Stress-strain state of concrete filled steel tubular columns of annular cross-section taking into account physical nonlinearityKazbek Khashkhozhev, Anton Chepurnenko, Tatyana Polyakova, Marina Grigoryan and Batyr YazyevE3S Web Conf., 281 (2021) 01007DOI: https://doi.org/10.1051/e3sconf/202128101007