Giron Prefab Building System.

A number of factors related to the incorporation of large masses of students during the previous decade, led from 1970 on to an increased demand for schools, a demand that should be met in a short period, something which could not be achieved with the methods and resources used so far. Driven by the emergence of the plan of Basic Secondary Schools in the Countryside (ESBEC) the following tasks were immediately undertaken:

  • Typification of school buildings.
  • Design of a single industrializable construction system that would respond to any school building complex.
  • Creation of the material resources for the industrial production of elements, construction and assembly.

Given the required massiveness and the existing economic and technical conditions, the system to be designed should meet, as closely as possible, the following general conditions:

  • Use of domestically produced materials.
  • Use of highly industrialized production techniques, well known in the country and with relatively low investment requirements.
  • Use of highly mechanized construction techniques, but that would not require a high level of qualification in the greater part of the workers.
  • Aiming towards an open constructive system that would allow its use in the greatest possible number of projects.

This resulted in what is known as the Girón Building System, which consists of precast reinforced and prestressed concrete components designed to be produced in fixed production facilities from which they would be transported to different assembly sites.

Once the system was designed, production facilities were built in different regions of the country so demand would be met even in the most remote locations. The large volume of school buildings also required a new organizational structure, so specialized construction brigades were organized, equipped with cranes and other necessary equipment; these in turn were divided in sub-brigades for foundations, assembly and terminations, which allowed that the same brigade could work sequentially in different sites.

The system has proven its flexibility for design, to the point that its use has spread to all social buildings, such as hospitals, hotels, offices, etc., and together with the established material and organizational base has allowed to satisfy a good part of the existing demand.

General characteristics:

It is essentially composed by a reinforced concrete skeleton structure with flooring formed by reinforced or prestressed ribbed concrete slabs with a Double-T cross section. The outer walls and partitions are also of reinforced concrete. Some of them contribute to resisting the horizontal forces acting as diaphragm walls when the skeleton is insufficient for this purpose, with the peculiarity that these diaphragm walls do not have to coincide in the same vertical plane or continue down to the foundation, facts that makes the composition of each floor level easier for the architects.

The structure can withstand working loads or overloads of 300 and 600 Kg/m2, wind pressures of 175 kg/m2 and earthquakes up to grade 7, according to the M.S.K scale.

The system allows a modular network of 6.00 x 6.00 m or 6.00 x 7.50 m or or any combination thereof.

Buildings up to 5 levels with 3.30 m floor to floor heights can be built with this system.

In buildings of one to two levels, floor heights of 4.20 m are possible in the ground floor.

Components:

Structural frame's breakdown:

  • Foundation plate, cast in situ.
  • Prefabricated vase used for embedding columns.
  • Lower column fraction, which is embedded directly into the vase. When the cross section is greater than 0.30 x 0.40 m is known as pedestal.
  • Beams that go from one column to the other, including the corresponding overhangs; only the lower section is prefabricated, its final resistance being achieved after the joint between the beam and the Double-T ribbed slabs is cast.
  • Column's intermediate or top fraction; going from the top level of a floor's beams to the underside of the next floor's beams which it supports; each fraction of this type is known as column.
  • Exterior walls and partitions also of reinforced concrete, some of them contributing to resistance to horizontal stress acting as diaphragm walls.

Connection between the frame's parts:

  • Plate-vase connection: achieved by the foundation plate's concrete hardening around the prefabricated vase's legs.
  • Vase-pedestal or vase-column connection: achieved by the vertical element's embedment in the vase and the hardening of the concrete poured between the two elements.
  • Beam-slab joint: achieved by the hardening of the concrete poured on the slabs' end portions that embed the additional reinforcement steel mesh completing the beam's section and unifying the floor slab.
  • Column-beam-column joints: by the hardening of the mortar poured into the beam's gaps and the complementary beam joint in addition to the overlapping of the connected elements' protruding rods.

Connection between frame and panels:

  • It is mainly performed by welding the metal inserts anchored on the surfaces of the prefabricated elements.

Prefabricated System's components:

According to their function they can be categorized into the groups described below:

  • Group 1: Vases
  • Group 2: Pedestals
  • Group 3: Beams
  • Group 4: Slabs
  • Group 5: Eave beams (VL)
  • Group 6: Columns
  • Group 7: Panels
  • Group 8: Stairs

Production Facilities:

In the late '70s there were 20 plants producing system components in the country. The elements are manufactured in metal molds, and in some plants, exceptionally, closure panels and divisions were fabricated using vertical molding batteries or basculating tables. In the other plants they were made through stackable horizontal molding.

Technical and Economic Indices:

Structure (not including foundations, closures and partition walls)

Precast concrete: 0,208 m3/m2 
"In situ" concrete: 0,025 m3/m2 
Total concrete: 0,233 m3/m2 
Steel in prefabricated elements:
 
  • using reinforced concrete Double-T ribbed slabs:
32 Kg/m2 
  • using prestressed concrete Double-T ribbed slabs:
22 Kg/m2 
Steel used for in situ cast elements: 2,33 Kg/m2 

Prefab concrete / Total concrete:

0,893 

In situ concrete / Total concrete =

0,107 

Design Systematizing:

In order to facilitate the design of Girón structures 6 different brochures have been published giving designers from different specialties the information needed for developing their projects.

Within this information, vertical loads for most of the possible layouts are included, as are a series of graphics and tables which allow a quick selection of the required types of columns, vases and foundations.

The drawings of standard details have also been printed, so that the time devoted to preparing each project's documentation is greatly reduced.


Source: L. Abrahantes, R. Rodríguez, R. Barbosa, R. Togores, E. Marín, Informe sobre el Plan de Construcciones Escolares, circa 1982.