Abstract: As a typical engineering component, thin-walled square tube is widely used in construction, ocean and aerospace fields. Its structure may be subjected to the repeated blast loads. It is of practical significance to the research on dynamic response of thin-walled square tube under repeated blast loads. Experimental and numerical investigations were carried out on the dynamic response of thin-walled steel square tubes subjected to single and repeated blasting loads. The impact experiments of thin-walled square tube with 4 mm in wall thickness and 100 mm in cross-section width were made in the explosion field. Based on the full restart function of LS-DYNA and Euler-Lagrange coupling method, the dynamic responses of square tubes subjected to single or repeated blast loads laterally are numerically simulated, and the damage effects under different explosion numbers are described．A numerical method is proposed to reflect the material damage after blast load by damage factor. The results show that the deformation of square tubes subjected to repeated blast loads causes a damage accumulation. Under the same blast load, the deformed square tube has bigger effective strain increment than that of undamaged square tube. In the area around the mid-point, the sides and the plastic hinge position of square tube, the effective strain increment of the former is 2.47-3.88 times of the latter, which may cause the square tube to be damaged more seriously. The two sides of square tube are the weak areas, so it is easy to produce large plastic strain due to stress concentration, and a special protection is needed. Key

Key words: thin-walledsquaretube, repeatedblastload, dynamicresponse, fullrestart, materialdamage