293 FALSEWORK - TECHNICAL INFORMATION - 2023 FALSEWORK TECHNICAL DATA - CRABTOUR For any justifications adapted to your worksite, please contact our design offices, present throughout France, for advice and support in your studies. Single tower fitted with stabilisers The tower must be stabilised against wind loads, in particular during assembly and dismantling. For normal wind conditions, it is advisable to limit the height of the tower to 3.5 times the smaller dimension of the base. For taller structures, the towers should be connected together or anchored to the structure to ensure stability in all directions. The stabilisers comprise MULTICRAB uprights, ledgers and diagonal braces. STABILITY H < 3 L h < 3,5 l h < 3,5 l l l l L Tours en plot Tour isolée l L H < 3 l h < 3,5 l DISTRIBUTION ON THE GROUND •APPLICATION FOR PUBLIC WORKS Preparing the land on which the towers are to bear on must be done carefully. Every effort must be made to reduce the importance of the differential subsidence that is highly prejudicial for towers to bear the load. Avoid heterogeneous ground or ground that is subject to washouts by running water. According to the types of ground encountered and the extent of the vertical loads per standard, a distribution in solid timber can be established on a cement-treated base or on a reinforced concrete sill of sufficient dimensions on the surface and in depth, or use any other system that ensures effective distribution of the loads on the ground. In any case, it is imperative that the bearing force of the ground be ensured and to check that the pressure brought on by the distribution is less there. Example of distribution of cement-treated base This is ground resistant to 0.8 bars, with a load per standard of 6,000 daN and a distribution in double solid timber over a height of 16 cm. Assuming a transmission of the forces at 45°, the surface concerned at the ground level is S = (2h + 15)2. The pressure has to be less than 0.8 bar (daN/cm2): •CONSTRUCTION APPLICATION In a building, the tower usually bears on concrete slab floor and does not require any particular preparation. A wooden plank must however be inserted between the adjustable baseplate or the footplate and the concrete so as to absorb the small irregularities of the ground. This wedge will always be wider than the plate of the adjustable baseplate or footplate. It may be necessary to provide sub-falsework for the support slabs from the lower floors if they are unable to take the vertical load. 6 000 daN S ≤ 0.8 daN/cm² 6 000 daN (2h + 15)² ≤ 0.8 daN/cm² √ (6 000/0.8) - 15 2 h ≥ h = 36 cm 15 cm 16 cm h 20 cm h h Plate of the baseplate 15 cm × 15 cm Solid timber 8 cm × 22 cm Cementtreated base The cement-treated base thickness must be at least: 36 -16 = 20 cm Also check the strength of the cement-treated base. Single tower Tower in blocks
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