Deep embedment shear strenghtening of reinforced concrete continuous T-beams

Abstract

The need to extend the lifetime of our structures is crucial due to social, environmental and economic significance. Substantial number of existing buildings, need to be adapted to meet the requirements of the 21st century. There is no doubt that existing RC beams, which have shear deficiencies, will need strengthening. These deficiencies may occur due to insufficient shear reinforcement, reduction in steel area due to corrosion, increased service load or construction defects. Despite numerous studies, shear behaviour before or after strengthening is still not fully understood, particularly in continuous concrete structures which are the norm. This experimental work investigates strengthening of the existing reinforced concrete continues structures, deficient in shear by using the Deep Embedment (DE) technique. The experimental campaign involved mechanical testing of ten push-off specimens and ten two-span continuous T-beams in order to analyse and discuss the aspects related to the effectiveness of the DE technique and the types of failures of the system. An important connection was established between the push-off testing and the continuous T-beam results. Average recorded peak strains in the Deep Embedment bars in the continuous beams compare pretty well with equivalent peak strains recorded in the push-off specimens. This important finding suggests that push-off tests are indeed representative of results from the real beam tests when it comes to determining the levels of strain mobilised in the DE FRP bars. Different variables such as the type of DE bar material (steel, CFRP or GFRP), inclination of DE bars (900 or 450) and spacing between DE bars were studied. The results obtained have demonstrated that this technique is able to increase significantly the load carrying capacity of RC continuous beams which were originally deficient in shear. A significant increase in shear capacity was obtained in all the adopted strengthening configurations. The ultimate shear capacity increased on average by more than 60% across all the beams, demonstrating that the DE technique is indeed an effective solution for the strengthening of continuous RC T-beams deficient in shear, whether vertical or inclined bars were adopted and regardless of the type of DE bar material used. A powerful analytical approach, based on the upper- bound theory of plasticity, was developed and applied to unstrengthened specimens to produce realistic assessments of shear capacity. The upper-bound model was then extended to specimens strengthened using the deep embedment technique, producing accurate predictions for all specimens strengthened with steel, CFRP or GFRP bars. It was shown that the proposed upper-bound method is able to offer good shear predictions.

Date of Award	19 Jun 2019
Original language	English
Awarding Institution	University of Bath
Sponsors	European Commission
Supervisor	Antony Darby (Supervisor) & Mark Evernden (Supervisor)