![]() The side plates are usually lashed into place (Group 3) and secured with bamboo or timber dowels (Group 4B). This joint is used to extend the length of culms having a similar diameter the side plates are typically fabricated of half- or quarter-culm sections of a larger diameter. The main purpose of this section is to investigate feature extraction from optimized frequency responses, combining with the PCA method to overcome varying air gaps and the lift-off effect for defect classification in two-layer structures.Ī similar joint classification, combining Groups 3 and 4B is the butt joint with side plates shown in Fig. 20.26(b). Rich frequency information has not been analyzed through PCA/ICA. Although the PCA/ICA method is already used in PEC defect classification, the previous studies only used the time response as the PCA/ICA input 46 93. In recent years, some features from the frequency response have been used to reduce these effects. Defect classification in these structures is more difficult due to the lift-off effect and interlayer air gaps. As mentioned before, multilayer structures are widely used in aircrafts, and some defects, such as corrosion, occur on the second layer. However, defect classification in these studies was mainly focused on surface defects, subsurface defects, and metal thickness change/loss. 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 How can I tell if a bar was spliced with the 'B' or 'C' lap splice lengths per the table? Can anyone shed any light on this? I trued searching for chapter 12 of ACI 318-83 but can't find it.Yunze He. Can anyone shed any light on this? Also this statement is confusing to me. There is then a table that gives lap splice lengths for Class 'B' and Class 'C' for both 'top' and 'other' bars.įirst off I'm not sure what are Class 'C' lap splices. THE LENGTH OF LAP SPLICES SHALL BE CLASS "B" WHERE NO MORE THAN 1/2 THE BARS ARE LAP SPLICED WITHIN THE LENGTH TABULATED BELOW AND CLASS "C" WHERE MORE THAN 1/2 THE BARS ARE LAP SPLICED WITHIN THE LENGTH TABULATED BELOW." "UNLESS CALLED OUT OTHERWISE ON THE PLANS. In the general notes section for the rebar lap splices I see this statement: ![]() I can't find any information on the design code used but I would guess the ACI 318-83 that was revised in 1986. I'm reviewing an existing concrete and masonry structure that was designed in 1989.
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