Stone has over millennia been used for structures which naturally develop compression under gravity loads. This study focuses on segmental stone beams with artificially induced compression. Prototype specimens were fabricated using epoxy adhesive for longitudinal shear transfer between prestressed steel strands and pre-cut Valange limestone blocks with mortar inter-block joints. Each specimen was prestressed by a single strand, to enable focus on the fundamental mechanics. Each strand was tensioned against the stone, then released after the epoxy became structurally active, so this is a form of pretensioning which eliminates external anchors and elastic shortening losses, and which enables agile construction because it can be implemented either at the factory or on site. Specimen details were informed by pullout tests. One specimen type entailed concentrically pretensioned square-section stone blocks, the other eccentrically pretensioned rectangular-section blocks. One concentric-strand specimen was strain-gauged near both ends to enable identification of the transfer zone, while an eccentric-strand specimen was instrumented at midspan with strain and displacement gauges to quantify pretensioning-induced camber and strains. Vibration tests were conducted on both specimens, then an eccentric-strand specimen was tested to ultimate in three-point flexure while a concentric-strand specimen was subjected to fire. The results reveal good damping, a high and consistent elastic modulus for the stone based alternately on local and global data, beneficial delay of external load-induced cracks at the joints due to the pretensioning and protection of the epoxy by the stone over an extended period in fire. The ultimate limit state under load entailed gradual spalling of stone in the peak compression zone followed by a dominant crack which was asymmetric about midspan. These results strongly hint at the viability of pretensioned stone beams for low-carbon floor applications. (C) 2020 Elsevier Ltd. All rights reserved.
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