A circular steel pipe fined with water may be cracked immediately when the water becomes frozen. However, it is worth to note that a square pipe will not be cracked at the first time of repeated freezings due to the large bending deformation from square to circular in the cross section. The volumetric change, deformation, stress-strain, inside temperature and inside pressure of the regular square steel pipe were measured during the repeated freezing tests, and the data was numerically analyzed. The obtained results are as follows. 1) The regular square steel pipes can be durable for the second time of the repeated freezing tests with large plastic deformation as well as elastic. All the test pieces are cracked by the corner edges of the cross section and failed at the third test. 2) While repeating the freezing tests for the same pipe, the inside pressure is increased, but the hoop strain is decreased reversely. 3) The assumption that deformed curves for the lateral cross section and for the longitudinal section are circular and quadratic respectively is almost appropriate for the real deformation of test pipes. The difference in the volumetric increment between the calculated and the measured equals 0.4％ for the first time and 2.3％ for the second time of the freezing tests.
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