ORIGINAL ARTICLE Crack width prediction of FRC beams in short and long term bending condition Emilia Vasanelli • Francesco Micelli • Maria Antonietta Aiello • Giovanni Plizzari Received: 30 August 2012 / Accepted: 7 March 2013 / Published online: 26 March 2013 Ó RILEM 2013 Abstract The use of short ﬁbers inside concrete matrix is an effective method for reducing the vulnerability of concrete constructions subjected to harsh environment. The action of the short ﬁbers in reducing the crack opening is the main issue that needs a research effort in order to optimize the expected results. At the moment the analytical prediction of the crack width and spacing in ﬁber reinforced concrete (FRC) structural elements under bending loads is still an open problem. A crack width relationship for FRC/ RC elements similar to those developed for plain concrete structural members would be desirable for designers and engineers involved in the design of FRC structural elements. The recent development of important technical design codes, such as RILEM TC 162 TDF and the new Model Code (MC) 2010, embrace this idea. However further validation of these models by experimental results is still needed. On the other hand the study of the inﬂuence of a sustained load on crack width in presence of a short ﬁbers reinforcement is a topic almost unexplored and important at the same time. In this research the cracking behaviour of full-scale concrete beams reinforced with both traditional steel bars and short ﬁbers has been analyzed under short and long term bending condition. A theoretical prediction of crack width and crack spacing was carried out according to international design provisions based on different analytical models. The theoretical results are dis- cussed and compared in order to highlight the differences between the available models and to check the reliability of the theoretical predictions on the basis of the experimental data. A modiﬁed relationship to take into account of the presence of stirrups has been proposed on the basis of experimental results; further- more, some critical aspects, such as the inﬂuence of the type of ﬁbers and the effect of loading-time, have been underlined that should be addressed in future research work. Keywords Fiber reinforced concrete  Cracking  Service life Variables f Fts FRC constant stress value assumed over the tension part of the cross-section f eq1 Post-cracking strength obtained by tests performed on notched beams in four point bending condition according to UNI 11039 w max Maximum crack width E. Vasanelli Institute for Archaeological and Monumental Heritage (CNR-IBAM.), via per Monteroni, 73100 Lecce, Italy F. Micelli (&)  M. A. Aiello Department of Engineering for Innovation, University of Salento, via per Monteroni, 73100 Lecce, Italy e-mail: francesco.micelli@unisalento.it G. Plizzari Department of Civil Engineering, University of Brescia, Architecture, Land and Environment, via Branze 43, 25123 Brescia, Italy Materials and Structures (2014) 47:39–54 DOI 10.1617/s11527-013-0043-3