RC BEAMS SHEAR-STRENGTHENED WITH FABRIC-REINFORCED-CEMENTITIOUS-MATRIX (FRCM) COMPOSITE

The interest in retrofit/rehabilitation of existing concrete structures has increased due to degradation and/or introduction of more stringent design requirements. Among the externally-bonded strengthening systems fiber-reinforced polymers is the most widely known technology. Despite its effectiveness as a material system, the presence of an organic binder has some drawbacks that could be addressed by using in its place a cementitious binder as in fabric- reinforced cementitious matrix (FRCM) systems. The pur- pose of this paper is to evaluate the behavior of reinforced concrete (RC) beams strengthened in shear with U-wraps made of FRCM. An extensive experimental program was undertaken in order to understand and characterize this composite when used as a strengthening system. The labo- ratory results demonstrate the technical viability of FRCM for shear strengthening of RC beams. Based on the experi- mental and analytical results, FRCM increases shear strength but not proportionally to the number of fabric plies installed. On the other hand, FRCM failure modes are related with a high consistency to the amount of external reinforcement applied. Design considerations based on the algorithms proposed by ACI guidelines are also provided

Masonry Walls Strengthened with Fabric-Reinforced Cementitious Matrix Composite Subjected to In-Plane and Out-of-Plane Load

A natural evolution of ferrocement has been the replacement of the reinforcing steel with new composite materials. Not only has this addressed the issue of possible durability problems associated with steel corrosion, but has opened the possibility of using thin-section cementitious products as repair materials. Fabric-reinforced cementitious matrix (FRCM) is a class of composite systems that has recently emerged as an alternative to traditional retrofitting methods like fiber-reinforced polymers (FRP), steel plate bonding, section enlargement, and external post-tensioning for repairing and strengthening reinforced concrete (RC) and masonry structures. FRCM consists of a reinforcing phase (fabrics) embedded into a matrix (cementitious mortar) adhered to concrete or masonry structural members and acts as supplemental, externally-bonded reinforcement. The goal of this dissertation is to experimentally and analytically investigate the effectiveness of FRCM to retrofit existing masonry structures; to evaluate the flexural and shear capacity of FRCM walls; to develop structural design procedures; and, to compare FRCM and FRP externally strengthened masonry walls. The dissertation is articulated in three studies. The first study (Study 1) investigates masonry walls externally strengthened with FRCM subjected to diagonal compression; the second (Study 2) focuses on FRCM strengthened walls subjected to out-of-plane loading; and the third (Study 3) presents a comparison between experimental results in this research program and other research programs using FRP systems when the normalized shear or flexural capacity is related to a calibrated reinforcement ratio

URM Walls Strengthened with Fabric-Reinforced Cementitious Matrix Composite Subjected to Diagonal Compression

AbstractUnreinforced masonry (URM) walls have been constructed for the past millennia and are still widely used today. URM walls have proven to have low shear strength and are prone to brittle failure when subjected to in-plane loads caused by earthquake or wind. Retrofitting URM walls is accomplished internally and externally using current techniques, such as placing steel bars in the cavities and grouting, posttensioning with steel tendons, stitching, and adhering fiber-reinforced polymers (FRP) to increase capacity and enhance pseudoductility. In this study, a fabric-reinforced cementitious matrix (FRCM) system is applied to URM walls to determine its feasibility as an alternative external strengthening technology. The experimental program consists of testing a total of nine clay brick walls under diagonal compression. Two FRCM strengthening reinforcement schemes are applied, namely, one and four reinforcement fabrics. An analytical model is used to calculate the shear capacity of strengthened URM walls and compare its results with the experimental database. The effect of limitations in design approach on shear capacity of strengthened walls is discussed

Shear strengthening of un-reinforced concrete masonry walls with fabric-reinforced-cementitious-matrix

In this paper, the in-plane behavior of un-reinforced concrete masonry walls externally strengthened with a fabric-reinforced cementitious matrix (FRCM) system is investigated. The experimental program consists of testing nine un-reinforced concrete masonry walls strengthened on both sides with two different FRCM schemes (one and four reinforcement fabrics). The analytical model as per ACI 549-13 is used to predict the shear capacity of the strengthened walls. The effects of design limitations in the approach proposed by ACI 549-13 are also discussed. Finally, experimental data from other research programs using fiber-reinforced polymer (FRP) composites are presented to demonstrate that when normalized shear capacity is related to a calibrated reinforcement ratio, the two overlay strengthening technologies match well