Effect of SFRP confinement on circular and square concrete columns

This paper reports on an experimental investigation that evaluates the effectiveness of newly developed material, steel fibre reinforced polymer (SFRP) sheets to confine small-scale plain concrete circular and square columns. Different parameters were investigated including: number of SFRP layers (1, 2, and 3), target concrete compressive strength (25, 30, and 35 MPa), cross-section of the columns (circular and square), and corner radius for square columns (3, 6, 10, and 25 mm). The experimental investigation was conducted in three phases. In Phase I, 36 circular specimens (150 mm diameter × 300 mm height) and in Phase II, 36 square specimens (150 mm side length × 300 mm height) were tested. In each phase, the specimens were divided into three groups according to concrete compressive strength. In each group, three specimens were tested without wrapping for comparison purposes, and three specimens for each number of layers. In Phase III, 12 SFRP wrapped (one layer) square specimens with a target concrete compressive strength of 25 MPa were tested to investigate the effect of varying the corner radii on the confined compressive strength. The specimens were tested under monotonic concentric uni-axial compression load. Results showed that SFRP confinement improved the performance of both circular and square specimens in terms of axial strength and ductility; however, the improvement for square specimens was not as prominent as that for circular specimens. Rounding the corners of the square specimens improves the situation for square specimens and performance enhances with increasing corner radius. The confined concrete compressive strength was predicted using equations available in different codes and models and compared with experimental results.

► Investigated the effectiveness of SFRP sheets to confine concrete columns.
► Confining circular and square columns with SFRP increased their capacity/ductility.
► Performance enhancement of square columns is not as prominent as that of circulars.
► Increasing the number of SFRP layers increased the strength/ductility of columns.
► Capacity/ductility of confined square columns increased with increasing corner radius.