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CONTENTS
Volume 36, Number 1, July 2025
 

Abstract
Ultra-high-performance concrete is an extremely heterogeneous material with large variations of materials. The strength of the concrete is majorly dependent on the mix design and its material properties. In this research, an attempt is made to develop a model for compressive strength prediction and optimized mix design of reactive powder concrete (RPC) by a Mamdani-based Fuzzy Interface System (FIS). A total set of 8 main parameters influencing the strength of the concrete were considered as input variables. 130 experimental data were used, in which 100 datasets were collected from various works of literature and 30 datasets were collected through self-conducted experimental investigations. 150 rules were set based on the permutation and combination of various material inputs. 30 test results were considered to check the efficiency of the FIS output by applying various membership functions and defuzzification methods. The predicted results show the potential efficiency of FIS in the prediction of the compressive strength and mix design of reactive powder concrete. The experimental analysis was found accurate to the analytical prediction, thus proving a perfect correlation between the experimental analysis and the soft computing techniques. The average accuracy was found to be 98-99% for Triangular, Gaussian, Pimf, D-Sigmoidal, and G-Bell functions. Whereas S-Curve, Z-Curve, and sigmoid curve failed miserably by providing inconsistent and inaccurate prediction when used. But the same curves proved their efficiency of 98-99% when used as hybrid functions with the highly precised membership functions like Triangular, Gaussian, Pimf, D-Sigmoidal, and G-Bell membership functions. Further to the predicted results obtained from soft computing, these were checked with the experimental results (with same mix design and input parameters). The R2 values obtained by using Triangular, Gaussian, Pimf, D-Sigmoidal, and G-Bell functions with various defuzzification methods were found out to be 0.99, which ensures a highly accurate prediction analysis. Whereas the curve like S-Curve, Sigmoidal, and Z-Curve resulted the R2 values in the range of 0.31 to 0.81, showing highly inconsistent and inaccurate values. But, when combined as hybrid, it resulted in R2 value of 0.96 to 0.99, which is highly accurate value.

Key Words
compressive strength; defuzzification method; fuzzy logic; membership functions; prediction; reactive powder concrete

Address
Akshay Nadiger: 1) Department of Civil Engineering, Amrita School of Engineering, Coimbatore, Amrita Vishwa Vidyapeetham, India, 2) Larsen & Toubro Construction, Chennai, India
Mini K.M: Department of Civil Engineering, Amrita School of Engineering, Coimbatore, Amrita Vishwa Vidyapeetham, India

Abstract
Advancing theoretical research in structural modeling poses significant challenges compared to experimental investigations of complex systems. To explore size-dependent bending behavior, this study introduces a novel "Tri-coated FGM" shell model that incorporates spatial variations in material properties. The research examines two types of coated FG shells, Hardcore and Softcore, and proposes five distribution patterns. Four structures are analyzed: plates, cylindrical, spherical, and hyperbolic-paraboloid shells. By reducing the number of variables from five to four and incorporating shear deformation effects, a simplified displacement field is proposed. Analytical solutions, derived using the Galerkin method and the virtual work principle, address various boundary conditions. A comprehensive parametric analysis is performed to assess the impact of different FG nanoshell types, distribution patterns, gradient material distribution, length scale parameter (nonlocal), and material scale parameter (gradient).

Key Words
coated functionally graded material; deflection and stresses; Galerkin method; higher-order shear deformation theory; shell structures

Address
Ahmed Amine Daikh: 1) Department of Technical Sciences, Center University Salhi Ahmed, Naâma 45000, Algeria, 2) Laboratoire d'Etude des Structures et de Mécanique des Matériaux, Département de Génie Civil, Faculté des Sciences et de la Technologie, Université Mustapha Stambouli, Mascara 29000, Algeria
Mohamed A. Eltaher: Faculty of Engineering, Mechanical Engineering Department, King Abdulaziz University, Jeddah P.O. Box 80204, Saudi Arabia

Abstract
A new strategy for improving the convergence and efficiency of the class of domain decomposition known as interface variable related Schur complement techniques for simulating mechanical, electrical and thermal problems in the presence of cross points is examined in this work. To be more precise, we're not just interested in domain decomposition into two parts with the same physical properties, but rather in more general splitting components. In the first case, we obtain optimal convergence with a good pre-conditioner in two iterations, while the problem remains difficult in the second case. The primary objective is therefore to fill in some of the gaps in these problem domain decomposition techniques and to contribute to the solution of extremely difficult large-scale industrial problems. A parallel sparse direct solver of the multi-core environment of the whole system is used and each part of the system is handled independently of the change of the mesh or the shifting of the mathematical method of resolution, and subsequently, the interface is treated as boundary condition. The numerical experiments of our algorithm are performed on a few models arising from discretizations of partial differential equations using the finite element method and a meshless method.

Key Words
domain decomposition method; finite element method; meshless method; parallel computing; Schur complement

Address
Saad Hassouna and Abdelaziz Timesli: Hassan II University of Casablanca, National Higher School of Arts and Crafts (ENSAM CASABLANCA), LISIME Laboratory, 20670 Casablanca, Morocco
Abderrazak Ramadane: International University of Casablanca, Laboratory "Mathematiques et Sciences de l'ingenieur", Route Provinciale 3020, 50169, Casablanca, Morocco
Abderrahim Azouani: Sultan Moulay Slimane University, National School of Applied Sciences of Khouribga, LIPIM Laboratory, Bd Béni Amir, 77, Khouribga, Morocco

Abstract
This study presents enhanced multilayer perceptron (MLP) neural network models—MLP-Bat and MLP-TLBO—for predicting the compressive strength of concrete columns transversely confined with carbon fiber-reinforced polymer (CFRP) sheets and transverse steel reinforcement (TSR) such as ties or spirals. A comprehensive experimental database was compiled from the literature and utilized for artificial neural network (ANN) modeling. The proposed models were benchmarked against existing empirical formulations and theoretical models. Results demonstrated that the MLP-Bat model outperformed the MLP-TLBO model and empirical formulations in terms of prediction accuracy, with statistical coefficients of MAE=6.953, RMSE=7.857, and R2=0.988 for MLP-Bat, compared to MAE=7.865, RMSE=7.391, and R2=0.981 for MLP-TLBO, and MAE=11.875, RMSE=9.323, and R2=0.948 for the empirical model. These findings highlight the superior accuracy of the MLP-Bat model, making it a reliable tool for predicting the axial strength of CFRP-confined concrete columns reinforced with TSR.

Key Words
artificial neural networks; axial strength; Bat optimization algorithm; CFRP; columns; MLP-TLBO

Address
Mohammed Berradia: Department of Civil Engineering, Laboratory of Structures, Geotechnics and Risks (LSGR), Hassiba Benbouali University of Chlef, B.P 78C, Ouled Fares Chlef 02180, Algeria
Nabil Ben Kahla and Muhammad Arshad: 1) Department of Civil Engineering, College of Engineering, King Khalid University,
PO Box 394, Abha 61411 Kingdom of Saudi Arabia, 2) Center for Engineering and Technology Innovations, King Khalid University, Abha 61421, Saudi Arabia
Ali Raza: Department of Civil Engineering, University of Engineering and Technology Taxila, 47050, Pakistan
Elhem Ghorbel: CY Cergy Paris University, 5 mails Gay LUSSAC, Neuville-sur-Oise—Cergy-Pontoise CEDEX 95031, France

Abstract
The study aimed at developing a Binary coded Genetic Mutation of Unified Particle Swarm Optimization (BCGM-UPSO) algorithm for structural design optimization of reinforced concrete (RC) space framed structures while adhering to safety, serviceability, and construction feasibility criteria. The study focuses on optimizing the design of two RC space framed structures (G+8 and G+10 stories) considering seismic loads (IS 1893 Part-I) and wind loads (IS 875 Part-III). Structural analysis of the space framed structures is carried out to derive design loads for beams and columns. GA-UPSO is implemented in MATLAB for cost optimization, incorporating material costs (formwork, concrete, reinforcement) and constraints like IS 456 safety and serviceability requirements. The algorithm also addressed reinforcement feasibility during construction, including curtailment requirements. Numerical analyses confirmed the accuracy of BCGM-UPSO in producing cost-optimized designs. Monte Carlo simulations demonstrated the robustness and consistency of the algorithm. The developed optimized design of multistorey space framed structure is directly applicable to construction projects, offering significant cost savings while ensuring compliance with structural and construction standards. This study demonstrates the practical utility of evolutionary mutation on swarm intelligence techniques, specifically UPSO, in addressing complex engineering challenges, such as cost-effective and feasible design of RC structures under realistic loading and design constraints. The BCGM - UPSO algorithm presents a robust and consistent approach to achieving cost-efficient designs for multistorey RC space framed structures, ready for immediate implementation in construction projects without further modifications.

Key Words
binary coded genetic mutation; seismic load; space framed structured structures; STAAD Pro; unified particle swarm optimization; wind load

Address
Payel Chaudhuri: Adamas University, Barasat, Kolkata-700126, India
Swarup K. Barman: KU Leuven, Gent, Belgium

Abstract
In recent decades, there has been an increase in research focused on nanotechnology, examining its remarkable properties and investigating its applications across various domains, including microelectronics, energy, mechanics, and biology. This paper examines the vibration of zigzag single-walled carbon nanotubes utilizing stress-strain gradient theory. The governing equations, along with boundary conditions, are employed to understand the influence of Young's modulus on the vibrations of a zigzag construction. Consequently, the Young's modulus of the tube is elevated for the impact of shape change through simulation on the structural flexibility of zigzag single-walled carbon nanotubes. Different graphs are developed to measure tube Young's modulus and vibration frequencies. The frequencies lie in the terahertz spectrum to investigate the smallest influences on the vibrations of zigzag single-walled carbon nanotubes. The zigzag index ranges as (6, 0), (9, 0), and (14, 0). When vibration happens in a zigzag tube with the designated indices, one can observe the complete mechanism of frequencies. Under both boundary conditions, Young's modulus increases the frequency surges at stiffness values of 1.0 and 1.5. As the frequency rises, the stuff gets stiff. Computational methods are used to evaluate the present findings for validity and correctness.

Key Words
accuracy and validity; boundary conditions; simulation; Young's modulus

Address
Mohamed A. Khadimallah and Elimam Ali: Department of Civil Engineering, College of Engineering in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj, 11942, Saudi Arabia
Muzamal Hussain: Department of Mathematics, University of Sahiwal, 57000, Sahiwal, Pakistan
Saima Akram and Madiha Tahir: Department of Mathematics, Government College Women University, Faisalabad, 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 hydrogen resource is regarded as the most promising clean energy source in the future, which has a disadvantage of extremely explosive characteristics while mixture with air. In order to protect the surroundings of the hydrogen station or other hydrogen source in the future, the impact mechanism on the surroundings with the explosion proof coating or not was compared and analyzed. Four walls at different distances from the hydrogen charge center and different scenarios with the explosion proof coating on front of the walls or not were implemented by using the numerical calculation software ANSYS/LS-DYNA in this paper. The dynamic compressive and tensile failure was set in the models to simulate the fractures generated by the impact of the blast strain waves. Results show that a huge broken zone at 200 cm and a small broken zone at 400 cm on back of the walls with no explosion proof coating and only a small broken zone at 200 cm with explosion proof coating on front of the walls finally. The positive peak of the dynamic strain waves at distance of 200 cm is 12x104 ue and larger than all of others. The positive peak of the dynamic strain is larger than the negative peak of that on front of the walls, while the negative peak of the dynamic strain is larger than the positive peak of that on back of the walls which showed an opposite result. The peak particle velocity on back of the walls with explosion proof coating is larger than all others except for the point on front of the center wall at 200 cm with explosion proof coating. It indicated that the explosion proof coating provides a good protective effect on the surrounds.

Key Words
dynamic response; explosion proof coating; hydrogen explosive; numerical investigation

Address
Fei Liu: 1) College of Emergency Management, Nanjing Tech University, Nanjing 211816, China, 2) State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Shenzhen University, Shenzhen, 518060, China
Pingfeng Li: Guangdong Hongda Holdings Group Co., Ltd, Guangzhou 510510, China
Zhirong Wang, Bi Chen and Jie Xiao: College of Emergency Management, Nanjing Tech University, Nanjing 211816, China

Abstract
Structural deficiencies in older buildings often require retrofitting or rehabilitation to improve durability and safety. Fiber Reinforced Polymer (FRP) composites are widely used in civil engineering for their effectiveness in restoration, offering superior performance in strengthening and reinforcing structures. This study examines the flexural strength improvement of High Strength Concrete-Reinforced Concrete (HSC-RC) beams using Hybrid Fiber Reinforced Polymer (HyFRP) composites, which combine Carbon-FRP (CFRP) and Glass-FRP (GFRP) laminates. Eight groups of beams underwent four-point bending tests, including both experimental and numerical analyses. One group was a control, while others used either single-layer GFRP or varying HyFRP configurations. The key variable was the arrangement of FRP layers, with beams reinforced by two to five layers of Single/Hybrid FRP composites. Beams with three layers of GFRP increased strength by 37.5% compared to the control, suggesting that beyond three layers, strength gains diminish. Beams strengthened with HyFRP laminates applied to their sides (100 mm wide, 100 mm spaced, and 3000 mm long) showed a 12.5% strength improvement. The optimal configuration was two layers of GFRP and two of CFRP, providing the best balance of strength and ductility, with glass fibers enhancing ductility and carbon fibers contributing to strength. Minimal de-bonding was observed, indicating effective epoxy bonding. Finite Element analysis closely aligned with the experimental results.

Key Words
carbon fibre; flexural strength; glass fibre; HyFRP; strengthening

Address
Kaarthic S E: Department of Civil Engineering, Salem College of Engineering and Technology, Perumapalayam, Salem - 636 111, Tamilnadu, India
Ramasamy V: Department of Civil Engineering, Adhiparasakthi Engineering College, Melmaruvathur - 603 319, Tamilnadu, India

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