Bending Performance of Masonry Walls Strengthened With Near-Surface Mounted FRP Bars.
Bending Performance of Masonry Walls Strengthened With
Near-Surface Mounted FRP Bars.
Bajpai, K.; Kuthinh, D.
North American Masonry Conference, 9th. Proceedings.
June 1-4, 2003, Clemson, SC, 1052-1063 pp, 2003.
Available from:FOR MORE INFORMATION CONTACT: North American Masonry
walls; masonry; literature review; epoxies; mechanical
properties; adhesives; concretes; tests; deflection
Unreinforced masonry (URM) buildings constitute an
important part of the building stock, and are vulnerable
to earthquakes. Retrofitting of existing masonry walls
with near surface mounted, non-corrosive
fiber-reinforced polymer (FRP) bars, is an attractive
option. Previous research has shown that it is difficult
to develop the full tensile strength of the bars, which
are attached with epoxy in grooves pre-cut in the
masonry and mortar joints. In this study, epoxy
strengthened with short glass fibers allows close to
full strength development of 6.5 mm (114 in) diameter
glass FRP bars in 185 mm (7.3 in), or less than half a
concrete masonry unit length. This fiber-reinforced
epoxy should be effective for other types of bars as
well. With full anchorage assured, FRP bars provide an
efficient method of strengthening masonry walls against
out-of-plane bending. Three narrow (2.85 m x 0.40 m x
0.20 m or 112 in x 16 in x 8 in), grouted, concrete
masonry beams reinforced to 45% of balanced ratio and
four wide (2.85 m x 0.80 m x 0.20 m or 112 in x 32 in x
8 in) beams reinforced to 66% of balanced ratio were
tested in four-point bending. All seven beams exhibited
consistent flexural behavior, with ultimate failure
precipitated by tensile rupture of the reinforcement at
an average ratio of span to maximum deflection of 42.
The ACI (530-02) equations predict the flexural strength
of these FRP externally reinforced concrete masonry
beams conservatively, with a mean ratio of measured to
predicted strength of 1.37 and a coefficient of
variation of 0.057. There was no difference in behavior
between reinforcement parallel or perpendicular to the
mortar bed joints. The unexpected shear failure of one
FRP reinforced, ungrouted beam needs further