Guang-Ming Wu

1. Bridge engineering, as an important component of highway construction, has developed rapidly in recent years. A bridge-erecting machine is a key piece of construction equipment during high-speed...

Laminated rubber bearings in bridges often face environments with occlusion, insufficient illumination, and clutter from nearby objects, which makes it challenging to recognize the bearing ...

Acoustic emission (AE) technology has been extensively applied in the damage assessment of steel strands; however, it remains inadequate in identifying and quantifying the number of strand fractures, which limits the accuracy and reliability of prestressed structure monitoring. In this study, a test platform based on practical engineering was built. The AE monitoring method using a waveguide rod was applied to identify signals from different numbers of strand fractures, and their acoustic characteristics were analyzed using Fourier transform and multi-bandwidth wavelet transform. The propagation attenuation behavior of the AE signals in the waveguide rod was then analyzed, and the optimal parameters for field monitoring as well as the maximum number of plates suitable for series beam plates were determined. The results show that AE signals decrease exponentially with an increasing propagation distance, and attenuation models for various AE parameters were established. As the number of strand fractures increases, the amplitude of the dominant frequency increases significantly, and the energy distribution shifts towards higher-frequency bands. This finding introduces a novel approach for quantifying fractures in steel strands, enhancing the effectiveness of AE technology in monitoring and laying a foundation for the development of related technologies.

Prestressed steel tendons, as the key load-bearing component of prestressed concrete girders, will inevitably suffer damage, threatening the bridge’s safety and durability. Existing methods of locating damage to prestressed steel tendons necessitate the arrangement of numerous acoustic emission (AE) sensors outside the girder. To reduce the AE monitoring costs of the actual bridge, a dual-sensor AE localization method is proposed to monitor which steel tendon is damaged in a prestressed concrete girder. The key to implementing the proposed method is using a waveguide rod to preconnect the prestressed steel tendons inside the girder. To validate the feasibility of the proposed method, simplified positioning tests were performed on a test platform connected by waveguide rods, which includes connection forms of rebar welding, rebar adhesion, steel plate welding, and steel plate adhesion. Furthermore, the practicality of the proposed method was demonstrated by preinstallation of waveguide rods within a posttensioned prestressed hollow slab. Results indicate the dual-sensor localization method could precisely determine which prestressed steel tendon is suffering damage regardless of ambient AE noise, where AE wave velocity for localization could be selected empirically. The proposed method helps to reduce the cost of AE-based tendon breakage monitoring of bridges.

The fabricated shear wall with a grouting sleeve is used widely in structural engineering. The damage characteristics of a fabricated shear wall reinforced with angle steel of inadequate grouted material strength were investigated using acoustic emission (AE) technology under a horizontal repeated load. The results showed that evaluation of the AE energy and Ib value exposed the crack expansion and damage evolution of the fabricated shear walls; the sudden rise in the energy level predicted the occurrence of micro-cracks in the shear wall. The trends of the AE accumulated energy and accumulated hysteretic energy of the specimens had a good correlation. The AE Ib value results illustrated that the destruction was most serious inside the shear wall with an inadequate grouted material strength at the failure stage. The trends of AE HI and S_r could better characterize the crack propagation of the shear walls. The AE damage model was proposed based on the Park–Ang damage model incorporating fractal energy density, which could effectively evaluate the damage degree of shear walls under repeated loading.