Although a great deal of research has been carried out in recent years on t
he use of plate bonding for strengthening reinforced concrete (RC) structur
es, so far this work has generally been limited to RC beams and one-way sla
bs, with little work on two-way slabs. This paper presents the results of a
recent study on the behavior and strength of two-way square RC slabs bonde
d with a steel plate. Experimental load-deflection curves, failure modes, a
nd strengths of plated slabs under a central concentrated load are first re
ported. These results show that debonding failures are unlikely in these pl
ated slabs, contrary to the case of plated beams, and there are significant
strength gains due to the bonded steel plate as a result of a modified yie
ld line pattern. Yield line analyses are then described for these slabs, an
d the results are found to match experimental results closely. The yield li
ne method is thus suitable for practical use to determine the strength of t
hese plated slabs.