Force combination was added

StructureHelperCommon/Models/Forces/IForceTuple.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace StructureHelperCommon.Models.Forces
+{
+    public interface IForceTuple
+    {
+        double Mx { get; set; }
+        double My { get; set; }
+        double Nz { get; set; }
+        double Qx { get; set; }
+        double Qy { get; set; }
+        double Mz { get; set; }
+
+    }
+}