What are the different between Case I, II, III and IV in Figure 6.1?

AWS D1.1 2015 Figure 6.1—Discontinuity Acceptance Criteria for Statically Loaded Nontubular and Statically or Cyclically Loaded Tubular Connections.

  1. Case I
    case I

  2. Case II
    case II

  3. Case III
    case III

  4. Case IV
    case IV