/BING_FACTSHEET_3

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FACTSHEET N째 3

Repetitive loads on flat roofs: an improved method to predict potential future damage A flat (or low slope) roof is often exposed to dynamic mechanical loads e.g. by pedestrian traffic or small vehicles. These loads occur during construction of the building or for regular maintenance of installations on the roof. After a few loads some materials tend to lose their compressive strength, resulting in a deeper imprint of e.g. the foot on the waterproofing. The stress in the waterproofing may lead to cracks, or to penetration of a mechanical fixer through the waterproofing if the imprint is close by. Therefore the insulation material and the waterproofing may be severely damaged, resulting in a leaking roof.

Figure 1: Example of a damaged roof In the current practice no methods are available to assess the effect of a dynamic load on the long term performance of a roof construction. Often the compressive strength and/or point load resistance of the insulation material is used as an indication, but this method only applies a load once, and thus can not show deterioration due to repetitive loads on the same spot of the roof.

A new method for assessing the effect of repetitive loads To predict potential damage due to repetitive loads, a new method was developed simulating pedestrian traffic on a roof. A machine was built, simulating the repetitive walking of the foot (with a shoe) of a man of 75 kg with a roll of waterproofing of 25 kg. The number of load cycles can be adjusted, simulating the intensity of the repetitive loading of the roof.

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