Punching strength is a critical point in the design of flat slabs and due to the lack of a theoretical method capable of explaining this phenomenon, empirical formulations presented by codes of practice are still the most used method to check the bearing capacity of slab-column connections. This paper discusses relevant aspects of the development of flat slabs, the factors that influence the punching resistance of slabs without shear reinforcement and makes comparisons between the experimental results organized in a database with 74 slabs carefully selected with theoretical results using the recommendations of ACI 318, EUROCODE 2 and NBR 6118 and also through the Critical Shear Crack Theory, presented by Muttoni (2008) and incorporated the new fib Model Code (2010).Keywords: flat slab, punching shear, reinforced concrete, codes.O dimensionamento à punção é um ponto crítico no projeto de lajes lisas e devido à falta de um método teórico capaz de explicar este fenômeno a verificação da capacidade resistente de ligações laje-pilar é feita normalmente utilizando-se as recomendações de normas de projeto. Este artigo discute aspectos relevantes do surgimento do sistema de lajes lisas, dos fatores que influenciam na resistência à punção de lajes sem armadura de cisalhamento e faz comparações entre os resultados experimentais de um banco de dados com 74 lajes cuidadosamente selecionadas com resultados teóricos utilizando-se as recomendações das normas ACI 318, EUROCODE 2 e NBR 6118 e também através da Teoria da Fissura Crítica de Cisalhamento, apresentada por Muttoni (2008)

This paper presents the results of seven experimental tests in reinforced concrete wide beams, aiming to investigate their performance when subjected to shear, using prefabricated truss stirrups as shear reinforcement, as well as a supplementary reinforcement to control cracks by delamination. The main analysed variables were: position of the supplementary reinforcement, inclination of the shear reinforcement, and spacing between stirrups. Results showed that strength increments of up to 142% were obtained using the prefabricated truss stirrups. Furthermore, the experimental results were compared with the theoretical shear strength estimates of the tested beams, following the recommendations of NBR 6118 (2014), Eurocode 2 (2004), and ACI 318 (2014), in order to evaluate the safety level of these codes when designing concrete elements subjected to shear with the reinforcement used in this paper.

This paper presents results of eight experimental tests carried to evaluate the mechanical performance of unconnected "W" stirrups.Reinforced concrete wide beams were tested and their characteristics were idealized to represent column strips in flat slab buildings. The main variables were: the type of shear reinforcement; the shear span to effective depth ratio (av/d); and the flexural (ρl) and shear (ρw) reinforcement ratios. In general, both the response and the shear resistance of the structural elements with unconnected "W" stirrups was similar to those elements with vertical closed stirrups. Increments of shear resistance of up to 84% were achieved, indicating that they have high potential for use as shear reinforcement in slab-column connections.

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This paper presents and discusses the procedures adopted for repairing and strengthening a damaged reinforced concrete corbel of an industrial biomass boiler. The reinforced concrete corbel was subjected to concrete spalling, favoring the risk of the main tie reinforcement slip in the anchorage zone. The proposed solution involved a local repair with a polymeric mortar and subsequent strengthening using carbon fiber reinforced polymer (FRP) sheets, attending the requirements imposed by the in site conditions and the design plans. The intervention allowed the confinement of the concrete zone subjected to spalling and provided additional safety for the main tie reinforcement of the corbel. The applied technique was demonstrated to be fast, reliable, practical, and cheaper than other available solutions, such as section enlargements with concrete jacketing.