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CONTENTS
Volume 34, Number 1, July 2024
 

Abstract
The design of disturbed regions in reinforced concrete structures usually applies the well known Strut and Tie Method (STM). As an alternative, the Stringer-Panel Method (SPM), an intermediate model between STM and the Finite Element Method (FEM), consists in dividing a structure into two distinct elements: the stringers (which carry axial forces) and panels (which carry shear forces). SPM has already showed good applicability in manual calculations and computer implementations, and its most known application was SPanCAD, an AutoCAD plugin for linear and nonlinear analysis by SPM. Unfortunately, SPanCAD was discontinued by the developers, and it's not compatible with the most recent versions of AutoCAD. So, this paper aims to present a computer program that was developed as an upgrade to the latter: the Stringer Panel Modelling Tool (SPMTool), which is intended to be an auxiliary design tool and it presents improvements, in comparison to SPanCAD. It is possible to execute linear and nonlinear analysis by three distinct formulations: Modified Compression Field Theory (MCFT), Disturbed Stress Field Model (DSFM) and Softened Membrane Model (SMM). The nonlinear results were compared to experimental data of reinforced concrete elements that were not designed by SPM; these elements were also analyzed in SPanCAD. On overall, SPMTool made more realistic predictions to the behavior of the analyzed structures than SPanCAD. Except for DSFM predictions for corbels (1.24), in overall average, the ultimate load predictions were conservative (0.85 to 0.98), which is a good aspect for a design tool. On the other hand, the cracking load predictions presented overestimations (1.06 to 1.47) and higher variations (25.59% to 34.25%) and the post-cracking behavior could not be accurately predicted; for this use case, a more robust finite element software is recommended.

Key Words
disturbed regions; nonlinear analysis; reinforced concrete; Stringer-Panel Method

Address
André Felipe Aparecido de Mello: Engineering Faculty, Universidade Federal da Grande Dourados, Dourados/MS, Brazil
Leandro Mouta Trautwein and Luiz Carlos de Almeida: Civil Engineering, Architecture and Urbanism Faculty, Universidade Estadual de Campinas, Campinas/SP, Brazi
Rafael Alves de Souza: Civil Engineering Department, Universidade Estadual de Maringá, Maringá/PR, Brazil

Abstract
This study explores the failure mechanisms of 'I' shaped non-persistent cracks under uniaxial loads through a combination of experimental tests and numerical simulations. Concrete specimens measuring 200 mm*200 mm*50 mm were manufactured, featuring 'I' shaped non-persistent joints. The number of these joints varied from one to three, with angles set at 0, 30, 60, and 90 degrees. Twelve configurations, differing in the placement of pre-existing joints, were considered, where larger joints measured 80 mm in length and smaller cracks persisted for 20 mm with a 1 mm crack opening. Numerical models were developed for the 12 specimens, and loading in Y-axis direction was 0.05 mm/min, considering a concrete tensile strength of 5 MPa. Results reveal that crack starting was primarily influenced by the slope of joint that lacks persistence in relation to the loading direction and the number of joints. The compressive strength of the samples exhibited variations based on joint layout and failure mode. The study reveals a correlation between the failure behavior of joints and the number of induced tensile fracture, which increased with higher joint angles. Specimen strength increased with decreasing joint angles and numbers. The strength and failure processes exhibited similarities in both laboratory testing and numerical modeling methods.

Key Words
experimental investigation; joint orientation; non-continuous joints in "I" shape configuration; PFC2D

Address
Vahab Sarfarazi and Nima Babanouri: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran
Soheil Abharian: Department of Civil and Environmental Engineering, Western University, London, ON, Canada

Abstract
This paper presents the detailed experimental and analytical investigation on the evolution of static (Es) and dynamic modulus of elasticity (Ed) of concrete having 0%, 35%, and 50% FA used as partial cement replacement. Destructive and nondestructive tests were conducted on cylindrical specimens to evaluate the compressive strength and MoE of concrete in compression at the age of 28, 56, 90, and 150 days for all mixes. Experimental results show that the concrete having 35% FA achieved compressive strength and MoE similar to plain concrete at the age of 90 days, while 50% FA concrete attained satisfactory compressive strength and MoE at the age of 150 days. The comprehensive statistical analysis has been carried out in two ways on the basis of the experimental results. Firstly, the 28-day crushing strength of plain concrete in compression was used to design the models for the prediction of Es and Ed of fly ash concrete at any age and percentage replacement of FA. Secondly, using the values of UPV and RHN, models have been developed to predict the age or time-dependent Es and Ed of fly ash concrete. These models will be helpful in assessing the Es and Ed of fly ash concrete without knowing the 28-day crushing strength of plain concrete in compression in the laboratory. Hence, the suggested models in the present study will be beneficial in conducting the health assessment of fly ash based concrete structures.

Key Words
age-dependent; analytical solutions; dynamic modulus of elasticity; fly ash concrete; model assessment; non-destructive testing; static modulus of elasticity

Address
Department of Civil Engineering, Z.H. College of Engineering & Technology, Aligarh Muslim University, India

Abstract
The present study concerns a removal of chloride ions and structural behaviour of concrete beam at electrochemical chloride extraction (ECE). The electrochemical properties included 1000 mA/m2 current density for 2, 4 and 8 weeks. It was found that an increase in the duration of ECE resulted in an increase in the extraction rate of chlorides, in the range of 35-85%, irrespective of chloride contamination. In structural behaviour, the strength and maximum bending moment of specimen was always lowered by ECE. Moreover, the flexural rigidity and bending stiffness were reduced by the loss of effective cross-section area in the linear elastic range. Simultaneously, the inertia moment was substantially subjected to 70% loss of the cross-section by the tensile strain at the condition of the failure. However, a lower rate of the inertia moment reduction was achieved by ECE, implying the higher resistance to the cracking, but the higher risk of deformation.

Key Words
cracking; ECE; flexural rigidity; inertia moment reduction; strength; structural behaviour

Address
Department of Civil and Environmental Engineering, Hanyang University, 55 Hanyangdeahak-ro, Sangnok-gu, Ansan, Gyeonggi-do, 15588, Republic of Korea

Abstract
In this research, we considered fractional order optimal control models for cancer, HIV treatment and glucose.These models are based on fractional order differential equations that describe the dynamics underlying the disease.It is formulated in term of left and right Caputo fractional derivative. Pontryagin's Maximum Principle is used as a necessary condition to find the optimal curve for the respective controls over fixed time period. The formulated problems are numerically solved using forward backward sweep method with generalized Euler scheme.

Key Words
Caputo fractional derivative; fractional order differential equations; Pontryagin

Address
Mohamed Amine Khadimallah: Department of Civil Engineering, College of Engineering in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj, 11942, Saudi Arabia
Shabbir Ahmad: Department of Mathematics, COMSATS University Islamabad, Lahore Campus, Pakistan
Muzamal Hussain: 1) Department of Mathematics, University of Sahiwal, Sahiwal, Pakistan, 2) Department of Mathematics, University of Sahiwal, Sahiwal, 57000, Punjab, Pakistan
Abdelouahed Tounsi: 1) YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea, 2) Department of Civil and Environmental Engineering, King Fahd University of Petroleumand Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia

Abstract
In symmetric cryptography, a cryptographically secure Substitution-Box (S-Box) is a key component of a block cipher. S-Box adds a confusion layer in block ciphers that provide resistance against well-known attacks. The generation of a cryptographically secure S-Box depends upon its generation mechanism. In this paper, we propose a novel framework for the construction of cryptographically secure S-Boxes. This framework uses a combination of linear fractional transformation and permutation functions. S-Boxes security is analyzed against well-known security criteria that include nonlinearity, bijectiveness, strict avalanche and bits independence criteria, linear and differential approximation probability. The S-Boxes can be used in the encryption of any grayscale digital images. The encrypted images are analyzed against well-known image analysis criteria that include pixel changing rates, correlation, entropy, and average change of intensity. The analysis of the encrypted image shows that our image encryption scheme is secure.

Key Words
block cipher; image encryption; linear fractional transformation; permutation function; substitution-box

Address
Razi Arshad: Department of Computing, School of Electrical Engineering and Computer Sciences, National University of Sciences and Technology, Islamabad 44000, Pakistan
Mudassir Jalil: Department of Mathematics, Comsats University Islamabad, Islamabad, 44000, Pakistan
Muzamal Hussain: Department of Mathematics, University of Sahiwal, Sahiwal, 57000, Punjab, Pakistan
Abdelouahed Tounsi: 1) YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea, 2) Department of Civil and Environmental Engineering, King Fahd University of Petroleumand Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia

Abstract
One well-known reason for using Fiber Reinforced Polymer (FRP) composites is to improve concrete strength and strain capacity via external confinement. Hence, various studies have been undertaken to offer a good illustration of the response of FRP-wrapped concrete for practical design intents. However, in such studies, the strength and strain of the confined concrete were predicted using regression analysis based on a limited number of test data. This study presents an approach based on artificial neural networks (ANNs) to develop models to predict the strength and strain at maximum stress enhancement of circular concrete cross-sections confined with different FRP types (Carbone, Glass, Aramid). To achieve this goal, a large test database comprising 493 axial compression experiments on FRP-confined concrete samples was compiled based on an extensive review of the published literature and used to validate the predicted artificial intelligence techniques. The ANN approach is currently thought to be the preferred learning technique because of its strong prediction effectiveness, interpretability, adaptability, and generalization. The accuracy of the developed ANN model for predicting the behavior of FRP-confined concrete is commensurate with the experimental database compiled from published literature. Statistical measures values, which indicate a better fit, were observed in all of the ANN models. Therefore, compared to existing models, it should be highlighted that the newly developed models based on FRP type are remarkably accurate.

Key Words
artificial neural networks (ANNs); circular concrete cross-sections; concrete confinement; fiber reinforced polymers (FRP); strain at maximum load; strain model; strength model

Address
Yaman S. S. Al-Kamaki, Mezgeen S. Ahmed and Mand K. Askar: Highways and Bridges Engineering, Technical College of Engineering, Duhok Polytechnic University (DPU), Duhok, Kurdistan Region, Iraq
Abdulhameed A. Yaseen: Civil Engineering Department, College of Engineering, University of Duhok (UoD), Duhok, Kurdistan Region, Iraq
Razaq Ferhadi: College of Engineering, The American University of Kurdistan (AUK), Duhok, Kurdistan Region, Iraq

Abstract
Strain-hardening cement-based composites (SHCC) under cracked condition exhibits remarkable capillary absorption due to water ingress from multiple cracks. Surface treatment using water repellent agents is an effective way for improving water resistance of SHCC, but the water resistance may remarkably decrease when cracks penetrate impregnation depth. Another way is to add water repellent agents directly into the mixture, offering SHCC integral water repellency even if cracks form later. However, although integral water repellent treatment has been proved feasible by previous studies, there is still lack of simulation work on the treated SHCC for evaluating its durability. This study presents a simulation method for capillary absorption of cracked SHCC with integral treatment based on a multi-scale approach proposed in the authors' previous work. The approach deals with water flows in bulk matrix and multiple cracks using two individual transport equations, respectively, whereas water absorbed from a crack to its adjacent matrix is treated as the mass exchange of the two equations. In this study, the approach is enhanced for the treated SHCC by integrating the influencing of water repellency into the two transport equations as well as the mass exchange term. Using the enhanced approach, capillary absorption of water repellent SHCC under cracked condition is simulated, showing much more reduced water ingress than the untreated concrete, which is consistent with total absorption data from previous tests. This approach is also capable of simulating water spatial distribution with time in treated SHCC reasonably.

Key Words
capillary absorption; integral water repellence; multi-scale modeling; multiple fine cracks; silane treatment; strain-hardening cement-based composites (SHCC)

Address
Yao Luan: Department of Civil and Environmental Engineering, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama-shi, Saitama 335-8570, Japan
Tetsuya Ishida: Department of Civil Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

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