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CONTENTS
Volume 86, Number 2, April25 2023
 


Abstract
In the present work, the vibration characteristics of sandwich nanocomposite shells, fortified with graphene platelets (GPLs) have been researched. The shell has been considered as the stadium roof shape with double curvatures under vibration due to earthquake. The nanocomposite has the matrix of concrete which is fortified with uniform or linear dispersions of GPLs. Also, the core possesses cellular type square architecture for which the effective elastic modulus has been defined in the context of relative density based relations. Based upon the classic shell strains containing two identical curvatures, the governing equations have been established and solved through differential quadrature approach. It will be seen that the vibrational frequencies rely on the core relative density, height of layers, the amount and dispersions of GPLs and even shell geometric parameters.

Key Words
architecture; composites; design; dynamics; graphene platelet; nanocomposite; stadium

Address
Abeer Qasim Jbur: Department of Architectural Engineering, Al-Mustansiriyah University, Baghdad 10001, Iraq
Wael Najm Abdullah: Department of Architectural Engineering, Al-Mustansiriyah University, Baghdad 10001, Iraq
Nadhim M. Faleh: Engineering Collage, Al-Mustansiryah University, P.O. Box 46049, Bab-Muadum, Baghdad 10001, Iraq
Zahraa N. Faleh: Department of Architectural Engineering, University of Baghdad, Iraq

Abstract
This work applies a four-known quasi-3D shear deformation theory to investigate the bending behavior of a functionally graded plate resting on a viscoelastic foundation and subjected to hygro-thermo-mechanical loading. The theory utilizes a hyperbolic shape function to predict the transverse shear stress, and the transverse stretching effect of the plate is considered. The principle of virtual displacement is applied to obtain the governing differential equations, and the Navier method, which comprises an exponential term, is used to obtain the solution. Novel to the current study, the impact of the viscoelastic foundation model, which includes a time-dependent viscosity parameter in addition to Winkler's and Pasternak parameters, is carefully investigated. Numerical examples are presented to validate the theory. A parametric study is conducted to study the effect of the damping coefficient, the linear and nonlinear loadings, the power-law index, and the plate width-tothickness ratio on the plate bending response. The results show that the presence of the viscoelastic foundation causes an 18% decrease in the plate deflection and about a 10% increase in transverse shear stresses under both linear and nonlinear loading conditions. Additionally, nonlinear loading causes a one-and-a-half times increase in horizontal stresses and a nearly two-times increase in normal transverse stresses compared to linear loading. Based on the article's findings, it can be concluded that the viscosity effect plays a significant role in the bending response of plates in hygrothermal environments. Hence it shall be considered in the design.

Key Words
hygrothermal environment; quasi-3D theory; static bending response; viscoelastic foundation

Address
Ismail M. Mudhaffar: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
Abdelbaki Chikh: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Université Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algérie
Abdelouahed Tounsi: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia; Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea; Interdisciplinary Research Center for Construction and Building Materials, KFUPM, 31261 Dhahran, Saudi Arabia
Mohammed A. Al-Osta: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia; Interdisciplinary Research Center for Construction and Building Materials, KFUPM, 31261 Dhahran, Saudi Arabia
Mesfer M. Al-Zahrani: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia; Interdisciplinary Research Center for Construction and Building Materials, KFUPM, 31261 Dhahran, Saudi Arabia
Salah U. Al-Dulaijan: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia; Interdisciplinary Research Center for Construction and Building Materials, KFUPM, 31261 Dhahran, Saudi Arabia

Abstract
To predict the rheological behaviours along with the compressive strength of self-compacting concrete that incorporates environmentally friendly ingredients as cement substitutes, a comparative evaluation of machine learning methods is conducted. To model four parameters, slump flow diameter, L-box ratio, V-funnel time, as well as compressive strength at 28 days-a complete mix design dataset from available pieces of literature is gathered and used to construct the suggested machine learning standards, SVM, MARS, and Mp5-MT. Six input variables-the amount of binder, the percentage of SCMs, the proportion of water to the binder, the amount of fine and coarse aggregates, and the amount of superplasticizer are grouped in a particular pattern. For optimizing the hyper-parameters of the MARS model with the lowest possible prediction error, a gravitational search algorithm (GSA) is required. In terms of the correlation coefficient for modelling slump flow diameter, Lbox ratio, V-funnel duration, and compressive strength, the prediction results showed that MARS combined with GSA could improve the accuracy of the solo MARS model with 1.35%, 11.1%, 2.3%, as well as 1.07%. By contrast, Mp5-MT often demonstrates greater identification capability and more accurate prediction in comparison to MARS-GSA, and it may be regarded as an efficient approach to forecasting the rheological behaviors and compressive strength of SCC in infrastructure practice.

Key Words
compressive strength; gravitational search algorithm; machine learning; rheological properties; selfcompacting concrete

Address
Pouryan Hadi, KhodaBandehLou Ashkan, Hamidi Peyman and Ashrafzadeh Fedra: Department of Civil Engineering, Urmia Branch, Islamic Azad University, Urmia, Iran

Abstract
In the case of designing control devices in a building, reliance on experimental formulation or engineering concepts without using optimization algorithms leads to non-optimal solutions or design parameters, which makes the use of control devices costly and unreasonable. The optimization algorithms are capable of identifying the required number of parameters for a specific design problem, however, this process is difficult and inefficient in dealing with some specific optimal design processes. This paper aims to introduce an upgraded version of the salp swarm algorithm to handle some engineering design. The performance of the new upgraded algorithm is tested using some benchmark test functions as well as a six-story benchmark building equipped with semi-active MR dampers. The simulation results show that the proposed algorithm can be successfully applied to get an optimal design of the MR dampers in the building.

Key Words
MR damper; optimum design; salp swarm algorithm; structural control; upgraded salp swarm algorithm

Address
Farzad Raeesi, Hedayat Veladi, Bahman Farahmand Azar, Sina Shirgir and Baharak Jafarpurian: Tabriz Faculty of Civil Engineering, Tabriz University, Tabriz, Iran

Abstract
The textile industry has benefited from nanotechnology in various fields of application as the use of nanomaterials, and nanotechnology is multiplying. Nanoparticles can increase the performance of textiles by up to 100 times when used in finishing, coating, and dyeing techniques, providing them with capabilities they did not previously possess. Nanotechnology is used in the textile chemical industry to produce sports mats with stain resistance, flame resistance, wrinkle resistance, moisture management, antimicrobial quality, and UV protection. The incorporation of nanomaterials into fabrics can have a significant effect on their properties, including shrinkage, strength, electrical conductivity, and flammability. Various inventions and innovations may result from nano-processed textiles in the future, thus leading to the advancement of science. This article presents the construction of sports engineering structures with high resistance to improve the quality of sports training. The mechanical properties of sports mats are improved with the help of nanotechnology. Strength, elasticity, and tear resistance are among these properties. This method enables the production of elastic, durable, and tear-resistant sports mats.

Key Words
engineering structures; high resistance; nanotechnology; sports mats; sports training

Address
Lin He: College of Sports and Health Sciences, Guangxi Minzu University, Nanning 530006, Guangxi, China
Qiyuan Deng: College of General Studies, Guangxi Vocational College of Technology and Business, Nanning 530006, Guangxi, China

Abstract
To calculate the vibrations of a tout cable subjected to axial support excitations, a nonlinear relationship of cable force and the support displacement under static situations are employed to depict the quasi-static vibration of the cable. The dynamic components of quasi-static vibration are inputted as "direct loads" to cause the parametric vibrations on the cable. Both the governing equations of motion and deformation compatibility for parametric vibrations are then derived, which indicates the high coupling of cable parametric force and deformation. Numerical solutions, based on the finite difference method, are put forward for the parametric vibrations, which is validated by the finite element method under periodic axial support excitations. For the quasi-static response, the shorter cables are more sensitive to support excitations than longer ones at small cable force. The quasi-static cable force makes the greatest contribution to the total cable force, but the parametric cable force is responsible for the occurrence of cable loosening at large excitation amplitudes. Moreover, this study also revealed that the traditional approach, assuming a linear relationship between quasi-static cable force and axial support displacement, would result in some great error of the cable parametric responses.

Key Words
axial support excitation; parametric vibration; quasi-static vibration; resonant period; Taut cable

Address
Jiang Yi: Department of Civil Engineering, Guangzhou University, University Town, Fanyu District, Guangzhou, China
Yingqi Liu: School of Transportation and Logistics Engineering, Wuhan University of Technology, Wuchang District, Wuhan, China; Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China

Abstract
Fourier series-based models in the time domain are frequently established to represent individual bouncing loads, which neglects the stochastic property of human bouncing activity. A power spectral density (PSD) model in the frequency domain for individual bouncing loads is developed herein. An experiment was conducted on individual bouncing loads, resulting in 957 records linked to form long samples to achieve a fine frequency resolution. The Welch method was applied to the linked samples to obtain the experimental PSD, which was normalized by the bouncing frequency and the harmonic order. The energy, energy distribution center, and energy distribution shape of the experimental PSD were investigated to establish the PSD model. The proposed model was used to analyze structural vibration responses using stochastic vibration theory, which was verified via field measurements. It is believed that this framework can evaluate the vibration capacity of structures excited by bouncing crowds, such as concert halls and grandstands.

Key Words
human bouncing load; human-induced vibration; spectral model; stochastic vibration theory

Address
Jiecheng Xiong: School of Civil Engineering, Zhengzhou University, 100 Kexue Road, Zhengzhou, P.R. China
Jun Chen: College of Civil Engineering, Tongji University, 1239 Siping Road, Shanghai, P.R. China

Abstract
The uncertainties involved in structural performances are of importance when the optimum number and property of seismic retrofit devices are determined. This paper proposes a seismic retrofit design framework for asymmetric soft-first-story buildings, considering uncertainties in the soil condition and seismic retrofit device. The effect of the uncertain parameters on the structural performance is used to find a robust and optimal seismic retrofit solution. The framework finds a robust and optimal seismic retrofit solution by finding the optimal locations and mechanical properties of the seismic retrofit device for different realizations of the uncertain parameters. The structural performance for each realization is computed to evaluate the effect of the uncertainty parameters on the seismic performance. The framework utilizes parallel processing to decrease the computationally intensive nonlinear dynamic analysis time. The framework returns a robust design solution that satisfies the given limit state for every realization of the uncertain parameters. The proposed framework is applied to the seismic retrofit design of a five-story asymmetric soft-first-story case study structure retrofitted with a viscoelastic damper. Robust optimal parameters for retrofitting a structure to satisfy the limit state for the different realizations of the uncertain parameter are found using the proposed framework. According to the performance evaluation results of the retrofitted structure, the developed framework is proved effective in the seismic retrofit of the asymmetric structure with inherent uncertainties.

Key Words
asymmetric structures; multi-objective optimization; robust optimization; seismic retrofit; soft-first story; soil structure interaction; uncertainty

Address
Assefa Jonathan Dereje and Jinkoo Kim: Department of Civil Engineering and Architectural Engineering, Sungkyunkwan University, Suwon, Republic of Korea

Abstract
The use of the ordinary double nut (i.e., ODN) composed of a master nut (i.e., M-nut) and a slave nut (i.e., S-nut) is a highly efficient method to prevent bolts loosening. A novel double nut (i.e., FODN) composed of a master nut (i.e., M-nut) and flat slave nut (i.e., FS-nut) is proposed to save raw materials. The bolt fastening tests with single nut, ODN and FODN are performed to investigate the preload and counterbalance forces. Corresponding finite element analysis (FEA) models are established and validated by comparing the preload with the experimental results. The load-bearing capacity, the extrusion effect, and the contact stress of each engaged thread for ODN and FODN are observed by FEA. The experimental and simulated results revealed that the bolt fastening with double-nut has different load-transferring mechanisms from single-nut. Nevertheless, for double-nut/bolt assemblies, the FS-nut can provide load transfer that is like that of the S-nut, and the FODN is a reasonable and reliable fastening method. Furthermore, based on the theory of Yamamoto, a formula considering the extrusion effect is proposed to calculate the preload distribution of the double-nut, which is applicable to varying thicknesses of slave-nuts in double-nut/bolt assemblies.

Key Words
bolt fastening; counterbalance force; double nut; load-transferring mechanism; tightening torque

Address
Qiyu Li: College of Civil Engineering, Research Center of Tower Mast Structure, Nanjing Tech University, Nanjing 211816, China
Dachang Zhang: College of Civil Engineering, Research Center of Tower Mast Structure, Nanjing Tech University, Nanjing 211816, China
Hao Xu: Wuxi Metro Construction Co., Ltd., Wuxi 214063, China
Yibi Li: College of Civil Engineering, Research Center of Tower Mast Structure, Nanjing Tech University, Nanjing 211816, China
Weiqun Chen: Nanrui Electric Power Design Corporation Limited, Nanjing 211100, China
Kaixuan Zhang: The IT Electronics Eleventh Design & Research Institute Scientific and Technological Engineering Corporation Limited, Wuxi 214063, China

Abstract
A supplementary reinforced concrete wall can be used to improve the seismic behavior of a buckling restrained braced frame as a mixed system. In such a novel system, the total lateral force is resisted by the combination of the RC wall system and the BRBF. There is not enough research on the response modification factor of such a mixed system. This paper investigates the response modification factor, and such relevant factors as ductility reduction factor and over strength factor for a system consisting of reinforced concrete wall and buckling restrained braced frame. To this purpose, nonlinear incremental dynamic analysis as well as static push over analysis are used for 6- to 14-story sample structures. The results show that for mixed considered systems, the mean value of response modification factor varies approximately from 7 to 9.

Key Words
buckling restrained braced frame; IDA; reinforced concrete wall; response modification factor

Address
Hamid Beiraghi and Behdad Abbaspour: Department of Civil Engineering, Mahdishahr Branch, Islamic Azad University, Mahdishahr, Iran


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