Muhammad Rashid* Int. Journal of Engineering Research and Application www.ijera.com ISSN : 2248-9622, Vol. 6, Issue 9,(Part-5) September.2016, pp.54-57 www.ijera.com 54 | Page Cyclic Response of Reinforced Concrete Moment Resisting Beams Repaired with Epoxy Injection Muhammad Rashid* *(Department of Civil Engineering, University of Engineering & Technology Peshawar, KPK, Pakistan) ABSTRACT This paper presents the results of a quasi-static cyclic test carried out on a reinforced concrete special moment resisting beam to study the efficiency of traditional repair techniques in restoring the strength and stiffness capacity of damaged RC beams. The beam was tested in a cantilever mode and was subjected to a standard loading protocol with increasing amplitude of displacement cycles. The final damage state of the beam consisted of severe cracking and spalling of the cover concrete. The cracks were repaired with low-viscosity injection epoxy and the spalled concrete was repaired with early-strength grout. The repaired specimen was subjected to the same loading protocol as the original specimen to study the efficiency of the repair technique employed. It was observed that epoxy injection is not effective in restoring the strength and stiffness of beams with bar slip of longitudinal bars at the support end. Keywords - Bar slip, epoxy injection, reinforced concrete, reparability, strength, stiffness, I. INTRODUCTION Modern seismic design codes [1-3] design buildings with the objective to avoid collapse and save human lives. Structures are designed for seismic forces that are considerably smaller than the design-level forces, and therefore they are prone to damage during large earthquakes [4]. Reinforced concrete special moment resisting frames are designed according to the principles of capacity design; which states that damage should be concentrated at fixed locations in beams, often called plastic hinges. The plastic hinges are located at the ends of beams and should be proportioned and detailed to respond primarily in flexure mode rather than brittle modes of response such as shear. This philosophy forms the basis of almost all the modern seismic design codes [1-3]. However, the subject of reparability of damaged reinforced concrete structures, after being subjected to an earthquake, has been addressed rarely. The performance of reinforced concrete moment resisting frames, designed to modern codes, in the recent earthquake of Christchurch (2011) was satisfactory but raised the issue of reparability of reinforced concrete structural components [5-6]. A large number of damaged reinforced concrete frames had to be demolished due to the lack of sufficient experimental evidence to justify the use of traditional repair techniques in restoring the capacity of damaged reinforced concrete structural elements. This paper addresses the issue of reparability of reinforced concrete structural elements through an experimental program. Since there has been a rampant increase in the construction of reinforced concrete frames around the world (especially Pakistan), therefore, it is considered necessary to bring the issue of reparability of reinforced concrete beams to the knowledge of concerned authorities and structural design engineers. To achieve this task, it was necessary to conduct an experimental program to study the efficiency of repair techniques and highlight the associated problems with different repair techniques. Quasi-static cyclic testing is conducted on a special moment resisting beam to study the efficiency of epoxy injection and grout patching in the restoring the strength and stiffness of a damaged beam. Epoxy injection was chosen to be studied due to its ease of application as in a real structure the repair process is complicated by the presence of floor slab and infill walls. II. LITERATURE REVIEW Popov et al. (1975) tested three full-scale short cantilever reinforced concrete beams and one half-scaled interior beam-column joint representative of third floor framing of a 20 story RC moment resisting frame. Two repair schemes were investigated i.e. repair with a rapidly setting epoxy resin and concrete depending on the damage state of the beam. It was observed that the performance of beams repaired using epoxy resin was satisfactory but exhibited some loss of stiffness due to bond. Additionally, replacing severely damaged concrete using fresh concrete was found to be a satisfactory solution. Corazao and Durrani (1989) carried out a detailed experimental investigation on repair of reinforced concrete sub-assemblages subjected to quasi-static cyclic loading. A total of eleven sub-assemblages were tested, which consisted of five exterior beam-column connections and six two bay frames. Different repair techniques were studied depending on the type and extent of damage. It was found that epoxy injection is suitable for repairing cracks in beams and slabs and its effectiveness in beam- column joints depends on the quality of work. In case of severe damage, such as damage to core concrete, the strength can be effectively restored by replacing the damaged concrete. Reinforcement jacketing and addition of external rolled steel elements were found to be reliable ways of restoring strength and stiffness. III. EXPERIMENTAL WORK The cross sectional dimensions of the beam are 12in. x 18 in. with a length of 96 in. The beam had 3-#8 bars in the top and bottom layer giving a longitudinal reinforcement ratio of 1.26%. The transverse reinforcement was provided according to the confinement requirements of ACI-318 for beams. RESEARCH ARTICLE OPEN ACCESS