دانلود رایگان مقاله انگلیسی ارزیابی مقاومت طراحی برای بتن و اعضای کامپوزیت فولاد و بتن - الزویر 2018

abstract

This study evaluates the performance of the design equations given in the Australian/New Zealand bridge and steel structures design standards AS 5100.6, AS 4100 and NZS 3404.1 based on reliability analysis. For this evaluation, the following two methods were utilised: (i) a capacity factor calibration method to meet the target reliability level when there are a limited number of steel yield strength tests; and (ii) an inverse reliability analysis method to calculate the required minimum number of steel yield strength tests to achieve the target reliability level when using capacity factors provided in the design standards. The methods were applied to steel and composite members including I-beams, hollow section columns, CFST columns, and composite beams. To ensure the adoptability of imported steel for these members, structural steel that conforms to European, Korean, Japanese, American, Chinese and Australasian manufacturing standards were considered in the analyses. The results showed that, for an infinite range of manufacturing data, the capacity factors were insensitive to the different manufacturing tolerances. Furthermore, when a limited number of mechanical tests were available, a much larger number of results were needed to achieve the target capacity factor for composite members in comparison with non-composite members. Finally, when considering hollow sections used as columns, the current design equations were unable to deliver the target reliability levels for any of the manufacturing standards used internationally.

Conclusions

This study evaluated the performance of the design equations given in the Australasian steel and composite design standards AS/NZS 5100.6 [53], AS 4100 [35], NZS 3404.1 [11] and AS/NZS 2327 [52], when the coefficient of variation of steel yield strength was unknown, and there was only a small amount of test data. A capacity factor calibration method was developed when there were infinite or a limited number of material property test data, and an inverse procedure was also developed to calculate the minimum number of material property test data required to achieve the target reliability level for a given capacity factor. The proposed methods were applied to structural members including I-beams, hollow section columns, CFST columns, and composite beams, the following results were obtained: (i) capacity factors for various COV values of steel yield strength; and (ii) The minimum number of material tests required to achieve the target reliability. From the reliability analysis, it was found that the design equations for I beams in AS/NZS 5100.6 [53], AS 4100 [35], and NZS 3404.1 [11] provided safety for a various range of the COV of steel yield strength, and the number of 7–20 material tests were required for the COV of steel yield strength of 7–10%. However, the reliability of hollow section columns was highly depended on the COV of section thickness, and the current design standards are unconservative by not delivering the targeted reliability level. In this case two options are available to remedy this situation: the capacity factors need to be reduced (for partial factor design standards, such as the Eurocodes, it is difficult to see how γM0 = 1.0 is justified); or the manufacturing tolerances for hollow section product standards need to be significantly tightened (the results from this study, suggest that the thickness tolerance should reduce from 10% to 1% of the section thickness).