Abstract

SEISMIC REHABILITATION OF REINFORCED MASONRY COLUMNS USING CFRP AND GFRP WRAPS

NIMA FARNIA - Ph.D.
Concordia University 2011


Compared to reinforced concrete, there are relatively fewer experimental and analytical studies that address the behaviour of masonry columns under combined axial load and cyclic flexure. There exist reinforced concrete masonry (RCM) columns that are part of the moment resisting system of masonry structures that are in need for seismic upgrade. Wrapping such susceptible RCM columns with carbon fibre-reinforced polymer (CFRP) or glass fibre-reinforced polymer (GFRP) composites is expected to enhance the seismic behaviour of reinforced masonry columns considerably. This study focuses on assessing the seismic performance of RCM columns wrapped with CFRP or GFRP composites.

In the experimental phase of this study, nine 1.4 m reinforced masonry columns were constructed and tested when subjected to constant axial force and cyclic lateral excitations. The columns have a cross-section of 390mm×390mm and were constructed using bull-nosed concrete units. The first column had no FRP wraps and was used as a control specimen while the other eight columns were wrapped using different number of layers of CFRP (or GFRP) sheets or different wrapping schemes. From the tests, the effect of FRP wraps on improving the ductile behaviour, strength and energy dissipation capacity of RCM columns were quantified.

Furthermore, the experimental program extended to develop a stress-strain model for grouted concrete masonry strengthened with carbon fiber-reinforced polymer (CFRP) composites. Twelve five-block high prisms were constructed using bull-nose concrete blocks. As the study focuses on evaluating the contribution of FRP wraps in enhancing concrete masonry behaviour, the test variable was set to be the volumetric ratio of FRP material, and via detailed instrumentation, tests were conducted to measure the confining effect of the FRP material.

Finally, a macro model that is capable of simulating the cyclic lateral load-deformation response of FRP-strengthened reinforced concrete masonry (RCM) columns is proposed. The data obtained from experimental results and the proposed strain-stress model were used for developing the nonlinear macro model, and it is shown that there is a good correlation between the experimental results and the predictions of the proposed model be it the load-deformation backbone curve or the full load-deformation hysteretic response of FRP-strengthened RCM columns.