Resumo Esse trabalho apresenta um estudo acerca da compatibilização dos esforços solicitantes no revestimento entre modelos de maciço contínuo e de anel sobre apoios para o projeto de túneis, a partir da calibração de carregamentos impostos aos modelos de anel sobre apoios. Uma revisão das premissas de compatibilização e do cálculo de carregamentos de compatibilização “ideal”, que levam a resultados idênticos entre hierarquias de modelos é apresentada. Um estudo de caso foi desenvolvido, ilustrando que mesmo com significativa simplificação dos carregamentos calibrados, se eles possuírem magnitude e distribuição que remetam às do carregamento de compatibilização “ideal”, compatibilidade razoável, e potencialmente melhor que aquela obtida com carregamentos impostos usais genéricos, pode ser obtida. Motivada por tal observação, uma análise paramétrica da magnitude e distribuição do carregamento de compatibilização “ideal” foi efetuada, resultando conclusões que anteveem a estimativa de carregamentos de compatibilização simplificados diretamente da definição do problema físico.

Abstract This work presents a study on the compatibilization of the lining load results between continuous ground mass and bedded beam models for tunnel design, through the calibration of the loads imposed to the bedded beam models. A review on compatibilization premises and the computation of “ideal” compatibilization loads, which yield identical results between model hierarchies is presented. A case study was developed, illustrating that even with significant simplification of the calibrated loads, if they bear magnitude and distribution that resembles those of the “ideal” compatibilization load, reasonable compatibility, potentially better than that of usual generic imposed loads, may be obtained. Motivated by this observation, a parametric study on the magnitude and distribution of the “ideal” compatibilization load was performed, yielding conclusions that foresee the estimation of simplified compatibilization loads directly from the physical problem definition.

Abstract The construction methods currently adopted for multi-story concrete buildings resorts the strategy to cast columns and slabs with high and normal compressive concrete strength, respectively. The intersection region affects the load transfer performance of the columns, causing expressive confinement stress in interior columns. However, when the confinement is only provided by two sides, as corner columns, it is not enough to increase the lateral stress. The structural behavior of corner columns, represented by isolated columns, also called sandwich column, is investigated in this paper through numerical nonlinear models. The lateral stresses induced by the uniaxial load applied to the sandwich columns are computed when the influence of concrete strength column-slab ratio, slab thickness and the column width ratio and the biggest dimension of the column’s cross section were tested. A set of expressions were proposed to calculate the effective compressive strength of the column based on numerical results. The predicted effective strength has shown a good agreement with experimental results collected from the literature.

Resumo Frequentemente, a resistência requerida do concreto não é atingida nas construções brasileiras. Parcialmente para solucionar este problema, uma nova revisão da Norma Brasileira ABNT NBR 12655 foi emitida em 2015. Esta revisão mantém os critérios insuficientemente rigorosos definidos na revisão anterior de 1996, para a avaliação das resistências à compressão de concreto em estruturas existentes e em construção. Essa avaliação pode ser baseada em muito poucas amostras de teste, até mesmo no resultado de um único teste. É mostrado aqui que esses critérios são claramente inseguros. Critérios alternativos são propostos, baseados em uma abordagem Bayesiana. Os critérios propostos são verificados contra resultados de algumas centenas de ensaios realizados em estruturas reais de diferentes características, pontes e edifícios.

Abstract Frequently the required concrete resistance is not attained in Brazilian constructions. Partially to circumvent this problem, a new revision of Brazilian Standard ABNT NBR 12655 was issued in 2015. This revision maintains the insufficiently stringent criteria for evaluation of the concrete compression strength in existent and under construction structures of the revision of 1996. This evaluation can be based on very few test specimens, even in the result of a single test. It is shown herein that these criteria are clearly unsafe. Alternative criteria are proposed, based in a Bayesian approach. The proposed criteria are checked against some hundred tests done on actual structures of different characteristics, bridges and buildings.

Abstract Structural reliability theory has long been recognized as the proper tool to guide selection of partial safety factors in limit state structural design codes. Brazilian design codes, however, have never been through this calibration process. This paper addresses the reliability-based calibration of partial safety factors of Brazilian design codes for loads (NBR8681:2003), and for steel (NBR8800:2008) and concrete (NBR6118:2014) structures. The study is based on an extensive dataset of load and strength variables, addressing the Brazilian reality, as much as possible. Calibration minimizes the variations of reliability indexes of the most diverse structures designed according to the codes of interest, with regard to a target reliability index chosen by the analyst. The main result of calibration is to make reliability indexes more uniform, for different design configurations. In case of Brazilian codes, this could be achieved by increasing main variable loads, and reducing the combination values of secondary loads. This paper presents results that are not (yet) recommended for adoption in Brazilian codes, but which should be discussed with the community in order to reach minimal consensus.