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CONTENTS
Volume 42, Number 5, March10 2022
 

Abstract
The article deals with the possibilities of vibration stimulation. Based on the stability analysis, a multi-scale approach with a modified whole-building model is implemented. The motion equation is configured for a controlled bridge with a MDOF (multiple dynamic degrees of freedom) Tuned Mass Damper (M-TMD) system, and a combination of welding, excitation, and control effects is used with its advanced packages and commercial software submodel. Because the design of high-performance and efficient structural systems has been of interest to practical engineers, systematic methods of structural and functional synthesis of control systems must be used in many applications. The smart method can be stabilized by properly controlling the high frequency injection limits. The simulation results illustrate that the multiple modeling method used is consistent with the accuracy and high computational efficiency. The M-TMD system, even with moderate reductions in critical pressure, can significantly suppress overall feedback on an unregulated design.

Key Words
energy equations; structural control; tuned mass damper

Address
ZY Chen:School of Science, Guangdong University of Petrochemical Technology, Maoming 525000, Peoples R China

Yahui Meng:School of Science, Guangdong University of Petrochemical Technology, Maoming 525000, Peoples R China

Ruei-Yuan Wang:School of Science, Guangdong University of Petrochemical Technology, Maoming 525000, Peoples R China

Sheng-Hsiang Peng:Department of Civil and Environmental Engineering, University of California, Irvine, CA, 92697, U.S.A

Yaoke Yang:School of Computer Science, Zhongyuan University of Technology, Zhengzhou 450007, Peoples R China

Timothy Chen:Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, U.S.A.

Abstract
In the present paper, the numerical dynamic analysis of a functionally graded nano-scale nonuniform tube was investigated according to the high-order beam theory coupled with the nonlocal gradient strain theory. The supposed crosssection is changed along the pipe length, and the material distribution, which combines both metal and ceramics, is smoothly changed in the pipe length direction, which is called axially functionally graded (AFG) pipe. Moreover, the porosity voids are dispersed in the cross-section and the radial pattern that the existence of both material distribution along the tube length and porosity voids make a two-dimensional functionally graded (2D-FG) truncated conical pipe. On the basis of the Hamilton principle, the governing equations and the associated boundary conditions equations are derived, and then a numerical approach is applied to solve the obtained equations.

Key Words
2D-FG; AFG; dynamic analysis; nonlocal strain gradient theory; nonuniform pipe; porous material

Address
Ruihua Zhang:College of Mechanical Engineering, Nantong Vocational University, Nantong 226007, Jiangsu, China

Yiqing Cao: School of Mechanical and Electrical Engineering, Putian University, Putian 351100, Fujian, China


Abstract
To study the eccentric compressive performance of the basalt-fiber reinforced recycled aggregate concrete (BFRRAC)-filled circular steel tubular stub column, 8 specimens with different replacement ratios of recycled coarse aggregate (RCA), basalt fiber (BF) dosage, strength grade of recycled aggregate concrete (RAC) and eccentricity were tested under eccentric static loading. The failure mode of the specimens was observed, and the relationship curves during the entire loading process were obtained. Further, the load-lateral displacement curve was simulated and verified. The influence of the different parameters on the peak bearing capacity of the specimens was analyzed, and the finite element analysis model was established under eccentric compression. Further, the design-calculation method of the eccentric bearing capacity for the specimens was suggested. It was observed that the strength failure is the ultimate point during the eccentric compression of the BFRRAC-filled circular steel tubular stub column. The shape of the load-lateral deflection curves of all specimens was similar. After the peak load was reached, the lateral deflection in the column was rapidly increased. The peak bearing capacity decreased on enhancing the replacement ratio or eccentric distance, while the core RAC strength exhibited the opposite behavior. The ultimate bearing capacity of the BFRRAC-filled circular steel tubular stub column under eccentric compression calculated based on the limit analysis theory was in good agreement with the experimental values. Further, the finite element model of the eccentric compression of the BFRRAC-filled circular steel tubular stub column could effectively analyze the eccentric mechanical properties.

Key Words
basalt fiber; eccentric compression; experimental study; finite element analyses; recycled aggregate; concrete-filled steel tube; ultimate bearing capacity

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

Songpeng Zhang:School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454003, China

Junna Yang:School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454003, China/ School of Water Conservancy, North China University of Water Resources and Electric Power, Zhengzhou 450046, China

Xu Chen:School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454003, China

Gaoqiang Zhou:School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454003, China

Abstract
This paper presents the results from reliability analyses of the current Eurocode 4 (EN 1994-1-1) and AISC 360-16 design models for predicting the resistance of headed stud shear connectors within profiled steel sheeting, when the ribs are oriented transverse to the supporting beam. For comparison purposes, the performance of the alternative "Luxembourg" and "Stuttgart" model were also considered. From an initial database of 611 push-out tests, 269 cases were included in the study, which ensured that the results were valid over a wide range of geometrical and material properties. It was found that the current EN 1994-1-1 design rules deliver a corrected partial safety factor γM* of around 2.0, which is significantly higher than the target value 1.25. Moreover, 179 tests fell within the domain of the concrete-related failure design equation. Notwithstanding this, the EN 1994-1-1 equations provide satisfactory results for re-entrant profiled sheeting. The AISC 360-16 design equation for steel failure covers 263 of the tests in the database and delivers γM*≈2.0. Conversely, whilst the alternative "Stuttgart" model provides an improvement over the current codes, only a corrected partial safety factor of γM* =1.47 is achieved. Finally, the alternative "Luxembourg" design model was found to deliver the required target value, with a corrected partial safety factor γM* between 1.21 and 1.28. Given the fact that the Luxembourg design model is the only model that achieved the target values required by EN 1990, it is recommended as a potential candidate for inclusion within the second generation of Eurocodes.

Key Words
composite steel and concrete structures; design models; Eurocode 4; headed studs; partial safety factors; reliability; shear resistance; statistical evaluation

Address
Valentino Vigneri:Faculty of Science, Technology & Communication, University of Luxembourg, 6 Rue Richard CoudenhoveKalergi, 1359 Luxembourg, Luxembourg/ ETH Zurich, D-BAUG, Institute of Structural Engineering, 8093 Zürich, Switzerland

Stephen J. Hicks:University of Warwick, School of Engineering, Coventry, CV4 7AL, United Kingdom

Andreas Taras:ETH Zurich, D-BAUG, Institute of Structural Engineering, 8093 Zürich, Switzerland

Christoph Odenbreit:Faculty of Science, Technology & Communication, University of Luxembourg, 6 Rue Richard CoudenhoveKalergi, 1359 Luxembourg, Luxembourg

Abstract
In presented paper, moving load problem of simply supported axially functionally graded (AFG) beam is investigated under temperature rising based on the first shear beam theory. The material properties of beam vary along the axial direction. Material properties of the beam are considered as temperature-dependent. The governing equations of problem are derived by using the Lagrange procedure. In the solution of the problem the Ritz method is used and algebraic polynomials are used with the trivial functions for the Ritz method. In the solution of the moving load problem, the Newmark average acceleration method is used in the time history. In the numerical examples, the effects of material graduation, temperature rising and velocity of moving load on the dynamic responses ofAFG beam are presented and discussed.

Key Words
axially functionally graded material; moving load problems; Ritz Method; temperature effects

Address
Ş.D. Akbaş:Department of Civil Engineering, Bursa Technical University, 16330, Bursa, Turkey

Abstract
Structural materials can experience large plastic deformation under extreme cyclic loading that is caused by events like earthquakes. To evaluate the seismic safety of a structure, accurate numerical material models should be used. For a steel structure, the cyclic strain hardening behavior of structural steel should be correctly modeled. In this study, a combined hardening model, consisting of one isotropic hardening model and three nonlinear kinematic hardening models, was used. To determine the values of the combined hardening model parameters efficiently and accurately, the improved opposition-based particle swarm optimization (iOPSO) model was adopted. Low-cycle fatigue tests were conducted for three steel grades commonly used in Korea and their modeling parameters were determined using iOPSO, which was first developed in Korea. To avoid expensive and complex low cycle fatigue (LCF) tests for determining the combined hardening model parameter values for structural steel, empirical equations were proposed for each of the combined hardening model parameters based on the LCF test data of 21 steel grades collected from this study. In these equations, only the properties obtained from the monotonic tensile tests are required as input variables.

Key Words
combined hardening model; empirical equation; inelastic cyclic; low cycle fatigue test; model parameter; optimization; regression; structural steel

Address
Sang Whan Han:Department of Architectural Engineering, Hanyang University, Seoul 04673, Korea

Jungho Hyun:Department of Architectural Engineering, Hanyang University, Seoul 04673, Korea

EunSeon Cho:Department of Architectural Engineering, Hanyang University, Seoul 04673, Korea

Kihak Lee:Department of Architectural Engineering, Sejong University, Seoul 05006, Korea

Abstract
To investigate and predict the long-term time-dependent behavior, such as creep, shrinkage, and relaxation of PS strands, and prestress loss in prestressed steel–concrete composite beams, named Precom, full-scale tests were conducted and the collected data were compared with those obtained from the two proposed analytical models. The combined effective modulus method (EMM)-empirical model proposed with a flowchart considered the creep effect to determine the prestress loss. Conversely, the age-adjusted effective modulus method (AEMM) with CEB-FIP equation was developed to account for the concrete aging. The results indicated that the AEMM with CEB-FIP model predicts the long-term behavior of Precom effectively.

Key Words
AEMM with CEB-FIP equation; combined EMM-empirical model; long-term time-dependent behavior prestressed steel I-beam-concrete composite beam (Precom)

Address
Deokyong Sung:Department of Civil and Railroad Engineering, Daewon University College, 316 Daehak, Jecheon-si, Chungbuk 27135, Republic of Korea

Seongwon Hong:Department of Safety Engineering, Korea National University of Transportation,
50 Daehak-ro, Chungju-si, Chungbuk 27469, Republic of Korea

Abstract
In this paper, a vibration-based method using the change ratios of modal data and the experience-based learning algorithm is presented for quantifying the position, size, and interface layer of delamination in laminated composites. Three types of objective functions are examined and compared, including the ones using frequency changes only, mode shape changes only, and their combination. A fine three-dimensional FE model with constraint equations is utilized to extract modal data. A series of numerical experiments is carried out on an eight-layer quasi-isotropic symmetric (0/-45/45/90)s composited beam for investigating the influence of the objective function, the number of modal data, the noise level, and the optimization algorithms. Numerical results confirm that the frequency-and-mode-shape-changes-based technique yields excellent results in all the three delamination variables of the composites and the addition of mode shape information greatly improves the accuracy of interface layer prediction. Moreover, the EBL outperforms the other three state-of-the-art optimization algorithms for vibration-based delamination detection of composites. A laboratory test on six CFRP beams validates the frequency-and-mode-shape-changesbased technique and confirms again its superiority for delamination detection of composites.

Key Words
delamination detection; experience-based learning algorithm; finite element modeling; laminated composite structure

Address
Weili Luo:School of Civil Engineering, Guangzhou University, Guangzhou, P.R. China

Hui Wang:School of Civil Engineering, Guangzhou University, Guangzhou, P.R. China

Yadong Li:School of Civil Engineering, Guangzhou University, Guangzhou, P.R. China

Xing Liang:School of Civil Engineering, Guangzhou University, Guangzhou, P.R. China

Tongyi Zheng:School of Civil Engineering, Guangzhou University, Guangzhou, P.R. China

Abstract
This work presents a comprehensive study on the surface energy effect on the axial frequency analyses of AFGM nanorods in cylindrical coordinates. The AFGM nanorods are considered to be thin, relatively thick, and thick. In thin nanorods, effects of the inertia of lateral motions and the shear stiffness are ignored; in relatively thick nanorods, only the first one is considered; and in thick nanorods, both of them are considered in the kinetic energy and the strain energy of the nanorod, respectively. The surface elasticity theory which includes three surface parameters called surface density, surface stress, and surface Lame constants, is implemented to consider the size effect. The power-law form is considered for variation of the material properties through the axial direction. Hamilton's principle is used to derive the governing equations and boundary conditions. Due to considering the surface stress, the governing equation and boundary condition become inhomogeneous. After homogenization of them using an appropriate change of variable, axial natural frequencies are calculated implementing harmonic differential quadrature (HDQ) method. Comprehensive results including effects of geometric parameters and various material properties are presented for a wide range of boundary condition types. It is believed that this study is a comprehensive one that can help posterities for design and manufacturing of nano-electro-mechanical systems.

Key Words
free axial vibration; functionally graded materials; harmonic differential quadrature method; nanorod; surface energy

Address
Reza Nazemnezhad:School of Engineering, Damghan University, Damghan, Iran

Hassan Shokrollahi:Department of Mechanical Engineering, Faculty of Engineering, Kharazmi University, Tehran, Iran

Abstract
In this paper, hyperbolic shear deformation plate theory is developed for thermal buckling of functionally graded plates with porosity by dividing transverse displacement into bending and shear parts. The present theory is variationally consistent, and accounts for a quadratic variation of the transverse shearstrains across the thickness and satisfies the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factors. Three different patterns of porosity distributions (including even and uneven distribution patterns, and the logarithmic-uneven pattern) are considered. The logarithmic-uneven porosities for first time is mentioned. Equilibrium and stability equations are derived based on the present theory. The non-linear governing equations are solved for plates subjected to simply supported boundary conditions. The thermal loads are assumed to be uniform, linear and non-linear distribution through-the-thickness. A comprehensive parametric study is carried out to assess the effects of volume fraction index, porosity fraction index, aspect ratio and side-to-thickness ratio on the buckling temperature difference of imperfect FG plates.

Key Words
functionally graded materials; porosity; stability equations; thermal buckling

Address
Lazreg Hadji:Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City 70000, Vietnam/ Department of Civil Engineering, University of Tiaret, BP 78 Zaaroura, Tiaret, 14000, Algeria

Mohammadreza Amoozgar:School of Computing and Engineering, University of Huddersfield, Huddersfield HD1 3DH, U.K.

Abdelouahed Tounsi: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/ Material and Hydrology Laboratory, University of Sidi Bel Abbes 22000, Algeria

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