Merge pull request #217 from ritchie46/removeElementOrphanedNodes

Remove orphaned nodes in remove_element()

Author: brookshsmith

anastruct/fem/system.py

@@ -477,12 +477,20 @@ def remove_element(self, element_id: int) -> None:
             element_id (int): ID of the element to remove
         """
         element = self.element_map[element_id]
-        for node_id in (element.node_id1, element.node_id2):
+        node_id1 = element.node_id1
+        node_id2 = element.node_id2
+
+        # Remove element object itself from node maps
+        for node_id in (node_id1, node_id2):
             self.node_element_map[node_id].remove(element)
             if len(self.node_element_map[node_id]) == 0:
                 self.node_element_map.pop(node_id)
             self.node_map[node_id].elements.pop(element_id)
+            # Check if node is now orphaned, and remove it and its loads if so
+            if len(self.node_map[node_id].elements) == 0:
+                system_components.util.remove_node_id(self, node_id)
 
+        # Remove element_id
         self.element_map.pop(element_id)
         if element_id in self.loads_q:
             self.loads_q.pop(element_id)

anastruct/fem/system_components/util.py

@@ -78,6 +78,56 @@ def append_node_id(
         system.node_map[node_id2] = Node(node_id2, vertex=point_2)
 
 
+def remove_node_id(
+    system: "SystemElements",
+    node_id: int,
+) -> None:
+    """Remove the node id from the system
+
+    Note that this function does NOT check if the node is still used in the system. It is
+    intended to be used as a helper function to `remove_element()` and others, not to be
+    used directly by users.
+
+    Args:
+        system (SystemElements): System in which the node is located
+        node_id (int): Node id of the node
+    """
+    node = system.node_map[node_id]
+    system._vertices.pop(system.node_map[node_id].vertex)
+    system.node_map.pop(node_id)
+    if node_id in system.loads_point:
+        system.loads_point.pop(node_id)
+    if node_id in system.loads_moment:
+        system.loads_moment.pop(node_id)
+    if node in system.supports_fixed:
+        system.supports_fixed.remove(node)
+    if node in system.supports_hinged:
+        system.supports_hinged.remove(node)
+    if node in system.supports_rotational:
+        system.supports_rotational.remove(node)
+    if node in system.internal_hinges:
+        system.internal_hinges.remove(node)
+    if node in system.supports_roll:
+        ind = system.supports_roll.index(node)
+        system.supports_roll.remove(node)
+        system.supports_roll_direction.pop(ind)
+        system.supports_roll_rotate.pop(ind)
+    if node_id in system.inclined_roll:
+        system.inclined_roll.pop(node_id)
+    if node in [item[0] for item in system.supports_spring_x]:
+        ind = [item[0] for item in system.supports_spring_x].index(node)
+        system.supports_spring_x.pop(ind)
+    if node in [item[0] for item in system.supports_spring_y]:
+        ind = [item[0] for item in system.supports_spring_y].index(node)
+        system.supports_spring_y.pop(ind)
+    if node in [item[0] for item in system.supports_spring_z]:
+        ind = [item[0] for item in system.supports_spring_z].index(node)
+        system.supports_spring_z.pop(ind)
+    if node_id in [item[0] for item in system.supports_spring_args]:
+        ind = [item[0] for item in system.supports_spring_args].index(node_id)
+        system.supports_spring_args.pop(ind)
+
+
 def det_vertices(
     system: "SystemElements",
     location_list: Union[

tests/test_e2e.py

@@ -1016,3 +1016,31 @@ def it_results_in_correct_deflections():
             assert system.get_node_results_system(1)["uy"] == approx(
                 -w * l**4 / (8 * EI)
             )
+
+    def context_remove_element():
+        @pspec_context("Removing an element from a propped beam")
+        def describe():
+            pass
+
+        system = SystemElements()
+        system.add_element([[0, 0], [10, 0]])
+        system.add_element([[10, 0], [15, 0]])
+        system.add_support_hinged(1)
+        system.add_support_hinged(2)
+        system.q_load(q=-1, element_id=1)
+        system.q_load(q=-1, element_id=2)
+        system.point_load(node_id=3, Fy=-10)
+        system.remove_element(2)
+        system.solve()
+
+        def it_removes_element():
+            assert len(system.element_map) == 1
+            assert not (2 in system.loads_q)
+
+        def it_removes_orphaned_node():
+            assert len(system.node_map) == 2
+            assert not (3 in system.loads_point)
+
+        def it_results_in_correct_reactions():
+            assert system.get_node_results_system(1)["Fy"] == approx(-5)
+            assert system.get_node_results_system(2)["Fy"] == approx(-5)