Strengthening of continuous low strength RC U-Shaped beams using different techniques

In this paper, different strengthening techniques have been implemented in order to enhance
both flexural and shear strengths at the intermediate support of continuous RC beams made of
low strength concrete. Four two-equal span continuous RC beams made of concrete strength of
target cube strength of about 18 MPa have been prepared and cast of u-shaped cross-sections.
One beam was control un-strengthened beam, while the remaining beams were strengthened
using three different techniques; namely, Externally Bonded Carbon Fiber Reinforced Polymer
(EB-CFRP) sheets, external thin layer of Engineered Cementitious Composites (ECC) material
and externally bonded steel plates. All strengthening materials were applied at the intermediate
support and extended between the mid-span points at both sides. All beams have the same
concrete dimensions and internal reinforcement detailing. The overall cross-sectional
dimensions were 600mm width by 330mm total depth and 2100mm center-to-center span. For
the mid-span sections and away from the supporting points, the cross section was u-shaped of
80mm flange thickness and 100mm web thickness. The experimental test results showed that
all strengthened beams showed increased sustain loads by about 94%, 103% and 123%
respectively, for strengthened beams by EB-CFRP sheets, ECC material and steel plates
compared to that of the un-strengthened beam. Thus, the strengthening technique based on
steel plates exhibited the outermost ultimate capacity. On the other hand, the strengthening
technique based on ECC material enabled the strengthened beam to show about 96% of the
ductility index for un-strengthened beam.