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CONTENTS
Volume 35, Number 2, February 2025
 

Abstract
This study proposes an intelligent and simplified approach utilizing the fuzzy inference system (FIS) for predicting the serviceable deflection up to the yielding point of PCM-overlay reinforced concrete (RC) beams. The established FIS incorporates eleven logical linguistic variables, enabling the deflection to be conveniently determined by two input parameters: reinforcement area and applied loads. To assess the prediction accuracy, a finite element analysis (FEA) model is constructed, successfully replicating the load-deflection relationship compared to experimental results across various PCM-overlay reinforcement ratios. Subsequently, the ratio of experimental results to FIS predictions is compared with those obtained from FEA analysis. Both FIS and FEA-generated load-deflection curves accurately predict the serviceable deflection observed in experimental results, with a ratio of 0.96 for FIS and 0.84 for FEA. This demonstrates FIS's capability to reasonably predict serviceable deflection without the need for complex FEA modeling and analysis typically performed conventionally. Furthermore, the predictive performance of FIS is validated using previously published 18 test cases of overlay-strengthened RC beams, resulting in an assessment of prediction performance at 0.89. Therefore, the FIS presented in this study can be considered as an alternative method for predicting serviceable deflection and assessing design capacity, offering a viable alternative to conventional FEA methods.

Key Words
finite element analysis; fuzzy inference system; PCM-overlay beam; serviceable deflection

Address
Khuram Rashid: Department of Architectural Engineering and Design, Faculty of Civil Engineering, University of Engineering and Technology, Lahore, Pakistan
Asif Ali: Department of Mathematics, Faculty of Science and Technology, Virtual University of Pakistan, Pakistan
Muhammad Akram Tahir: Faculty of Engineering, University of Central Punjab, Lahore, Pakistan
Muhammad Safdar: Design Engineer, RH Consulting and Holding Pty Limited, Sydney, Australia
Minkwan Ju: Department of Civil and Environmental Engineering, Yonsei University, Seoul, Republic of Korea

Abstract
A novel easy-to-splice mechanical coupler (EtSMC) involving a sleeve, two caps, two racks, two rack guides, and two springs is introduced; this coupler easily and tightly connects two rebars through a simple manual operation (without any tool) on a construction site. The mechanical performance (including the pull force/stroke curve of the EtSMC assembly) is experimentally examined via tensile testing in air. A finite element analysis (FEA) model that minimizes simplification of the conceptual design is presented; the spring reaction is assumed to be mechanically symmetrical. The experimental tensile test is numerically analyzed using a fully implicit elastoplastic FEA function and a multi-body treatment scheme based on the tetrahedral MINI-element technique. The predictions are in qualitatively good agreement with the experimental data in terms of both the pull force/stroke curve and the damaged regions of the racks and rack guides. Small differences between the curves can be attributed to some experimental slip between parts.

Key Words
easy-to-splice; implicit elastoplastic FEA; mechanical coupler; pull force-stroke curve; slip distance; strength

Address
Sukhwan Chung and Seongmin Jang: MFRC, Research and Development Center, 1209-A, 12, Dongbu-ro 169beng-gil, Jinju-si, Gyeongsangnam-do, 52818, Republic of Korea
Ildong Seo and Nakyoung Lee: Dae Jung Metal Co.,Ltd, Research and Development Center, 26-62, Sangdong-ro 375ben-gil, Sngdong-myeon, Gimhae-si, Gyeongsangnam-do, 50805, Republic of Korea
Wanjin Chung: Department of Mechanical System Design Engineering, Seoul National University of Science and Technology, 232, Gongneung-ro, Nowon-gu, Seoul, 01811, Republic of Korea
Mansoo Joun: Engineering Research Institute, School of Mechanical Engineering, Gyeongsang National University, 103-403, 501, Jinju-daero, Jinju-si, Gyeongsangnam-do, 52828, Republic of Korea

Abstract
The objective of this investigation is to determine the stress redistribution due to the cable stress relaxation, concrete creep and shrinkage of structural members in a concrete cable-stayed bridge. To accomplish such complex analyses, the generalized Maxwell model is used for the cable stress relaxation model of the cable members, whereas the models used for the shrinkage and creep are based on the ACI 209R-92 design code. A computational program is developed to calculate the parameters for the generalized Maxwell model, whereas ABAQUS user subroutines are established to simulate the shrinkage and creep behaviors of concrete members. All the processes are set up as an evaluation system for practical usage. The influence of these factors as well as the simultaneous influence of different factors on the stress redistribution are investigated and evaluated. Moreover, the effect of cable type on stress redistribution is also investigated. The findings of these investigations reveal that the stress values in cable elements increased up to 9.63%, and the redistribution rate increased by up to 34.04% in girder elements and 87.17% in pylon elements. Concrete creep and shrinkage increase the rates of redistribution in structural members, particularly pylons. The findings also show that the cable type with low relaxation rates should be used to minimize the effect of cable stress relaxations.

Key Words
cable-stayed bridge; cable stress relaxation; concrete creep; concrete shrinkage; stress redistribution

Address
Tien-Thang Hong: 1) Faculty of Civil Engineering, Thuyloi University, 175 Tayson, Hanoi, Vietnam, 2) Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 05006, South Korea
Seung-Eock Kim and Duc-Kien Thai: Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 05006, South Korea

Abstract
Nonlinearity occurs in abundance in nature and most of these nonlinear phenomena's are of great importance. Many of these nonlinear phenomena's can be modeled in the form of nonlinear partial differential equations. Among nonlinear partial differential equations an important class is that of evolution equations. Evolution equations arise in many areas such as modeling of water waves. In this work, a modified version of Exp-function method is used to find analytical solutions of Modified KdV equation. The results obtained are verified by substituting them back into the original differential equations. Moreover, to re-verify the results, 2 dimensional and 3 dimensional plots for each of the solution sets are also plotted.

Key Words
Exp-function; modified KdV equation; nonlinear phenomena; partial differential equations

Address
Muhammad Asad Iqbal: Department of Mathematics, University of Poonch, Rawalakot, AJK, Pakistan
Muzamal Hussain: Department of Mathematics, University of Sahiwal, Sahiwal, 57000, Faisalabad, Pakistan
Muhammad Safeer and Muhammad Taj: Department of Mathematics, University of Azad Jammu and Kashmir, Muzaffarabad, 1300, Azad Kashmir, Pakistan
Abdelouahed Tounsi: 1) YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea, 2) Department of Civil and Environmental Engineering, King Fahd University of Petroleum and Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia

Abstract
The purpose of the present work is to study the forced vibrations of piezoelectric (Sensor) -functionally graded material (FGM)-piezoelectric (actuator) slender sandwich beams submitted to active control. In the analytical formulation, both the proportional and derivative potential feedback control are considered via sensor and actuator layers by using the Bernoulli theory. The harmonic balance method is coupled with a one mode Galerkin procedure for a simply supported beam. The geometrically nonlinear coupling and piezoelectric effects lead to a nonlinear frequency amplitude equation governed by several complex coefficients. The frequency response curves are presented and discussed for various gain parameters and material properties.

Key Words
actuator; functionally graded material (FGM); nonlinear vibration; piezoelectric; sensor

Address
Hadj Youzera: 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
Khaled Mohamed Khedher: Department of Civil Engineering, College of Engineering, King Khalid University, Abha 61421, Saudi Arabia
Mohamed Abdelaziz Salem: Department of Mechanical Engineering, College of Engineering, King Khalid University, Abha 61421, Saudi Arabia
Sid Ahmed Meftah: Laboratoire de Modélisation et Simulation Multi-échelle, Université de Sidi Bel Abbes, Alegria
Abdelouahed Tounsi: 1) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia, 2) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Thanh Cuong-Le: Center for Engineering Application & Technology Solutions, Ho Chi Minh City Open University, Ho Chi Minh City, Vietnam

Abstract
Nanotechnology is a significant research discipline that revolutionized our understanding and capacity for controlling the natural world. This study investigated the efficiency of incorporating Nano-Titanium (NT) or glass powder (GP) into the concrete mixes as cement additions, focusing on the material and structural levels. The standard material tests demonstrated that the addition of 0.75% NT resulted in an improvement of 15% in splitting tensile strength. Furthermore, a 12% increase was recorded due to a 20% GP provision. Fifteen reinforced concrete beams were tested on a structural level to investigate the impact of adding NT by 0.75% and 1.5% and GP by 10% and 20% on the flexural response. The experimental variables also include the type of reinforcing, such as steel, ductile hybrid bars, and hybrid schemes that use both steel and GFRP bars. A novel ductile hybrid bar has been produced to tackle the problems of steel corrosion and FRP ductility. The experimental test results were analyzed regarding flexural capacity, cracking load, failure mode, and load-deflection curves. The results revealed that hybrid bars significantly enhanced the bending stiffness and ductility index comparable to steel-reinforced concrete beams. Furthermore, the flexural capacity at the post-peak level was enhanced due to NT fiber bridging capabilities. 3D nonlinear finite element analysis was implemented to confirm the test results, which proved relatively accurate in forecasting the beams' flexural behavior. Finally, the ACI 318-19 simplified formula for forecasting the nominal capacity of the beams was compared to the experimental results for design purposes.

Key Words
cement replacement; flexural performance; glass powder; hybrid bars; hybrid schemes; nano-titanium

Address
Mostafa M. Khalil and Mohammed Hisham: Department of Civil Engineering, Faculty of Engineering at Shoubra, Benha University, 108 Shoubra St., Shoubra 11691, Cairo, Egypt
Ibrahim A. El-Azab: Department of Civil Engineering, Benah Faculty of Engineering, Benha University, Benha, Egypt

Abstract
The extraction of bridge frequency is the most crucial step in the indirect measurement method based on vehicle bridge coupling. However, the body signals of the test vehicle collected using this method often only obtain the fundamental frequency (the first order bridge frequency) of the bridge, while high-order bridge frequencies are difficult to identify and extract. by studying the higher-order bridge frequencies, a more comprehensive understanding of the vibration characteristics of the bridge structures can be obtained, and a more accurate assessment of the health status of the bridge structures can be made. This article proposes a method for extracting high-order frequencies of bridges by changing the parameters of the test vehicle to adjust the frequency of the vehicle. Firstly, change the mass and stiffness of the test vehicle to increase the vehicle frequency to be greater than the first order frequency of the bridge and closer to the second order frequency. Then, quickly collect the vehicle body signal when the test vehicle passes the bridge. Finally, use signal processing techniques such as bandpass filtering to extract the second order bridge frequency of the bridge, and the remaining higher order bridge frequency can be obtained similarly. This paper uses changing vehicle frequency to excite the vibration of high-order frequencies of bridges. Theoretical derivation and numerical simulation verification show that the proposed method can effectively enhance the vibration of high-order modes of bridges, with obvious recognition effect, strong noise resistance and high efficiency, which can promote the application of indirect measurement method in bridge structural health monitoring.

Key Words
bridge engineering; high order bridge frequency; indirect measurement method; numerical simulation; test vehicle frequency

Address
Jingchao Wang: School of Architecture and Materials, Chongqing College of Electronic Engineering, Chongqing, 401331, China
Yixin Chen: 1) State Key Laboratory of Bridge Engineering Safety and Resilience and Key Laboratory of Bridge Earthquake Resistance Technology, Ministry of Communications, PRC, Chongqing, 400067, China, 2) China Merchants Chongqing Communications Technology Research & Design Institute Co., Ltd., Chongqing, 400067, China, 3) Chongqing Wukang Technology Co., Ltd., Chongqing, 404100, China
Zulin Huang: Chongqing University of Science and Technology, China, Chongqing, 401331, China
Xiaokun Tan: China Southwest Architectural Design and Research Institute Co., Ltd., Chengdu, China

Abstract
Reliability-Based Design Optimization (RBDO) allows designers to minimize cost function while guaranteeing minimal performances cast as admissible failure probabilities related to some performance functions. Uncertainties in the geotechnical design exist in estimating in-situ engineering soil properties and determining subsoil profiles. Due to the uncertain properties of backfill soil and also foundation soil, the stability evaluation of retaining walls must take in consideration uncertainties in the structural design of the wall (Juang 2013). RBDO based on the first order reliability method (FORM) is presented in this paper for gravity retaining wall design. In the first part, we will focus on the choice of the better RBDO method to be used to optimize the shape of the wall taking into account variability of backfill and the soil support layer two variants of retaining wall are compared. The second part of this paper is dedicated to some parametric analyses. Through original parametric studies to evaluate the effect of the random variables (r.v.) distribution, r.v. dispersion and correlalations betwen r.v. etc., we prove that the variability of soil parameters should not be neglected as most works in this context. We even performed an optimization considering the variability of design variables (it corresponds to execution defects and are rarely taken into account in the literature) and evaluated their costs on the implementation of the structure. Rather, it should be accepted as a positive contribution to geotechnical design, as its modeling and consistent use lead, with limited additional calculations and conceptual effort on the part of the designer, to a more reliable and economical design.

Key Words
gravity wall; MPA; RBDO; retaining wall; RIA; weight optimization

Address
Noureddine Rhayma and Mohamed Khorchani: 1) Department of civil engineering, National School of Engineering of Gabes, University of Gabes, Tunisia, 2) Mechanical Modelling, Energy & Materials (M2EM) Laboratory, LR24ES23, ENIG, University of Gabes. Gabes, Tunisia
Pierre Breul: Institut Pascal - UMR CNRS, Clermont Auvergne INP, Clermont Auvergne University, Clermont-Ferrand, France

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