Interação solo x estrutura. Análise de um caso de obra com acompanhamento dos recalques

Abstract

In structural analysis, the hypothesis of non-displaceable supports has been used for many years due to its simplicity, by neglecting the effect of soil settlement. When submitted to small displacements, the foundations can cause load redistribution. The analysis of the interaction between soil, foundation and structure is important for the development of an adequate design, being suggested by the Brazilian NBR standard for foundation design, especially for some situations. The present research analyzes a real case study that includes the monitoring and analysis of settlements during the construction. The focus was on studying the soil-structure interaction (SSI) of a 21-storey reinforced concrete building on mixed foundations, consisting mostly of footings. The analyzes carried out in the software (SAP2000) included relevant aspects regarding the modeling of the structure and behavior of the soil (by means of springs). Comparisons were made between the model considering fixed supports and considering the interaction effect. The AOKI LOPES (1975) method was adopted for the settlement estimation and an iterative process was used for the SSI. The results has shown the redistribution of the column loads, with a tendency of loading relief in the central columns and loading increase in the periphery. The Settlement Factor (AR) has proven to be an interesting parameter to indicate a trend in the behavior of load transfer from columns, as a preliminary analysis. In relation to settlements, the effect of SSI results in a more uniform behavior when the iso-settlement curves are compared to that analyzed without considering the SSI. It is worth highlighting that since the project comprehends foundations laid very close to the rigid layer (impenetrable to percussion), and the massif is composed of a residual material with high resistance, the soil-structure interaction is evident, but not very significant in the present case. Ultimately, the author emphasizes the importance of performing the investigations and instrumentations with quality, so that the analyzes can, in fact, reflect the reality.