The main conclusions, from a technical point of view, highlight the following re-propping systems inconveniences:Partial down-striking after 6 days instead of 3.
The floor form release has to be made 6 days after concreting instead of after 3 like in the recoverable system of partial down-striking.
The study also concludes that:
1st - In the RE-PROPPING systems, the recovery is generally made after 6 days instead of 3. In order to recover material after 3 days a double amount of props has to be placed or else very special down striking precautions have to be taken. This process has to be planned and supervised by efficient technical personnel. See conditions included in the technical report.
2nd - Incorrect transmission of loads: The cross distribution of props on the supports of the PROPPED floors supports the load in the opposite way (long) of the props of the floor being concreted, which highlights the recommendations made in the previous paragraph.
The assembly operations of the re-propping systems offer besides inconveniences that must be considered:
1.- It requires MORE LABOUR as the props have to be placed TWICE.
2.- This system requires MORE REFERENCES, (END MAIN GIRDER, INTERMEDIATE MAIN GIRDER, SUPPORT AND SUPPORT GIRDER) instead of 3 (MAIN GIRDER, DROPHEAD and SUPPORT GIRDER). There is no coincidence in the location of the upper floor props and the lower floor ones, which could produce punching on the slab. On releasing forms, the structure supports important stresses, as it is unloaded during the re-propping.
3.- SECURITY: There are more risks as the PANEL HAS A SMALLER SUPPORT on the main girders wings and even smaller when these are covered with concrete.
4.- FINISHES: due to the accumulation of concrete on the wings, the panel does not always rest at the same height; the panel –timber– and the prop –metal– buckle in different ways, producing BIGGER MARKS ON THE CONCRETE.
