PSI - Issue 5

Hołowaty J. et al. / Procedia Structural Integrity 5 (2017) 1043 – 1050 Hołowaty / Structural Integrity Procedia 00 ( 2017) 000 – 000

1048

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Fig. 2. Tensile curves for three conditions of steel specimens from stringer I380 (bridge No. 3) .

The results of tensile testing on three types of specimens from bridge No. 3 (stringers) are given in Table 3 and the tensile curves are shown in Fig. 2. It is easy to see that the results are comparable for the normalized and annealed specimens, with only small differences. Therefore, the steels on the remaining bridges were not tested in the annealed condition. Table 3 gives the average values of the mechanical properties for the five bridges, obtained from tensile testing on normalized and annealed specimens tested in a Zwick/Roell computer-controlled material testing machine. For comparison, the results of the steel hardness tests are also given. According to the hardness measurement results, ultimate strength f uB was calculated. Brinell hardness tests were carried out under standard conditions using an indentation steel sphere of 10 mm diameter with a test weight of 29 430 N sustained for 15 s. The results for the steels indicate a wide range of values for particular material parameters. The differences between the values of upper and lower yield strength (f yH – f yL ), in the case of specimens S are from 5 to 25 MPa. i.e. 1.4 and 9.0 % of f y (f yH ). Specimens N range from 16 to 39 MPa which is 5.7 and 13.9 % of f y . A significant effect of ageing appeared in the steels from bridges Nos. 2 and 5 (C = 0.030 and 0.025 %). The yield strength f y in steel from bridge No. 2 increased by 21 % while for bridge No. 5 it was quite the opposite, dropping by 22 %. For the remainder of the bridges the change in f y values were inconsiderable.

Table 4. Charpy impact energy for the steels. Type of specimen Number of specimens Bridge No.

Impact energy KV ( J )

-20 ºC

-10 ºC

0 ºC 28.6 10.9

10 ºC

20 ºC

11.9

15.9

41.8

53.9 47.8 13.9 28.2 37.7 66.3 12

15

1 2 3 4 5 1 2 3 4 5 3

7.4 3.9 3.8 5.3 5.6

-

-

9

4.6 5.8 8.3 7.2

5.5 6.3

8.2

15 15 15 15 15 15 15 15 15 15 15 9

S

9

10.7 12.1 47.5 63.4 39.6 37.7 52.1 22.7

13

24.7 55.4 60.7 65.4 86.7 33.4 13.6 14.1 -

25.9 24.2 12.6 14.4 8.5

35.7

-

230.6 116.2 107.4 283.3

32.9 21.1 17.3

N

6.5 4.6 4.6

13

57

8.1 9.3

9.8

16.2 18.5

A

11.5