Abstract: In order to solve the instability problem of antiarch beam with U-shaped steel section, finite element model of which has been built with the co-assistance of CAD and ANSYS, the built-in non-linear buckling analytical module has simulated three kinds of sections including U25, U29, and U36 respectively, and all of them is under the impact of radical uniformly distributed load, thus relationship between buckling load, ultimate bearing force and central angle of antiarch is able to come into being, where the curve between vertical load and displacement of the uttermost point in the antiarch is monitored. The results have shown that, critical buckling load reaches its peak value as central angle is 70° as to all those three sections, then the load will glide down at the rate of 4.0% with the continuous increase of the angle, it thus manifests that 70° for central angle is optimum for overall stability. If the angle is less than 70°, the load will mount at the rate of 34.3%, however, if the angle is more than 70°, the mounting rate of the load will mitigate at the rate of 14.5%. The results have provided feasible methodology and theoretical foundation for engineering practice.

Key words: ANSYS, U-shaped steel, antiarch beam, ultimate bearing force, buckling load, stability