**3. Construction characteristics**

one main central arch are the ones in Konitsa (**Figure 7a** and **b**) and the one in Plaka (**Figure 7c** and **d**). These stone-masonry bridges are very similar in the dimensions of the central arch, although the Arachthos river crossing by the Plaka Bridge is longer (75-m total span) due to adjacent additional arches at both ends (**Figure 7c**), whereas the main arch of the Konitsa Bridge is supported directly at the nearby slopes of the rocky Aoos river gorge. As will be presented briefly in Chapter 9 (see also figures 10g and 11 as well as section 7.3), the Plaka Bridge collapsed almost a year ago (31 January 2015). As can be seen in **Figure 7b** and **d**, the main central arch of both the Konitsa and the Plaka stone bridges has a clear span of nearly 40 m

Apart from the Plaka and Konitsa stone bridges, three more bridges will be examined in the present study. These stone bridges are depicted in **Figure 8a**–**f** and are namely the Kokorou Bridge, the Tsipianis Bridge and the Kontodimou Bridge. As can be seen in **Figure 8b** and **d**, the main central arch of the Kokorou Bridge has a clear span of 24.69 m and a rise of 12.71 m, whereas the Tsipianis Bridge has a clear span of 26.00 m and the rise 13.65 m. As can be seen, the central main arch of these two bridges has similar dimensions. Finally, the clear span of

**Figure 8.** (a) and (b) Kokorou stone bridge, Kipoi Village, East Zagori, Ipiros (width 2.85 m); (c) and (d) Tsipianis stone bridge, Milotades Village, East Zagori, Ipiros (width 2.80 m); (e) and (f) Kontodimou stone bridge, Kipoi Village, East

and a rise of 20 m.

80 Structural Bridge Engineering

Zagori, Ipiros (width 2.77 m).

the Kontodimou Bridge is 14.50 m and the rise 7.40 m.

The construction characteristics of the various parts of these bridges are thought to bear some significance in the effort to understand the static, dynamic and earthquake behaviour of these structures. One can distinguish the following main structural components:

**Figure 9.** (a) Main central arch supported on the extension of the rocky part of the river bank at both ends; (b) main arch supported on right and left mid-piers which are also formed including adjacent arch; (c) wooden formwork for the support of the main central arch. Construction of the right and left abutments; and (d) construction of the main central arch preceded by the construction of the right and left abutments.

**1.** The main primary central arch is founded on abutments at either end of the bridge. These abutments are extensions of the rocky part of the river bank (**Figure 9a**). In the case of a mid-pier, which was constructed on the dry part of the river bed, a separate foundation footing is constructed at a certain depth that is not easy to estimate. In case of relatively large river widths, the main arch was founded on right and left mid-piers that were also supporting adjacent arches as is seen in **Figure 9b**. A wooden formwork was employed to support the main arch during construction (**Figure 9c**).


**8.** Because the primary and secondary main arches were constructed at different construction stages, there is a continuous cylindrical joint that lies between them (see **Figure 10a**– **f**). As revealed by the remains of the collapsed Plaka Bridge, wooden beams with iron inserts were employed to connect the primary and secondary arches at certain intervals.

mid-pier, which was constructed on the dry part of the river bed, a separate foundation footing is constructed at a certain depth that is not easy to estimate. In case of relatively large river widths, the main arch was founded on right and left mid-piers that were also supporting adjacent arches as is seen in **Figure 9b**. A wooden formwork was employed

**2.** The construction of the main central arch was preceded by the construction of its foundation at both ends together with the construction of the abutments that were raised up

**3.** The construction of the main central arch was followed in many cases with the construction of a secondary central arch on top of the main central arch (**Figures 9d** and **10a**–**f**). **4.** Finally, the mandrel walls were constructed above the abutments in order to form together with the arches the main passage (deck) at the top of the bridge. In certain cases, this passage is protected at both sides at the deck level by an in-built continuous stone parapet that rises approximately 0.5 m above the deck level (**Figures 7a**, **c** and **8a**, **c**). In the case of the Kontodimou Bridge, this parapet is formed by individual stones in-built at intervals

**5.** The thickness of the primary and secondary arches of the main span varies considerably. The primary arch for the Konitsa Bridge with a clear span of 40 m has a thickness of 1.30 m And The Secondary Arch A Thickness of 0.59 m (**Figures 7b** and **10a**). The primary arch of the Plaka Bridge again with a clear span of 40 m has a thickness of 0.73 m and the secondary arch a thickness of 0.68 m (**Figures 7d** and **10b**). The primary arch of the Kokorou Bridge with a clear span of 24.69 m has a thickness of 0.81 m and the secondary arch a thickness of 0.35 m (**Figures 8b**, **10c** and **d**). The primary arch of the Tsipiani Bridge with a clear span of 26 m has a thickness of 0.50 m and the secondary arch a thickness of 0.40 m (**Figure 8d**). Finally, the primary arch of the Kontodimou Bridge with a clear span of 14.5 m has a thickness of 0.70 m and the secondary arch a thickness of 0.30 m (**Figures 8f**, **10e** and **f**). These thickness values are approximate and correspond to the arch thickness at the maximum rise; in some cases, the primary and the secondary arch thicknesses vary having an increased thickness in the areas where these arches join the abutments. **6.** The construction of both the primary and secondary main central arches as well as the rest of the arches was constructed with stones that were shaped in a very regular prismatic shape. In this way, the mortar joints of the masonry construction for these arches are relatively very small. The same holds for the foundation and the abutments up to a certain height. For these structural parts, according to oral tradition, special attention was paid

**7.** On the contrary, neither the shape nor the quality of the stones or the mortar was of equal importance for the mandrel walls. As can be seen in **Figure 10g** that depicts the remaining part of the Plaka Bridge, these mandrel walls were internally constructed with some form of rubble. However, in order to protect these parts from the weather conditions, the mandrel walls were also encased within facades of good-quality stone masonry (**Figure**

to support the main arch during construction (**Figure 9c**).

for the quality of the stone and mortar to be employed.

of approximately 1.6 m.

82 Structural Bridge Engineering

**10g**).

to a certain height in order to resist the thrust of the central arch.

**9.** Iron ties were also used to connect the two opposite faces of the primary arch in many bridges. These iron ties are visible in the photos of the main central arch of the Plaka Bridge before its collapse and they are still in place at the parts of the arch that were salvaged after its collapse (**Figures 11** and **12**). The iron ties were also used to connect the opposite faces of the primary arch of the main span in Tsipianis Bridge (**Figure 13**) and in Voidomatis bridge at Klidonia (**Figure 14**).

**Figure 10.** (a) Konitsa Bridge with the primary and secondary arches of the central span; (b) Plaka Bridge with the primary and secondary arches of the central span; (c) and (d) Kokorou Bridge with the primary and secondary arches of the central span; (e) and (f) Kontodimou Bridge with the primary and secondary arches of the central span; and (g) stone-masonry construction visible for the internal part of the mandrel walls of the remaining parts of Plaka Bridge.

**Figure 11.** Connection with wooden beams and iron inserts between the primary and secondary arches of the Plaka Bridge.

**Figure 12.** Iron ties used to connect the two opposite faces of the primary arch in Plaka Bridge.

**Figure 13.** Iron ties used to connect the two opposite faces of the primary arch in Tsipianis Bridge.

**Figure 14.** Iron ties used to connect the two opposite faces of the primary arch in Voidomatis Bridge.
