ConcreteBucklingCalculator was added

StructureHelperLogics/NdmCalculations/Buckling/DeltaELogicSP63.cs

@@ -0,0 +1,36 @@
+using StructureHelperCommon.Infrastructures.Exceptions;
+using StructureHelperCommon.Infrastructures.Strings;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace StructureHelperLogics.NdmCalculations.Buckling
+{
+    public class DeltaELogicSP63 : IConcreteDeltaELogic
+    {
+        const double deltaEMin = 0.15d;
+        const double deltaEMax = 1.5d;
+
+        readonly double eccentricity;
+        readonly double size;
+        public DeltaELogicSP63(double eccentricity, double size)
+        {
+            if (size <= 0 )
+            {
+                throw new StructureHelperException(ErrorStrings.SizeMustBeGreaterThanZero + $", actual size: {size}");
+            }
+            this.eccentricity = eccentricity;
+            this.size = size;
+        }
+
+        public double GetDeltaE()
+        {
+            var deltaE = Math.Abs(eccentricity) / size;
+            deltaE = Math.Max(deltaE, deltaEMin);
+            deltaE = Math.Min(deltaE, deltaEMax);
+            return deltaE;
+        }
+    }
+}