R.C. columns strengthened by PBO-FRCM under axial force and bending moment

Abstract

Fabric-Reinforced Cementitious Matrix (FRCM) systems, also known as Textile Reinforced Concrete (TRC) are nowadays widely used as confining material to enhance both strength and deformation capacity of columns of seismic resistant r.c. frames. In the past, when carbon fiber was used in the textile, experimental results showed that the efficiency of the wrapping is limited by the connection between substrate and fiber, which is not as effective as when epoxy resins are used. To improve the strength of the connection between fibres and mortar binder in FRCM system, the use of p-Phenylene BenzobisOxazole (PBO), having a molecular structure capable of establishing chemical bonds with hydrated compounds in a special inorganic binder, was recently suggested. The efficiency of this new confining system was demonstrated by a large number of compression test on concrete specimens with different cross section shapes e dimensions, confinement amount, concrete strength, and cross section corner radius. By contrast, few experimental researches report the behaviour of large scale specimens under external action able to resemble the actual behaviour of columns of moment resistant frames. In this context, results of experimental tests on ten reinforced concrete columns with square or rectangular cross section, two different concrete strength, unconfined or wrapped with two or four layer of textile, subject to axial load and bending moments are here presented and discussed