ABSTRACT
Fiber reinforced cementitious matrix (FRCM) is a noncorrosive two-dimensional high strength fiber reinforced polymer (FRP) mesh saturated with inorganic cementitious mortar.This novel system is evolving as a viable option for retrofitting damaged RC structures.This system is fire resistant, easy to apply and eliminates the toxic hazard of epoxy bonded FRP. While past research investigated the potential of FRCM in shear and flexural applications, limited studies explored the confinement of short columns with different cross sections, particularly using finite element (FE) analysis. In this study, a three-dimensional (3D) nonlinear finite element (FE) model is developed using ABAQUS to investigate the performance of the retrofitting system on corrosion damaged RC columns. Poly-paraphenylene-ben-zobisoxazole (PBO) fibers are modeled in this study. Loading condition is displacement-controlled loading condition and material nonlinearities in concrete, cement mortar and composite are adapted in the FE model. The FE models are validated against experimental studies in published literature. A total of 40 columns are modeled and a parametric study is conducted considering the effects of cross section type (square vs circular), number of FRCM layers (1, 2, 3 and pre-damage severity (mild, moderate and severe). Retrofitting corrosion damaged RC columns with PBO-FRCM effectively resorted and enhanced the original axial capacity and ductility at all damage levels irrespective of cross section shape. Enhancement in axial capacity of 20% was observed in square and 35% in circular columns while axial ductility enhancement of 42% was observed in square and 164% in circular columns. Results also indicated a positive correlation between number of FRCM Layers and axial capacity and ductility enhancement. The performance enhancement is more pronounced in the circular columns. All strengthened specimens failed by matrix damage, indicating effectiveness of the strengthening system. Comparison of column axial capacity computed using ACI 549.4R-13 provisions against FEA revealed that the code provisions underestimate the axial capacity of square and circular short RC columns retrofitted with PBO-FRCM by an average of 20%.
