Although it is well documented that infills significantly affect the dynamic characteristics and the seismic response
of the bare basic structural system, codes are reluctant to encourage consideration of infills as main structural elements,
mainly due to structural uncertainties and computational complexities. Part of the uncertainties are due to the very
many parameters affecting the behavior of the system, such as infill materials, reinforcing of infills, connection to the surrounding
frame, geometry, relative stiffness and strength, local construction techniques etc. In the present paper three successive
experimental programs, conducted at the R/C and Masonry Structures Laboratory of the Aristotle University, are
described, commented and discussed. All of them refer to single-storey one-bay 1:3 scale R/C moment resisting frames.
The first program consisted of 18 specimens, 2 bare and 16 unreinforced masonry (URM) infilled. The second program
was an extension and a supplement of the previous one. It consisted of 20 more specimens, 6 bare and 14 URM infilled.
The third program was directed towards the investigation of quick and low cost strengthening methods of R/C frames
damaged by earthquakes, using several infill techniques. For this purpose 10 of the damaged specimens of the first program
were repaired and strengthened.