Add logic for converting beam shear calculator input data

StructureHelperLogics/Models/BeamShears/Logics/IGetDirectShearForceLogic.cs

@@ -12,6 +12,6 @@ namespace StructureHelperLogics.Models.BeamShears
         /// Returns value of shear force at the end of inclined section
         /// </summary>
         /// <returns>Value of shear force at the end of inclined section</returns>
-        double CalculateShearForce();
+        IForceTuple CalculateShearForce();
     }
 }