FLEXURAL STRENGTHENING OF RC BEAMS USING FERROCEMENT LAMINATES
The study reported herein was carried out to investigate the behaviour reinforced concrete beams strengthened in flexure using ferrocement laminates attached onto the soffits (tension face). Five aspects were studied; 1) the theoretical ultimate and serviceability characteristics of the strengthened beams, 2) the concrete/ferrocement interfacial shear strength with various types of surface preparations and shear connectors, 3) the methods of attachment of the ferrocement laminates, 4) the effect of the level of damage in the original beams prior to repair, and 5) the performance of the strengthened beams under cyclic loads. The experimental programme comprised the testing of twenty-four double-shear push-out specimens and twelve full-scale T-beams. The beams were simply supported and loaded at mid-span. Theoretical reIationships between the volume fraction of reinforcement in the ferrocement laminate, the increase in ultimate flexural capacity of the strengthened beams, and the shear stress at the original beam/ferrocement laminate interface were derived and compared with the experimental results and available test data from other studies. The results show that the strength and serviceability characteristics of the strengthened beams were significantly improved compared to the unstrengthened control beam. The behaviour of the strengthened beams may be estimated within reasonable accuracy using conventional design methods as recommended by BS8110:Part 1:1985. The original beam/ferrocement laminate interfacials hear stress was estimated to be about 2.5 times larger than the elastically derived predictions using conventional shear flow equation. A non-dimensionalised design chart relating the shear stress at the concrete/ferrocement interface to the volume of reinforcement in the ferrocement laminate and the improvement in moment capacities of the strengthened beam is proposed. Beams completely damaged under short term loading condition may be restored to greater strength and serviceability. Cyclic loading with a maximum load greater than 50% of the theoretical flexural capacity caused rapid deterioration of the composite action at the concrete/ferrocement interface.
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