The big changes that are observed the last decades in all the sectors of human life were not possible not to influence considerably, also, the construction activity.
New technologies, new methods of planning, new ways of construction, new materials and new regulations are some of the characteristics of current time. One of the developments of the last decades is the growth of combined structures from steel and concrete. In these structures the two most popular materials, the steel and the armed concrete, are combined with the most optimal way so that they can give sure, functional, durable in the time and economic structures. The use of combined structures is very widespread in most advanced countries of world. Besides their exceptional antiseismic behaviour, it renders them particularly popular in earthquake regions.

METALKAT S.A.

METALKAT has given emphasis in the combined structures the last years. A big number of projects as residences and multi-level buildings have been completely excellent with this type of structure. As it is reported above, the main structural materials that are used are the steel and the concrete.
In a combined structure house the pillars and the joists are from steel and the floorings from concrete. For the roof it can also be used concrete or tile.
For the masonry, there are a lot of choices of structural materials as conventional bricks, YTONG or ALFABLOCK, 3D, STONE etc.
In the end the completion of the remaining works is done  with the same way as in the conventional structures. The most important advantages of this type of structure are:
SPEED (FAST TIME OF DELIVERY)
EXCELLENT SEISMIC BEHAVIOR
RELIABILITY
PRECISION
PRECISE APPLICATION OF STATIC STUDY

Historical Retrospection

The combined structural elements are presented for first time in the decade 1920 in Japan, where reticular joists and props of complex cross-sections from cornerly, were encased in concrete. In Europe, the use of combined joists began in Germany in the end of 1940, in a period of insufficiency of steel. In 1956 the first relative regulation DIN 4239 "Combined joists in buildings" was published, based on the flexible theory and the method of allowed tendencies. However, the use of combined elements in buildings had big blossoming mainly in the decade of the 80s with prominent the Britain, in which these structures possess the 60% of the market in building projects. In Japan, the corresponding percentages are 64%, in USA 50%, while in the rest of Europe about 33%.

Today, it has been drawn up by the European Committee of Standardisation (CEN), the European Code 4 that concerns exclusively in the combined structures and in which are contained the rules of planning and implementation of structural projects from combined elements. It is about a Regulation, in which the knowledge and the experience, in last decades, of technicians and scientists that have dealt with such type manufactures have been incorporated.

In the Hellenic space the combined structures are not widespread, mainly because the lack in knowledge and experience of the students and the constructors and technicians. It should be noted that the responsible Ministry almost prohibits in the proclamations of public competitions, even the offer of iron and combined bridges. However, recently the need of rapid implementation of many projects and they are related with the Olympic Games, made public and private institutions to turn to the combined structures.

Despite all these, the distribution of combined structures and in Greece constitutes, one could say, an one way road, for reasons of functionalism, but mainly for reasons of speed of construction and economy. We can therefore say that it is clearly issue of time, this type of constructions, to have in Greece the acceptance that it has, not only in the rest of Europe, but also in world level.