PSI - Issue 11

Luigi Ascione et al. / Procedia Structural Integrity 11 (2018) 202–209 L. Ascione et al./ Structural Integrity Procedia 00 (2018) 000 – 000

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Table 1 – Tests of environmental durability

Test Duration (hours)

Stress Retention (%)

Reference standard

Type of treatment

Test condition

ASTM D 2247-11 ASTM E 104-02 ASTM D 1141-98 ASTM C 581-03 ASTM D7705/D7705M

Moist

 90%; 38 ± 2 °C

85 (1000 hours) 80 (3000 hours)

1000 and 3000

Saline

Immersion at 23 ± 2 °C

Immersion in solution with pH= 12.5; 23± 2°C

Alkaline

Table 2 summarizes the number of tests required to the Manufacturer on each FRCM system to be qualified.

Table 2 – Summary of the homologation tests Test

Number of specimens

Mechanical tests Tensile test on dry mesh 9 Tensile test on FRCM coupons 9 Debonding test 9 Durability tests Unconditioned specimens 4 Freeze-thaw cycles 4 Moist environment

2 x 4 = 8 (1 for the test duration of 1000 hours and 1 for 3000 hours)

Saline environment Alkaline environment

2 x 4 = 8 2 x 4 = 8

Total

59

4. Acceptance tests

The acceptance tests:  are mandatory and should be carried out under the responsibility of the Director of the works;  have to be performed simultaneously to the strengthening intervention;  have to be performed on specimens made on site, following the installation procedure prescribed by the Manufacturer. For each type of FRCM strengthening system to be installed, 6 specimens shall be prepared. The dimensions of the specimens are the same as those specified for the FRCM coupon tensile tests. The test is considered passed if the mean value of the tensile ultimate stress is not lower than 85% of the tensile characteristic tensile ultimate stress  u,f , as determined during the homologation phase, and is higher than at least 15% of the conventional limit stress  lim,conv determined during the same phase. In the case of a negative result, the tests can be repeated on additional 6 specimens. In this case, the mean value of the failure stress is evaluated on the 12 specimens subjected to tensile test. If the result is still unsatisfactory, the FRCM composites cannot be accepted. The use of the conventional limit strain allows for designing the FRCM strengthening intervention by avoiding an explicit verification with respect to the possible phenomenon of end debonding, otherwise necessary when such kind of phenomenon is possible. End debonding might occur when the tensile stress in the FRCM system is maximum at its end, as in the case of seismic loading. The same does not happen for strengthening masonry panels under out-of plane loads, as well as concrete beams subjected to gravitational loads. Instead, in the verifications governed by the phenomenon of intermediate debonding, the following values have to be utilized:   lim,conv =  ·  lim,conv and   lim,conv = E f ·   lim,conv . 5. Main design provisions