design of FRP reinforced concrete columns using ML may be considered for design codes.
Abstract
Concrete carbonation is a continuous and slow process from the outside to the inside, in which its penetration slows down with the increased depth of carbonation. In this paper, the results of the evaluation of the measurement of concrete carbonation depth using a non-destructive ultrasonic testing method are presented. According to the results, the relative nonlinear parameter caused more sensitivity in carbonation changes compared to Rayleigh's fuzzy velocity. Thus, the acoustic nonlinear parameter is expected to be applied as a quantitative index to recognize carbonation effects. In this research, combo diagrams were developed based on the results of ultrasonic testing and the experiment to determine carbonation depth using a phenolphthalein solution, which could be considered as instructions in the projects involving non-destructive ultrasonic test methods. The minimum and maximum accuracy of this method were 89% and 97%, respectively, which is a reasonable range for operational projects. From the analysis performed, some useful expressions are found by applying the regression analysis for the nonlinearity index and the carbonation penetration depth values as a guideline.
Key Words
carbonation; concrete; influenced parameters in carbonation; non-destructive test; ultrasonic test
Address
Javad Royaei, Fatemeh Nouban and Kabir Sadeghi: Department of Civil Engineering, Near East University, Lefkosa, Via Mersin 10, Turkey
Abstract
In this paper, the effect of semi-rigid connections on the stability bearing capacity of cross-bracings in steel tubular transmission towers is investigated. Herein, a prediction method based on the hybrid model which is a combination of particle swarm optimization (PSO) and backpropagation neural network (BPNN) is proposed to accurately predict the stability bearing capacity of cross-bracings with semi-rigid connections and to efficiently conduct its probabilistic assessment. Firstly, the establishment of the finite element (FE) model of cross-bracings with semi-rigid connections is developed on the basis of the development of the mechanical model. Then, a dataset of 7425 samples generated by the FE model is used to train and test the PSO-BPNN model, and the accuracy of the proposed method is evaluated. Finally, the probabilistic assessment for the stability bearing capacity of cross-bracings with semi-rigid connections is conducted based on the proposed method and the Monte Carlo simulation, in which the geometric and material properties including the outer diameter and thickness of cross-sections and the yield strength of steel are considered as random variables. The results indicate that the proposed method based on the PSOBPNN model has high accuracy in predicting the stability bearing capacity of cross-bracings with semi-rigid connections. Meanwhile, the semi-rigid connections could enhance the stability bearing capacity of cross-bracings and the reliability of crossbracings would significantly increase after considering semi-rigid connections.
Address
Zhengqi Tang: School of Civil Engineering, Chongqing University, Chongqing, China
Tao Wang: School of Transportation Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, China; Chongqing Research Institute of Harbin Institute of Technology, Harbin Institute of Technology, Chongqing, China
Zhengliang Li: School of Civil Engineering, Chongqing University, Chongqing, China
Abstract
Physical and chemical factors can cause traditional timber constructions to lose structural integrity. Knowing the dynamic properties of the building components is vital to avoid damage to the buildings from dynamic effects, a subset of physical effects. In this work, spruce and scotch pine wooden beams that had been strengthened in three distinct ways with carbon fiber strengthened polymer (CFRP) were investigated for changes in their dynamic properties. For this, CFRP was used to strengthening unstrengthened wooden beams in the form of bottom confinement, U-shaped confinement, and full confinement after the dynamic parameters of the beams were determined. By using experimental modal analysis with both freefree and fixed-fixed boundary conditions, the beams' initial natural frequencies were identified.
Key Words
composite strengthening; experimental modal analysis; finite element analysis; natural frequency; wooden beam
Address
Nur Sunar and Habib Uysal: Department of Civil Engineering, Ataturk University, Erzurum 25240, Turkey
