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CONTENTS
Volume 76, Number 1, October10 2020
 

Abstract
The aim of this paper is to simply present live load factor calculation methodology formulation with the addition of a simple new future load projection procedure to previously proposed two methods. For this purpose, Oregon Weigh-in-Motion (WIM) data were used to calculate live load factors by using WIM data. These factors were calculated with two different approaches and by presenting new simple modifications in these methods. A very simple future load projection method is presented in this paper. Using four different WIM sites with different average daily truck traffic (ADTT) volume, and all year data, live load factors were obtained. The live load factors, were proposed as a function of ADTT. ADTT values of these sites correspond to three different levels which are approximately ADTT= 5,000, ADTT = 1,500 and ADTT ≤ 500 cases. WIM data for a full year were used from each site in the calibration procedure. Load effects were projected into the future for the different span lengths considering five-year evaluation period and seventy-five-years design life. The live load factor for ADTT=5,000, AASHTO HS20 loading case and five-year evaluation period was obtained as 1.8. In the second approach, the methodology established in the Manual for Bridge Evaluation (MBE) was used to calibrate the live load factors. It was obtained that the calculated live load factors were smaller than those in the MBE specifications, and smaller than those used in the initial calibration which did not convert to the gross vehicle weight (GVW) into truck type 3S2 defined by AASHTO equivalents.

Key Words
bridges; load rating; weigh-in-motion; truck loadings; live load factors

Address
Arcan Yanik and Christopher Higgins: 1School of Civil and Construction Engineering, Oregon State University, Corvallis, 97331, Oregon, USA
2Department of Civil Engineering, Istanbul Technical University, Maslak, 34469, Istanbul, Turkey
Christopher Higgins: School of Civil and Construction Engineering, Oregon State University, Corvallis, 97331, Oregon, USA

Abstract
The objective of this paper is to study the deformation in transversely isotropic thermoelastic solid using new modified couple stress theory subjected to ramp-type thermal source and without energy dissipation. This theory contains three material length scale parameters which can determine the size effects. The couple stress constitutive relationships are introduced for transversely isotropic thermoelastic solid, in which the curvature (rotation gradient) tensor is asymmetric and the couple stress moment tensor is symmetric. Laplace and Fourier transform technique is applied to obtain the solutions of the governing equations. The displacement components, stress components, temperature change and couple stress are obtained in the transformed domain. A numerical inversion technique has been used to obtain the solutions in the physical domain. The effects of length scale parameters are depicted graphically on the resulted quantities. Numerical results show that the proposed model can capture the scale effects of microstructures.

Key Words
new modified couple stress theory; length scale parameters; transversely isotropic; ramp type heat; Laplace and Fourier transform

Address
Department of Basic and Applied Sciences, Punjabi University, Patiala, Punjab, India

Abstract
In this paper, the deflection and buckling analyses of porous nano-composite piezoelectric plate reinforced by carbon nanotube (CNT) are studied. The equations of equilibrium using energy method are derived from principle of minimum total potential energy. In the research, the non-local strain gradient theory is employed to consider size dependent effect for porous nanocomposite piezoelectric plate. The effects of material length scale parameter, Eringen

Key Words
deflection and buckling analyses; porous materials; nanocomposite; carbon nanotube; nonlocal strain gradient theory; principle of minimum total potential energy

Address
Department of Solid Mechanics, Faculty of Mechanical Engineering, University of Kashan, P.O. Box: 87317-53153, Kashan, Iran

Abstract
It is very important to allocate valuable resources efficiently when reconstructing buildings after earthquake damage. This paper proposes the use of a simple seismic retrofitting system to make buildings more resilient than the stiffer systems such as the shear walls implemented in Chile after the earthquake in 2010. The proposal is based on the use of steel chevron-type braces in RC buildings as a dual system to improve the seismic performance of multistory buildings. A case study was carried out to compare the proposal with the shear wall solution for the typical seismic Chilean RC building from the structural and economic perspectives. The results show that it is more resilient than other stiffer seismic solutions, such as shear walls, reduces the demand, minimizes seismic damage, gives reliable earthquake protection and facilitates future upgrades and repairs while achieving the level of immediate occupancy without the costs of the shear walls system.

Key Words
Chevron-type steel bracing; Shear walls; Earthquake reconstruction; Resilient seismic structure; Seismic performance; Performance based design

Address
Francisco J. Pallarés and Luis Pallarés: ICITECH, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
David Domínguez: University of Talca, Faculty of Engineering, Department of Construction Engineering and Management, Talca, Chile

Abstract
Pretensioned concrete (PC) is widely used in contemporary construction. Bond of prestressing strand is significant for composite-action between the strand and concrete in the transfer and flexural-bond zones of PC members. This study develops a new methodology for quantifying the bond of 18-mm prestressing strand in PC members based on results of a pullout test, the Standard Test for Strand Bond (STSB). The experimental program includes: (a) twenty-four pretensioned concrete beams, using a wide range of concrete compressive strength; and (b) twelve untensioned pullout specimens. By testing beams, the transfer length, flexural-bond length, and development length were all measured. In the STSB, the pullout forces for the strands were measured. Experimental results indicate a significant relationship between the bond of prestressing strand to the code-established design parameters, such as transfer length and development length. However, the code-predictions can be unconservative for the prestressing strands having a low STSB pullout force. Three simplified bond equations are proposed for the design applications of PC members.

Key Words
pretensioned concrete; prestressing strand; bond; transfer length; development length; STSB; design application

Address
Canh N. Dang: 1Department for Management of Science and Technology Development, Ton Duc Thang University, Ho Chi Minh City, Vietnam
2Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam
José R. Martí-Vargas:Institute of Concrete Science and Technology (ICITECH), Universitat Politècnica de València, 4G,
Camino de Vera s/n, 46022 Valencia, Spain
W. Micah Hale:University of Arkansas, Department of Civil Engineering, 4190 Bell Engineering Center, Fayetteville, AR 72701, USA

Abstract
Shear walls are structural members in buildings that are used extensively in reinforced concrete frame buildings, and almost exclusively in the UK, regardless of whether or not they are actually required. In recent years, the UK construction industry, led by the Concrete Centre, has questioned the need for such structural elements in low to mid-rise reinforced concrete frame buildings. In this context, a typical modern, 5-storey residential building is studied, and its existing shear walls are replaced with columns as used elsewhere in the building. The aim is to investigate the impact of several design variables, including concrete grade, column size, column shape and slab thickness, on the building

Key Words
high-rise RC buildings; wind actions; concrete grade; concrete section size; column shape; slab thickness; shear wall

Address
1School of Computing and Engineering, University of West London, London, United Kingdom
2Civil Engineering, School of Computing and Engineering, University of West London, London, United Kingdom
3Principal Structural Engineer, the Concrete Centre, London, United Kingdom
4Structural Engineering, Department of Civil and Environmental Engineering, Brunel University, London, United Kingdom

Abstract
In this paper, an improved experience-based learning algorithm (EBL), termed as IEBL, is proposed to solve the nonlinear hysteretic parameter identification problem with Bouc-Wen model. A quasi-opposition-based learning mechanism and new updating equations are introduced to improve both the exploration and exploitation abilities of the algorithm. Numerical studies on a single-degree-of-freedom system without/with viscous damping are conducted to investigate the efficiency and robustness of the proposed algorithm. A laboratory test of seven lead-filled steel tube dampers is presented and their hysteretic parameters are also successfully identified with normalized mean square error values less than 2.97%. Both numerical and laboratory results confirm that, in comparison with EBL, CMFOA, SSA, and Jaya, the IEBL is superior in nonlinear hysteretic parameter identification in terms of convergence and accuracy even under measurement noise.

Key Words
experience-based learning; Bouc–Wen model; hysteretic parameters; nonlinear system identification; lead-filled steel tube dampers

Address
Weili Luo, Tongyi Zheng, Huawei Tong, Yun Zhou: School of Civil Engineering, Guangzhou University, Guangzhou, P.R. China
Zhongrong Lu: Department of Applied Mechanics, Sun Yat-sen University, Guangzhou, P.R. China

Abstract
This study presents an analytical approach to investigate the thermodynamic behavior of functionally graded beam resting on elastic foundations. The formulation is based on a refined deformation theory taking into consideration the stretching effect and the type of elastic foundation. The displacement field used in the present refined theory contains undetermined integral forms and involves only three unknowns to derive. The mechanical characteristics of the beam are assumed to be varied across the thickness according to a simple exponential law distribution. The beam is supposed simply supported and therefore the Navier solution is used to derive analytical solution. Verification examples demonstrate that the developed theory is very accurate in describing the response of FG beams subjected to thermodynamic loading. Numerical results are carried out to show the effects of the thermodynamic loading on the response of FG beams resting on elastic foundation.

Key Words
FGMs beams; Three-dimensional theory; undetermined integral forms; elastic foundation; thermodynamic effect

Address
Rabbab Bachir Bouiadjra, Attia Bachiri, Samir Benyoucef: 1Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Algeria
Rabbab Bachir Bouiadjra: Department of Civil Engineering, University Mustapha Stambouli of Mascara, Algeria
Bouazza Fahsi: Laboratoire de Modelisation et Simulation Multi-echelle, Universite de Sidi Bel Abbes, Algeria
Fabrice Bernard: Laboratoire de Genie Civil et Genie Mecanique, INSA de Rennes, France

Abstract
In this piece of work, carbon nanotubes motion equations are framed by Kelvin’s method. Employment of the Kelvin’s method procedure gives birth to the tube frequency equation. It is also exhibited that the effect of frequencies is investigated by varying the different index of polynomial function. By using volume fraction for power law index, the fundamental natural frequency spectra for two forms of single-walled carbon nanotubes are calculated. The influence of frequencies against length-to-diameter ratios with varying power law index are investigated in detail for these tubes. Throughout the computation, it is observed that the frequency behavior for the boundary conditions follow as; clamped-clamped, simply supported-simply supported and these frequency curves are higher than that of clamped-free curves. Computer software MATLAB is utilized for the frequencies of single-walled carbon nanotubes.

Key Words
material structure; Kelvin’s approach; CNT; fraction law

Address
Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan

Abstract
This manuscript tends to investigate influences of nanoscale and surface energy on a static bending and free vibration of piezoelectric perforated nanobeam structural element, for the first time. Nonlocal differential elasticity theory of Eringen is manipulated to depict the long–range atoms interactions, by imposing length scale parameter. Surface energy dominated in nanoscale structure, is included in the proposed model by using Gurtin–Murdoch model. The coupling effect between nonlocal elasticity and surface energy is included in the proposed model. Constitutive and governing equations of nonlocal-surface perforated Euler–Bernoulli nanobeam are derived by Hamilton’s principle. The distribution of electric potential for the piezoelectric nanobeam model is assumed to vary as a combination of a cosine and linear variation, which satisfies the Maxwell’s equation. The proposed model is solved numerically by using the finite-element method (FEM). The present model is validated by comparing the obtained results with previously published works. The detailed parametric study is presented to examine effects of the number of holes, perforation size, nonlocal parameter, surface energy, boundary conditions, and external electric voltage on the electro-mechanical behaviors of piezoelectric perforated nanobeams. It is found that the effect of surface stresses becomes more significant as the thickness decreases in the range of nanometers. The effect of number of holes becomes significant in the region 0.2≤ɑ ≤0.8. The current model can be used in design of perforated nano-electro-mechanical systems (PNEMS).

Key Words
perforated piezoelectric nanobeams; surface energy; nonlocal elasticity; mechanical behaviors; finite element method.

Address
Mohamed A. Eltaher: Mechanical Engineering Dept., Faculty of Engineering, King Abdulaziz University, Jeddah 21589, Saudi Arabia
Mohamed A. Eltaher, Fatema-Alzahraa Omar, Waleed S. Abdalla, Abdallah M. Kabeel
and Amal E. Alshorbagy: Mechanical Design and Production Dept., Faculty of Engineering, Zagazig University, Zagazig, 44519, Egypt


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