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CONTENTS
Volume 98, Number 4, May25 2026
 

Abstract
During service, reinforced concrete structures are exposed to various environmental conditions that can lead to corrosion damage in both the concrete and rebar, resulting in mass loss and degradation of the mechanical properties of these materials. This paper presents the results of an analysis of the behavior of short reinforced concrete columns with varying degrees of corrosion damage to the concrete and rebar, as well as the effects of strengthening these columns using different techniques and repair mate-rials. From the interaction curves between bending moment and axial force, we estimated the effect of corrosion damage intensity on the ultimate load capacity of the columns. Additionally, these interaction curves were utilized to evaluate the effectiveness of three different methods for strengthening columns that experienced specific corrosion damage, including the loss of concrete cover and part of the cross-section of the main reinforcement bars. The results indicated that the load-bearing capacity of the columns after strengthening significantly depends on the chosen strengthening techniques and the mechanical properties of the repair materials, as well as the loading conditions of the column. Therefore, when selecting reinforcement methods, techniques, and repair materials, it is crucial to consider the values of the sectional forces, particularly the relationship between the bending moment and axial force.

Key Words
concrete loss; corrosion of reinforcement; FRP; load-bearing capacity; RC columns; strengthening

Address
Jacek Korentz: Institute of Civil Engineering, University of Zielona Góra, 65-417 Zielona Góra, Licealna 9, Poland

Abstract
Steel shear walls are an innovative system that resist to lateral loads such as wind and earthquakes. In this paper, the effect of knee element on the behavior of moment resisting frame with steel shear wall has been numerically investigated by changing parameters such as the number and types of link beam (bending, bending-shear and shear behavior), shear wall thickness and span length-to-height ratio. The results showed, the most effective one that affect the bending behavior of the frame is the case with 4 link beams with shear behavior dominated. Also, by changing the length of the link beam from bending to bending-shear and then shear behavior, the values of stiffness, bending strength and dissipated energy have increased. Failure mode in this system depends on how the shear plate is connected to the boundary members. In the absence of knee element, stress is notably concentrated at the interface of beam to the column connection, Conversely, with the inclusion of 4 link elements, the damage and stress concentration are dispersed away from the links and widely distributed in the filler plate thus the maximum plastic capacity of steel shear plate is used. The results demonstrate that incorporating four shear-dominated link beams provides the most balanced improvement, enhancing the lateral stiffness, ultimate strength, and cumulative energy dissipation by up to 143%, 102%, and 112%, respectively, compared to an unreinforced wall. The performance of moment-resisting frames without link beams is characterized by a less effective distribution of stress and inelastic strain compared to other samples and in contrast, the presence of link beams has been associated with a re-hardening effect in the force-displacement response of steel shear walls, resulting in improved bending performance.

Key Words
finite element; link beam (knee element); steel moment resisting frame; steel shear walls

Address
Shahram Tabasheri, Yahya Nassira: Department of Civil Engineering, Za.C., Islamic Azad University, Zanjan, Iran
Ali Ghamari: Department of Civil Engineering, Il.C., Islamic Azad University, Ilam, Iran

Abstract
Cosine Functionally Graded (CFG) plates offer a smoother material transition and better stiffness-toweight ratios than traditional grading profiles. In this study, we investigate the buckling behavior of these plates using a recently developed Higher-Order Zigzag Theory (HOZT). The high-fidelity data generated from our HOZT model served as the training set for a Gradient Boosting Machine (GBM) algorithm. We used key parameters such as skew angle (o), boundary conditions, aspect ratio (a/b), side-to-thickness ratio (a/h) and gradient index (R) as input features to predict the critical buckling load (Pcr). Our numerical results, show that the GBM model is remarkably accurate. A parametric dataset is generated considering key variables, including skew angle (0o-60o), aspect ratio (a/b), side-to-thickness ratio (a/h=5-100), boundary conditions, and material gradient index (R). The results show that the non-dimensional critical buckling load significantly increases with skew angle (up to ~150% increase from 0o to 60o) and decreases with increasing a/h, with the most pronounced variation observed for a/h<=20.The GBM model demonstrates excellent predictive capability, with deviations from finite element results remaining negligible (typically less than 1% across all tested cases). Overall, this work demonstrates that coupling physics-based simulations with data-driven models is a highly effective way to reduce costs while maintaining the precision needed for the rapid stability assessment of advanced structures.

Key Words
cosine functionally graded; finite element; gradient boosting machine; gradient index; HOZT; skew plate

Address
Tayeb Si Tayeb: University of Ahmed Ben Yahia El Wancharissi, 38000 Tissemsilt, Algeria; Laboratory of Geomatics and Sustainable Development, Ibn Khaldoun University of Tiaret, Algeria
Mohamed-Ouejdi Belarbi: Laboratoire de Recherche en Génie Civil, LRGC, Université de Biskra B.P. 145, R.P., Biskra 07000, Algeria
Tan Ngoc Nguyen: Department of Architectural Engineering, Sejong University, Seoul, 05006, Republic of Korea
Smain Bezzina: Deanship of Scientific Research, King Abdulaziz University, Jeddah, Saudi Arabia
Mohammed Sid Ahmed Houari: Laboratoire d'Etude des Structures et de Mécanique des Matériaux, Département de Cénie Civil, Faculté des Sciences et de la Technologie, Université Mustapha Stambouli, B.P. 305, Mascara, Algeria

Abstract
Short-crossbeam backfill in gob-side entry retaining is prone to lateral instability due to the caving gangue compression from gob, and lateral force point and angle are key influence factors on the stability. The instability of short crossbeam manifested as normal-stress bending failure and shear-stress cutting failure. The optimal bearing zone was in the transition zone between shear and compression. As loading point moved to the end, normal-stress failure load increased with crack propagation from the middle to the end, and shear-stress cutting load appeared at the position near the end and crack propagated towards the support point. Failure load was positively correlated with AE information, the correlation coefficients of loading positions and angles were 0.9722 and 0.9006 respectively. The influence of loading angle was less on failure load than the one of loading position: failure load increased by 2.60 times and by 1.16 times with loading position from the middle to the end and with loading angle from 0o to 30o respectively. The higher failure load, the greater fracture energy, the simpler crack propagation, and the more vertical the crack. The theoretical failure load of the maximum loading angle was consistent with the test result with 0.84% difference.

Key Words
AE information; failure process; intensity characteristics; mechanical model; normal-shear stress; short crossbeam support

Address
Yajun Xin: School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan, China; Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization, Jiaozuo, Henan, China
Qi Liu: School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan, China
Hongying Ji: School of Resources and Environment, Henan Polytechnic University, Jiaozuo, Henan, China
Yinquan Liang: Yunnan Dongyuan Zhenxiong Coal Industry Co., Ltd., Zhaotong, Yunnan, China
Jichun Kang: School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan, China
Jinwu Ren: Yonghua Energy Co., Ltd., Henan Energy and Chemical Industry Group, Luoyang, Henan, China
Hongjuan Dong: Mining Institute, Inner Mongolia Science and Technology University, Baotou, Inner Mongolia, China

Abstract
Acoustic methods are widely used for non-destructive concrete testing. They detect internal flaws while preserving structural integrity. Nevertheless, current detection methods primarily depend on manual judgment, which is laborious, time-consuming, expensive, and susceptible to misjudgment and oversight. This study established an efficient and accurate detection system for identifying defects in concrete structures. Experimental data is first collected through ultrasonic tomography scans. To compensate for limited test data, numerical simulations generate extensive datasets with varied defect locations, enabling development and optimization of a 1D-CNN model using the dataset. This network structure is then applied to the experimental data for detecting defects in concrete structures. Values of 0.9708 and 0.9440 are achieved by the models which validates its effectiveness in practical applications and generalization ability. This method successfully combines convolutional neural networks with ultrasonic techniques. It enables the automatic detection of internal defects and provides a new effective approach for nondestructive testing of concrete structures.

Key Words
concrete; convolutional neural networks; defect; linear regression; non-destructive testing; ultrasonic tomography

Address
Fengyi Zhang, Lihua Wang, Yameng Wang, Wenjing Ye, Yongdong Pan: School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, PR China

Abstract
In this paper, free vibration and buckling analysis of functionally graded Timoshenko beams are investigated. Stiffness and mass of Timoshenko beam are assumed to change using an exponential function along the beam length. Fredholm transformation approach is applied to solve the governing equation of motion. The usual method for applying Fredholm transformation is approximation of mode shape function by a power series that this method needs four repetitive integrations to obtain weak form of the governing equation. In this paper, a novelty is introduced into usual approach that is approximation of bending moment acting on the cross section of the beam by a power series. This novelty requires two successive integrations to obtain the weak form. Therefore, the mathematical process required is shorter and simpler. Regarding two integrations, two constants appear in the resulting weak form equation that are determined using appropriate boundary conditions for Timoshenko beam. Approximation of bending moment results in a system of linear algebraic equations that the natural frequencies are determined by calculation of a non-trivial solution for this system of equations. Buckling analysis of Timoshenko beam is also presented and the buckling loads are determined for beams with various end boundary conditions. The efficiency and accuracy of the presented approach are investigated through comparison of the numerical results with those available in the existing literature.

Key Words
bending moment approximation; buckling load; integral equation; natural frequency; Timoshenko beam; weak form

Address
Mehrdad Mohammadnejad: Department of Civil Engineering, Birjand University of Technology, Birjand, Iran

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