The corrosion of reinforcement in concrete is the most common degradation phenomenon of reinforced concrete structures. Reinforced concrete elements subjected to corrosion generally crack due to the expansive nature of oxides. One very important task is estimating the corrosion level using a non-destructive method in order to establish both the actual safety of the structure and a priority intervention plan. Many researchers have studied the relationship between the corrosion phenomenon and the corresponding crack openings and their evolution; several statistical analyses, based on test data from experimental campaigns under a wide range of test conditions, are available. The present work attempts to contribute to finding a relationship between the crack opening and the amount of corrosion induced in the reinforcing bars. The result of the analysis is that only a reduced number of tests can be used to establish an empirical model based on a reliable set of test data. A simple relationship between crack opening and corrosion penetration is not recommended, due to the different parameters that are able to influence this correlation. Therefore, two fundamental parameters, the ratio of the concrete cover to the rebar diameter and the concrete strength, have also been considered. The considerations made regarding these parameter test results have been rearranged and the result is a formulation that shows reduced scatter.

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Discussions have been underway in fib (Fédération Internationale du Béton) about advancing the fib Model Code for concrete structures. These include the fib international workshop in The Hague (June 2015), the fib MC2020 Core Group meeting in Madrid (December 2015), and a series of follow‐up worldwide consultations on the fib ambition regarding the new developments in structural codes, including the special session on Model Code in the fib Symposium in Maastricht (June 2017). This paper discusses the main aspects of the development of fib MC2020, which is envisaged as a single‐merged general code fully integrating the provisions for the design of new concrete structures with matters relating to existing concrete structure. It needs to deal effectively with both the design of structures and all the activities associated with the through‐life management of existing concrete structures, including matters such as their in‐service assessment and interventions upon them. To that end, MC2020 will take sustainability as a fundamental requirement, based upon a holistic treatment of societal needs and impacts, life‐cycle cost and environmental impacts. This paper discusses the main aspects of the development of fib MC2020. As part of this, the envisaged contribution of fib T10.1: Model Code 2020 is reviewed. However, recognizing the overall ambition of the fib MC2020 project, it is clear that all fib commissions, along with other bodies able to make contributions on relevant topics, will need to work together to assemble the breadth of knowledge and expertise which will be required for the fib MC2020 project.

The definition of design equations from semi-empirical or empirical models is a matter of fundamental importance in structural engineering. The direct application of partial safety factors for materials strength in such models is not appropriate in order to obtain design formulations coherent with some level of reliability, as empirical or semi-empirical formulations are calibrated adjusting empirical coefficients to fit a set of experimental data. Therefore, applying partial safety factors on material properties alone does not allow a correct estimation of structural reliability. In this paper, a reliability-based design bond strength relationship for tensed lapped joints and anchorages in reinforced concrete structures is derived applying a consistent reliability format. The semi-empirical model for mean laps and anchorages strength calculation proposed in fib Bulletin No 72 is studied. The probabilistic calibration of this model is performed defining the related model uncertainties, grounding on an extensive experimental database and distinguishing between new and existing structures. As a conclusion, the design expression for bond strength proposed by the authors is compared to current standards and its implications in laps and anchorage design in reinforced concrete structures are analyzed. K E Y W O R D Sbond strength, empirical and semi-empirical models, laps and anchorages, model uncertainties, structural reliability

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Semi-probabilistic safety formats for the non-linear analysis of reinforced concrete structures are of practical interest for structural designers. The safety format proposed in EN 1992-2 enables a safety assessment through a non-linear structural analysis and the application of a global safety factor, which is defined as the ratio between the representative and design values of the material resistances. A more realistic estimate of the global safety factor can be obtained from the distribution of the structural response. This paper proposes a safety format based on the mean values of the material resistances and a global resistance factor. Its practical application in the structural design of concrete beams and columns is also presented.

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