Fire-damaged R/C Members Repair With High-Performance Fibre-Reinforced Jacket A. Leonardi, A. Meda and Z. Rinaldi Department of Civil Engineering, University of Rome ‘‘Tor Vergata’’, Via del Politecnico 1, 00133 Rome, Italy ABSTRACT: A new repair technique, developed for fire-damaged R/C structures and based on the application of jackets made of high-performance fibre-reinforced concrete, is presented and dis- cussed. The proposed technique may be in principle applied to both beams and columns, as shown in this article. At first, the residual bearing capacity of the reference members is determined for different values of the fire duration. At this aim, an analytical model based on the direct integration of the hot or residual mechanical properties of the three materials (concrete, steel and fibre-reinforced concrete), throughout the member cross section, is here adopted. Then, after discussing the pros and cons of the application of concrete jacketing to the structural cases in question, the performance of the composite structures is analytically investigated, to make comparisons with the performance of the original undamaged structures, as well as with that of damaged structures. Finally, the fire resistance of the repaired members is evaluated, to show the effectiveness of the proposed technique. KEY WORDS: fire resistance, high-performance fibre reinforcement, jacketing, repair Introduction Repair and strengthening of existing R/C structures is of great interest not only for extending their service life, but also – and rather often – for their rehabili- tation after being damaged during exceptional events such as earthquake and fire. The preliminary question for any designer involved in the rehabilitation of fire-damaged structures is to check whether any specific repair strategy may be appropriate compared to partial or total demolition, followed by reconstruction. As a matter of fact, it has been shown recently that repairing fire-damaged structures, after a proper assessment campaign, may be the right choice [1, 2]. Hence, evaluating the residual bearing capacity of a fire-damaged structure is a necessary step before choosing any specific repair technique. To this end, knowing materials residual properties after the fire is of primary importance, with reference to both con- crete and steel [3–5]. Luckily, new techniques for the assessment of fire damage in R/C structures have been recently developed [6], and deriving the residual properties of concrete and steel after a fire is nowa- days much less uncertain than in the past. For repairing fire-damaged structures, different solutions are available, such as partial reconstruction, adoption of R/C jacketing or use of externally bonded fibre-reinforced polymers (FRP). As should be expected, the choice of the repair technique has to do with the damage level and with the use of the structure after being repaired. At this stage, the designer should be aware of two require- ments: the repaired structure should exhibit not only a sufficient bearing capacity in ordinary conditions, but also an adequate fire resistance, because a second fire cannot be ruled out. A new technique has been recently proposed for strengthening R/C structures via thin jackets made of high-performance fibre-reinforced cementitious composites (HPFRCC, see [7, 8]). These materials are characterised by a high compressive strength, which is accompanied by a rather high tensile strength, as well as by a hardening behaviour in tension. As the traditional reinforcement is no longer necessary, the usual limits specified for the minimum cover do not apply to the jacket (no rebars and stirrups), and the thickness of the jacket can be as small as 30–40 mm. The effectiveness of HPFRCC jackets for repairing fire-damaged R/C beams and columns is investigated in this article, by performing a number of numerical analyses, where Coccia and Rinaldi’s model [9] – based on the direct integration of temperature- dependent materials constitutive laws – is adopted. A first analysis is carried out for a number of selected ‘reference’ sections of both beams and col- umns, subjected to different fire exposures under the standard fire ISO 834 [10], to evaluate their residual 28 Ó 2010 Blackwell Publishing Ltd j Strain (2011) 47 (Suppl. 2), 28–35 doi: 10.1111/j.1475-1305.2010.00731.x An International Journal for Experimental Mechanics