This paper presents an experimental study for the structural performance of reinforced concrete (RC) exterior beam–column joints rehabilitated using carbon-fiber-reinforced polymer (CFRP). The present experimental program consists of testing 10 half-scale specimens divided into three groups covering three possible defects in addition to an adequately detailed control specimen. The considered defects include the absence of the transverse reinforcement within the joint core, insufficient bond length for the beam main reinforcement and inadequate spliced implanted column on the joint. Three different strengthening schemes were used to rehabilitate the defected beam–column joints including externally bonded CFRP strips and sheets in addition to near surface mounted (NSM) CFRP strips. The failure criteria including ultimate capacity, mode of failure, initial stiffness, ductility and the developed ultimate strain in the reinforcing steel and CFRP were considered and compared for each group for the control and the CFRP-strengthened specimens. The test results showed that the proposed CFRP strengthening configurations represented the best choice for strengthening the first two defects from the viewpoint of the studied failure criteria. On the other hand, the results of the third group showed that strengthening the joint using NSM strip technique enabled the specimen to outperform the structural performance of the control specimen while strengthening the joints using externally bonded CFRP strips and sheets failed to restore the strengthened joints capacity.

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In this paper, Isoparametric finite element formulations are derived for special elements for representing the steel-concrete interface. Curved multi-noded Isoparametric element for reinforcing steel idealization is proposed. In addition, special thin Isoparametric element in a form of a sheath is suggested in order to model the bond-slip characteristics. Special provisions are taken into account to avoid numerical difficulties. The proposed elements are incorporated in non-linear finite element program DMGPLSTS and applied to the problem of tension stiffening of reinforced concrete members. The results are noted to reflect a softer overall response attributable to the slip effect.

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The effect of short-term repeated loading on very-high-strength concrete prisms of various sizes has been experimentally investigated. Concrete batches made of local materials were cast using different types of coarse aggregate. The level of cyclic preloading was altered and the corresponding influences on the ultimate strength, strain and modulus of elasticity were monitored. The effect of changing the number of cycles at a certain preloading level was investigated. For certain loading levels the number of cycles to failure was observed. The size of the specimens tested was noted to have a significant effect on the stress–strain parameters. Behavioural modelling using the concepts of continuous damage mechanics was conducted. On the basis of the experimentally observed behaviour, a mathematical expression for the damage variable was derived. Simulation by the proposed damage model captured most of the salient features of the response such as the effect of cyclic preloading at different levels, the number of cycles to failure in fatigue tests and the stress–strain curves.

An experimental and analytical study on 15 specimens of lap splices embedded in nonconventional concrete without confining reinforcement was performed under direct tension. The experimental program involved two groups of straight-ended and anchored-ended bars; three different techniques were employed with different splice lengths. For straight-ended bars, conventional lap splice was studied as a benchmark. The anchored-ended steel bars were hooks, hooks intersecting with cross bars, and plate-end bars. It was found that, the used techniques not only achieved higher tensile stress at failure, but also different modes of failure were observed. Besides, a splice length of five times bar diameter was found to be sufficient to achieve the nominal yield stress of the reinforcing steel bar in the case of anchored-ended bars. Finally, an analytical model was proposed in order to predict the ultimate tensile stress of the straight-ended spliced bars. The accuracy of the proposed model was verified against the test results of 137 existing specimens from previous research. The comparison showed good agreement between the results of the proposed model and the test results.