PSI - Issue 64

Paula Folino et al. / Procedia Structural Integrity 64 (2024) 1452–1459 Folino et al. / Structural Integrity Procedia 00 (2019) 000 – 000

1458

7

preserved the structural integrity of the composite structural element, permitting to achieve ultimate displacements approximately 50 % greater than those corresponding to the case of jackets with reinforcing steel bars but without fibers. a

(a)

(b)

Figure 3. (a) Unjacketed beam cracking pattern; (b) SCHSC jacketed beam cracking pattern.

(a)

(b)

Figure 4. (a) SCFRHSC 30mm jacketed beam cracking pattern; (b) SCFRHSC 60mm jacketed beam cracking pattern Contrary to expectations, rough surface preparation before adding the jacket did not result in substantial strength increases. However, in two beams where no surface preparation was performed, a debonding of the jacket was observed by the end of the test, particularly for thicker jackets. In spite of the obtained strength results, it was concluded that this step is fundamental for maintaining the composite structural system integrity. On the one hand, while the SCHSC jackets achieved the highest strengths, casting was more challenging due to the arrangement of reinforcement bars and the reduced thickness of the jacket. On the other hand, the SCFRHSC jackets permitted to almost duplicate the reference beam strength with much thinner thicknesses and with substantially less construction complexity than required in the case of using reinforcement bars. It is worth noting that computing the used materials in each beam, and defining an efficiency factor as a ratio between the total mean increase in load capacity (in MN) with respect to that of the reference beams and the concrete volume (in m 3 ), it follows that the thinnest jacket with steel fibers achieved the best material efficiency and can be considered a more sustainable alternative (See Table 1Table 8). However, the decision regarding what jacket type should be adopted will depend on the structural constraints. Table 8. Efficiency factor for each jacket case as the ratio between mean peak load increment and the corresponding involved concrete volume Jacket thickness Concrete volume Steel content

Load capacity increase D [kN]

Efficiency= D [MN]/Vol[m 3 ] [MN/m 3 ]

[mm]

Vol [m 3 ]

[kg]

SCHSC (Typical reinforced concrete jacket) SCFRHSC (Fiber reinforced, no steel bars) SCFRHSC (Fiber reinforced, no steel bars)

60

0.0389

2.65 (68.2kg/m 3 )

123.4-48.5= 74.9

1.93

60

0.0389

2.33 (60.0kg/m 3 ) 102.6.4-48.5= 54.1

1.39

30

0.0173

1.04 (60.0kg/m 3 )

87.5-48.5= 39.0

2.26

5. Conclusions In this paper the results of an experimental campaign aimed at contributing to existing knowledge related to the performance of self-compacting fiber-reinforced concrete used as concrete jacketing of existing reinforced concrete