Add extended force tuple result

StructureHelperCommon/Models/States/IStateCalcTermPair.cs

@@ -0,0 +1,13 @@
+using StructureHelperCommon.Infrastructures.Enums;
+
+namespace StructureHelperCommon.Models.States
+{
+    /// <summary>
+    /// Implements pair of limit state and calculeation term
+    /// </summary>
+    public interface IStateCalcTermPair
+    {
+        LimitStates LimitState { get; set; }
+        CalcTerms CalcTerm { get; set; }
+    }
+}