The Critical Scaled Distance For Local Buckling Of Steel Columns Under Blast Loading

Steel buildings collapse with blast loading, mainly due to the destruction of key components in a blast. Column is one of the main load-bearing members for steel frame structures. In numerous cases around the world, the local buckling is considered as another structural failure mode for steel columns or other steel members in an explosion, which has an adverse effect on the remaining carrying capacity. H-shaped and rectangular steel columns, which are two commonly used column types in steel buildings, are studied to investigate the local buckling of steel columns under blast loading and analyze key factors for the critical scaled distance of local buckling of steel columns under blast loading and finally derive a formula for the critical scaled distance. Relevant results can provide a reference for the blast resistant design and reasonable blast protection distance, which has important practical value and significance in structural safety and protection works. The main work of this thesis concludes the following aspects.(1) Currently available dynamic buckling criteria were analyzed and summarized. B-R criteria is selected to analyze the local buckling of steel columns under the blast loading. An approach to examine the local buckling of steel columns and determine the critical scaled distance is put forward.(2) Local buckling of steel columns under blast loading is examined on its influences on the vertical bearing capacity of steel columns. Injury indicators based on the vertical bearing capacity of steel columns can change significantly because of local buckling of steel columns under blast loading, and moderate damage can even occur in steel columns.(3) Based on the B-R criteria, four parameters including the quantity of explosive material, the width-thickness ratio of the plate, the height of the steel column and the yield strength of steel are examined on their influences on the critical scaled distance of local buckling of square steel columns under blast loading. Studies show that the quantity of explosive material and the width-thickness ratio of the plate are more significant to the critical scaled distance under blast loading. Compared with the static loading, the requirement of the width-thickness ratio of the plate is more stringent for the local buckling control of steel columns under blast loading.(4) Based on the B-R criteria, five parameters including the quantity of the explosive material, the width-thickness ratio of the flange, the height-thickness ratio of the web, the height of the steel column and the yield strength of steel are examined on their influences on the critical scaled distance of local buckling of H-shaped steel columns under blast loading applied in the direction of major axis of steel columns. Studies show that the quantity of the explosive material and the width-thickness ratio of the flange are more significant to the critical scaled distance of local buckling under blast loading. Compared with the local buckling under static loading, the height-thickness ratio of the web of the steel column has little effect on the local buckling, since the dynamic local buckling occurs only at the flanges when the blast loading is applied in the direction of the major axis.(5) Based on the results of finite element simulation, the formulas to predict the critical scaled distance of local buckling for square steel columns and H-shaped steel columns under blast loading are proposed and verified with further simulation results.