Abstract
This paper presents a careful theoretical investigation into interfacial stresses in composite aluminum-slab reinforced
concrete beam bonded by a prestressed hybrid carbon-glass composite material. The model is based on equilibrium and
deformations compatibility requirements in and all parts of the strengthened beam, i.e., the aluminum beam, the slab reinforced concrete, the hybrid carbon-glass composite plate and the adhesive layer. The theoretical predictions are compared with other existing solutions. Numerical results from the present analysis are presented both to demonstrate the advantages of the present solution over existing ones and to illustrate the main characteristics of interfacial stress distributions. It is shown that the stresses
at the interface are influenced by the material and geometry parameters of the composite beam. This research is helpful for the understanding on mechanical behaviour of the interface and design of the hybrid structures.
Key Words
adhesive bonding plate; aluminum-concrete composite beam; composite plate; interfacial stresses; shear lag
effect; slip; strengthening
Address
Rabahi Abderezak, Tahar Hassaine Daouadji and Bensatallah Tayeb: Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria; Department of Civil Engineering, Ibn Khaldoun University of Tiaret, Algeria
Abstract
This work presents a comparison between analytical and finite element analysis for bending of porous sandwich functionally graded material (FGM) plates. The plate is rectangular and simply supported under static sinusoidal loading. Material properties of FGM are assumed to vary continuously across the face sheets thickness according to a power-law function in terms of the volume fractions of the constituents while the core is homogeneous. Four types of porosity are considered. A refined higher-order shear with normal deformation theory is used. The number of unknowns in this theory is five, as against six or more in other shear and normal deformation theories. This theory assumes the nonlinear variation of transverse shear stresses and satisfies its nullity in the top and bottom surfaces of the plate without the use of a shear correction factor. The governing equations of equilibrium are derived from the virtual work principle. The Navier approach is used to solve equilibrium equations. The constitutive law of the porous FGM sandwich plate is implemented for a 3D finite element through a subroutine in FORTRAN (UMAT) in Abaqus software. Results show good agreement between the finite element model and the analytical method for some results, but the analytical method keeps giving symmetric results even with the thickness stretching effect and load applied to the top surface of the sandwich.
Key Words
Abaqus; FORTRAN (UMAT); porous sandwich functionally graded material (FGM) plates; the Navier
Address
Imad Benameur: Structures & Advances Materials Laboratory in Civil Engineering and Public Works, Faculty of Technology, Civil Engineering and Public Works Department, University of Sidi Bel Abbes, Algeria
Youcef Beldjelili: Structures & Advances Materials Laboratory in Civil Engineering and Public Works, Faculty of Technology, Civil Engineering and Public Works Department, University of Sidi Bel Abbes, Algeria
Abdelouahed Tounsi: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering and Public Works Department, University of Sidi Bel Abbes, 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
Abstract
The classical optimal control (COC) method has been widely used for linear quadratic regulator (LQR) problems of structural control. However, the equation of motion of the structure is incorporated into the optimization model as the constraint condition for the LQR problem, which needs to be solved through the Riccati equation under certain assumptions. In this study, an explicit optimal control (EOC) method is proposed based on the explicit time-domain method (ETDM). By use of the explicit formulation of structural responses, the LQR problem with the constraint of equation of motion can be transformed into an unconstrained optimization problem, and therefore the control law can be derived directly without solving the Riccati equation.
To further optimize the weighting parameters adopted in the control law using the gradient-based optimization algorithm, the sensitivities of structural responses and control forces with respect to the weighting parameters are derived analytically based on the explicit expressions of dynamic responses of the controlled structure. Two numerical examples are investigated to demonstrate the feasibility of the EOC method and the optimization scheme for weighting parameters involved in the control law.
Key Words
active control; explicit time-domain method; linear quadratic regulator; optimization; sensitivity analysis
Address
Taicong Chen: School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510640, China; State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou 510640, China; Guangdong Artificial Intelligence and Digital Economy Laboratory, Guangzhou 510335, China
Houzuo Guo: School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510640, China; Department of Civil and Environmental Engineering, University of Macau, Macao 999078, China
Cheng Su: School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510640, China; State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou 510640, China; Guangdong Artificial Intelligence and Digital Economy Laboratory, Guangzhou 510335, China
Abstract
The major objective of this paper is to study the receding contact problem between two functional graded layers under a flat indenter. The gravity is assumed negligible, and the shear moduli of both layers are assumed to vary exponentially along the thickness direction. In the absence of body forces, the problem is reduced to a system of Fredholm singular integral equations with the contact pressure and contact size as unknowns via Fourier integral transform, which is transformed into an algebraic one by the Gauss–Chebyshev quadratures and polynomials of both the first and second kinds. Then, an iterative speediest descending algorithm is proposed to numerically solve the system of algebraic equations. Both semi-analytical and
finite element method, FEM solutions for the presented problem validate each other. To improve the accuracy of the numerical result of FEM, a graded FEM solution is performed to simulate the FGM mechanical characteristics. The results reveal the potential links between the contact stress/size and the indenter size, the thickness, as well as some other material properties of FGM.
Key Words
finite element analysis; functionally graded material (FGM); receding contact; singular integral equation
Address
Cong Wang, Jie Yan: Intelligent Policing Key Laboratory of Sichuan Province, Sichuan Police College, Longtouguan Road No. 186 of Luzhou City, China
Rui Cao: Jiangsu Key Laboratory of Engineering Mechanics, School of Civil Engineering, Southeast University, Sipailou Road No.2 of Nanjing City, China
Abstract
The design of honeycomb sandwich structures is often challenging because these structures can be tailored from a variety of possible cores and face sheets configurations, therefore, the design of sandwich structures is characterized as a time-consuming and complex task. A data-driven computational approach that integrates the analytical method and Artificial Neural Network (ANN) is developed by the authors to rapidly predict the design of sandwich structures for a targeted maximum structural deflection. The elaborated ANN reverse design approach is applied to obtain the thickness of the sandwich core, the thickness of the laminated face sheets, and safety factors for composite sandwich structure. The required data for building ANN model were obtained using the governing equations of sandwich components in conjunction with the Monte Carlo Method. Then, the functional relationship between the input and output features was created using the neural network Backpropagation (BP) algorithm. The input variables were the dimensions of the sandwich structure, the applied load, the core density, and the maximum deflection, which was the reverse input given by the designer. The outstanding performance of reverse ANN model revealed through a low value of mean square error (MSE) together with the coefficient of determination (R2) close to the unity. Furthermore, the output of the model was in good agreement with the analytical solution with a maximum error 4.7%. The combination of reverse concept and ANN may provide a potentially novel approach in designing of sandwich structures. The main added value of this study is the elaboration of a reverse ANN model, which provides a low computational technique as well as saves time in the design or redesign of sandwich structures compared to analytical and finite element approaches.
Key Words
aluminum honeycomb core; ANN reverse design; Artificial Neural Network; laminated fiber reinforced plastic face sheets; Monte Carlo Method; sandwich structure
Address
Mortda M. Sahib: Faculty of Mechanical Engineering and Informatics, University of Miskolc, Hungary; Basrah Technical Institute, Southern Technical University, Basrah, Iraq
György Kovács: Faculty of Mechanical Engineering and Informatics, University of Miskolc, Hungary
Abstract
Based on first-order shear deformation theory, a wave propagation model of graphene platelets reinforced metal foams (GPLRMFs) circular plates is built in this paper. The expressions of phase-/group- velocities and wave number are obtained by using Laplace integral transformation and Hankel integral transformation. The effects of GPLs pattern, foams distribution, GPLs weight fraction and foam coefficient on the phase and group velocity of GPLRMFs circular plates are discussed in detail. It can be inferred that GPLs distribution have great impacts on the wave propagation problems, and Porosity-I type distribution has the largest phase velocity and group velocity, followed by Porosity-III, and finally Porosity-II; With the increase of the GPLs weight fraction, the phase- and group- velocities for the GPLRMFs circular plate will be increased; With the increase of the foam coefficient, the phase- and group- velocities for the GPLRMFs circular plate will be decreased.
Key Words
circular plate; graphene platelets reinforced metal foams; metal foams; phase velocity; group velocity; wave propagation
Address
Lei-Lei Gan, Jia-Qin Xu and Gui-Lin She: College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400044, China
Abstract
Reinforced concrete (RC) shear wall structures are one of the most widely used structural systems to resist seismic
loading all around the world. Although there have been several efforts to provide conceptually simple procedures to reasonably assess the seismic demands of structures over recent decades, it seems that lesser effort has been put on a number of structural forms such as RC shear wall structures. Therefore, this study aims to represent a simple linear response spectrum-based method which can acceptably predict the nonlinear displacements of a non-ductile RC shear wall structure subjected to an individual
ground motion record. An effective period and an equivalent damping ratio are introduced as the dynamic characteristics of an equivalent linear SDOF system relevant to the main structure. By applying the fundamental mode participation factor of the original MDOF structure to the linear spectral response of the equivalent SDOF system, an acceptable estimation of the nonlinear displacement response is obtained. Subsequently, the accuracy of the proposed method is evaluated by comparison with another approximate method which is based on linear response spectrum. Results show that the proposed method has better estimations for maximum nonlinear responses and is more utilizable and applicable than the other one.
Key Words
effective period; equivalent damping ratio; equivalent linear SDOF system; linear response spectrum;
maximum nonlinear displacement; non-ductile RC structure
Address
Saman Yaghmaei-Sabegh, Shabnam Neekmanesh: Department of Civil Engineering, University of Tabriz, Tabriz, Iran
Nelson Lam: Department of Infrastructure Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia
Anita Amirsardari: Centre for Smart Infrastructure and Digital Construction, Swinburne University of Technology, Melbourne, Victoria, Australia
Nasser Taghizadieh: Department of Civil Engineering, University of Tabriz, Tabriz, Iran
Abstract
In the present study, the limit point buckling and postbuckling behaviors of sinusoidal, shallow arches with pinned supports subjected to localized sinusoidal loading, based on the Euler-Bernoulli beam theory, are numerically analyzed. There are some studies on the buckling of sinusoidal shallow arches under the effect of sinusoidal loading. However, in these studies, the sinusoidal loading acts along the horizontal projection of the entire shallow arch. No study has been found in the relevant literature pertaining to the stability of the shallow arches subjected to various lengths of sinusoidal loading. Therefore, the purpose of this paper is to contribute to the literature by examining the effect of the length of the localized sinusoidal loading and the initial rise of the shallow arch on the limit point buckling and postbuckling behaviors. Equilibrium paths corresponding to certain values of the length of the localized sinusoidal loading and various values of the initial rise parameter are presented. It has been observed that the length of the sinusoidal loading and the initial rise parameter affects the transition from no buckling to limit point instability remarkably. The deformed configurations of the sinusoidal shallow arch under localized loading regarding buckling and postbuckling states are illustrated, as well. The effects of the length of the localized sinusoidal loading on the internal forces of the shallow arch are investigated during various stages of the loading.
Key Words
equilibrium path; limit point instability; localized sinusoidal loading; postbuckling; shallow arch
Address
Ayfer Tekin Atacan: Department of Civil Engineering, Yildiz Technical University, 34220, Istanbul, Turkey
Abstract
Many codes allow designers to use the bending moment diagram computed by elastic analysis and modify it by a certain amount of moment redistribution (MR) to account for plastic behaviour of continuous beams. However, several researchers indicated that the MR at the ultimate limit state (pu) for some beams deviate significantly from the specified values of various codes. This paper examines the applicability of the provisions on pu in ACI 318-19 and Eurocode 2 through numerical investigations and comprehensively explores the influencing factors. The results show that some parameters not considered in those codes influence pu to a certain extent, where the ratio of tensile reinforcement ratio at intermediate support to tensile reinforcement ratio at midspan (ps1/ps2) and load type are crucial parameters to consider. The specific combination of these two parameters may make the codes overestimate or significantly underestimate the pu. On the other hand, the yield state of both critical sections is found to have an important influence on the influence degree of each parameter on pu. The yield conditions are investigated, and an empirical judgment equation is proposed. In addition, the influence laws of the critical parameters on pu have been further proved by theoretical derivation. Finally, due to pt is found to have a better linear correlation with Bu than xu/d, equations as a function of pt for predicting the pu of continuous beams under the two loads are proposed, respectively.
Key Words
ACI 318-19; continuous beams; Eurocode 2; moment redistribution; yield conditions; yield state of both
critical sections
Address
Da Luo: School of Civil Engineering, Chang'an University, Xi'an, 710061, P.R. China
Zhongwen Zhang: Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, 210000, P.R. China
Bing Li: School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore
Abstract
In order to deeply reveal the working mechanism of ultra-high performance concrete (UHPC) filled steel tubular columns (UHPCFSTs) under cyclic loading, a three-dimension (3D) macro-mesoscale finite element (FE) model was established considering the randomness of steel fibers and the damage of UHPC. Model correctness and reliability were verified based on the experimental results. Next, the whole failure process of UHPC reinforced with steel fibers, passive confinement effect and internal force distribution laws were comprehensively analyzed and discussed. Finally, a simplified and practical method was proposed for predicting the ultimate bending strengths of UHPCFSTs. It was found that the non-uniform confinement effect of steel tube occurred when the drift ratio exceeded 0.5%, while the confining stress increased then decreased afterwards. There was preferable synergy between the steel tube and UHPC until failure. Compared with experimental results, the ultimate bending strengths of UHPCFSTs were undervalued by the current code provisions such as AISC360-10, EC4 and GB50936 with computed mean values (MVs) of 0.855, 0.880 and 0.836, respectively. The proposed practical method was highly accurate, as evidenced by a mean value of 1.058.
Key Words
cyclic behavior; macro-meso model; UHPCFST; ultimate bending strengths; working mechanism
Address
Heng Cai: School of Civil Engineering, Hubei Polytechnic University, Huangshi 435003, China; School of Civil Engineering, Wuhan University, Wuhan 430072, China
Fangqian Deng: School of Civil Engineering, Wuhan University, Wuhan 430072, China
