Shear strengthening reinforcement

Bousselham, A. and Chaallal, O. (2004), Shear strengthening reinforced concrete beams with fiber-reinforced polymer Assessment of influencing parameters and required research , ACI Structural Journal, Vol. 101, Issue 2, pp. 219-227. 

Fibre reinforced polymer (FRP) composite materials for shear strengthening... 

Usually, for shear design the well-known classical truss model is used. The shear strengthening design also requires knowledge and understanding of the cmcial failure modes of the externally bonded shear reinforcement (EBSR). 

TTiantafillou, T. C. (1998). Shear strengthening of reinforced concrete beams using epoxy-bonded FRP composites. ACI Structural Journal 95(2) pp. 107-115. 

Shear strengthening of an r.c. beam can be carried out by applying one or more layers of sheet bonded to the external surface of the member to be strengthened. The reinforcement strips can be applied in a continuous or discontinuous mode and with a variable inclination angle (Fig. 5.6). 

Differently from what was described in the technical document of the CNR, the CSLLPP guidelines do not allow for the installation of a shear strengthening with a complete side bonding of the reinforcements, due to the high risk of debonding. 

Zhang Z and Hsu C T T (2002), Shear strengthening of RC beams using carbon fiber reinforced polymer strips , in 15th ASCE Engineering Mechanics Conference, New York, 1-8. 

Chen, J. F. and Teng, J. G. (2008), Shear strengthening of reinforced concrete (RC) beams with fibre-reinforced polymer (FRP) composites , in Strengthening and Rehabilitation of Civil Infrastructures Using Fibre-reinforced Polymer (FRP) Composites, eds L. C. Hollaway and J. G. Teng. Woodhead Publishing in Materials, Cambridge, UK. 

Pellegrino, C. and Modena, C. (2002), Fiber reinforced polymer shear strengthening of RC beams with transverse steel reinforcement , Journal of Composites for Construction, Vol. 6, Issue 2, pp. 104—111. 

Yapa, H. D. and Lees, J. M. (2009), Optimum shear strengthening of reinforced concrete beams with prestressed carbon fibre reinforced polymer (CFRP) straps . Proceedings of the 4th Advanced Composites in Construction (ACIC 09), eds S. Halliwell and C. Whysall, NetComposites, pp. 214-226. 

Zhang, Z., Hsu, C.-T. and Moren, J. (2004), Shear strengthening of reinforced concrete deep beams using carbon fiber reinforced polymer laminates . Journal of Composites for Construction, Vol. 8, Issue 5, pp. 403 14. 

Steel Under Earthquake Excitations Reinforcing steel in external reinforced crmcrete jackets for the retrofit and strengthening of existing reinforced concrete or steel members comes mainly in the form of bars. Usually, the stress-strain behavior under tension-compression is cmcial to assess the longitudinal bars contribution. The stress-strain behavior under tension is of interest for the transverse reinforcement (stirmps). Steel dowels and stud shear connectors may involve shear (or tensile) behavior of steel- or bond-related issues. External steel plates may be considered under multiaxial loading (i.e., in cases of shear strengthening in order to estimate their yield stress). Bond-related issues may concern bar-concrete interfaces, bar-resin-concrete interfaces (NSM applications), or plate-resin-concrete interfaces under cyclic loading. 

It is important to note material such as those plastics or wood that are weak in either tension or compression will also be basically weak in shear. For example, concrete is weak in shear because of its lack of strength in tension. Reinforced bars in the concrete are incorporated to prevent diagonal tension cracking and strengthen concrete beams. Similar action occurs with RPs using fiber filament structures. 

Fibre reinforced poiymer (FRP) composite materiais for strengthening of existing concrete structurai members (flexural, shear, confinement)... 

Similar to the design of flexural strengthening, the following states for the shear design of reinforced concrete (RC) members can be distinguished as the stmctural loads increase ... 

Several equations for the concrete contribution can be found in the relevant literature. However, this equation describes the design shear resistance of a RC member without shear reinforcement. It is important to note that this definition for the concrete contribution is different from the definition of State r given above in this section. To determine Erc, the load at the first shear crack should be calculated. Additionally, all the usual design verifications for RC (failure of the concrete struts, shift of moment line, etc.) have to be considered. For ductility reasons, the member should have a minimum internal shear reinforcement ratio, otherwise strengthening is not recommended. 

Strength criteria for anisotropic materials do not directly take into account the dependence of the adhesion-cohesion interaction. At the same time, increase in cohesion strength does not always result in adhesion strengthening, and vice versa. An attempt to optimize the ratio of adhesion and cohesion strengths for composite materials reinforced with fibers was made in [378]. For complete realization of cohesion strength a, of the reinforcement fibers of diameter d and length I, the minimum adhesive resistance under shear Xadh should fulfill the correlation... 

Midlands police car park soon after construction, as a result of a deficiency in conventional reinforcement, has been well publicised. Here again, additional bonded plate reinforcement was installed in order to control further cracking under live load. An 11 m span, 2 m deep reinforced concrete beam at a shop in Bootle was strengthened to provide a 10% increase in ultimate moment capacity. In so doing it was calculated that the mean horizontal shear stress resisted by the adhesive was 9.84 N/mm. ... 

The purpose of the above is to specify requirements for a cold-cure adhesive to permit either the repair or strengthening of existing concrete structures by bonding on additional external steel plate reinforcement, or the construction of steel/concrete composite units in which wet concrete is poured on to steel freshly coated with a layer of adhesive. In both cases the adhesive serves to resist the interfacial shear stresses necessary to ensure structural composite action between the steel and concrete. For these purposes a cold-cure adhesive is defined as one which is capable of curing to the required strength between the temperatures of 10 °C and 30 °C. 

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