Index: Riskeer/Piping/src/Riskeer.Piping.Plugin/PipingPlugin.cs
===================================================================
diff -u -r2ebb464e7e1e88253d336c8e78a39afb9161639b -r378ab0afb1cc9b9dd0497b4ef72dc28976602c15
--- Riskeer/Piping/src/Riskeer.Piping.Plugin/PipingPlugin.cs	(.../PipingPlugin.cs)	(revision 2ebb464e7e1e88253d336c8e78a39afb9161639b)
+++ Riskeer/Piping/src/Riskeer.Piping.Plugin/PipingPlugin.cs	(.../PipingPlugin.cs)	(revision 378ab0afb1cc9b9dd0497b4ef72dc28976602c15)
@@ -928,10 +928,13 @@
                 (sender, args) => AddCalculation(() => new ProbabilisticPipingCalculationScenario(), context.WrappedData));
         }
 
-        private static void AddCalculation(Func<IPipingCalculation<PipingInput>> createCalculationFunc, CalculationGroup parentGroup)
+        private static void AddCalculation<TCalculationScenario>(Func<TCalculationScenario> createCalculationScenarioFunc, CalculationGroup parentGroup)
+            where TCalculationScenario : IPipingCalculationScenario<PipingInput>
         {
-            IPipingCalculation<PipingInput> calculation = createCalculationFunc();
-            calculation.Name = NamingHelper.GetUniqueName(parentGroup.Children, RiskeerCommonDataResources.Calculation_DefaultName, c => c.Name);
+            TCalculationScenario calculation = createCalculationScenarioFunc();
+            calculation.Name = NamingHelper.GetUniqueName(parentGroup.Children.OfType<TCalculationScenario>(),
+                                                          RiskeerCommonDataResources.Calculation_DefaultName,
+                                                          c => c.Name);
 
             parentGroup.Children.Add(calculation);
             parentGroup.NotifyObservers();
Index: Riskeer/Piping/test/Riskeer.Piping.Plugin.Test/TreeNodeInfos/PipingCalculationGroupContextTreeNodeInfoTest.cs
===================================================================
diff -u -rcaf4f0f0d8b0a7272a1577db7c341546a83e6d40 -r378ab0afb1cc9b9dd0497b4ef72dc28976602c15
--- Riskeer/Piping/test/Riskeer.Piping.Plugin.Test/TreeNodeInfos/PipingCalculationGroupContextTreeNodeInfoTest.cs	(.../PipingCalculationGroupContextTreeNodeInfoTest.cs)	(revision caf4f0f0d8b0a7272a1577db7c341546a83e6d40)
+++ Riskeer/Piping/test/Riskeer.Piping.Plugin.Test/TreeNodeInfos/PipingCalculationGroupContextTreeNodeInfoTest.cs	(.../PipingCalculationGroupContextTreeNodeInfoTest.cs)	(revision 378ab0afb1cc9b9dd0497b4ef72dc28976602c15)
@@ -916,11 +916,11 @@
 
                 plugin.Gui = gui;
 
-                var calculationItem = new SemiProbabilisticPipingCalculationScenario
+                var semiProbabilisticCalculationScenario = new SemiProbabilisticPipingCalculationScenario
                 {
                     Name = "Nieuwe berekening"
                 };
-                group.Children.Add(calculationItem);
+                group.Children.Add(semiProbabilisticCalculationScenario);
 
                 nodeData.Attach(observer);
 
@@ -936,12 +936,65 @@
                     Assert.AreEqual(2, group.Children.Count);
                     ICalculationBase newlyAddedItem = group.Children.Last();
                     Assert.IsInstanceOf<SemiProbabilisticPipingCalculationScenario>(newlyAddedItem);
-                    Assert.AreEqual("Nieuwe berekening (1)", newlyAddedItem.Name,
-                                    "An item with the same name default name already exists, therefore '(1)' needs to be appended.");
+                    Assert.AreEqual("Nieuwe berekening (1)", newlyAddedItem.Name);
                 }
             }
         }
+        
+        [Test]
+        public void GivenCalculationGroupWithProbabilisticCalculation_WhenClickOnAddSemiProbabilisticCalculationItem_ThenCalculationAddedWithSameName()
+        {
+            // Setup
+            using (var treeViewControl = new TreeViewControl())
+            {
+                var group = new CalculationGroup();
+                var parentGroup = new CalculationGroup();
+                var pipingFailureMechanism = new PipingFailureMechanism();
+                var assessmentSection = mocks.Stub<IAssessmentSection>();
+                var nodeData = new PipingCalculationGroupContext(group,
+                                                                 parentGroup,
+                                                                 Enumerable.Empty<PipingSurfaceLine>(),
+                                                                 Enumerable.Empty<PipingStochasticSoilModel>(),
+                                                                 pipingFailureMechanism,
+                                                                 assessmentSection);
+                var parentNodeData = new PipingCalculationGroupContext(parentGroup,
+                                                                       null,
+                                                                       Enumerable.Empty<PipingSurfaceLine>(),
+                                                                       Enumerable.Empty<PipingStochasticSoilModel>(),
+                                                                       pipingFailureMechanism,
+                                                                       assessmentSection);
 
+                var menuBuilder = new CustomItemsOnlyContextMenuBuilder();
+
+                var gui = mocks.Stub<IGui>();
+                gui.Stub(cmp => cmp.Get(nodeData, treeViewControl)).Return(menuBuilder);
+                mocks.ReplayAll();
+
+                plugin.Gui = gui;
+
+                var probabilisticCalculationScenario = new ProbabilisticPipingCalculationScenario
+                {
+                    Name = "Nieuwe berekening"
+                };
+                group.Children.Add(probabilisticCalculationScenario);
+
+                using (ContextMenuStrip contextMenu = info.ContextMenuStrip(nodeData, parentNodeData, treeViewControl))
+                {
+                    // Precondition
+                    Assert.AreEqual(1, group.Children.Count);
+
+                    // Call
+                    contextMenu.Items[contextMenuAddSemiProbabilisticCalculationIndexNestedGroup].PerformClick();
+
+                    // Assert
+                    Assert.AreEqual(2, group.Children.Count);
+                    ICalculationBase newlyAddedItem = group.Children.Last();
+                    Assert.IsInstanceOf<SemiProbabilisticPipingCalculationScenario>(newlyAddedItem);
+                    Assert.AreEqual("Nieuwe berekening", newlyAddedItem.Name);
+                }
+            }
+        }
+
         [Test]
         public void ContextMenuStrip_ClickOnAddProbabilisticCalculationItem_AddProbabilisticCalculationToCalculationGroupAndNotifyObservers()
         {
@@ -976,11 +1029,11 @@
 
                 plugin.Gui = gui;
 
-                var calculationItem = new SemiProbabilisticPipingCalculationScenario
+                var probabilisticCalculationScenario = new ProbabilisticPipingCalculationScenario
                 {
                     Name = "Nieuwe berekening"
                 };
-                group.Children.Add(calculationItem);
+                group.Children.Add(probabilisticCalculationScenario);
 
                 nodeData.Attach(observer);
 
@@ -996,12 +1049,70 @@
                     Assert.AreEqual(2, group.Children.Count);
                     ICalculationBase newlyAddedItem = group.Children.Last();
                     Assert.IsInstanceOf<ProbabilisticPipingCalculationScenario>(newlyAddedItem);
-                    Assert.AreEqual("Nieuwe berekening (1)", newlyAddedItem.Name,
-                                    "An item with the same name default name already exists, therefore '(1)' needs to be appended.");
+                    Assert.AreEqual("Nieuwe berekening (1)", newlyAddedItem.Name);
                 }
             }
         }
+        
+        [Test]
+        public void GivenCalculationGroupWithSemiProbabilisticCalculation_WhenClickOnAddProbabilisticCalculationItem_ThenCalculationAddedWithSameName()
+        {
+            // Setup
+            using (var treeViewControl = new TreeViewControl())
+            {
+                var group = new CalculationGroup();
+                var parentGroup = new CalculationGroup();
+                var pipingFailureMechanism = new PipingFailureMechanism();
+                var assessmentSection = mocks.Stub<IAssessmentSection>();
+                var nodeData = new PipingCalculationGroupContext(group,
+                                                                 parentGroup,
+                                                                 Enumerable.Empty<PipingSurfaceLine>(),
+                                                                 Enumerable.Empty<PipingStochasticSoilModel>(),
+                                                                 pipingFailureMechanism,
+                                                                 assessmentSection);
+                var parentNodeData = new PipingCalculationGroupContext(parentGroup,
+                                                                       null,
+                                                                       Enumerable.Empty<PipingSurfaceLine>(),
+                                                                       Enumerable.Empty<PipingStochasticSoilModel>(),
+                                                                       pipingFailureMechanism,
+                                                                       assessmentSection);
 
+                var menuBuilder = new CustomItemsOnlyContextMenuBuilder();
+
+                var gui = mocks.Stub<IGui>();
+                gui.Stub(cmp => cmp.Get(nodeData, treeViewControl)).Return(menuBuilder);
+
+                var observer = mocks.StrictMock<IObserver>();
+                observer.Expect(o => o.UpdateObserver());
+                mocks.ReplayAll();
+
+                plugin.Gui = gui;
+
+                var semiProbabilisticCalculationScenario = new SemiProbabilisticPipingCalculationScenario
+                {
+                    Name = "Nieuwe berekening"
+                };
+                group.Children.Add(semiProbabilisticCalculationScenario);
+
+                nodeData.Attach(observer);
+
+                using (ContextMenuStrip contextMenu = info.ContextMenuStrip(nodeData, parentNodeData, treeViewControl))
+                {
+                    // Precondition
+                    Assert.AreEqual(1, group.Children.Count);
+
+                    // Call
+                    contextMenu.Items[contextMenuAddProbabilisticCalculationIndexNestedGroup].PerformClick();
+
+                    // Assert
+                    Assert.AreEqual(2, group.Children.Count);
+                    ICalculationBase newlyAddedItem = group.Children.Last();
+                    Assert.IsInstanceOf<ProbabilisticPipingCalculationScenario>(newlyAddedItem);
+                    Assert.AreEqual("Nieuwe berekening", newlyAddedItem.Name);
+                }
+            }
+        }
+
         [Test]
         public void ContextMenuStrip_ClickOnValidateAllItem_ValidateAllChildCalculations()
         {