Fix beam shear force calculator

StructureHelperCommon/Models/Materials/Libraries/IMaterialFactorLogic.cs

@@ -0,0 +1,15 @@
+using StructureHelperCommon.Infrastructures.Enums;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace StructureHelperCommon.Models.Materials.Libraries
+{
+    public interface IMaterialFactorLogic
+    {
+        List<IMaterialSafetyFactor> SafetyFactors { get; }
+        (double Compressive, double Tensile) GetTotalFactor(LimitStates limitState, CalcTerms calcTerm);
+    }
+}