The mechanical properties of large-span space structures are complicated and change greatly during its construction. So it is necessary to monitor the real time status of the structure to ensure the safety of the construction process. However, the number of monitoring points is often very large due to the space structure's large number of members and three-dimensional forcing characteristics. An optimization method for reducing monitoring points is proposed based on the characteristics of certain correlation between different members' mechanical responses during construction in this paper. Firstly, the comprehensive correlation matrix of structural response was established by using correlation coefficient method and grey correlation degree method, and the cluster correlation matrix with block characteristics was calculated by the bond energy algorithm, so as to construct the classification and optimization principle of reducing measuring points. Then, LSTM neural network was used to build a response prediction model, and the in-situ monitoring data was used to train and verify the prediction model. The results show that Pearson correlation coefficient and B-type grey correlation can effectively explore the similarity between the change size and trend of spatial structural responses. At the same time, LSTM neural network can learn to optimize the response correlation between the measuring points and its related measuring points, realizing the global monitoring of the structure.
Accurate measurement of fatigue crack length is essential for routine maintenance of steel bridges, and automated technologies have already been applied in maintenance operations. However, conventional image processing strategies suffer from complex and multi-source interference in steel box girders. This study proposed a two-stage method combining region recognition and morphological processing to diminish noise in fatigue crack images, thereby improving the accuracy of crack recognition and length measurement. The object-recognition-former (OBFormer) model was built to detect and isolate the fatigue crack regions, leveraging the advanced feature extraction module and localization capabilities. Optimized Canny algorithm was utilized to suppress noise and extract the skeletal line of the fatigue crack from detected regions. The length of the crack was calculated by modifying the coordinate system of the crack plane and quantifying the number of pixels along the skeletal line. Experimental results showed that the OBFormer model effectively handled complex background interference and accurately detected the fatigue crack regions, with a mean average precision (mAP) of 91%. After morphological processing, the length of the crack skeleton was accurately calculated with a relative error of less than 5%. The proposed methodology provides a reliable and efficient solution for fatigue crack measurement, offering significant potential for real-world applications in structural health monitoring and bridge maintenance.
The unique band gap characteristics of periodic structures result in varying degrees of attenuation of elastic wave propagation across different frequency ranges. With the increasing demand for periodic grid structures, particularly long-span grids, in various sectors of industry and daily life, the issues of vibration reduction and isolation in such structures have become increasingly prominent. Inspired by the periodic properties of phononic crystals, this study conducts a mechanical analysis of grid rod elements, derives the corresponding periodic equations, and investigates their underlying periodic mechanisms. Numerical simulations confirm the existence of band gaps in steel and aluminum hybrid grid rods and examine the effects of the rod's Elastic modulus, density, and inner radius on these band gap characteristics. Finally, the impact attenuation performance of the steel-aluminum hybrid grid rod is compared with that of pure steel and pure aluminum grid rods. The results show that: (1) with increasing Elastic modulus, the starting frequency, end frequency, and width of the widest band gap all increase, while the starting frequency, end frequency, and width of the 13th-order band gap first increase and then disappear; (2) with increasing density, the width of the widest band gap decreases, and the starting frequency, end frequency, and width of the 16th-order band gap all decrease until it disappears; (3) with increasing inner radius, the width of the widest band gap increases, and the starting frequency, end frequency, and width of the 19th-order band gap all increase, with low-frequency band gaps gradually emerging; and (4) compared to steel and aluminum grid rods, the steel and aluminum hybrid grid rod exhibits superior impact wave attenuation performance, with the band gap characteristics of single-rod elements playing a critical role in suppressing vibrations throughout the entire grid structure. Copyright (c) 2026 by The Hong Kong Institute of Steel Construction. All rights reserved.
To investigate the effect of openings on the flexural performance of large-section partially encased composite beams (referred to as large-section PEC beams), static tests were conducted on five large-section PEC beams with different configurations. The study focused on the influence of web openings in the primary and secondary beams on the flexural performance, ductility, and failure modes of the specimens under four-point bending. The results indicate that under static loading, all specimens exhibited good ductility, with strength-to-yield ratios ranging from 1.18 to 1.30, and retained some strength reserves after reaching the yield load. Web openings slightly reduced the load-bearing capacity and sectional stiffness of the specimens. The strain in the main steel component and the concrete strain along the section height approximately exhibited a linear distribution, conforming to the plane section assumption. A finite element model was developed based on the test results. The load-deflection curves and stress contours matched well with the experimental results, and the error between the simulated and experimental ultimate load-bearing capacities was within 10%. The flexural load-bearing capacity calculated using the proposed method for large-section PEC beams with web openings showed minor deviations from the experimental values, with minimal influence from size effects, confirming the safety and reliability of the adopted formulas.
Existing theoretical rotational curve calculation methods for end plate-bolted joints often overlook component-level load transfer mechanisms and full deformation processes. This paper introduces a full-process subcomponent analysis method, which systematically evaluates the force-deformation behavior of joint domains, bolts, end plates, and stiffeners at critical failure stages. Simplified models and formulas are developed to calculate the load-bearing capacity and rotation angles of each component. The proposed method was validated through experiments, numerical simulations, and a practical engineering case. The results show that the proposed method accurately predicts joint rotational behavior, with the end plate thickness and bolt configuration significantly influencing load distribution. By revealing the load transfer mechanisms and clarifying the physical meaning of each component's role in joint rotation, the findings of this study provide a robust theoretical foundation for holistic structural analysis and large-scale computation of steel structures.
