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CONTENTS
Volume 37, Number 1, January 2026
 

Abstract
Many of the structures and mechanical systems used have elements in contact. Determining the contact pressures and contact areas that occur after the applied load in the systems in contact is extremely important for the structure to continue its function. On the other hand, it is also known that one of the most important parameters affecting the contact pressures and contact areas of the elements in contact is the material of these elements. Although many studies have been carried out in the literature to determine the contact pressures and areas of the structures in contact with various analytical and numerical methods, it seems that no study has been conducted on how the contact pressures and contact areas will be affected by the changes in the mechanical properties of the materials in these structures. In this context, in this study, friction stir process was applied to structural steel with different parameters and the effects of this process on the strength and elongation values of the steel were examined. Afterwards, the changes in strength and elongation values were reflected in the models created with finite elements (FEM) and artificial neural networks (ANN), and the effects of material properties changing at changing loads on contact pressures and distances during contact were investigated. As a result of the investigations, it was determined that after the friction stir process, the strength value of the steel increased and the elongation values decreased compared to the base material in all parameters. Also, it has been determined that the increase in the strength of the material is extremely effective on the increase of contact pressures, and the contact areas generally decrease with the decrease in the elongation values of the material.

Key Words
artificial neural network; contact problem; finite element analysis approach; friction stir process; structural steel

Address
(1) Dursun Murat Sekban:
Department of Marine Engineering Operations, Karadeniz Technical University, 61530, Trabzon, Turkiye;
(2) Dursun Murat Sekban:
Trabzon Teknokent, WMS Engineering Services Industry Trade Limited Company, 61080, Trabzon, Turkiye;
(3) Ecren Uzun Yaylaci:
Faculty of Fisheries, Recep Tayyip Erdogan University, 53100, Rize, Turkiye;
(4) Mehmet Emin Ozdemir:
Department of Civil Engineering, Cankiri Karatekin University, 18100, Cankiri, Turkiye;
(5) Murat Yaylaci:
Department of Civil Engineering, Recep Tayyip Erdogan University, 53100, Rize, Turkiye;
(6) Murat Yaylaci, Idris Turna:
Faculty of Turgut Kiran Maritime, Recep Tayyip Erdogan University, 53900, Rize, Turkiye;
(7) Murat Yaylaci:
Dijitalpark Teknokent, Murat Yaylaci-Luzeri R&D Engineering Company, 53100, Rize, Turkiye;
(8) Abdelouahed Tounsi:
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia;
(9) Abdelouahed Tounsi:
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria.

Abstract
This study applies the digital Real-Time Hybrid Testing with a Shake Table (RTHT‐ST) method to verify the control performance of the Polynomial Sliding Isolators with Variable Curvature - Floor Isolation System (PSIVCFIS). The Hardware-in-the-loop (HIL) simulation is also used in this research, where both primary structures and subsystems are numerical models embedded in the single-task processor environment, with real-time communication through the shared common RAM network hardware (SCRAMNet) with optical fiber interface (digital) or the traditional Analog-to-Digital/Digital-to-Ananlog (AD/DA) converters with BNC connectors (analog). The dynamic characteristics and operational limitations of the shake table are analyzed through the HIL simulation before and after the digital RTHT‐ST to ensure system stability, equipment safety, and to investigate the key issue related to the discrepancy between the Shaking Table Test (STT) and the digital RTHT-ST. The adopted control device, the PSIVCFIS, is tested as a subsystem through the digital RTHT-ST using the Multi-Axial Seismic Test (MAST) system at the southern branch of the National Center for Research on Earthquake Engineering (NCREE). The passive control performance is compared with its STT results conducted earlier using the shaking table at the northern branch of the NCREE.

Key Words
hardware-in-the-loop; multi-axial seismic test system; polynomial sliding isolators with variable curvature; real-time hybrid testing with a shake table; SCRAMNet; shaking table test

Address
(1) Qi-Yang Liao, Shih-Yu Chu, Yan Tang:
Department of Civil Engineering, National Cheng Kung University, No.1, University Road, Tainan, Taiwan;
(2) Chan-Jung Kang:
Department of Civil Engineering, I-Shou University, No.1, Sec. 1, Syuecheng Road, Kaohsiung, Taiwan;
(3) Yun-Hsi Lai:
Department of Civil & Building, CTCI Corporation, Taipei, Taiwan;
(4) Che-Wei Chang:
Dayan Engineering Consultant, Taichung, Taiwan;
(5) Yan Tang:
Development Engineering Division, Land Administration Bureau, Tainan City Government, Tainan, Taiwan.

Abstract
Seismic isolation systems are widely used in structural engineering to mitigate earthquake-induced damage by decoupling structure displacement from ground motion. Building on this principle, this study investigates the effectiveness of a novel eddy current damping (ECD) mechanism integrated into a roller seismic isolation bearing (RSIB) system to enhance seismic performance. The proposed non-contact energy dissipation device contro s seismic-induced displacements while minimizing wear-related issues in traditional friction-based damping systems. A scaled RSIB model coupled with the ECD device was tested under free vibration and seismic excitation. Besides, a numerical model was developed to simulate the response to both far- and near-fault earthquakes and evaluate RSIB performance. The results indicate that increasing braking force reduces isolator displacements but leads to higher absolute accelerations. Displacement reductions of up to 72% were achieved, ensuring that movements remained within the physical limits. However, higher braking forces also increased peak acceleration. The equivalent damping ratioimproved by up to 61.58%, confirming the ability of the ECD to enhance energy dissipation. The numerical model accurately reproduced the experimental results, and the key dynamic parameters of the RSIB and ECD systems were identified. The findings demonstrate that eddy current damping can be effectively integrated into roller seismic isolation systems to enhance energy dissipation and displacement control in RSIB systems. However, the optimal braking force must be carefully selected based on the expected seismic demands to achieve a trade-off between displacement control and acceleration performance. Future research should focus on full-scale implementation and an ECD device optimized for target-breaking force.

Key Words
eddy current damping; multiple rollers arranged; non-contact energy dissipation; roller bearings; roller isolation system; sloped bearing plate

Address
Civil Engineering Program, Universidad Militar Nueva Granada, kilometer 2, Cajica-Zipaquira road, 250247, Cajica/Cundinamarca, Colombia.


Abstract
This paper presents a new damage detection technique for simply supported beams and highway bridges, utilizing the generalized curvature quotient difference method. A convolutional neural network (CNN) system was developed in in conjunction with this method to effectively identify damage locations and intensities in steel girder highway bridges, even amidst noise interference. The proposed damage index is calculated using the stiffness matrix of an intact element, allowing it to detect various damage scenarios in both simply supported beams and the validated finite element model of the I-40 bridge. Simulations were conducted using different bending mode shapes, specifically the first mode for the simply supported beam and the second and third modes for the I-40 bridge model. The results illustrate that the combined approach of the proosed index and the CEEMD noise-canceling method effectively identifies damage locations under both noisy and noise-free conditions. After omitting noise-polluted data, this index was used as input data to train the CNN system. The trained CNN system rechecked the damage locations and achieved precise intensity estimations for multiple unspecified damages (up to four occurring simultaneously), even under noisy conditions. This technique, along with the CNN system, addresses previous research limitations such as the impact of noise (especially near the supports), low speed, low precision, huge input data, and time-consuming training network. The outcomes of this method indicate clarity and accuracy in determining the location and intensity of either multiple or single damage scenarios, even in the presence of noise up to 15%.

Key Words
damage detection; deep convolution neural network; generalized curvature quotient method; noisy condition; steel girder bridge; structural health monitoring

Address
(1) Sara Zalaghi, Armin Aziminejad, Mir Hamid Hosseini:
Department of Civil Engineering, SR.C., Islamic Azad University, Tehran, Iran;
(2) Hossein Rahami:
School of Engineering Science, College of Engineering, University of Tehran, Tehran, Iran;
(3) Abdolreza S. Moghadam:
International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran.

Abstract
Damage detection of steel tube in in-service steel grid structures (SGSs) is essential for maintaining structural safety. Ultrasonic guided waves (UGWs) enable non-destructive detection of micro-damage using singlepoint excitation. UGWs hold significant potential for inspecting tube members. However, tube members in SGSs are typically connected by spherical joints, and echoes reflected from the joint can potentially obscure damage identification using UGW signals. To address this issue, an enhanced UGW-based damage detection method for steel tube with spherical joints (STSJs) is proposed. First, the low-frequency torsional T(0,1) mode UGW is selected as the excitation signal. Next, a bidirectional control strategy for UGW excitation and reception is proposed and incorporated into the UGW-based damage detection method. This strategy employs the pulse-echo method, enabling the same set of transducers to both excite and receive signals. Two transducer rings are positioned a quarter wavelength apart, with a phase shift of π/2 between their signals. This configuration not only suppresses excitation signals in non-detection direction, but also attenuates reception signals from that direction, effectively mitigating interference caused by spherical joints and significantly enhancing the signal-to-noise ratio for damage detection. Subsequently, the reflection coefficient method is used to locate damage in STSJs. This strategy facilitates UGW-based damage detection in STSJs without the need for reference signals. The effectiveness of the proposed method is validated through an experiment on a notched STSJ specimen. Results indicate that by eliminating the interference signals, the proposed method achieves a damage localization error of 0.08%, demonstrating potential applicability of the method for practical damage detection in STSJs.

Key Words
damage detection; directional control; spherical joints; steel tube; ultrasonic guided wave

Address
(1) Xian Xu, Yi Zhang, Tingting Shu, Yaozhi Luo:
Department of Civil Engineering, Zhejiang University, Hangzhou, China;
(2) Xian Xu:
Center for Balance Architecture, Zhejiang University, Hangzhou, China.

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