Precast system for tertiary
PANDAL® is the latest and most advanced precast concrete system for tertiary buildings developed by DLC consulting. The PANDAL® system allows the construction of multi-storey frame buildings using entirely precast pre- stressed R.C. slabs (Pandal® slabs) spaced by trussed R.C. plates, single hollow core Pandal® or inverted T beams in pre-stressed R.C., R.C. columns with corbels and foundation footings. In the most typical version slabs, beams and column corbels are in the thickness of the slab. The cladding is made with R.C. panels, typically arranged in horizontal, but it is compatible with different façade systems. The frame structure can be stiffened with the flexural connection of beams and pillars or used in combination with precast load-bearing lightened walls (Master® walls), so to obtain coupled wall-frame structures. All elements are connected with dry mechanical devices that provide high speed of assemblage.
The system, due to its high freedom in composition, allows the realisation of a wide range of tertiary buildings, such as malls or multifunctional centres, office buildings, schools, stations, hospitals, car parks. The structural optimisation of the system has led to the attainment of a m3 of concrete per m2 ratio referred to the complete structure equal to only 0,16 for the frame structure and to 0,20 for the coupled wall-frame structure.
The PANDAL® system is set with a dual technology solution based on the maximum module span:
The Pandal® slab is an element in pre-stressed R.C. with lower flange having a standard width of 2,4 m. Its shape allows for high flexural and torsional stiffness and resistance with reduced thickness and consequent high lightness. Normally it is used to create decks with flat soffit and floor with elements spaced by trussed plates with a maximum inter-axis of 5 m, closed at the bottom with accessible ceiling. The slabs can also be placed in adjacency (in this case the slab is called Domus®). R.C. trussed plates bear on special recesses left on the upper edges of the slab elements, closing the floor. An in-situ pouring of a completing screed may be executed, especially in case of distanced slab elements.
the Pandal® slab is produced with 350, 500 and 600 mm depth and the edges can be provided with corbels.Its low weight allows to cover spans of up to 16 m.The positioning of the pre-stressing strands ensures high fire resistance.
PANDAL® and inverted-T beam
The beams in r.c.p. supporting the beams have Pandal® box section (Pandal® beam) or inverted T.
The box beams, having a maximum width of 2.5 m, can greatly reduce the span by optimizing the structure of the floor.
The terminal part may be provided with saddle for the support on the capital of the pillar in the slab thickness.
A special reinforced slab, called Tragolo functions as a connecting beam between the columns in a orthogonal direction to the main beams and supports the curtain perimeter where there is no edge beam.
COLUMNS AND FOUNDATIONS
The columns usually have square cross section. They are provided with corbels sustaining PANDAL® or reverse-T beams. The corbel can also be asymmetrical.
For ease of production, the lateral and corner columns may be geometrically identical to the central one and having the same reinforcement. This eases future expansion of the building.
Foundations are typically made with precast pockets completed in-situ with concrete pouring of the footing base. Mechanical connections are used for installation of the columns and for the joints between columns.
R.C. sandwich cladding panels with continuous thermal insulation placed in between the inner grid screed and the outer suspended screed are the standard cladding. Both horizontal and vertical panels are connected to the column corbels, the beams or the tragolos. Any other type of cladding can be alternatively applied.
In between the two concrete layers a natural ventilation chamber can be left.
The panels and their connections are energetically optimised so to get a total envelope transmittance U down to 0,18 W/m2K.
Several finishes techniques c an be mechanically applied to the outer surface of the panels, also in combination, among which:
COLUMNS AND FOUNDATIONS
The frames of PANDAL® system offer the possibility to clamp after assemblage selected beam-column joints by activating the Kaptor® connection and grouting the interface with special mortar.
With proper design, the rotation of the beam edges is prevented and the frame it is stiffened increasing its energy dissipation properties and consequently improving its seismic performance.
The use of pre-stressing for the control of the deformation and the activation of the joint at the edges of the beams leaving the dead carried in simple support leads to structural optimisation of the distribution of stresses in the elements, resulting in substantial savings.
DOMUS DRY® + PANDAL®
For all buildings where walls are required, for example tower buildings, the PANDAL® system may be used in combination with the DOMUS DRY® system to obtain a coupled wall-frame structure.
The walls are made with fully precast light-weighted Master® elements, each of them having the inter-storey height and length up to 12 m.
The Master® wall elements, produced in high-precision moulds with extractable lightening cores, are connected in vertical with the Kaptor® system and may be connected horizontally through rigid or dissipative devices to form bracing cores.
The walls may also be placed along the perimeter of the building, and in this case they are provided with a suspended screed having the same insulation features of that of the cladding panel.The floor may be made by spaced Pandal® elements or by adjacent Domus® elements.
Interviews and more information on:
The PANDAL® and the mixed PANDAL® + DOMUS DRY® systems were selected as innovative structures in the frame of the Safecast research project funded by the European Commission.
A full-scale precast prototype of a multi-storey building assembled with this system and tested in the standard PANDAL®, PANDAL® with adaptable restraint and mixed PANDAL® + DOMUS DRY® versions has been subjected to a seismic experimental campaign at the ELSA laboratory of the Joint Research Centre of Ispra (Italy).
It is the largest precast structure ever built for scientific purposes.