A conventional method to study the durability of Glass Fiber Reinforced Polymer (GFRP) rebars is to carry out tensile tests on the corroded GFRP bars. The degree of corrosion of the GFRP bars could be quantified based on the measured ultimate tensile strength and the calculated strength reduction. However, it is difficult to directly monitor the reduction in tensile strength of the GFRP rebars that are embedded in concrete; therefore, this method cannot be implemented in real engineering practices. This study presents the reduction in elastic modulus of the GFPR rebars by real-time monitoring of the strain of the GFRP rebars, and then establishes the degradation model of the elastic modulus for the GFRP rebars in an alkaline corrosion environment. Therefore, the relationship between tensile strength and elastic modulus of GFRP rebars is proposed and verified by the experimental data obtained from the literature. The results show that it is feasible to use the Arrhenius equation to simulate the degradation model of the elastic modulus of the GFRP rebars. Thus, the tensile strength of the GFPR rebars can be related to its elastic modulus. Using the proposed relationship, the durability of GFRP rebars can be predicted by real-time monitoring of the elastic modulus of the GFRP rebars.
Compared with the traditional reinforced concrete columns, the concrete-filled steel tubular columns with a better restraint effect of steel tube on core concrete showed higher bearing capacity and ductility under static loads. However, except static loads, concrete-filled steel tubular columns are commonly exposed to the extreme dynamic loads including earthquake, explosion, and impact. The study on dynamic behavior of concrete-filled steel tubular columns is extremely significant to ensure their safety against such dynamic loads. In this article, a polyvinylidene fluoride piezoelectric smart sensor was proposed to monitor the axial impact bearing capacity of specimen based on stress monitoring under impact loads. The concrete-filled steel tubular columns with smart sensor embedded were tested, which considered the effects of both hammer impact heights and steel tube thickness on the axial impact bearing capacity. The impact bearing capacity calculated based on the monitoring results of polyvinylidene fluoride sensor is in good agreement with the measured values, which verifies the feasibility of this method. Moreover, it is found that the failure mode of concrete-filled steel tubular short columns is the local tearing failure or local buckling. In addition, non-linear finite element models were also established to study the effect of different parameters on the axial bearing capacity. The simplified formula for calculating the axial impact bearing capacity of concrete-filled steel tubular short columns was proposed based on the large amount verified model. Through the comparison between the calculation value and the test value, the formula is found to well reflect the axial impact bearing capacity of concrete-filled steel tubular short columns, which provides a reference for similar research.
The authors analyze the existing technologies in the field of cross-network data exchange and their deficiencies in ensuring the safe transmission of data. We propose a technology to improve the security of data exchange across networks, which is based on trusted computing. We design an audit method of the data exchange to prevent the leakage of sensitive information, investigate the subject of the leak and ensure the integrity of the data transmission. We have proved the credibility of the method and the ability of data security protection in the process of cross network data exchange, by protecting data files and applications.
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