The Application and interpretation of linear finite element analysis results in the design and detailing of hogging moment regions in reinforced concrete flat plates

Abstract

Structural engineers have used finite element methods for the design of reinforced concrete plate type structures for decades. The theory behind this method is well researched, however, there is still a lack of direction on how to use the information obtained from this type of analysis to practically design reinforced concrete structures for strength and serviceability criteria. The literature study reviews the analysis of concrete plate type structures using traditional and finite element methods and highlights the difference between linear and non-linear finite element analysis. It is apparent that when designing and detailing using a FE analysis, a great deal is left up to engineering judgement, especially in areas of the structures where peak load effects (singularities) are experienced. In this thesis these peak areas are investigated, in an effort to provide insight into the actual behaviour of the structure as opposed to the theoretical results obtained from a FE analysis. The research consists of both numerical, (linear and non-linear FE analyses) and practical experimental work performed on different types of concrete plate type structures, including concrete pad foundations and simply supported flat slabs. The response to loading, i.e: cracking characteristics, softening of the concrete, moment redistribution, variation of the strain in reinforcement across the section, and deflection is observed and discussed. The results show that the traditional simplified methods are adequate with respect to overall strength. Finite element peaks or singularities may be averaged or smoothed without compromising durability and serviceability. Suggestions on how the reinforcement obtained from linear finite element methods be detailed are given.