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CONTENTS
Volume 95, Number 3, August10 2025
 

Abstract
This study investigates the mechanical performance of laterally loaded structural glass laminated with Polyurethane (PU) interlayer through finite element modeling using Abaqus. The scope is to assess different structural configurations and quantify their behavior, focusing on variations in glass plate thickness and laminating interlayer. The PU layer is modeled as a non-linear elastic hardening material. A parametric exploration of two-layered glass plates bent in dual directions, based on a 4-point bending test setup, reveals that thinning the laminating surface increases structural rigidity, resulting in reduced deflection. Furthermore, asymmetrically constructed plates with a thinner lower layer and a thicker upper layer in a 5:1 ratio demonstrate a 38.46% increase in maximum load bearing on the bottom surface of the lower layers. These findings suggest practical strategies for enhancing the strength and durability of laminated glass structures. The collective work underscores the practical applications of interlayer advancements within the industry, encompassing improvements in safety, performance, and costeffective design solutions.

Key Words
computational analysis; interlayer behavior; laminated glass strength; parametric study; polyurethane; structural durability

Address
Reza Shamim: DGTI, Hubei University of Technology, Wuhan 430068, China

Abstract
In dynamic analyses of steel buildings, the most common approach to model the material nonlinearity is the concentrated plasticity (CP) model. In this paper, the accuracy of this practice is evaluated by comparing the seismic responses obtained with this approach with those of the distributed plasticity (DP) model. Regular plane steel moment frames with 4, 10, 15 and 20 levels, representing low-, mid- and high-rise steel buildings, were considered in the study. Results indicate that bending moments in beams and columns, axial forces in exterior columns, and interstory shears, are underestimated on average by up to 30%, 21%, 28%, respectively, if the CP formulation is adopted, a reason for this is that, the CP approach inadequately capture the nonlinear behavior inside of the members, since they are assumed to remain fully elastic except at plastic hinges which develop at the member ends. Axial loads in interior columns, unlike those of the exteriors, are accurately predicted with the CP approach, this is due, in part, to the fact that axial loads on columns come from three sources whose combined effect on the exterior columns is different than that of the interiors. Unlike the case of forces, the interstory displacements can be underestimated or overestimated, if the CP approach is used in the seismic analyses, the maximum values of underestimations and overestimation are 16% and 14%, respectively. One reason for having overestimation for the case of interstory displacements is due to the fact that the contribution of the higher modes to the response in terms of displacements is different than that of forces. In addition, the contribution of such higher modes may have been enhanced for the case of the CP formulation. The earlier results clearly demonstrate that, in general, the seismic response of steel buildings with moment resisting frames are underestimated if the CP approach is adopted, leading to nonconservative designs. Hence, it is strongly suggested to use the DP formulation in the seismic analysis. A rough correction can be made by increasing the seismic response by a 25% when using the CP formulation. More research is needed considering other situations to reach more general conclusions.

Key Words
concentrated and distributed plasticity; MDOF systems; nonlinear response; steel buildings

Address
Mario D. Llanes-Tizoc, Federico Valenzuela-Beltran, Juan D. Trasviña-Soberanes, Edén Bojorquez, Victor Baca-Machado and Alfredo Reyes-Salazar: Facultad de Ingeniería, Universidad Autónoma de Sinaloa, Ciudad Universitaria, Culiacán, Sinaloa, CP 80000, México

Abstract
In this study, the free vibration of a simply supported sandwich beam was investigated using the finite element method. The core layer of the beam is made of an isotropic material, while the top and bottom surfaces consist of carbon nanotube-added and carbon fiber-reinforced composite layers. The finite element modeling of the composite sandwich beam is based on Euler-Bernoulli beam theory. The Halpin-Tsai model was used to model the carbon nanotube-added fiber-reinforced composite layers on the upper and lower surfaces. The stress between the layer surfaces, natural frequency, and displacement values were computed using a MATLAB code developed based on the finite element method. In this study, the effects of the carbon nanotube ratio, fiber orientation angle, and core-height to beam-height ratio (h/H) on natural frequency, displacement, and stress values were investigated. For the investigated beam designs, the largest increase in the first natural frequency at 0o was 71.88%, while the largest decrease was 57.22% at 70o. The largest displacement increase was 720% at 70o, whereas the smallest displacement decrease was 49.2% for h/H=0.25. The largest stress increase was 26.53% at 0o, while the smallest stress decrease was 77.65% at 70o for h/H=0.75. For the beam with h/H=0.25 and porosity=0, the largest increase in the first natural frequency at 70o was 55.8%, the smallest displacement decrease was 62.5%, and the smallest core layer stress decrease was 62.14% for Vnt=0.5. For the beam with h/H=0.25 and Vnt=0, the smallest decrease in the first natural frequency at 70o was 3.25%, the largest displacement increase was 8.86%, and the smallest core layer stress decrease was 46.58% for porosity=0.5. It was observed that the investigated parameters significantly affect the natural frequency, displacement, and stress values.

Key Words
composites; fiber reinforced; finite element method; free vibration; static analysis; structural design

Address
Yusuf Cunedioğlu and Burak Devecioğlu: Department of Mechanical Engineering, Niğde Ömer Halisdemir University, Niğde, Türkiye

Abstract
Due to environmental and architectural considerations, the partially infilled exterior walls of reinforced concrete (RC) condominium buildings are typically cast monolithically with the surrounding beams and/or columns. Generally, their mechanical contribution to structural resistance is neglected due to the variety in the opening types and only their weight is considered in the structural design phase. Parapet wall is very common among the various partially infilled exterior walls. In this study, the mechanical influences of the parapet wall on the structural resistances of RC building frames against lateral seismic and progressive collapse failure were investigated. From the nonlinear static pushover and pushdown analyses of seven seismically designed RC building frames, the seismic and column-loss resistances with and without the parapet walls were compared. The analysis results revealed that the presence of parapet walls enhanced both the lateral seismic resistance and the progressive collapse resistance under column loss. The mechanical influences of the parapet walls decreased with increased span length, seismic design force, and number of stories of the RC building frames. For the five-story building frames, the normalized seismic resistance can be enhanced by 22% to 62%, depending on the span length. Moreover, the normalized progressive collapse resistance varies with the span length and the location of the removed column. An increase of 50% to 207% is observed under corner-column loss, and 28% to 162% under side-column loss. However, both the seismic and progressive collapse resistance enhancements may decrease to less than 10% for the fifteen-story building frame. From the variation of the amplification of resistance, it is practically acceptable to neglect the resistance contribution of the exterior RC parapet walls for medium-to-high building frames located in high seismic hazard zones.

Key Words
exterior parapet wall; progressive collapse resistance; RC building frame; seismic resistance

Address
Meng-Hao Tsai: Department of Civil Engineering, National Pingtung University of Science and Technology, No.1, Shuefu Road, Neipu, Pingtung 912, Taiwan

Abstract
This paper offers a comprehensive examination of the static behavior of functionally graded antisymmetric angle-ply bio-inspired helicoidal carbon nanotube-reinforced laminated composite nanoplates for the first time. The influences of nanoscale and microstructure are examined using a modified nonlocal strain gradient continuum model. A newly developed Galerkin approach is utilized to analyze the static response of these plates. The global stability equations are derived using Hamilton's principle in conjunction with higher-order shear deformation theory. The analysis examines three distinct helicoidal CNTs configurations—helicoidal-linear (HL), helicoidal-exponential (HE), and helicoidal-semicircular (HS)—alongside four varieties of nanotube distribution patterns: UD, FG-X, FG-O, and FG-A. A comprehensive parametric analysis is conducted to examine the influence of geometric dimensions, material characteristics and boundary conditions on the buckling behavior of functionally graded, bio-inspired helicoidal laminated composite nanoplates.

Key Words
angle-ply; bio-inspired helicoidal CNTs reinforced laminated laminates; buckling; Galerkin method; size dependent; temperature dependent

Address
Ali Alnujaie: Department of Mechanical Engineering, College of Engineering and Copmuter Sciences, Jazan University,
P.O Box 45124, Jazan, Saudi Arabia; Engineering and Technology Research Center, P.O. Box 114, Jazan 82817, Saudi Arabia
Ahmed A. Daikh: Artificial Intelligence Laboratory for Mechanical and Civil Structures, and Soil, University Centre of Naama, P.O. Box 66, Naama 45000, Algeria; Laboratoire d'Etude des Structures et de Mécanique des Matériaux, Département de Génie Civil, Faculté des Sciences et de la Technologie, Université Mustapha Stambouli, B.P. 305, R.P. 29000 Mascara, Algérie
Mofareh H. Ghazwani: Department of Mechanical Engineering, College of Engineering and Copmuter Sciences, Jazan University, P.O Box 45124, Jazan, Saudi Arabia; Engineering and Technology Research Center, P.O. Box 114, Jazan 82817, Saudi Arabia
Mohammed Y. Tharwan: Department of Mechanical Engineering, College of Engineering and Copmuter Sciences, Jazan University, P.O Box 45124, Jazan, Saudi Arabia
Alaa A. Abdelrahman: Mechanical Design & Production Department, Faculty of Engineering, Zagazig University, Zagazig 44519, Egypt; Industrial Engineering Department, Jeddah International College (JIC), P.O. Box 23831, Jeddah, Saudi Arabia
Amr E. Assie: Department of Mechanical Engineering, College of Engineering and Copmuter Sciences, Jazan University,
P.O Box 45124, Jazan, Saudi Arabia; Mechanical Design & Production Department, Faculty of Engineering, Zagazig University, Zagazig 44519, Egypt
Mohamed A. Eltaher: Mechanical Engineering Department, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabia; Mechanical Design and Production Department, Faculty of Engineering, Zagazig University, Egypt

Abstract
Long-span river-crossing bridges, while enhancing regional connectivity, generate low-frequency underwater vibrations and noise due to vehicular traffic, which negatively impacts the aquatic environment and organisms. To address this, a novel method for controlling ultra-low frequency vibration and noise of a long-span suspension bridge is proposed, based on the bandgap characteristics of periodic structures. Through theoretical analysis, parametric optimization, and numerical simulations, the optimized bandgap ranges are determined as 2.92-5.18 Hz for periodic pile rows and 2.81-6.71 Hz for the tower's phononic crystal structure, effectively covering the dominant vibration frequencies of both the bridge tower and surrounding soil. Furthermore, a vibro-acoustic coupling model is established to validate the effectiveness and feasibility of the proposed method, and the results show that this new method can achieve the maximum vibration and noise reduction of 13 dB. This research provides a new approach and theoretical framework for controlling ultra-low-frequency underwater noise and vibrations in longspan bridges, contributing to aquatic ecosystem preservation and sustainable infrastructure development.

Key Words
phononic crystal; suspension bridge; ultra-low frequency; vibration and noise control

Address
Xiaodong Song: School of Transportation, Southeast University, Nanjing 211189, China
Kun Zuo: China Railway Britech Co., Ltd., Wuhan 430034, China
Changyu Wang: School of Transportation, Southeast University, Nanjing 211189, China

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