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CONTENTS
Volume 82, Number 6, June25 2022
 


Abstract
This paper is devoted to the presentation of a numerical study on vibration behavior of composite panels reinforced by glass fibres and carbon nanotubes (CNTs) subjected to thermal environments. The effect of temperature variation has been included as thermal load acting on in-plane direction of the panel. To model the composite material, a micromechanical model which contains random dispersion of nanotubes and single-direction fibers has been selected. The geometry of the panel has been considered to have a single curveture along its width. Based on the above assumptions, the governing equations have been derived by using thin shell theory capturing the panel curveture and also nonlinear deflections. Finally, the panel dependence on various factors such as the curveture, nanotube amount, fiber volume, fiber direction and temperature variation has been researched.

Key Words
fibre-reiforced composite; numerical method; shell theory; thermal load; vibrations

Address
Mouayed H.Z. Al-Toki: Technical College, Middle Technical University, Baghdad, Iraq
Hayder A.K. Ali, Ridha A. Ahmed, Nadhim M. Faleh, Raad M. Fenjan: Engineering Collage, Al-Mustansiriah University, P.O. Box 46049, Bab-Muadum, Baghdad 10001, Iraq

Abstract
The nonlocal elasticity as well as Mindlin's first-order shear deformation plate theory are proposed to investigate thermal vibrational of a nanoplate placing on a three-factor foundation. The Winkler-Pasternak elastic foundation is connected with the viscous damping to obtain the present three-parameter viscoelastic model. Differential equations of motion are derived and resolved for simply-supported nanoplates to get their natural frequencies. The influences of the nonlocal index, viscous damping index, and temperature changes are investigated. A comparison example is dictated to validate the precision of present results. Effects of other factors such as aspect ratio, mode numbers, and foundation parameters are discussed carefully for the vibration problem. Additional thermal vibration results of nanoplates resting on the viscoelastic foundation are presented for comparisons with future investigations.

Key Words
nanoplate; natural frequencies; nonlocal; thermal vibration; visco-Pasternak

Address
Ashraf M. Zenkour: Department of Mathematics, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia; Department of Mathematics, Faculty of Science, Kafrelsheikh University, Kafrelsheikh 33516, Egypt

Abstract
Effects of coal tensile strength and plow configuration on the coal fragmentation process was modeled by twodimensional particles flow code (PFC2D). Three tensile strength values, 0.5, 1,5 and 3.5 MPa were considered in this numerical study. The cutters of plow penetrated in the coal for 4 mm at a rate of 0.016 m/s. According to the PFC manual, the local damping factor was 0.7. Three failure mechanism of coal during the fragmentation process by plow were modelled. The coal material beneath the cutters showed the elastic, plastic and fracturing behaviors in this analysis. In all the models, the plastic zone was fractured and some micro-cracks were induced but the elastic zone remained undamaged. It was observed that the tensile strength affected the failure mechanism of coal significantly and as it increased the extent of the fractured zone underneath the plow cutter decreased during the fragmentation process.

Key Words
coal plow; particle flow code; tensile strength

Address
Jinwei Fu, Hadi Haeri: School of Civil Engineering and Transportation, North China University of Water Resources and Electric Power, Zhengzhou,450046, China
Vahab Sarfarazi: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran
Mohammad Fatehi Marji: Mine Exploitation Engineering Department, Faculty of Mining and Metallurgy, Institution of Engineering, Yazd University, Yazd, Iran
Tong Li: School of Civil Engineering and Transportation, North China University of Water Resources and Electric Power, Zhengzhou,450046, China

Abstract
This work presents a simple exponential shear deformation theory for the flexural and free vibration responses of thick bridge deck. Contrary to the existing higher order shear deformation theories (HSDT) and the first shear deformation theory (FSDT), the proposed model uses a new displacement field which incorporates undetermined integral terms and involves only two variables. Governing equations and boundary conditions of the theory are derived by the principle of virtual work. The simply supported thick isotropic square and rectangular plates are considered for the detailed numerical studies. Results of displacements, stresses and frequencies are compared with those of other refined theories and exact theory to show the efficiency of the proposed theory. Good agreement is achieved of the present results with those of higher order shear deformation theory (HSDT) and elasticity theory. Moreover, results demonstrate that the developed two variable refined plate theory is simple for solving the flexural and free vibration responses of thick bridge deck and can achieve the same accuracy of the existing HSDTs which have more number of variables.

Key Words
free vibration; isotropic plates; refined plate theory; static flexure; transverse shear stresses

Address
Fatima Zohra Djidar: Smart Structures Laboratory, University of Ain Témouchent, Faculty of Science & Technology, Civil Engineering Department, Algeria
Habib Hebali: Material and Hydrology Laboratory, Civil Engineering Department, Faculty of Technology, University of Sidi Bel Abbes, Algeria; Civil Engineering Department, Faculty of Science & Technology, University of Mascara, Algeria
Khaled Amara: Engineering and Sustainable Development Laboratory, University of Ain Temouchent, Ain Temouchent 46000, Algeria
Abdelouahed Tounsi: Material and Hydrology Laboratory, Civil Engineering Department, Faculty of Technology, 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
7Interdisciplinary Research Center for Construction and Building Materials, KFUPM, 31261 Dhahran, Saudi Arabia
Boudjema Bendaho: Material and Hydrology Laboratory, Civil Engineering Department, Faculty of Technology, University of Sidi Bel Abbes, Algeria
M.H. Ghazwani: Department of Mechanical Engineering, Faculty of Engineering, Jazan University, P.O Box 45124, Jazan, Kingdom of Saudia Arabia
Muzamal Hussain: Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan

Abstract
The suspension thyristor valve can generate tremendous vertical acceleration responses in layers and large tension forces in hangers. A shaking table test of a scaled-down model of thyristor valves suspended on a hall building is performed to qualify the risk of vertical uplift of two representative types of valves, the chain valve and the rigid valve. Besides, an analytical model is established to investigate the source of the slackening of hangers. The test results show that the valves frequently experience a large vertical acceleration response. The soft spring joint can significantly reduce acceleration, but is still unable to prevent vertical uplift of the chain valve. The analytical model shows a stiffer roof and inter-story connection both contribute to a higher risk of vertical uplift for a rigid valve. In addition, the planar eccentricity and short hangers, which result in torsional motion of the valve, increase the possibility of vertical uplift for a chain valve. Therefore, spring joints with additional viscous dampers and symmetric layout in each layer are recommended for the rigid and chain valve, respectively, to prevent the uplift of valves.

Key Words
analytical model; hanger slackening; suspension structure; thyristor valve; vertical uplift

Address
Zhenyu Yang: Earthquake Engineering Research & Test Center, Guangzhou University, Guangzhou, China
Chang He: School of Civil Engineering, Central South University, Changsha, China
Khalid M. Mosalam: Department of Civil and Environmental Engineering and the Pacific Earthquake Engineering Research Center, University of California, Berkeley, USA
Qiang Xie: Department of Civil Engineering, Tongji University, Shanghai, China

Abstract
This study presents the nonlinear free and forced vibrations of a cracked atomic force microscopy (AFM) cantilever by using the modified couple stress. The cracked section of the AFM cantilever is considered and modeled as rotational spring. In the frame work of Euler-Bernoulli beam theory, Von-Karman type of geometric nonlinear equation and the modified couple stress theory, the nonlinear equation of motion for the cracked AFM is derived by Hamilton's principle and then discretized by using the Galerkin's method. The semi-inverse method is utilized for analysis nonlinear free oscillation of the system. Then the method of multiple scale is employed to investigate primary resonance of the system. Some numerical examples are presented to illustrate the effects of some parameters such as depth of the crack, length scale parameter, Tip-Mass, the magnitude and the location of the external excitation force on the nonlinear free and forced vibration behavior of the system.

Key Words
atomic force microscopy; crack; free and forced vibrations; nonlinear vibration

Address
M. Alimoradzadeh: Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
Ş.D. Akbaş: Department of Civil Engineering, Bursa Technical University, 16330, Bursa, Turkey

Abstract
For the design of flexural and shear crack control for reinforced concrete (RC) beams related to serviceability and reparability ensuring, eight simply-supported normal-strength reinforced concrete (NSRC) beam specimens are tested and the existing high-strength reinforced concrete (HSRC) experimental data are included in the investigation of this work. According to the investigation results of flexural and shear cracks, this works modifies the existing design formulas to determine the spacing of the tensile reinforcement for the flexural crack control of a HSRC/NSRC beam design. Additionally, for a specified shear crack width of 0.4 mm, the allowable stresses of the shear reinforcement are also identified. For the serviceability and reparability ensuring of HSRC/NSRC beams, this works proposes the relationship curves between the maximum flexural width and allowable stress of the tensile reinforcement, and the relationship curves between the shear crack width and allowable shear force that can be used to do the crack width control directly.

Key Words
beam; flexural crack; high-strength reinforced concrete; normal-strength reinforced concrete; reparability; serviceability; shear crack

Address
Chien-Kuo Chiu, Jodie Saputra and Muhammad Dachrez Tri Kurnia Putra: Department of Civil and Construction Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan

Abstract
Structural damage identification (SDI) methods have been proposed to monitor the safety of structures. However, the traditional SDI methods using modal parameters, such as natural frequencies and mode shapes, are not sensitive enough to structural damage. To tackle this problem, this paper proposes a new SDI method based on transmissibility assurance criterion (TAC) and weighted Schatten-p norm regularization. Firstly, the transmissibility function (TF) has been proved a useful damage index, which can effectively detect structural damage under unknown excitations. Inspired by the modal assurance criterion (MAC), TF and MAC are combined to construct a new damage index, so called as TAC, which is introduced into the objective function together with modal parameters. In addition, the weighted Schatten-p norm regularization method is adopted to improve the ill-posedness of the SDI inverse problem. To evaluate the effectiveness of the proposed method, some numerical simulations and experimental studies in laboratory are carried out. The results show that the proposed method has a high SDI accuracy, especially for weak damages of structures, it can precisely achieve damage locations and quantifications with a good robustness.

Key Words
modal assurance criterion; objective function; schatten-p norm regularization; structural damage identification; structural health monitoring; transmissibility function

Address
Xian Zhong and Ling Yu: MOE Key Laboratory of Disaster Forecast and Control in Engineering, School of Mechanics and
Construction Engineering, Jinan University, Guangzhou, Guangdong 510632, China

Abstract
The effect of earthquakes in earthquake resistant structure design stages is influenced by the highest ground acceleration value, which is generally a strength-based approach in seismic codes. In this context, an energy-oriented approach can be suggested as an alternative to evaluate structure demands. Contrary to the strength-based approach, the strength and displacement demands of the structure cannot be evaluated separately, but can be evaluated together. In addition, in the energyoriented approach, not only the maximum effects of earthquakes are taken into account, but also the duration of the earthquake. In this respect, it can be said that the use of energy-oriented earthquake parameters is a more rational approach besides being an alternative. In this study, strength and energy-oriented approaches of earthquake parameters of 11 different periods of single degree of freedom systems were evaluated over 28 different earthquake situations. The energy spectra intended to be an alternative to the traditional acceleration spectra were created using the acceleration parameter equivalent to the input energy. Two new energy parameters, which take into account the effective duration of the earthquake, are proposed, and the relationship between the strength-oriented spectral acceleration parameters and the energy parameters used in the literature is examined by correlation study. According to the results obtained, it has been seen that energy oriented earthquake parameters, which give close values in similar period situations, will be a good alternative to strength oriented earthquake parameters. It was observed that the energy parameters were affected by the effective duration of the earthquake, unlike the strength-based parameters. It has been revealed that the newly proposed energy parameters considering the effective duration give good correlations. Finally, it was concluded that the energy parameters can be used in the design, and the newly proposed effective energy parameters can shorten the analysis durations.

Key Words
arias intensity; effective duration; effective energy; energy based earthquake parameter

Address
Ömer Faruk Nemutlu: Civil Engineering Department, Faculty of Civil Engineering, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey; Civil Engineering Department, Faculty of Engineering and Architecture, Bingol University, 12000, Bingöl, Turkey
Ali Sari: 1Civil Engineering Department, Faculty of Civil Engineering, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey
Bilal Balun: Architecture Department, Faculty of Engineering and Architecture, Bingol University, 12000, Bingöl, Turkey

Abstract
To better promote the development of fabricated buildings, this paper studies the seismic behavior of precast concrete beam-column bolted joint under vertical low cyclic loading. The experimental results show that cracks appear in the beam-column joint core area. Meanwhile, the concrete and the grade 5.6 bolts are damaged and deformed, respectively. Specifically, the overall structure of the beam-column joint remains intact, and the bolts have good energy dissipation capacity. Based on the experimental study, a new method of beam-column bolted connection is proposed in simulation analysis. The simulation results show that the bolts deform in the core area of the new beam-column joint, which enhances the concrete shear capacity legitimately and protects the T-end of the beam against shear failure. To summarize, both the experimental joint and the simulated joint prolong the service life by replacing the bolts under the seismic loading. The research results provide a reference for applications of the fabricated beam-column joint.

Key Words
beam-column joint; energy dissipation capacity; prefabricated; seismic behavior

Address
Yu Zhang and Kewei Ding: School of Civil Engineering, Anhui Jianzhu University, Hefei, 230601, China


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