Table 1.

Stress-strain relationship of the concrete under uniaxial compression.

$f_c^{*}\left(N/m{m}^2\right)$	15	20	25	30	35	40	45	50	55	60
${\epsilon }_c$$\left(\times {10}^{-6}\right)$	1370	1470	1560	1640	1720	1790	1850	1920	1980	2030
${\alpha }_a$	2.21	2.15	2.09	2.03	1.96	1.90	1.84	1.78	1.71	1.65
${\alpha }_d$	0.41	0.74	1.06	1.36	1.65	1.94	2.21	2.48	2.74	3.00
${\epsilon }_u/{\epsilon }_c$	4.2	3.0	2.6	2.3	2.1	2.0	1.9	1.9	1.8	1.8

Note： ${\epsilon }_u$ is the compressive strain of concrete when the stress on the descending section of the stress-strain curve is equal to 0.5 $f_c^{*}$.