**5. Laboratory tests for the stone masonry**

**Figure 20.** RION system and accelerometer system used in Konitsa Bridge field study. (a) Location of sensor at the

Shown in **Figure 21** are the post-wind gust bridge response (vertical acceleration) and the corresponding power spectrum associated with the trace segment between 12 and 16 s of the record [4]. The power spectrum associated with the decay segment clearly delineates (a) the

**Figure 21.** Decay segment of acceleration trace (vertical) and the corresponding power spectrum (7.75 Hz, damping

South part of Konitsa Bridge and (b) location of the sensor at the North part of Konitsa Bridge.

symmetric vertical mode (7.75 Hz).

90 Structural Bridge Engineering

ratio estimate of 1.6%).

A laboratory testing sequence was performed having as an objective to study in a preliminary way the mechanical characteristics of the basic materials representative of the materials employed to build the studied stone-masonry bridges [4]. For this purpose, stone samples were selected from the neighbourhood of the collapsed Plaka Bridge as well as from a quarry near the Kontodimou and Kokorou Bridges. Moreover, stone samples were also taken from the river bed of the Kontodimou Bridge. Furthermore, it was possible to take a mortar sample from the collapsed Plaka Bridge. From both the stone and mortar samples collected *in situ*, it was possible to form specimens of regular prismatic geometry. These specimens were subjected to either axial compression or four-point bending tests. For the compression tests, the loaded surfaces of the prisms were properly cupped. **Figure 23a** and **c** depict typical loading arrangements employed for the compression (stone and mortar specimens) tests, whereas **Figure 23b** depicts the loading arrangement employed for the four-point bending tests. The applied load was measured through a load cell and the deformation of the tested specimens was measured employing a combination of displacement sensors as well as a number of strain gauges. These measurements were continuously recorded with a sampling frequency of 10 Hz. Through these measurements, the mechanical characteristics of the tested specimens were obtained in terms of compressive strength, flexural tensile strength, Young's modulus of elasticity and Poisson's ratio. The obtained values of these mechanical parameters are listed in **Tables 2**–**6**.

**Figure 23.** (a) Testing in compression stone samples taken from Plaka Bridge; (b) testing in four-point flexure stone sample taken from the river bed of Kontodimou Bridge; and (c) testing in compression mortar samples taken from Plaka Bridge.



\*Reference slenderness ratio = 2.0.

employed to build the studied stone-masonry bridges [4]. For this purpose, stone samples were selected from the neighbourhood of the collapsed Plaka Bridge as well as from a quarry near the Kontodimou and Kokorou Bridges. Moreover, stone samples were also taken from the river bed of the Kontodimou Bridge. Furthermore, it was possible to take a mortar sample from the collapsed Plaka Bridge. From both the stone and mortar samples collected *in situ*, it was possible to form specimens of regular prismatic geometry. These specimens were subjected to either axial compression or four-point bending tests. For the compression tests, the loaded surfaces of the prisms were properly cupped. **Figure 23a** and **c** depict typical loading arrangements employed for the compression (stone and mortar specimens) tests, whereas **Figure 23b** depicts the loading arrangement employed for the four-point bending tests. The applied load was measured through a load cell and the deformation of the tested specimens was measured employing a combination of displacement sensors as well as a number of strain gauges. These measurements were continuously recorded with a sampling frequency of 10 Hz. Through these measurements, the mechanical characteristics of the tested specimens were obtained in terms of compressive strength, flexural tensile strength, Young's modulus of elasticity and Poisson's

ratio. The obtained values of these mechanical parameters are listed in **Tables 2**–**6**.

**Figure 23.** (a) Testing in compression stone samples taken from Plaka Bridge; (b) testing in four-point flexure stone sample taken from the river bed of Kontodimou Bridge; and (c) testing in compression mortar samples taken from Pla-

> **Compressive strength (MPa)**

**Slenderness ratio\***

**coefficient**

**/correction**

**Compressive strength (MPa) with correction due to slenderness\***

ka Bridge.

92 Structural Bridge Engineering

**Cross section (mm2 )**

**Height (mm)**

**Maximum load (KN)**

River 1a 58.5 × 48.5 74.0 310.2 124.0 1.383/0.82 101.7 River1b 61.5 × 48.3 61.0 230.5 77.6 1.111/0.70 54.3

**Code name of sample** \*\*The average compressive strength refers to a prism with a slenderness ratio = 2.

**Table 2.** Compression tests (22 January 2016) with stone samples taken near Kontodimou Bridge.


**Table 3.** Flexure tests (15 January 2016) with stone samples taken near Kontodimou Bridge.


\*Reference slenderness ratio = 2.0.

\*\*The average compressive strength refers to a prism with a slenderness ratio = 2.

**Table 4.** Compression tests (18 December 2015) with stone samples taken at Plaka Bridge.


**Table 5.** Flexure tests (18 December 2015) with stone samples taken at Plaka Bridge.


**Table 6.** Compression tests (28 January 2016) with mortar samples taken at Plaka Bridge.
