Extract sum shear force logic

StructureHelperCommon/Models/Forces/Logics/IGetLoadFactor.cs

@@ -0,0 +1,13 @@
+using StructureHelperCommon.Infrastructures.Enums;
+using StructureHelperCommon.Infrastructures.Interfaces;
+
+namespace StructureHelperCommon.Models.Forces
+{
+    /// <summary>
+    /// Implements logic for calculating factor of load
+    /// </summary>
+    public interface IGetLoadFactor
+    {
+        double GetFactor();
+    }
+}