To assess the strengthening ability of a strain hardening cementitious composite (SHCC), a layer of SHCC was applied to masonry beams subjected to bending. When compared to the strengthening performance of steel fibre reinforced self-compacting concrete (SFRSCC) layer for this type of brittle beams, the SHCC presented better workability in fresh state, and provided a higher load carrying capacity and deflection ductility even with a smaller layer thickness. By using the data derived from the experimental tests with the constituent materials of the strengthened masonry beams, the behaviour of the tested strengthened masonry beams was numerically simulated with good accuracy.
The effectiveness of a repair strategy, for damaged RC beam-column joints, that combines strain hardening cementitious composite (SHCC) and laminates of carbon fibre reinforced polymers (CFRP laminates) is assessed in the present work. According to this technique, existing concrete cover in the joint zone of the frame is replaced by a self-compacting SHCC. This thin layer of SHCC is reinforced with CFRP laminates that are bonded into the saw cut grooves. Two full-scale severely damaged interior RC beam-column joints were retrofitted using two different configurations for this technique: (i) applying the strengthening system in the front and rear faces of the specimens;(ii) jacketing all sides of the elements of the specimens with the strengthening system. The effectiveness of these 2 retrofitting configurations are assessed and compared by evaluating experimentally the hysteretic response, the dissipated energy, the degradation of secant stiffness, the displacement ductility and the failure modes of each repaired specimen, and also using the values of these indicators obtained in the virgin state of these specimens. This comparison revealed that the adopted retrofitting strategies can restore and even enhance the performance of this type of structural elements, mainly when the solution based on four-sided jacketing is used.
This paper is focused on the performance of a proposed scheme for seismic strengthening of shear deficient joints of 3D reinforced concrete (RC) corner beam-column connections. This technique is composed of a combination of GFRP sheets and a steel cage, and does not require perforating the existing concrete elements to anchor the FRP sheets. Two similar full-scale beam-column connections were made without any transverse reinforcement in their joint region. One of which was tested in its as-built condition, taken as control specimen, while the other one was tested after strengthening. Seismic behaviour of these specimens were studied under a cyclic loading pattern imposed simultaneously with a constant column's axial load. Comparison of the test results of these specimens revealed a noticeable improvement in the seismic response of the strengthened specimen. This achievement along with the application feasibility of this technique indicates the suitability of the proposed strengthening scheme for practical applications. Finally, the experimentally obtained joint shear strength of the control and retrofitted specimens are compared to the one estimated by the relationships of the softened strut-and-tie model and ACI-318, respectively. This comparison revealed a satisfactory prediction of joint shear strength for both specimens, the as-built and the strengthened one.
a b s t r a c tHybrid Composite Plate (HCP) is a reliable recently proposed retrofitting solution for concrete structures, which is composed of a strain hardening cementitious composite (SHCC) plate reinforced with Carbon Fibre Reinforced Polymer (CFRP). This system benefits from the synergetic advantages of these two composites, namely the high ductility of SHCC and the high tensile strength of CFRPs. In the materialstructural of HCP, the ultra-ductile SHCC plate acts as a suitable medium for stress transfer between CFRP laminates (bonded into the pre-sawn grooves executed on the SHCC plate) and the concrete substrate by means of a connection system made by either chemical anchors, adhesive, or a combination thereof. In comparison with traditional applications of FRP systems, HCP is a retrofitting solution that (i) is less susceptible to the detrimental effect of the lack of strength and soundness of the concrete cover in the strengthening effectiveness; (ii) assures higher durability for the strengthened elements and higher protection to the FRP component in terms of high temperatures and vandalism; and (iii) delays, or even, prevents detachment of concrete substrate. This paper describes the experimental program carried out, and presents and discusses the relevant results obtained on the assessment of the performance of HCP strengthened reinforced concrete (RC) beams subjected to flexural loading. Moreover, an analytical approach to estimate the ultimate flexural capacity of these beams is presented, which was complemented with a numerical strategy for predicting their load-deflection behaviour. By attaching HCP to the beams' soffit, a significant increase in the flexural capacity at service, at yield initiation of the tension steel bars and at failure of the beams can be achieved, while satisfactory deflection ductility is assured and a high tensile capacity of the CFRP laminates is mobilized. Both analytical and numerical approaches have predicted with satisfactory agreement, the load-deflection response of the reference beam and the strengthened ones tested experimentally.
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