**2. Archaic period**

natural environment by achieving the developmental objectives in a responsible way: *the present generations' responsibility to regenerate, maintain and improve planetary resources for use by future generations*. Nowadays, the idea has developed into specific disciplines, such as sustainable

In the development of civilisation, an extensive and well-organised transportation system, i.e., roads, railway, bridges, air transport and maritime and inland navigation, safe both for people and environment, is of primary importance. The development and constant modernisation of road and rail infrastructure is connected with significant pollution emissions into the air, soil and water. Investments are accompanied by noise and traffic disruptions. These negative side effects have an equally strong impact both on people and environment. In general, they can result in a temporary or even permanent closing or changing of wildlife corridors, animal herd

Roads and bridges, despite obvious differences, constitute a technically inseparable set. The name of the first and still functioning technical school, excellent *École nationale des ponts et chaussées* founded in 1747, is quite symptomatic here. Bridges as such belong to the elite area of civil engineering. This position stems from their civilisational, social, architectural as well

After the horrible experience of the first World War, the Briand-Kellogg treaty [3], renouncing war as an instrument of national policy, was concluded. History, including the most recent one, shows that military operations are still conducted on a different scale and so it happens that some are aimed at bridges. **Figure 1** shows the Hanoi bridge that was destroyed during the

Sustainable bridge construction refers to the minimisation of harmful emissions during bridge construction. It is equally important, however, to design durable bridges, i.e., with minimum serviceability of 100 years as stipulated in the design standards [4]. The bridge longevity results from the structure maintenance therefore its design should take into consideration the ease of

A design taking into account the future changes of traffic, both in terms of its volume and type, seems to be a great challenge. The existing methods of forecasting traffic changes cover periods

engineering, sustainable bridges [1] and sustainable design [2].

fragmentation, changing of nesting sites or habitats.

Vietnam War. Its crippled form is a dramatic monument to this war.

**Figure 1.** Hanoi Cầu Long Biên Bridge (1903) over the Red River—a war monument.

as military role.

2 Structural Bridge Engineering

its future maintenance.

The history of bridges can be told in many ways. It will always be a subjective representation, strongly affected by the author's attitude. This is also the case here.

The first large-scale bridge, recorded by Herodotus, was a structure for crossing the Dardanelles (Hellespont in the ancient times, the area of Çanakkale in Turkey at present), constructed by Greek constructor Mandrocles of Samos in 513 B.C. It was a ship pontoon bridge. Soon after, in 480 B.C., two other pontoon bridges were constructed by Xerxes' army, see *History of Herodotus* [6]. At the point of the bridge crossings, the Strait of the Dardanelles is 1.4 km wide. It should be noted that Herodotus' description of the bridges gives rise to doubts; therefore it can only be assessed in terms of likelihood.

In 55–53 B.C., during the wars with the Germanic peoples, Julius Caesar commissioned the construction of two wooden bridges over the river Rhine. At least two reconstructions of these bridges exist [7]. Another large-scale bridge was constructed during Emperor Trajan's war against Dacia in 105 A.D. by Greek architect Apollodorus of Damascus. Its remains, in the form of stone pillars, are to be found in a place with a poetic name: Turnu Severin. It was a wooden arch structure based on 20 massive supports where the Roman pozzolana cement was used. The bridge was immortalised in a relief on Trajan's column in the Foro di Traiano in Rome.

**Figure 2.** Arch-corbel system of Mycenaean bridges: (a) Bridge A; (b) Bridge B.

All of the aforementioned bridges do not exist anymore, but in Peloponnesus there are still two stone bridges constructed with so-called *Cyclopean boulders* to be found, known as Mycenaean Bridges. The period of the Mycenaean culture falls in the mid-Bronze Era from approx. 3000 B.C. to 1000 B.C. Hence, it can be inferred that the bridges are at least 3000 years old and for that reason are considered the oldest existing bridges in the world. Given their age, they are in a superb technical condition. They are not large-scale objects—the width of the light of the flow opening is approx. 1.5 m, its height approx. 2 m, **Figure 2**.

It should be highlighted that Mycenaean bridges were elements of the road system, which today is known as *Mycenaean Highways* [8] —which may be a slightly exaggerated name. The term was first introduced by A. Jansen, the author of one of the chapters of this book.

Mycenaean bridges are very interesting from the point of view of structural mechanics and construction technology. At the first glance, they seem to be arch structures. But if so, one must admit that these arches are rather accidental. The arrangements of boulders of which the arches are made demonstrate the lack of knowledge with regard to the essence of the arch behaviour. As a matter of fact, they are corbel structures which—as a result of seismic earthquakes—have been degraded to the present shape. Hence, the currently observed cyclopean boulder arches are a result of the transformation of the corbel system into a possible mixed arch-corbel static system. The effort and stability of Mycenaean bridges were analysed in the paper [9]. Identification of the technology of Mycenaean bridges is a great challenge, **Figure 2**. The cantilever slab technology enables construction without scaffolding. If indeed it was so, Mycenaean bridges were a major constructional achievement. Despite the fact that Mycenaean bridges constitute a part of the heritage of mankind, they have not been sufficiently studied. Paradoxically, apart from taking external measures, their ultra-historical character makes it impossible to conduct standard research.
