ABSTRACT
Concrete is the most commonly used construction material nowadays. With emerging cutting-edge technologies such as nanomaterials (graphene, carbon nanotubes, etc.), advanced sensing (fiber optics, computer tomography, etc.), and artificial intelligence, concrete can now achieve self-sensing, self-healing, and ultrahigh performance. The concept and functions of smart concrete have thus been partially realized. However, due to the wider application location (coastal areas, cold regions, offshore, and deep ocean scenarios) and changing climate (temperature increase, more CO2 emissions, higher moisture, etc.), durability monitoring (pH, ion penetration, carbonation, corrosion, etc.) becomes an essential component for smart concrete. Fiber optic sensors (FOS) have been widely explored in recent years for concrete durability monitoring due to their advantages of high sensitivity, immunity to harsh environments, small size, and superior sensitivity. The purpose of this review is to summarize FOS development and its application in concrete durability monitoring in recent years. The objectives of this study are to (1) introduce the working principle of FOS, including fiber Bragg grating (FBG), long-period fiber grating (LPFG), surface plasmon resonance (SPR), fluorescence-based sensors, and distributed fiber optic sensors (DFOS); (2) compare the sensitivity, resolution, and application scenarios of each sensor; and (3) discuss the advantages and disadvantages of FOS in concrete durability monitoring. This review is expected to promote technical development and provide potential research paths in the future for FOS in durability monitoring in smart concrete.
ABSTRACT
Bridge deformation consists of cross-section rotation and deflection, which are crucial parameters for bridge capacity evaluation and damage detection. The maximum value of deflection usually happens at mid-span while for rotation it happens at two-ends. Therefore, compared with deflection, rotation is more convenient for in-situ measurement since the bridge pier can be the reference point. In this study, a high-precision inclinometer for bridge rotation measurement was conceptualized, designed, and validated. The proposed inclinometer converted the small rotation of bridge section into the deformation of an elastomer. Strain gauges were then utilized to measure the elastomer deformation and thus the bridge rotation can be obtained. The dimensions and modulus of the elastomer were designed and chosen based on the theoretical analysis. Characteristics of the inclinometer were calibrated in lab and in-situ experiments at an in-service bridge were conducted to validate its feasibility and robustness. Test results showed that the proposed inclinometer had excellent performance in resolution and accuracy, which indicate its great potential for future bridge health monitoring.
Subject(s)
Elastomers , Reproducibility of Results , RotationABSTRACT
OBJECTIVE: To evaluate a new treatment method for temporomandibular joint acute disk displacement without reduction. METHODS: Twenty-one patients diagnosed as acute anterior disk displacement without reduction were treated by manipulation with the aid of joint cavity extension followed by anterior repositioning splint. All and eleven of twenty-one patients were re-examined two weeks after insertion of splint and at the end of treatment (3 approximately 6 months later). RESULTS: (1) Degree of maximum mouth opening was increased from 25.8 mm before treatment to 46.6 mm 2 weeks after, 48.1 mm at the end of treatment; (2) Mean pain level (VAS) dropped from 2.62 before treatment to 0.43 2 weeks after, 0.18 at the end of treatment; (3) Fricton's TMJ dysfunction index and craniomandibular index decreased from 0.337 and 0.185 respectively before treatment to 0.021 and 0.011 respectively 2 weeks after, 0.031 and 0.018 respectively at the end of treatment. CONCLUSIONS: The treatment method should be considered for acute anterior disk displacement without reduction if medication and physical therapy failed to have disk successfully reduced.
