Repair of Heavily Damaged RC Beams Failing in Shear Using U-Shaped Mortar Jackets

Abstract

The effectiveness of slightly reinforced thin U-shaped cementitious mortar jacketing for the repair of damaged shear-critical reinforced concrete beams is experimentally investigated. The test project includes two parts. In the first one, five concrete beams over-reinforced against flexure and under-reinforced against shear with different ratio of closed stirrups were initially subjected to monotonic loading until failure. The initially tested beams have been designed to fail in shear after wide diagonal cracking and to exhibit various strength and deformation capacities along with different levels of damages. In the second experimental part, the heavily damaged beams were jacketed with mild steel small diameter U-shaped transverse stirrups and longitudinal reinforcing bars. The retrofitted specimens using the proposed jacketing technique were tested again following the same four-point-bending load scheme. Based on the overall performance of the beams, it is deduced that the shear strength and deformation capability of the jacketed beams were substantially increased compared to the corresponding capacities of the initial beams. Further, although all beams failed in a shear abrupt manner, the retrofitted ones exhibited reduced brittleness and higher deflections at failure up to six times with respect to the initially tested specimens. The level of the initial damage influences the efficiency of the jacketing. Additional test data derived from relative shear-damaged beam specimens and retrofitted with similar thin jackets is also presented herein in order to establish the effectiveness of this repair system and to clarify the parameters affecting its structural reliability. Comparisons indicated that jacketed beams can alter the failure mode from brittle shear to ductile flexural under certain circumstances.

Experimental Study on the Effectiveness of Inorganic Bonding Materials for Near-Surface Mounting Shear Strengthening of Prestressed Concrete Beams

“…The review of past studies shows that the NSM shear strengthening of prestressed concrete beams with different bonding materials has not been explored in detail [26][27][28][29][30][31]. However, the effectiveness of organic resins such as epoxy and vinyl ester are compromised when exposed to elevated temperature and extreme weather conditions.…”

Shear Behavior of RC Beams Strengthened by External Vertical Prestressing Rebar

“…From the aspect of materials, steel fibre reinforced concrete (SFRC) [6][7][8] and ultra-high performance concrete (UHPC) [9][10][11] are used for shear reinforcement research. For existing concrete structures, carbon fibre reinforced polymer (CFRP) [12][13][14], carbon FRP ropes [15,16], steel plates [17,18], and other methods for shear reinforcement are utilized, such as U-shaped mortar jackets [19].…”

“…e present research group has used external tensile prestressed steel bars to strengthen the shear test using parameters such as tensile strength and vertical prestressed steel bar space, and the relevant results of the experimental part have been published in this journal [27]. U-shaped mortar jackets [19] can improve the rigidity and shear capacity of the structure, but it is a passive strengthening method. External vertical prestressing is an effective way to enhance the strength of concrete structure, but so far the strength efficiency and related influencing factors of this strengthening method have not been clearly explored.…”

Static and Dynamic Stiffness of Reinforced Concrete Beams Strengthened with Externally Bonded CFRP Strips

“…The anchoring strengthening methods were proposed. An additional shear strengthening method consists of applying of slightly reinforced thin U-shaped cementitious mortar jacketing [ 23 ]. The method is appropriate even in case of heavily damaged beams.…”