Abstract
The concept of strengthening reinforced concrete beams using epoxy-bonded steel plates
(EBSP) is a well-known solution in structural engineering, however, there is little information about
the effect of the width-to-thickness ratio of steel plates on the behaviour of steel-concrete composite
beams. This paper presents an experimental study of the flexural behaviour of under-reinforced
concrete beams, strengthened in flexure by externally-bonded steel plates (EBSP) of varying widthto-
thickness ratios. A total of 23 reinforced concrete beams were tested; 6 beams in Series 1 tests and
17 beams in Series 2 tests. One beam in Series 1 tests and two beams in Series 2 tests were regarded
as control specimens, whilst the remaining beams were strengthened with steel plates of different
width-to-thickness ratios. In each group, the width of the bonded steel plate varied from 75 mm to
175 mm, in increments of 25 mm. The beams were tested as simply supported, under two-point static
loadings until failure. From the experimental results, it was observed that the externally bonded steel
plates led to substantial increase in flexural stiffness, which resulted in an increase in the capacity and
cracking load of the strengthened beams and a decrease in vertical deflections and crack-widths,
compared to the control beams. It was also found that the width-to-thickness ratio of steel plates as
low as 12.5 can promote flexural yielding and extensive ductility in strengthened beams.