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This paper presents the results of an experimental study on the flexural behavior of carbon fibre reinforced polymer (CFRP) anchorage system strengthened reinforced concrete (RC) beams under the coupled effects of corrosion damage and sustained loading. The test beams were subjected to combined accelerated corrosion in 5% NaCl solution and sustained loads for 25, 50 and 100 days at 0% and 50% load levels of the virgin beam ultimate load capacity. The failure modes, load carrying capacity, deflection, ductility and strain response of the beams were investigated in detail. The results indicated that CFRP anchorage systems enhanced the yield and ultimate load of the corrosion-damaged beams. The use of CFRP anchorage system restored the ultimate load of corroded beams between 87.6% and 104.8% and the yield load between 81.9% and 92.7% with respect to those of the virgin beam. In contrast, the ductility and energy absorption index suffered a decline. CFRP-strengthened beams showed a reduction of 4.5%–28.9% for the ductility index compared with their counterparts without CFRP anchorage system. Sustained loads resulted in more considerable reductions in load-bearing capacity, greater loss of rebars mass, wider width of corrosion cracks, indicating a significant coupling effect between sustained loading and corrosion damage. Three typical failure modes of the CFRP-strengthened beams were observed and explained in the paper, thus revealing the failure mechanism of CFRP-strengthened beams. In the engineering practice of CFRP anchorage system, the coupled effects of corrosion damage and sustained loading on the strengthened systems should be taken into accountant comprehensively.

An experimental study was conducted to apply the acoustic emission (AE) technique to monitor the corrosion process and cracking behavior in large-scale reinforced concrete (RC) pile specimens. In this study, the underwater and tidal zones of six RC piles were exposed to accelerated, localized corrosion in a simulated marine environment to reach 5%, 10% and 20% steel mass loss. The two piles with 20% steel mass loss together with another reference pile without corrosion were continuously monitored during the test via three attached AE sensors. Tidal action had a significant impact on the AE signals; accordingly, a novel amplitude-duration-peak frequency-based AE signal filter (ADPF) was proposed, which achieved better performance than the previous amplitude-duration-based filters. Additionally, the conjoint analysis of AE signals and the fractal dimension of cover cracks throughout the corrosion period enabled global detection of localized corrosion-induced damage of piles, regardless of sensor location. This study also presents an integrated corrosion-induced damage detection framework and four models based on multi-layer perception (MLP) networks to predict the corrosion level of the underwater and tidal zones of piles in the marine environment.

This paper presents the details of an experimental and analytical study that addresses the influence of carbon fiber-reinforced polymer (CFRP) anchors on the bearing capacity and fatigue behavior of reinforced concrete beams strengthened by CFRP strips. The experimental set comprised seven beams from which four beams strengthened by CFRP strips and anchors of four different lengths were first subjected to cyclic loading, and subsequently loaded until failure under monotonic loading. The remaining three beams were designed to establish the baseline response. The residual bearing capacity, damage degree, cracking behavior and ultrasonic inspection were analyzed. The results showed that the length of CFRP anchors significantly influenced the residual bearing capacity and failure modes of the specimens. A deep anchoring depth may result in a brittle failure of the specimen at the mid-stage of cyclic loading. In addition, based on the good correlation between residual bearing capacity and the fractal dimension of surface cracks of the beams, a novel damage index was proposed. The results also demonstrated that fractal dimension analysis together with ultrasonic inspection could be exploited to assess damage levels when mechanical testing is not available.

The elastic properties such as shear moduli and shear moduli of freezing and thawing soil are important parameters for analyzing the stress distribution and thaw-subsidence of freezing soil and deformation of well casing embedded in freezing soil. This paper presents elastic properties obtained by conducting laboratory testing of sand samples from the area of soil. The bending elements were used to measure the shear wave (S-wave) velocities for evaluating the shear moduli during freezing and thawing. Nine pairs of testing specimens were conditioned from 25°C to -25 °C at an interval of 5 °C for examining the temperature effects during freezing and thawing process, respectively. The test parameters included dry density (1.6,1.8,2.0 g/cm3) and moisture content(6%,9%,the saturation). Test results showed that the wave velocities and the shear moduli in all types of specimens tested exhibit sharp change when the temperature adjacent to 0 °C, likely due to non-uniform freezing point depression caused by the varying structure among specimens. The increase of dry density has positive effect on shear modulus. However, the moisture content has a dual effect on the strength of the sand soil.