![]() His research showed that the PCA method has better classification performance. compared different feature extraction techniques including peak value and peak time, spectral characteristic analysis, PCA projection coefficient, and response shape curvature. proposed an ICA-based feature extraction technique for defect classification. In 2003, Sophian and Tian used PCA to extract time-domain features to classify defects. In addition, some statistical analysis methods, such as principal component analysis (PCA) and independent component analysis (ICA), have been investigated for feature extraction as well. Therefore some classification methods have been built based on frequency-domain features 74 80 90 91 92. In the frequency domain, the PEC response signals contain more information than regular EC testing. PEC defect classification theories and feature extraction techniques have been developed and studied, including the use of rich information from the time-domain response 46 75 77 89. PEC has been widely used in defect characterization 84 85 86 and corrosion detection 54 87, and it has been proved as an effective tool for quantitative characterization of hidden corrosion and cracks in multilayer aircraft structures 52 88. The transient or PEC technique presents an important advance over other EC methods because it rapidly acquires data over a wide range of frequencies, thereby providing more information in the frequency domain. Single-frequency ECT is routinely used to verify corrosion in the top skin and at the facing surface between two skins. It is well known that ECT is very useful for detecting cracks and corrosion in these structures, where the lift-off, presence of rivets, and interlayer air gaps are the main obstacles. ![]() Multilayer structures, such as lap splices and riveted structures, are widely used in aircraft fuselage. Ruizhen Yang, in Transient Electromagnetic-Thermal Nondestructive Testing, 2017 4.4.1.1 Background In conclusion, with the consideration of the current AASHTO LRFD code and the proposed guidelines, a safe and efficient non-circular column to circular drilled shaft connection can be constructed.Yunze He. Based on the findings from the experimental and analytical investigation, a set of design recommendations is provided for the design of non-contact splices in geometrically dissimilar bridge column to drilled shaft connections. The results of this study provide a basic understanding of the behavior of non-contact lap splices in non-circular columns to circular drilled shaft connections. Using the validated FEA models, a thorough parametric study was performed to understand the effect of the critical parameters. Furthermore, a three-dimensional finite element analysis (FEA) was performed on the test specimens, and the finite element simulated results were compared with the test outcomes. The angle of inclined cracks was observed to increase with increasing the non-contact splice distance. The increase in the non-contact splice distance yielded significant inclined cracks and splitting cracks in the non-contact lap splice zone. The test results showed that the specimens with larger non-contact splice distance generally exhibited lower lateral stiffness and lower capacity. The specimens were subjected to flexure action with both monotonic and cyclic loading. Eleven large-scale column-drilled shaft specimens were tested to investigate the effects of the critical parameters affecting the performance of non-contact lap splices: the non-contact distance between the spliced bars, the lap splice length and the amount of transverse reinforcement in the non-contact lap splice zone. This study presents an experimental and analytical investigation of non-contact lap splices in non-circular bridge column to circular drilled shaft connections. However, there is a concern on the safety and cost-effectiveness of such non-contact lap splices because the guidelines in the current AASHTO LRFD code and studies on this type of connection are limited. But, it is often required to provide a reinforcing steel splicing arrangement with non-contact lap splices due to the limitation of internal space or geometric irregularity for the connection of non-circular bridge columns interfacing directly with circular drilled shafts. Contact lap splices are widely used for the construction of reinforced concrete structures.
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