Fissuração em formas plásticas para lajes: análise numérica e caracterização experimental sob envelhecimento acelerado

Abstract

Ribbed slabs have been widely adopted as the flooring system for multi-family buildings. A major advantage of these systems, in addition to the possibility of using non-bonded prestressing, is the use of a standardized plastic formwork system that makes the execution process very efficient. The PavPlus® system from Impacto® has been widely used in several constructions; however, the useful life of the forms is affected by exposure to ultraviolet (UV) light, which causes the material to age. Another detrimental factor is the high deformations applied during the demolding phase, in addition to post-extraction handling. Due to these factors, recurrent and wellcharacterized cracks can be noticed after cycles of use, always close to the region of application of the extraction load, which requires the execution of repairs to the plastic forms. This work aims to mitigate the negative effects produced by the aging and extraction process on the plastic forms of ribbed slabs, further extending the useful life of these parts. For this purpose, experimental tensile, flexural and impact tests were performed on samples with different compositions aged in a UV chamber, aiming to evaluate the changes in the material's behavior and properties. After characterizing the material, numerical analyses were performed with elastoplastic constitutive models with damage, evaluating the effect of this on the behavior of the form in service and, in particular, on the extraction process. The results showed that UV radiation has a high potential to cause changes in the constitutive properties and mechanical behavior of the material, reducing the stiffness and other rupture limits that can contribute to the appearance of cracks. The numerical simulation of the use of the form for usual loads in service showed that no damage occurs, however, the pull-out process caused damage to the surface of the flange. The extraction model using the tool through the middle and corners of the form was studied to evaluate whether they are the causes of future damage.