The axial load P versus axial shortening u relation curves of all the specimens were recorded in the experiment.
The axial shortening (u) of the specimens was obtained by modifying the displacement transducer readings on the basis of the vertical strain gauge and dial gauges readings to eliminate the shortening caused by loose contact of devises.
The quantifications of axial stress–strain relation curves, defined as derived behavioral indices, are summarized
in Table 5. Comparisons and analysis of mechanical properties of all specimens are conducted as follows, combined
with the results in Fig. 10 and Table 5.