TECHNICAL PAPER Reliability-based evaluation of bond strength for tensed lapped joints and anchorages in new and existing reinforced concrete structures Giuseppe Mancini | Vincenzo I. Carbone | Gabriele Bertagnoli | Diego Gino Politecnico di Torino, Department of Structural Geotechnical and Buildings Engineering, Turin, Italy Correspondence Diego Gino, Politecnico di Torino, Department of Structural, Geotechnical and Buildings Engineering, Corso Duca degli Abruzzi 24, 10129, Turin, Italy. Email: diego.gino@polito.it 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 coeffi- cients to fit a set of experimental data. Therefore, applying partial safety factors on material properties alone does not allow a correct estimation of structural reli- ability. 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. KEYWORDS bond strength, empirical and semi-empirical models, laps and anchorages, model uncertainties, structural reliability 1 | INTRODUCTION The design formulations used in structural engineering always comply with a specific reliability level and are derived from resisting models by using a safety format. Resisting models based both on physical laws such as equilibrium of forces, and on semi-empirical or empirical formulations (e.g., References 1 and 2) fitted on experimen- tal results, are common in structural engineering. In the semi-probabilistic framework, safety assumptions are introduced applying partial safety factors to materials strength, and, for resisting models based on physical assumptions, this methodology leads to design expressions consistent with a specific reliability level. This does not happen in the case of empirical or semi- empirical resisting models that are based on experimental results. In such models, all the empirical coefficients that appear in the formulation should be calibrated using the mean values of material properties and the direct application of partial safety factors for material strength does not lead to a proper evaluation of reliability. Several methodologies for probabilistic calibration of physical, empirical, and semi-empirical models are proposed in the literature. 3–6 In order to apply these theoretical proce- dures consistently, an accurate assessment of model uncer- tainties is necessary as proposed in References 7–10. Received: 26 April 2017 Revised: 13 September 2017 Accepted: 14 September 2017 DOI: 10.1002/suco.201700082 Structural Concrete. 2017;1–14. wileyonlinelibrary.com/journal/suco © 2017 fib. International Federation for Structural Concrete 1 Discussion on this paper must be submitted within two months of the print publication. The discussion will then be published in print, along with the authors' closure, if any, approximately nine months after the print publication.