ABSTRACT Cable force estimation is critical for ensuring the structural health of cable-stayed bridges. This study assesses the accuracy of three vibration-based models – classical string theory, a least-squares beam formulation, and a two-mode beam combination – using lift-off test results as ground-truth validation. Field measurements were analysed to extract natural frequencies, which served as inputs to predict axial forces. The correlation between estimated forces and lift-off measurements was evaluated using the Pearson coefficient and mean absolute error (MAE). Results show strong agreement between vibration-based estimates and lift-off forces, with correlation coefficients ranging from 0.8610 to 0.8619. Beam-theory approaches outperformed the string model, achieving 7–8% lower MAE confirming that incorporating bending stiffness and multi-mode effects improves accuracy. However, small numerical differences suggest axial tension remains the dominant factor, with flexural rigidity having minor influence on long and slender cables. The near-perfect correlation between the beam-based models (r > 0.9996) highlights their internal consistency. Overall, these findings demonstrate that vibration-based models are reliable tools providing essential insights for structural health monitoring and maintenance strategies.

ABSTRACT Bolted joints are critical to engineering structures and their integrity is essential for safety and functionality. Traditional monitoring methods are often expensive and intrusive, necessitating the development of more efficient approaches. Preload loss in pretensioned bolts is inevitable in practice, making the reliable detection of loosening vital for structural reliability. This study presents a novel structural health monitoring (SHM) method based on vibration and percussive audio-emission signals generated during controlled percussion. A single bolted lap joint was subjected to percussion, and the resulting audio and vibration signals were recorded and analyzed in both the time and frequency domains to assess bolt tightness. As the bolt torque increased from 0 Nm to 25 Nm, significant variations were observed in signal characteristics. For the vibration signals, the Signal Energy, Peak-to-RMS ratio, and kurtosis changed by 48.84%, 61.02%, and 90.15%, respectively. For audio signals, the corresponding variations were 39.53%, 44.77% and 80.79%. Fast Fourier Transform (FFT) analysis showed a correlation between bolt tightening levels and frequency amplitudes, with slight frequency increases in both signal types with an increase in bolt torque. The results demonstrate that percussion-induced signals effectively reflect bolt tightness. Comparative analysis of vibration and audio responses highlights the potential of this multi-modal approach to enhance the reliability of bolted joint SHM applications.

ABSTRACT The integrity of concrete structures is paramount for the safety and longevity of civil infrastructure. Traditional methods for detecting cracks in these structures are often time-consuming, subjective and prone to human error. This study introduces an automated, high-performance crack detection system based on the YOLOv8 deep learning architecture, designed for real-time and accurate identification of cracks in concrete images. YOLOv8, renowned for its superior speed and accuracy, integrates a powerful convolutional backbone with decoupled head structures for detection and localisation, enabling the detection of fine and irregular crack patterns under varied lighting and background conditions. The system trained and tested on a comprehensive dataset of 4000 concrete images, achieved a precision of 91.80%, recall of 92.50% and overall accuracy of 93% in detecting cracked regions. For non-cracked images, the system demonstrated an accuracy of approximately 90%. These results underscore the model’s robustness in accurately identifying crack damages with minimal false positives and negatives, highlighting YOLOv8 as a reliable solution for automated structural health assessment.

ABSTRACT An innovative built-up beam section has recently been developed, comprising multiple 150 × 75 lipped channels mounted vertically and connected with screws through their lips and webs. These built-up sections offer a high section modulus, making them an economical option for use as rafters in portal and wide-span frames. However, current design codes do not provide specific guidance or rules for these sections. Predicting their flexural capacity and performance requires complex analyses, such as Finite Element Analysis, as well as experimental testing, both of which are costly and time intensive. To address this gap, a simplified design method is proposed based on the Direct Strength Method (DSM) from AISI and AS/NZS standards, which assumes a linear stress distribution across the cross-section. This approach enables straightforward prediction of the flexural capacity of such built-up sections. The accuracy of this design procedure has been validated by comparing predictions with experimental results.

ABSTRACT The time-domain method plays a significant role in structural wind-induced vibration analysis. The conventional approach typically involves three key steps: wind field simulation, dynamic vibration response calculation, and statistical analysis of the response. However, dynamic response analysis often relies on approximate methods and demands substantial computational effort. To address this limitation, this paper proposes a simplified closed-form approach, which significantly enhances the computational efficiency while maintaining accuracy. The core idea leverages the principle that the response of a harmonic input through a linear system remains harmonic. By exploiting this property, the solution for a linear system subjected to trigonometric excitation can be derived analytically, bypassing the need for the numerical integration of the vibration equations, which ensures both precision and efficiency. Furthermore, the Fast Fourier Transform (FFT) technique is employed to efficiently compute the structural response for a sum of trigonometric functions, drastically reducing the computational time. To demonstrate the method’s effectiveness, the along-wind vibration response of a 45 m transmission tower is analysed in the time domain. The proposed approach is validated against frequency-domain analysis and traditional time-domain methods. Results confirm that the method is computationally efficient and accurate, particularly for structures with a high number of degrees of freedom.

ABSTRACT The use of recycled aggregates (RA) is promising in concrete production for construction projects. Therefore, accurately predicting the compressive strength (CS) of this concrete is crucial for understanding the behaviour of such concrete. This study marks an inaugural effort to evaluate the AutoGluon framework for predicting CS for RA concrete. In this novel framework, categorical boosting (CatBoost), light gradient boosting machine (LightGBM), weighted ensemble (WeightENS) and extreme gradient boosting (XGBoost) were considered. The variables used for the modelling were curing days, quantity of cement, water, recycled aggregate, coarse aggregate and fine aggregate. Various statistical and graphical tools were used to evaluate the effectiveness of the proposed models. The findings showed that the CatBoost model achieved the highest prediction performance with a minimal root mean squared error (RMSE) of 1.45. The feature importance evaluation indicated that cement is the most influential variable for CS models. Overall, the study highlights that AutoGluon provides a reliable and robust framework for modelling in structural engineering. Additionally, AutoGluon eliminates the need for an exhaustive and time-intensive process of hyperparameter optimisation.

ABSTRACT A new double-deck steel truss arch bridge with a length of 408 meters is proposed for Qingshuitang Bridge. The upper deck serves as a six-lane highway in both directions, with a bridge deck width of 32 meters. The main arch ribs are constructed using steel box arches, equipped with lateral wind braces for enhanced stability. The main span employs a lightweight composite steel deck with double main girders and ultra-high-performance concrete to reduce self-weight and increase span length. The side spans and approach bridges utilize a double main girders + beam steel-concrete composite deck. The upper deck has a standard width of 24.5 meters, while the lower deck is designated for pedestrian and non-motorized traffic, with a width of 10 meters in the suspension area and 12 meters in the recreational area. Finite element analysis conducted using Midas software indicates that the static and dynamic performance of the bridge, as well as the forces acting on the bridge deck, meet the specified requirements.

ABSTRACT The masonry veneer wall system relies on metal wall ties to connect the outer masonry leaf to the internal frame, ensuring structural stability. In Australia, a masonry veneer wall typically consists of a timber frame that has galvanised wall ties fixed to the side of the timber studs, with a nail or screw, spanned across an air cavity to the external leaf of masonry. This study explores the impact of corrosion on the integrity of these wall ties, emphasising their susceptibility to failure during extreme events. Existing literature highlights tension failure in a veneer wall is the result of nail pull-out from the timber. In the current research, accelerated corrosion of an R2 (Z600) wall tie reveals that tensile strength reduction is due to decreasing tie cross section from corrosion, leading to wall tie fracture rather than nail pull-out. Understanding these failure mechanisms is crucial for building assessment and monitoring strategies for masonry structures, especially in regions prone to extreme wind or seismic activity in combination with corrosion susceptibility, such as coastal environments.

ABSTRACT Bolted joint behaviour is a key parameter in predicting transmission tower performance. Various types of joints are based on the number of bolts and their configuration. However, a few types of these joints were tested or modelled. In the present study, the load-deformation response of transmission tower joints as a joint behaviour was predicted using a simplified numerical model. Then, available experimental load-deformation responses of joints were used to verify the results of the proposed model. In the last step, the joint behaviours of a 400 kV transmission tower were predicted with the proposed numerical model. Then, the evaluation of the tower’s response was done with a numerical model in ABAQUS under testing loading conditions. Lastly, the deformation of a full-scale tested tower was compared with the numerical results. The numerical model results show a good agreement with the experimental results. The ultimate strength and its corresponding displacement at the full-scale model are predicted with an error of about 4%. Moreover, the failure mode of the transmission tower was not affected by the behaviour of the joints.

ABSTRACT The absolute maximum response (AMR) of structures might occur posterior to the end of earthquake excitations, hence, extending the dynamic analysis to the post-shaking phase is required. This phenomenon was found to be more common for long-period and low-damping structures, which are prevailing in regions of low-to-moderate seismicity like Australia. In this article, the mechanism of the occurrence of AMR in the post-shaking phase is first explained using single-degree-of-freedom (SDOF) systems subjected to a simple sine wave. Further investigation on real earthquake ground motions reveals that whether an extended analysis is required depends greatly on the characteristics of the post-significant duration phase. Finally, suitable metrics for describing ground motions that require extended analysis (EAGMs) are identified based on the Kolmogorov–Smirnov test. Regression analyses are then conducted to predict the probability of EAGMs.