Contribuição ao projeto otimizado de pavimentos rígidos pelo guia da Austroads baseado no método PCA de 1984

Abstract

The plain rigid pavement design proposed by the Portland Cement Association (PCA) in 1984, defined the model parameters, involves assuming an initial thickness of the slab and then using a series of tables and abacuses to verify the two criteria that govern the design: the flexural fatigue of the concrete slab and the erosion of the subgrade/subbase. It is necessary that each of these criteria be lower and close to 100%, to obtain safe and economical designs, respectively. If one of these criteria exceeds the prescribed 100%, the calculation must be repeated for a greater thickness or manipulate certain model parameters. In this perspective, the focus of this work was the hypothesis that the combined adjustment of the plate thickness with the tensile strength in the concrete bending (𝑓𝑐𝑓) may be the most economical solution for the design, as opposed to increasing the thickness, without disregarding structural safety. The design of a computational algorithm was developed to optimize the design of the rigid single deck board, seeking to combine thickness and 𝑓𝑐𝑓 capable of minimizing the cost of the design. At first, this culminated in the emergence of a conceptual model, by finite elements, defining the objective function cost of the square meter of plain rigid pavement plate (𝐶𝑝), as a function of thickness and 𝑓𝑐𝑓 optimized, but without consider phenomena of rupture (fatigue and erosion). Then, the studies and research that guided this work finally demonstrated the possibility of elaborating a computational algorithm, contemplating such phenomena, in the light of the original idea. It is proposed an algorithm for the optimization of the design of the plain rigid pavement, adopting the objective function of the conceptual model. For this purpose, we chose to use the AUSTROADS (2010) guide, which is based on the 1984 PCA method, and which brings together all the equations necessary for computational implementation. An analysis, with a conclusive opinion of the effects on the optimized design regarding the behavior of the parameters involved in the design, is performed. It is confirmed the thesis proposal that the combined adjustment of the thickness of the plate with the resistance allows the definition of designs more optimized against those in which the adjustment is allowed only in the thickness of the plate.