Strain hardening fibre reinforced cement composites for the flexural strengthening of masonry elements of ancient structures

Construction and Building Materials

2015

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h i g h l i g h t sThe efficiency of FRCM overlays was assessed as part of a masonry strengthening system. The strength increment of masonry walls was quantified by diagonal tensile tests. Monotonic and cyclic in-plane loading was applied to evaluate the behaviour of the walls.The key failure modes obtained experimentally and the basic mechanisms were examined. Experimental results were discussed and compared to the analytical model predictions. a b s t r a c tThe development of novel strengthening techniques to address the seismic vulnerability of masonry elements is gradually leading to simpler, faster and more effective strengthening strategies. In particular, the use of fabric reinforced cementitious matrix systems is considered of great potential, given the increase of ductility achieved with simple and economic strengthening procedures. To assess the effectiveness of these strengthening systems, and considering that the seismic action is involved, one important component of the structural behaviour is the in-plane cyclic response. In this work is discussed the applicability of the diagonal tensile test for the assessment of the cyclic response of strengthened masonry. The results obtained allowed to assess the contribution of the strengthening system to the increase of the load carrying capacity of masonry elements, as well as to evaluate the damage evolution and the stiffness degradation mechanisms developing under cyclic loading.

Section: Overlay Strengthening Techniquesmentioning

confidence: 99%

Assessment of overlay masonry strengthening system under in-plane monotonic and cyclic loading using the diagonal tensile test

Almeida

Pereira

Construction and Building Materials

2015

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“…The elastic modulus (E sh ), the stress at the first crack (f cr sh ), the tensile strength (f u sh ) and the tensile strain hardening capacity (ε u sh ) are introduced based on the average results of direct tensile tests and parameters for the softening regime are adopted from Ref. [35]. Values of the parameters used to define the tensile stressestrain relationship of the SHCC are reported in Table 4.…”

Section: Constitutive Laws Of the Materialsmentioning

confidence: 99%

Flexural strengthening of RC beams using Hybrid Composite Plate (HCP): Experimental and analytical study

Esmaeeli

Composites Part B: Engineering

2015

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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.

“…The average tensile stress at crack initiation and the average tensile strength of the SHCC was 2.43 MPa and 3.35 MPa, respectively, with a minimum tensile strain capacity of 1.3%. More details on mixture ingredients, mixing process and test setup of the SHCC can be found in [10,13,22]. …”

Section: Materials Properties Of Retrofitting Systemmentioning

confidence: 99%

“…The formation of multiple diffused hairline cracks through all the loaded length of the specimen during the hardening stage assures levels of ductility not possible to attain in conventional FRCs. By testing in bending masonry elements strengthened with a thin layer of SHCC applied to their tensile face, Esmaeeli et al [13] demonstrated that higher load carrying capacity and ductility is achievable when compared to flexural strengthening methodologies based on the use of thicker layers of selfcompacting steel FRC. Recently Esmaeeli et al [14] developed a thin prefabricated hybrid composite plate (HCP), composed of SHCC and CFRP laminate, with a high durability potential.…”

Section: Introductionmentioning

confidence: 98%

Retrofitting of interior RC beam–column joints using CFRP strengthened SHCC: Cast-in-place solution

Esmaeeli

Sena-Cruz

et al. 2015

Composite Structures

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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.