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CONTENTS
Volume 49, Number 4, November 25 2023
 

Abstract
A size dependent bending behavior of piezoelectrical flexoelectric layered perforated functionally graded (FG) composite nanobeam rested on an elastic foundation is investigated analytically. The composite beam is composed of regularly cutout FG core and two piezoelectric face sheets. The material characteristics is graded through the core thickness by power law function. Regular squared cutout perforation pattern is considered and closed forms of the equivalent stiffness parameters are derived. The modified nonlocal strain gradient elasticity theory is employed to incorporate the microstructure as well as nonlocality effects into governing equations. The Winkler as well as the Pasternak elastic foundation models are employed to simulate the substrate medium. The Hamiltonian approach is adopted to derive the governing equilibrium equation including piezoelectric and flexoelectric effects. Analytical solution methodology is developed to derive closed forms for the size dependent electromechanical as well as mechanical bending profiles. The model is verified by comparing the obtained results with the available corresponding results in the literature. To demonstrate the applicability of the developed procedure, parametric studies are performed to explore influences of gradation index, elastic medium parameters, flexoelectric and piezoelectric parameters, geometrical and peroration parameters, and material parameters on the size dependent bending behavior of piezoelectrically layered PFG nanobeams. Results obtained revealed the significant effects both the flexoelectric and piezoelectric parameters on the bending behavior of the piezoelectric composite nanobeams. These parameters could be controlled to improve the size dependent electromechanical as well as mechanical behaviors. The obtained results and the developed procedure are helpful for design and manufacturing of MEMS and NEMS.

Key Words
analytical methodology; elastic substrate; functionally grade core; modified nonlocal strain gradient theory; piezoelectric flexoelectric face sheets; size dependent bending

Address
Ali Alnujaie:Mechanical Engineering Department, Faculty of Engineering, Jazan University, P. O. Box 45142, Jazan, Kingdom of Saudi Arabia

Alaa A. Abdelrahman:Mechanical Design & Production Department, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt

Abdulrahman M. Alanasari:Department of Mechanical Engineering, Faculty of Engineering, University of Business and Technology, Jeddah, Saudi Arabia

Mohamed A. Eltaher:Mechanical Engineering Department, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah, Saudi Arabia
5Department of Mechanical Design and Production, Faculty of Engineering, Zagazig University, Zagazig, Egypt

Abstract
This study experimentally investigates the flexural behavior of steel-UHPC composite slabs composed of an innovative negative Poisson's ratio (NPR) steel plate and Ultra High Performance Concrete (UHPC) slab connected via demountable high-strength bolt shear connectors. Eight demountable composite slab specimens were fabricated and tested under traditional four-point bending method. The effects of loading histories (positive and negative bending moment), types of steel plate (NPR steel plate and Q355 steel plate) and spacings of high-strength bolts (150 mm, 200 mm and 250 mm) on the flexural behavior of demountable composite slab, including failure mode, load-deflection curve, interface relative slip, crack width and sectional strain distribution, were evaluated. The results revealed that under positive bending moment, the failure mode of composite slabs employing NPR steel plate was distinct from that with Q355 steel plate, which exhibited that part of highstrength bolts was cut off, part of pre-embedded padded extension nuts was pulled out, and UHPC collapsed due to instantaneous instability and etc. Besides, under the same spacing of high-strength bolts, NPR steel plate availably delayed and restrained the relative slip between steel plate and UHPC plate, thus significantly enhanced the cooperative deformation capacity, flexural stiffness and load capacity for composite slabs further. While under negative bending moment, NPR steel plate effectively improved the flexural capacity and deformation characteristics of composite slabs, but it has no obvious effect on the initial flexural stiffness of composite slabs. Meanwhile, the excellent crack-width control ability for UHPC endowed composite members with better durability. Furthermore, according to the sectional strain distribution analysis, due to the negative Poisson's ratio effect and high yield strength of NPR steel plate, the tensile strain between NPR steel plate and UHPC layer held strain compatibility during the whole loading process, and the magnitude of upward movement for sectional plastic neutral axis could be ignored with the increase of positive bending moment.

Key Words
composite slab; cooperative deformation; flexural behavior; negative Poisson

Address
Jin-Ben Gu and Qing-Xuan Shi:College of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, 710055, China

Jun-Yan Wang:Key Laboratory of Advanced Civil Engineering Materials, Tongji University, Ministry of Education, Shanghai, 201804, China

Yi Tao:1)College of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, 710055, China
2)State Key Laboratory of Green Building, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, 710055, China

Abstract
In this paper, the energy absorption capability of a novel cruciform composite lattice structure was evaluated through the simulation of compression tests. For this purpose, several test samples of Polylactic acid cellular reinforced with continuous glass fibers were prepared for compression testing using the additive manufacturing method of material extrusion. Using a conventional path design for material extrusion, multiple debonding is probable to be occurred at the joint regions of adjacent cells. Therefore, an innovative printing path design was proposed for the cruciform lattice structure. Afterwards, quasistatic compression tests were performed to evaluate the energy absorption behaviour of this structure. A finite element model based on local material property degradation was then developed to verify the experimental test and extend the virtual test method. Accordingly, different combinations of unit cell' dimensions using the design of the experiment were numerically proposed to obtain the optimal configuration in terms of the total absorbed energy. Having brilliant energy absorption properties, the studied cruciform lattice with its optimized unit cell dimensions can be used as an energy absorber in crashworthiness applications. Finally, a cellular structure will be suitable with optimal behavior in crush load efficiency and high energy absorption.

Key Words
additive manufacturing; cruciform lattice; energy absorption; FEM

Address
Hussain Gharehbaghi and Amin Farrokhabadi:Department of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran

Abstract
After a disaster like the catastrophic earthquake, the government have to use rapid assessment of the condition (or damage) of bridges, buildings and other infrastructures is mandatory for rapid feedbacks, rescue and post-event management. Many domain schemes based on the measured vibration computations, including least squares estimation and neural fuzzy logic control, have been studied and found to be effective for online/offline monitoring of structural damage. Traditional strategies require all external stimulus data (input data) which have been measured available, but this may not be the generalized for all structures. In this article, a new method with unknown inputs (excitations) is provided to identify structural matrix such as stiffness, mass, damping and other nonlinear parts, unknown disturbances for example. An analytical solution is thus constructed and presented because the solution in the existing literature has not been available. The goals of this paper are towards access to adequate, safe and affordable housing and basic services, promotion of inclusive and sustainable urbanization and participation, implementation of sustainable and disaster-resilient buildings, sustainable human settlement planning and manage. Simulation results of linear and nonlinear structures show that the proposed method is able to identify structural parameters and their changes due to damage and unknown excitations. Therefore, the goal is believed to achieved in the near future by the ongoing development of AI and control theory.

Key Words
AI Kalman filter; benchmark structural control problem; damage resilience; fuzzy control; nonlinear analysis; nonlinear hysteretic structure

Address
ZY Chen, Ruei-yuan Wang and Yahui Meng:Guangdong University of Petrochemical Technology, School of Science, Maoming 525000, P.R. China

Timothy Chen:School of Science, Guangdong University of Petrochemical Technology, P.R. China

Abstract
This paper is aimed at investigating the effect of multiple longitudinal stiffeners on the patch loading resistance of slender steel plate girders. Firstly, a numerical study is conducted through geometrically and materially nonlinear analysis with imperfections included (GMNIA), the model is validated with experimental results taken from the literature. The structural responses of girders with multiple longitudinal stiffeners are compared to the one of girders with a single longitudinal stiffener. Thereafter, a patch loading resistance model is developed through machine learning (ML) using symbolic regression (SR). An extensive numerical dataset covering a wide range of bridge girder geometries is employed to fit the resistance model using SR. Finally, the performance of the SR prediction model is evaluated by comparison of the resistances predicted using available formulae from the literature.

Key Words
artificial intelligence; longitudinal stiffener; machine learning; multiple stiffeners; patch loading; resistance; symbolic regression

Address
Carlos Graciano:Departamento de Ingenieria Civil, Universidad Nacional de Colombia, Facultad de Minas, Sede Medellin, A.A. 75267, Medellin, Colombia

Ahmet Emin Kurtoglu:Department of Civil Engineering, Igdir University, Şehit Bulent Yurtseven Campus, 76000 Igdir, Turkey

Balazs Kovesdi:Budapest University of Technology and Economics, Faculty of Civil Engineering, Department of Structural Engineering, H-1111 Budapest, Muegyetem rkp. 3, Hungary

Euro Casanova:Universidad del Bío-Bío, Departamento Ingenieria Civil y Ambiental, Avenida Collao 1202, Concepcion, Codigo Postal 4051381, Chile

Abstract
The functionally graded (FG) porous plates are usually characterized by the non-symmetric elastic modulus distribution through the thickness so that the plate neutral surface does not coincide with the mid-surface. Nevertheless, the conventional analysis models were mostly based on the plate mid-surface so that the accuracy of resulting numerical results is questionable. In this context, this paper presents the neutral surface-based static and free vibration analysis of FG porous plates and investigates the differences between the mid- and neutral surface-based analysis models. The neutral surface-based numerical method is formulated using the (3,3,2) hierarchical model and approximated by the last introduced natural element method (NEM). The volume fractions of metal and ceramic are expressed by the power-law function and the cosine-type porosity distributions are considered. The proposed numerical method is demonstrated through the benchmark experiment, and the differences between two analysis models are parametrically investigated with respect to the thickness-wise material and porosity distributions. It is found from the numerical results that the difference cannot be negligible when the material and porosity distributions are remarkably biased in the thickness direction.

Key Words
deflection and fundamental frequency; functionally graded porous plate; hierarchical model; mid- and neutral surfaces; Natural element method (NEM); porosity distribution

Address
J.R. Cho:Department of Naval Architecture and Ocean Engineering, Hongik University, Sejong 30016, Korea

Abstract
Aiming at the development trend of light weight and high strength of engineering structures, this paper experimentally investigated the seismic performance of circular-in-square high-strength concrete-filled double skin steel tubular (HCFDST) stub columns with out-of-code width-to-thickness (B/t) ratios. Typical failure mode of HCFDST stub columns appeared with the infill material crushing, steel fracture and local buckling of outer tubes as well as the inner buckling of inner tubes. Subsequently, the detailed analysis on hysteretic curves, skeleton curves and ductility, energy dissipation, stiffness degradation and lateral force reduction was conducted to reflect the influences of hollow ratios, axial compression ratios and infill types, e.g., increasing hollow ratio from 0.54 to 0.68 and 0.82 made a slight effect on bearing capacity compared to the ductility coefficients; the higher axial compression ratio (e.g., 0.3 versus 0.1) significantly reduced the average bearing capacity and ductility; the HCFDST column SCFST-6 filled with concrete obviously displayed the larger initial secant stiffness with a percentage 34.20% than the column SCFST-2 using engineered cementitious composite (ECC); increasing hollow ratios, axial compression ratios could accelerate the drop speed of stiffness degradation. The out-of-code HCFDST stub columns with reasonable design could behave favorable hysteretic performance. A theoretical model considering the tensile strength effect of ECC was thereafter established and verified to predict the moment-resisting capacity of HCFDST columns using ECC. The reported research on circular-in-square HCFDST stub columns can provide significant references to the structural application and design.

Key Words
failure mode; high-strength CFDST stub columns; high-strength steel; out-of-code; seismic behavior; strength model

Address
Jian-Tao Wang and Juan Wang:1)School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, P. R. China
2)Key Lab of Structural Engineering and Earthquake Resistance, Ministry of Education (XAUAT), Xi'an 710055, P. R. China

Yue Wei:Water Conservancy Bureau of Jinchuan District, Jinchang 737100, P. R. China

Yu-Wei Li and Qing Sun:Department of Civil Engineering, Xi'an Jiaotong University, Xi'an 710054, P. R. China

Abstract
To make up for the performance weaknesses of recycled aggregate concrete (RAC), expand the application range of RAC, and alleviate the environmental problems caused by excessive exploitation of natural coarse aggregates (NCA), this study proposes a basalt fiber-reinforced recycled aggregate concrete (BFRRAC)-filled square steel tubular columns that combines two modification methods of steel tube and fiber, which may greatly enhance the mechanical properties of RAC. The axial compression performance for BFRRAC-filled square steel tubular columns was reported during this study. Seven specimens with different replacement ratios of recycled coarse aggregate (RCA), length-diameter ratios, along with basalt fiber (BF) contents were designed as well as fabricated for performing axial compression test. For each specimen, the whole failure process as well as mode of specimen were discovered, subsequently the load-axial displacement curve has obtained, after which the mechanical properties was explained. A finite element analysis model for specimens under axial compression was then established. Subsequently, based on this model, the factors affecting axial compression performance for BFRRAC-filled square steel tubes were extended and analyzed, after which the corresponding design suggestion was proposed. The results show that in the columns with length-diameter ratios of 5 and 8, bulging failure was presented, and the RAC was severely crushed at the bulging area of the specimen. The replacement ratio of RCA as well as BF content little affected specimen's peak load (less than 5%). As the content of BF enhanced from 0 kg/m3 to 4 kg/m3 , the dissipation factor and ductility coefficients increased by 10.2% and 5.6%, respectively, with a wide range.

Key Words
axial compression test; basalt fiber; finite element analysis; recycled aggregate concrete; square steel tube

Address
Xianggang Zhang:1)School of Intelligent Construction, Wuchang University of Technology, Wuhan 430223, China
2)School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454003, China


Jixiang Niu and Dapeng Deng:School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454003, China

Wenlong Shen:School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China

Yajun Huang:School of Intelligent Construction, Wuchang University of Technology, Wuhan 430223, China


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