Shear and flexural strengthening

Shear and flexural strengthening due to new holes in a beam in a building in Switzerland (photo Empa). 

Shear and flexural strengthening with strips and fabrics in a cement factory in Poland (photo S P). 

Norris T, Saadatmanesh H, Ehsani MR, Shear and flexural strengthening of R/C beams with carbon fibre sheets, J Structural Eng, ASCE 123(7), 903-911, 1997. 

Fig. 10.3 Shear and flexural strengthening of r.c beams with CFRP...

Chaallal, O., Nollet, M. J. and Perraton, D. (1998), Strengthening of reinforced concrete beams with externally bonded fiber-reinforced-plastic plates Design guidelines for shear and flexure , Canadian Journal of Civil Engineering, Vol. 25, Issue 4, pp. 692-704. 

Derivations for almost all analytical models for FRP strengthened flexural members are based on the typical schematic FBDs of Fig. 10.14. This particular case represents a differential segment of an FRP strengthened beam under uniformly distributed load, and the bending stiffness of the FRP laminate is assumed to be much smaller than that of the beam to be strengthened. Forces, moments and stresses acting on these basic FBDs reflect the individual assumptions preset for any analysis. The interfacial adhesive shear and normal stress are denoted by t x) and a(x), respectively. Equation [10.19] is the mathematical representation of the basic definition of shear stress t(x) in the adhesive layer, which is directly related to the difference in longitudinal deformation between the FRP laminate at its interface with the adhesive and the beam s soffit. 

Strengthening of the connections is often the most cost effective upgrade for existing buildings if it does not require removal of existing interior walls and equipment. For a member to absorb blast energy and be structurally efficient, it must develop its full plastic flexural capacity. This requires a substantial increase in shear capacity at the connections to avoid failure. 

In the following sections, the design of flexural and shear strengthening as well as confinement are described. Note that these design methods are still under development and that all equations in these sections are presented without safety factors. In an actual design, safety factors must be applied. 

Ibiantafillou, T. C. and C. P. Antonopoulos (2000). Design of concrete flexural members strengthened in shear with FRP./owraa/ of Composites for Construction 4(4) pp. 198-205. 

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