Abstract
In this study, a combined strengthening technique is used to improve the flexural performance of prestressed concrete beams using CFRP sheets as EBR and prestressed steel strands as NSM. Seven prestressed beams were tested under four-point loading with one control specimen, one EBR CFRP sheet strengthened specimen, one NSM steel strand without prestress strengthened specimen and four specimens strengthened with a combination of EBR CFRP sheet and NSM steel strands prestressed from 0% to 70% of their tensile strength. The flexural responses and failure modes of the specimens were investigated and the variations due to the level of prestressing force in the PNSM steel strands were also assessed. A finite element model (FEM) was developed using ABAQUS to verify the flexural responses of the strengthened specimens. The test results revealed that the combined strengthening technique remarkably enhanced the flexural performance of the specimens. The serviceability, first crack, yield, and ultimate load capacities improved up to 44%, 49%, 55% and 70%, respectively when compared with the control specimen. The combined technique also ensured the flexural failure of the specimens with significant enhancement in stiffness and energy absorption. The results of the FEM model exhibited excellent agreement with the experimental results.
Highlights
Prestressed concrete (PC) has been used extensively in construction worldwide and faces challenges similar to reinforced concrete (RC) during construction and service, such as design errors, increasing traffic loads, environmental exposure, physical damage from vehicle accidents, etc., which may require structural strengthening (Lee et al, 2017)
The ultimate load showed the greatest improvement with about 65% to 70% increase in the CEBPNSM beams
In this study four strengthening techniques were examined by experimentally testing the flexural behavior of seven prestressed concrete beams and developing a numerical finite element model (FEM) model to simulate the behavior of the beam specimens
Summary
Prestressed concrete (PC) has been used extensively in construction worldwide and faces challenges similar to reinforced concrete (RC) during construction and service, such as design errors, increasing traffic loads, environmental exposure, physical damage from vehicle accidents, etc., which may require structural strengthening (Lee et al, 2017). Combining EBR and NSM (CEBNSM) is a recent advancement in structural strengthening which can enhance the effectiveness of strengthening and overcome some of the limitations of both techniques. Lim (2009) used a combination of EBR CFRP strips and NSM CFRP strips on nine RC T-beams. Flexural strength and stiffness significantly increased; failure occurred due to debonding of the EBR strips. The flexural capacity of the strengthened beams was enhanced, failure still occurred by debonding. Darain (2016) investigated the structural behavior of six RC beams strengthened with a combination of EBR CFRP fabric and NSM Failure was significantly delayed due to improved bond performance. Darain (2016) investigated the structural behavior of six RC beams strengthened with a combination of EBR CFRP fabric and NSM
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