Concrete-filled fiber-reinforced polymer tubes (CFFTs) have attracted interest for their structural applications in corrosive environments. However, a weak interfacial strength between the fiber-reinforced polymer (FRP) tube and the concrete infill may develop due to concrete shrinkage and inadequate concrete compaction during concrete casting, which will destroy the confinement effect and thereby reduce the load bearing capacity of a CFFT. In this paper, the lead zirconate titanate (PZT)-based ultrasonic time-of-flight (TOF) method was adopted to assess the concrete infill condition of CFFTs. The basic idea of this method is that the velocity of the ultrasonic wave propagation in the FRP material is about half of that in concrete material. Any voids or debonding created along the interface between the FRP tube and the concrete will delay the arrival time between the pairs of PZT transducers. A comparison of the arrival times of the PZT pairs between the intact and the defected CFFT was made to assess the severity of the voids or the debonding. The feasibility of the methodology was analyzed using a finite-difference time-domain-based numerical simulation. Experiments were setup to validate the numerical results, which showed good agreement with the numerical findings. The results showed that the ultrasonic time-of-flight method is able to detect the concrete infill condition of CFFTs.

Rock bolts, as a type of reinforcing element, are widely adopted in underground excavations and civil engineering structures. Given the importance of rock bolts, the research outlined in this paper attempts to develop a portable non-destructive evaluation method for assessing the length of installed rock bolts for inspection purposes. Traditionally, piezoelectric elements or hammer impacts were used to perform non-destructive evaluation of rock bolts. However, such methods suffered from many major issues, such as the weak energy generated and the requirement for permanent installation for piezoelectric elements, and the inconsistency of wave generation for hammer impact. In this paper, we proposed a portable device for the non-destructive evaluation of rock bolt conditions based on a giant magnetostrictive (GMS) actuator. The GMS actuator generates enough energy to ensure multiple reflections of the stress waves along the rock bolt and a lead zirconate titantate (PZT) sensor is used to detect the reflected waves. A new integrated procedure that involves correlation analysis, wavelet denoising, and Hilbert transform was proposed to process the multiple reflection signals to determine the length of an installed rock bolt. The experimental results from a lab test and field tests showed that, by analyzing the instant phase of the periodic reflections of the stress wave generated by the GMS transducer, the length of an embedded rock bolt can be accurately determined.

Metal loss in metallic structures, often as a result of corrosion, is a severe problem across multiple industries. Catastrophic consequence of structural failure due to such loss of structural metal requires an accurate determination and assessment of corrosion. Widely used electrochemical methods can only suggest the likelihood of the metal loss due to corrosion while failing to provide a quantitative measure of the accumulated amount of corrosion. Due to its unique advantages such as small size, light weight, resistance to electromagnetic interference and corrosion, fiber optic sensing technique has been emerging as a promising alternative for most sensing applications. In this paper, a novel type of ferromagnetic distance-based metal loss sensor is proposed based on the principle of fiber optic macro-bend loss. The proposed sensor is composed of the bended optical fiber, the magnet and a spring. The magnet is connected to the spring and the fiber bend is attached to the spring in such a way that the movement of the magnet will induce a change in bending radius of the optical fiber. Metal loss in the monitored sample increases the distance between the magnet and the metal surface and thereby reducing the magnetic force. A change in magnetic force will lead to the variation in light intensity loss of the fiber optic macro-bend, thus metal loss, such as in the form of corrosion pits, can be detected by the proposed metal loss sensor. The practicality of the proposed distance sensor for metal loss measurement is validated through scanning the fabricated corrosion samples.

As a cost-effective mobile development platform, MTK support the functions of recording video and sending multimedia message. In this paper, an anti-theft monitoring alarm system based on MTK is proposed and implemented. The design based on a high performance MTK chip of MT6226. The sensors and the alarm device attached to MT6226 through the interface of GPIO. Once one of the sensors detect abnormal signal, MT6226 call the thread of recording video, driving the alarm device. Then the MTK send a multimedia message which compressed by the video to the master. The experiment results show that the anti-theft monitoring alarm system based on MTK platform have achieved good performance on cost-effective and flexibility, which make up for the inadequacy of existing monitoring systems.