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Hydraulic calculation based on the reliability of the drainage channel

Deduced,[link widoczny dla zalogowanych], so there are some errors: the error with that formula, then = CqF 【4), for the correction factor, the mean value and coefficient of variation desirable 10 and 0.10. C, q with the uncertainty of the circumstances in different regions, F mean and coefficient of variation can be taken as, respectively,[link widoczny dla zalogowanych], 1.0 and O. 05: And, q the uncertainty of life as the design (design base period) and the assumed maximum storm rainfall duration varies. 2, hydraulic calculation based on reliability design flood discharge capacity of 2.1 set performance function, Q for the design flood discharge, the general limit state equation is: z = gtQQ) = Q a Q (5) According to the above analysis, equation (5) there are many uncertainties in the variables. For simplicity, the small drainage channel, the main factors can be taken only as a design variable. This temporarily take four variables, namely, the n,, the state r = loss il), where i is a constant = number of variables in order to simplify the calculation,[link widoczny dla zalogowanych], based n the normal distribution, mean. Coefficient of variation of 015; Y the mean coefficient of variation 0.20; as normal distribution, mean 1.0, coefficient of variation 0. I. Extreme value distribution can be described as disastrous in many natural phenomena, I-distributed computing extreme simplicity,[link widoczny dla zalogowanych], and hydrological stations recorded more than 9O% to 95% of the proposed confidence sets, so use extreme I-mode, mean, as variation factor, as long as 20 years of observational data can be determined, taking the literature in the reference coefficient of variation was 025. Performance function g () is: g () = semi-Y-Q (6) 2.2 Reliability-based design of hydraulic calculation if the design of small watershed drainage channel. Bu Zhiyu become pressure to ensure the reliability index for the overflow, the design of its parameters. For the Q, because I obey the extreme value type distributions. Parameters: 128212825.131qs0 · sign Qiu Zhang} [7) u: I: 0. 8J limp at the failure of Q corresponding CDF and PDF, if the first iteration. Assume that Q =, then there is: () = 0.5701l645} (8) () = Jn. A normal distribution. The '=, n = yuan, n = eight items on behalf of derivatives, there are: (Lu) (boiled) (dance) (Yi) one by one ix. 15]: _ 【】 l151 one by one P. i: 0.2 with n = a 0.2SQ by a first order approximation, the reliability of the conditions: n √ (-0.15) + (o) + (o) + os simplified formula (10) was: y - a = a Q-==================== mouth (1I1 √ 0 ... () flail 062s finishing (11) are: f1_ 【] 07251 ( ) a 2Q} Sichuan _l】 l0625) = 0f12) (12) is the reliability index in too, based on the calculation of the reliability of the hydraulic design of the first order approximation formula. If the second order moments, can be further sub-derivatives, based on iteration, omitted here. 3 Sample design of a rectangular drainage channel over the water depth, its bottom width defined as 0 ∞ m, bottom slope i = I / I (D, - ten years counted during the maximum flow design basis for the extreme value distribution of type I, which Mean = 1.55m3 / s, roughness average o02, requires a reliable indicator of 15 (corresponding to 93,319 percent reliable probability): (1) determine the value of design. If you press open channel flow equations to determine the value, obtained panned rectangular drainage water depth of 0.51m. (2) based on reliable design wins. with a first order approximation, according to equation (12), with Y = 0.0569 (rounded down unreasonable 0.0174). by = loss calculation, there have been water depth 0.79I13. (3) If over the water depth of 0.79m, with a determined value, the over flow of 286Is; if we take Lo = 10 (corresponding to Section reliable .13% probability .) according to equation (12) can be regarded = o039 (the corresponding probability is only 52.03% reliable): It can be seen as reliable indicators of the requirements of lower value than the water depth is also reduced. that the reliability design method of valuation of relatively low: the second thanks to: receive instructions from the text of the branches Professor Liu Zifang guidance, in this special token of appreciation!