Axially Loaded Confined Members

In the design of a reinforcement of colunms under normal-centered stress or with a little eccentricity with composite materials, it is necessary to size the reinforcement so as to have a factored value of the axial acting action N a (to be assessed according to the different combinations of load provided, as prescribed by the regulations in force), and a factored value of the resistance of the restrained member fulfill- 

The rise factor of the resistance k can be determined on the base of the experimental results of masomy test samples having similar featmes to those considered in the confinement intervention. As an alternative, the following ratio can be assumed  

The effective confinement stressis a function of the section shape and of the technique of intervention. By assuming as the volume of the masomy member and Vc,eff as the volume of the portion being efficiently confined, the following efficiency coefficient can be introduced  

The effectiveness of the confinement intervention can also be impacted by the spiral arrangement of the external binding. If Uf is the inclination angle of the fibers towards the plane of the member cross-section, the following coefficient ka is introduced  

The introduction of such a coefficient multiplying the confining lateral pressme fi affects the effective confinement stress, Tieff, induced by the external binding, as a consequence of its inclination. The above coefficient only concerns the contribution 

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Ductility of FRP-Confined Members Under Combined Bending and Axial Loading... 

FRP confinement can also be applied to conaete members subjected to combined bending and axial loads, so as to enhance their ductility and, only marginally, their axial capacity. 

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