Extract sum shear force logic

StructureHelperLogics/Models/BeamShears/Logics/IShearForceLogic.cs

@@ -0,0 +1,15 @@
+using StructureHelperCommon.Infrastructures.Interfaces;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace StructureHelperLogics.Models.BeamShears
+{
+    internal interface IShearForceLogic : ILogic
+    {
+        double GetShearForce();
+
+    }
+}