PSI - Issue 44

Ciro Del Vecchio et al. / Procedia Structural Integrity 44 (2023) 1411–1418 Ciro Del Vecchio et al. / Structural Integrity Procedia 00 (2022) 000 – 000

1415

5

2.1. Test setup The test setup consists of a steel reaction frame with two stiff steel heads connected by two hydraulic jacks (see Fig. 3), that allow the application of a constant axial load (in force control) on the wall during the tests. The tests were performed under a constant axial stress of 0.15 MPa corresponding to a typical condition under gravity loads at an intermediate floor of a masonry building. Furthermore, a variability of the axial stress from 0.10 MPa to 0.20 MPa was considered. The pull-out tests were performed by means of a hollow hydraulic jack and a steel reaction frame (colored in red in Fig. 2). An overview of the test setup, instrumentation and acquisition system is reported in Fig. 3. The total longitudinal displacement of the horizontal jack was measured by mean of an LVDT. Furthermore, the bar-to-grout slip was monitored by means of an LVDT. A strain gauge was placed on the steel bar to monitor its strain. Data on global and local deformation were acquired by means of a data acquisition system connected to a personal computer. 2.2. Material properties The masonry wallet was built by using yellow tuff stones and a cement-based mortar. The compression strength of tuff stone, determined by compression tests (Ceroni et al. 2017), is about 5.2 MPa while the tensile strength for flexure is about 1.3 MPa. The mechanical properties of 3 mortar specimens of the used mortar are summarized in Table 2 where the dimensions of the flexural specimen are w or the and h, for the width and height of the section, and l for the length. The specimens for compression are the two parts after the flexural failure.

Table 2. Mechanical properties of mortar used at the masonry joints. Flexural strength (UNI EN 196-1)

Compressive strength (UNI EN 196-1) ID w [mm] l [mm] F [N] R c [MPa]

ID w [mm] h [mm] l [mm]

F [N] R f [MPa]

1.1 1.2 2.1 2.2 3.1 3.2

40 40 40 40 40 40

40 16000 40 15040 40 15520 40 15200 40 14560 40 14400

10.0

J1

40

40

160

1710

4.0

9.5 9.7 9.5 9.1 9.0 9.5

J2

40

40

160

1540

3.6

J3

40

40

160

1520

3.6

Mean

3.7

Mean

Ribbed steel bars were used for the anchors. Mechanical characterization tests were performed on three samples to establish mechanical properties. For  10 and  14 bars, respectively, the mean yielding strength is 485.3 MPa and 488.7 MPa, the yielding strain is 0.25% and 0.26%, the hardening strain is 1.4% and1.8%, the strength is 608.4 MPa and 603.3 MPa and the ultimate strain is 10.1% and 10.5%. The anchors were injected by using a super-fluid expensive cementitious mortar whose mechanical properties are summarized in Table 3.

Table 3. Mechanical properties of mortar used for injections. Flexural strength (UNI EN 196-1)

Compressive strength (UNI EN 196-1) ID w [mm] l [mm] F [N] R c [MPa]

ID w [mm] h [mm] l [mm]

F [N] R f [MPa]

1.1 1.2 2.1 2.2

40 40 40 40 40 40

40 52800 40 51808 40 46880 40 52528 40 51808 40 52752

33.0 32.4 29.3 32.8 32.4 33.0 32.1

A1

40

40

160

3180

7.5

A2

40

40

160

1780

4.2

4181

9.8 3.1

A3

40

40

160

3.2

Mean

7.2

Mean