MONITORING OF DEFORMATIONS OF CONCRETE CELING SLABS OF MULTI-DWELLING UNIT
Contemporary building structures are to be carried out quickly and at low-cost. But does such execution not entail negative consequences? The use of fillers in concrete mixtures in the form of powder derived from electro-filters lowers the cost of the mix, but significantly extends increase in the strength of concrete. As a result, the concrete obtains its design strength not after 28, but for example, after 56 days. Sometimes the process takes even longer. Slower increase in strength also implies slower growth of the elastic modulus.
The celing element after 28 days is back propped and loaded for example with partition walls. Unfortunately, increases in deformation of concrete in this initial period of its life are so great that the widely used today plates with spans of more than 6m , deflection of permanent loads cause damage to the wall elements.
A monitoring system was designed, which over a long period of time (min. 10 years) will allow observation of the deformation of a certain monolithic slab at selected measuring points. Geokon strain sensors 4200 model was installed during concreting parallel to the direction of the main torque both in the middle of the span plate (at the location of the extreme positive torque) and the bearing walls (in place of extreme negative torque).
Figure 1. The sensors in the middle of the span plate (measuring strain at the lower and the upper surface of the ceiling)
Figure 2: View of the sensors in the middle of the span plate from the level of the upper reinforcing bar
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