PSI - Issue 64

Urs Meier et al. / Procedia Structural Integrity 64 (2024) 29–39 Meier/Winistörfer / Structural Integrity Procedia 00 (2019) 000 – 000

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between the two load-bearing systems in this test, so the load-bearing capacity could only be increased imperceptibly compared to the not post-strengthened beam #2.

Table 2. Summary of the procedure for the loading experiments. Beam External CFRP stirrups Post tensioning force [kN] First cracking V cr [kN] Ultimate Load V u [kN]

Loading pattern

#1 #2 #3 #4

yes

70

305 210 250 240

703 465 479 677

Monotonic shear load increase Monotonic shear load increase Monotonic shear load increase

no

none

yes

5

at the beginning no/ later yes

70

Loading of the not yet post-strengthened beam up to 75% of the maximum load of beam #2, afterwards unloading and post-strengthening with post tensioned CFRP stirrups, subsequent loading in the same direction until failure Monotonic load increase up to 67 % of the maximum load of beam #1, subsequent reversal of the load direction until failure

#5

yes

70

320

647

a)

b)

c)

d)

Fig. 2. Shear force versus vertical shear displacement: (a) comparison of post-strengthened and post-tensioned beam #1 with not post-strengthened reference beam #2; (b) comparison of post-strengthened and post-tensioned beam #1 with post-strengthened however not post-tensioned beam #3; (c) loading of the not yet post-strengthened beam up to 350 kN, afterwards unloading and post-strengthening with post-tensioned CFRP stirrups afterwards subsequent loading in the same direction until failure; (d) monotonic load increase up to 430 kN, unloading and subsequent reversal of the load direction until shear failure.

Fig. 3a. Disk-shaped central section of Beam #1 with four post tensioned CFRP stirrups spaced 500 mm apart.

Fig. 3b. Beam #1 after failure. The total mass of CFRP for external shear strengthening was only 830g.