PSI - Issue 64

Carmine Lima et al. / Procedia Structural Integrity 64 (2024) 849–856 Lima et al. / Structural Integrity Procedia 00 (2019) 000 – 000

855

7

where the α and β have to be calibrated from the experimental results. The following Fig. 7 summarizes the graphical representation of the obtained calibration for all the performed tests: in the case of C25/30 the a value was assume equal to 1.037 meanwhile  is equal to  ; for C60/75 samples the a and  values were assumed equal to 1.490 and 0.512, respectively; and in the case of UHP-FRC tests a is equal to 2.725 meanwhile b is equal to 1.122.

1200

1200

1200

C25/30

C60/75

C25/30

1000

1000

1000

800 Force [kN]

800 Force [kN]

800 Force [kN]

600

600

600

400

400

400

200

200

200

experimental theoretical

experimental theoretical

experimental theoretical

0

0

0

0

5

10

15

20

25

0

5

10

15

20

25

0

5

10

15

20

25

displacement [mm]

displacement [mm]

displacement [mm]

a

b

c

Fig. 7 Theoretical simulation of the load-displacement curves for the push-out tests

4. Conclusions The present paper reported the main results obtained from an experimental activity intended at investigating the behaviour of headed stud shear-connectors in concrete slabs of different strength. Specifically, three different concrete mixtures were considered to realised three slabs of variable thicknesses. The specimens were ideally designed with the aim to achieve comparable axial strength in the concrete slabs. The main empirical observations obtained from the experimental tests can be summarised as follows: - as expected, failure generally occurred after shear connection failure in all specimens, regardless of the concrete strength; - tests on specimens with UHPC slabs showed a lower strength and this probably due to both a different longitudinal distribution of the contact stresses throughout the stud shank and the absence of transversal steel stirrups; - the difference of the behaviour obtained in UHPC is even more apparent in terms of displacement capacity, which is significantly lower than in the other two series of specimens. Further studies, both experimental and numerical in nature, are needed to better understand the different behaviour of shear connectors within slabs characterised by variable thickness and mechanical properties. Conventional rebars, especially those place transversally, seem to play a significant role in controlling the failure mode and the resulting strength and displacement capacity. Further specimens with variable geometry and reinforcement will be performed; moreover refined 3D finite element models will be developed and analysed. Acknowledgment The experimental campaign proposed in this study has been developed as a part of the ReLUIS Ponti research project activities jointly carried out by the University of Salerno (IT) and the University of Naples “Federico II” (IT). References An, L., Cederwall, K., 1996. Push - out tests on studs in high strength and normal strength concrete. Journal of Constructional Steel Research, 36(1):15 - 29; EN 1992 - 1 - 1, 2004. Eurocode 2: Design of concrete structures - Part 1 - 1: General rules and rules for buildings. European Committee for standardization. ICS 91.010.30; 91.080.40.