PSI - Issue 44

Maria Teresa De Risi et al. / Procedia Structural Integrity 44 (2023) 966–973 De Risi, Ricci, Verderame / Structural Integrity Procedia 00 (2022) 000–000

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+2.0%/-3.0% drift. The response was ductile, controlled by the development of a flexural plastic hinge at beam’s end, with a softening associated to concrete cover spalling and buckling of longitudinal reinforcement at beam’s end and without significant progress of the cracking in joint panel.

test S

test CAM1

150

150

100

100

50

50

0

0

-50

-50

-100

-100

-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 drift [-] -150

-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 drift [-] -150

(a)

(b)

(c)

test 2NS

test CAM3

test CAM4

150

150

150

100

100

100

50

50

50

0

0

0

-50

-50

-50

-100

-100

-100

-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 drift [-] -150

-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 drift [-] -150

-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 drift [-] -150

(d)

(e)

(f)

Fig. 2. Beam shear-drift responses of specimens NS (a), S (b), CAM1 (c), 2NS (d), CAM3 (e), CAM4 (f).

Photographic images for all specimens at the end of test are reported in Figure 3. Based on the observed damage, it can be concluded that the CAM ® strengthening was very effective in preventing joint failure for specimens CAM1 and CAM4, compared to NS, in the latter case even with a lower value of f c . On the contrary, the presence of the CAM ® strengthening in specimen CAM3, compared to 2NS, was able to increase the joint shear strength, allowing the flexural yielding of the adjacent beam – i.e., modifying the failure mode from J (2NS) to BJ (CAM4) – but was not able to prevent joint collapse. The reasons for this response are investigated in the Section 3.2, when the local response is analyzed, looking at strain demand in strengthening strips and analyzing the stress state in the joint panel.

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 3. Photographic images at the end of test of specimens NS (a), S (b), CAM1 (c), 2NS (d), CAM3 (e), CAM4 (f).

3.2. Local response The local response of the tested specimens is analyzed starting from the shear stress-strain response of the joint panel. To this end, the shear strain (γ j ) is calculated starting from the strain measures provided by linear potentiometers