Efficacy of PBO-FRCM strengthening of RC columns in MRFs

Innovative materials and techniques are widespread used for the strengthening and rehabilita-tion of existing structures. Recent researches have been developed on new fiber reinforced composites in which epoxy resin is replaced by inorganic cementitious material. These kind of cement-based composite material is known as Fiber Reinforced Cementitious Matrices (FRCM) recently used also in combination with synthetic polymeric fibers named PBO. The efficiency of this new confining system has been demonstrated by a large number of com-pression tests on concrete specimens while there are only few experimental researches on the behaviour of large scale specimens under external action able to simulate the actual behaviour of columns in MRFs. This paper firstly presents the results of experimental tests on squared and rectangular speci-mens of medium-size concrete columns reinforced by PBO-FRCM subject to axial load; suc-cessively, an experimental campaign is performed on RC columns subjected to axial force and bending moment. Confined and unconfined columns, manufactured with different cross sections and concrete types, are tested. The experimental tests on concrete columns and RC pillars are reproduced through finite ele-ment models in which the behaviour of the confined concrete is simulated using the Concrete Damaged Plasticity model with properly adapted plastic parameters, according to recent stud-ies available in the literature. The stress-strain law used in the model is deduced from a clas-sical approach available in the literature for FRP confined concrete which is properly modified in order to take into account the efficiency reduction of FRCM with respect to FRP wraps.