PSI - Issue 10

A. Marinelli et al. / Procedia Structural Integrity 10 (2018) 104–111 A. Marinelli and M.R. Stewart / Structural Integrity Procedia 00 (2018) 000 – 000

108

5

(a)

(b)

Fig. 4. Failure modes observed after testing for (a) 200mm span and span/depth=4; (b) 200mm span and span/depth=6.

minutes and, given our interest in the post-peak behavior of the material till the specimen can bear no load, the duration of each test was 8-10 minutes. Typical fractured specimens are shown in Fig.4.

3. Experimental results

3.1. Typical results

Typical load-deflection at midspan and load-CMOD curves of Portland limestone specimens under three-point bending were directly derived from experimental recordings (Fig.5). A typical load-deflection curve consists of three distinct portions: up to the peak load the constitutive law is almost perfectly linear elastic. This region is abruptly terminated by a significant load drop which in turn leads to a third portion, characterized by a small slope, up to final disintegration of the specimens. The flexural strength R tf of each specimen was calculated according to the method proposed by BS EN 12372:2006 by application of the formula:

Fl

3

R

 tf

(1)

2

bh

2

where F is the breaking load (N), l the span, b the breadth and h the height of specimen (all in mm).

Span/Depth Ratio = 5/2 Span/ Depth Ratio = 4 Span/ Depth Ratio = 6

Span Depth ratio = 5/2

Span/ Depth ratio = 4

Span/ Depth ratio = 6

1800

1800

Span/Depth ra tio=

1600 1200

1600 1200

1600

1600

Span/Depth ra tio=

1400

1400

Span/Depth Ratio = 5/2 Span/ De 5/2

1200 Span/Depth Ratio = 5/2 Span/ Depth Ratio = 4 Span/ Depth Ratio = 6 5/2

1200

1000 Span/Depth Ratio = 5/2 Span/ Depth Ratio = 4 Spa 4.0 1800

1000

800 Span/Depth Ratio = 5/2 Span/ Depth Ratio = 4 Span/ Depth Ratio = 6 4.0 800 1800

800 400

800 400

Load (N)

600 Span/Depth Ratio = 5/2 Span/ Depth Ratio = 4 Span/ Depth Ratio = 6 6.0 Load (N) 1800

600

400 1800 o = 5/2 Span/ Depth Ratio = 4 Span/ Depth Ratio = 6 6.0

Load [N]

Load [N]

1600

400

1600

1800

200

200

1600

0

0

1600

0

0

1400

0.2 1600

0

0.1

0.3

0.4

0.5

0.6

0 0 0.4 0.4 1.2 Crack Mouth Opening Displacement [mm] 0.6 0.8 0.8 1 1.2 Crack Mouth Opening Displacement (mm) 0.2

1.4

1400

0

Deflection at Mid-span (mm ) 0.1 0.2 0.3 0.4 0.5 0.6 Deflection at mid-span [mm]

1400

1400

1400

1200

1200 (b) Fig. 5. (a) The load applied vs. deflection at mid-span for 200 mm spans; (b) The load applied vs. CMOD for 200 mm spans. 1200 1200

(a)

1200

1000

1000

1000

1000

1000

800

800

800

Load (N)

800

Load (N)

600 Load (N)

600

800

600

Load (N)

Load (N)