BPVC (2019) Sec VIII Div 2 Annex 3-F Calculations

[Ryanh1988]

Hi.

I having an issue with using BPVC (2019) Sec VIII Div 2 Annex 3-F.
I want to use the calculations in a spreadsheet.
The number of cycles calculated does not match what I read off the graphs.

To test the forumalae, I state my Sa is 100Mpa. The charts shows ±350000 cycles (Figure 3.F1M).
I used Formula 3-F.1, 3-F.2 & 3-F.21.
I calculate 619.45 cycles.
I have used the correct temperature correction formula in table 3-F.1 for metric, used 200000 Mpa for Et, calculate a Y = 1.989.

I have double checked the formula and they are correct in the speadsheet.

Am i missing something here?

 

[IdanPV]

Hi,

There are basically two ways to specify a permissible design life.
1. Formulas. Sa shall be calculate using Part 5, and then, by using Annex 3-F, you can calculate N. There is no use for Table 3-F.1 for this method.

2. Smooth Bar Fatigue Curves, Sa shall be calculate using Part 5, and then, use Table 3-F.1 for the Temp. correction factor and the applicable Figure to find out the number of cycles.

In you case:
1. Forumla:
(3-F.1) = Y=1.1507
10^Y=14.15 => Use Eq. 3-F.3
(3-F.3) => X=5.54
(3-F.21) => N=347,822.

2. Curve (Fig. 3-F.1M):
Table 3-F.1 = Sac=97.65MPa.
Figure 3-F.1M =~350,000

 

[Ryanh1988]

Hi IdanPV.

Thank you for the confirmation. I was under the impression if you where using mpa, the log function had to change as per table 3-F1.

 

[IdanPV]

Hi,

I used MPa, same as you did.

Table 3-F.1 has nothing to do with eq. 3-F.1.
If you using the equation form just follow the equations, you should not change equation 3-F.1 regardless of the unit system you are using.