CONFINEMENT OF RC RECTANGULAR COLUMNS USING GFRP

摘要

The confinement of Reinforced Concrete (RC) columns represents one of the most promising applications of Fiber Reinforced Polymer (FRP) to civil structures. The reasons for such upgrade could be generally related to durability issues, design or construction mistakes, increase of live loads or need for seismic retrofit. In all these cases, FRP laminates provide an effective and competitive strengthening technique and offers advantages such as easy and fast application, high durability, low impact on the use of the structure, negligible increase of structural mass as well as of member dimensions. The majority of studies have been performed on the confinement with FRP of circular columns, where the contribution of composites is fully exploited. A loss of effectiveness occurs in the case of square cross-sections where the presence of the corners reduces the confining action of the FRP jacket. Such problem becomes particularly critical for rectangular columns; despite that, very few studies have been conducted on them. The present paper deals with rectangular columns with high ratio between the sides of the cross-section. The experimental program concerning members subjected to axial load is herein presented and the upgrade technique using Glass FRP (GFRP) laminates is described. The effectiveness of such confining system is investigated also with respect to different fiber orientations (unidirectional, bidirectional and quadriaxial). Some preliminary experimental results are discussed in terms of column strength, failure mode and strains of the FRP jacket.