In March, Filigran Trägersysteme GmbH & Co. KG organized a „floors and walls“ series of seminars. More than a total of 500 planners and staff members of precast factories participated in the seminars which were held on six dates in the cities of Cologne, Melle, Hamburg, Leipzig, Erlangen, and Munich. Main topic was the application of Filigran semi-precast walls with lattice girders built as waterproof structure.
In respect of the semi-precast wall, Professor Hohmann emphasized two relevant changes: The requirement on the surface roughness inside of the precast panels has been increased. If, so far, a mean roughness depth of 0.9 mm had to be verified by the sand patch method, the new WP Code of Practice requires a value of 1.5 mm. This requirement corresponds to the verification of the load-bearing capacity for a rough joint in accordance with Eurocode 2. This subject was pointed out by Dr.-Ing. Johannes Furche of Filigran in a separate lecture. The required roughness of the untreated surface has to be ensured because in case of a semi-precast wall just the surface of the first shell can be roughened mechanically. Using previous comparative measurements, he demonstrated that five out of six semi-precast walls met the increased requirement even with untreated precast surfaces. Nevertheless, due to the large roughness depth, the manufactures will have to adjust the consistency, mix design, and compaction of the concrete purposefully in future.
Filigran design program revised
As third speaker, Dipl.-Ing. Ulrich Bauermeister of Filigran Trägersysteme GmbH & Co. KG explained the erection state of Filigran slabs. Tests using 40cm high Filigran EV lattice girders confirm potentially longer erection spans. The approval of lattice girder heights of 30 to 40 cm enables slab designs with lattice girder height alone even at slab thicknesses of more than 30 cm. So far, highly loaded floor slabs often required a combination of low girders for the erection state and high lattice girders as shear reinforcement. The associated Filigran design program is currently being revised in this respect. The new version will take the erection state using lattice girders with variable nodal points into account as well. A node distance diverging from 200 mm is of relevance when producing or using lattice girders with fixed lengths. A module for the verification of shear forces is also included in the current Filigran design program as well as a module for the punching shear verification of semi-precast slabs. The program is available at www.filigran.de free of charge.