16
Chapter 1
35
30
25
C
o 20
U
n 15
t
10
5
0
6
10
14
18
22
26
30
34
38
Rainfall
in inches
Figure 1.3 Rainfall data at civic center Los Angeles 1877-1997 for July 1-June 30.
Weibull solid line
/3= 1.58917+0.12731, 0 = 11.48905±0.76931 ~ =4.68106-4-0.23477,
Gaussian dotted line
p = 14.97683, ~ = 6.72417.
The variation Eq. (2.13) on/3 is 0.18572 and the ~ is 0.4310 (Eq. (2.16)).
goodness of fit evaluations find both the Weibull curve and the Gaussian
curve are acceptable distributions. Visual examination of Fig. 1.4 would
justify this.
The Example I. 1 is examined for this data and one of the parameters is
the class A and B basis stress levels for design. Using Eq. (1.32) and K = 2.25
(Fig. E. 1) for A basis and K = 1.80 (Fig. E. 1) for B basis./~ = 39,370 psi
s = 1057 psi and N= 24.
~A = 39,370 - 2.25(1057psi) = 36,992psi
(1.54)
~B = 39,370 - 1.80 (1057 psi) = 37,467 psi
(1.55)
A class C K=5.8, Fig. E.1 with N=24
~c = 39,370 - 5.80(1057 psi) = 33,239 psi
The/~ or Yc and ~--s can be corrected from N= 24 to infinite sample size
using Eqs. (1.30) and (1.31). The d.f. =24-1 =23, Table E.2 the t value