Experimental investigation on axially loaded adobe masonry columns confined by polymeric straps

Abstract

Due to widespread applications of adobe masonry construction in rural areas of many seismic-prone countries, there is a high demand for conducting research on retrofitting of adobe buildings; however, such research is scarce. Among various structural aspects, confinement of an assemblage of adobe (i.e., unbaked clay brick) units and mud mortar is of primary concern in the current paper. To this aim, scaled adobe columns were wrapped by polypropylene (PP) straps, which are low-strength and low-cost polymeric materials, and were tested under uniaxial compression. The PP straps are placed at a certain interval while the two ends of a strap are joined together by a steel wire. No bonding agent is used between the straps and adobe surface. Three series of adobe columns with different aspect ratios of the cross section and different arrangements of adobe units in the cross section plan are examined and the experimental results in terms of axial stress versus axial strain, crack patterns, lateral strain variations, and tensile strain in the confining straps are reported. The comparison between the non-retrofitted adobe specimens and their confined counterparts revealed that the proposed retrofit technique by use of PP straps is highly efficient in improving the compressive strength and, more importantly, the ultimate axial strain of adobe columns. Besides, the retrofitted adobe specimens could maintain a considerable amount of post-peak residual strength up to large axial displacements. Finally, the experimental outcomes on the compressive strength are compared with predictions of an equation available in the literature.