Circular Masonry Columns Confined with FRP

Emerging techniques that use fibre reinforced polymer (FRP) composites for strengthening and conservation of historic masonry are becoming increasingly accepted. Structural enhancement of masonry elements built with natural stones is frequently needed for columns which are prone to brittle failure under seismic forces or static overloads. External confinement techniques are commonly used to strengthen compression members. In this work an extended experimental work is presented in order to show the mechanical behaviour of circular masonry columns built with calcareous blocks that may be commonly found in Italy, especially in historical buildings. Carbon FRP sheets were used for external reinforcement, different amount of FRP reinforcement and different schemes of FRP reinforcement were studied. Strengthening was applied on specimens that were damaged under different levels of load. Different stacking schemes were used to build the columns. A new reinforcement technique was also tested using FRP bars for columns with cross section formed by four different blocks. Experimental results revealed the effectiveness of confinement also for damaged columns that were loaded with 80% of ultimate load before strengthening. A computation of the ultimate load was conducted using the Italian CNR recommendations to show the proposed design approach. A previously developed analytical model was applied for computation of expected experimental values.