Add beam shear classes

StructureHelperLogics/Models/BeamShears/IStirrupEffectiveness.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace StructureHelperLogics.Models.BeamShears
+{
+    public interface IStirrupEffectiveness
+    {
+        double MaxCrackLengthFactor { get; set; }
+        double StirrupShapeFactor { get; set; }
+        double StirrupPlacementFactor { get; set; }
+    }
+}