PSI - Issue 28

Kais Douier et al. / Procedia Structural Integrity 28 (2020) 986–993 Douier et al./ Structural Integrity Procedia 00 (2020) 000–000

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3.3. Material properties The concrete used to cast the RC beams in this study developed and average compressive strength of 40 MPa after 28 days of curing. The steel used for internal reinforcement achieved an average yielding stress and modulus of elasticity of 590.4 MPa and 199.9 GPa, respectively. The utilized galvanized steel mesh consisted of galvanized steel cords. Each steel cord is made of 5 wires, 2 of which are wrapped around the rest at a high torque angel. The steel mesh used in this study is GeoSteel G1200 which had a tensile strength of 3000 MPa, elastic modulus of 190 GPa, strain at failure is 2 %, and it had a cord density of 3.15 cord/cm, as reported by the manufacturer (KeraKoll, n.d.). The cement based mortar used to bond GSM sheet to concert surfaces is called GeoLite geo-mortar, which had a tensile strength of 10 MPa and an adhesive bond strength of 2 MPa ,as reported by the manufacture (Rating & Strengths, n.d.). The composite CFRP sheets used was V-Wrap C200H that had a tensile strength of 1240 MPa, modulus of elasticity of 73.77 GPa, and strain at failure of 1.7%, as reported by the manufacturer (V-Wrap TM C200H, 2014). The epoxy used to install the CFRP sheets was V-Wrap 700 with a tensile strength of 72.4 MPa (Solutions & Adhesive, 2011). 3.4. Specimen design and preparation The specimen’s bottom surface was roughened in preparation of installing the GSM sheets as flexural external reinforcement. After which mortar cement was placed on the roughened surface and the first GSM sheet was placed on top of it. Then a second layer of mortar along with the second GSM sheet was installed on top of the first layer. The beam was then cured with water so that the mortar does not crack. Moreover, the U-wrap anchors were designed using Eq. 1 to reduce the concentration of stresses at the ends of GSM flexural strengthening sheets. Thus, full debonding and concrete cover separation of the flexural externally bonded reinforcement system could be avoided. The specimen’s surface was roughened and thoroughly cleaned before applying the U-Wrap anchors. Then the CFRP sheets were submerged in epoxy resin to achieve full impregnation of the laminates. After that the sheets were placed on the specimens and more epoxy was applied with a soft paint roller to remove air bubbles. ���������� � �� � �� �� � ������������ �� � �� � �� �� � ������ (1) where: ���������� is the area of fibers used for anchorage. � is the area of flexural reinforcement fiber. �� is the ultimate tensile strength of flexural reinforcement fiber. � is the anchors fiber modulus of elasticity. � is the shear coefficient. �� is the anchors fiber ultimate strain. 3.5. Test setup The RC beams were subjected to four-point loading, with a clear span of 1700 mm between supports. The loads were applied at 250 mm away from the specimens’ mid span, as shown in Fig. 4. The specimens were tested with an INSTRON universal testing machine at a loading rate of 2 mm/min.

Fig. 4. RC beams test setup