Merge pull request #216 from ritchie46/triangularLoadsInsertNodeFix

Correctly split triangular q-loads in insert_node()

Author: brookshsmith

anastruct/fem/examples/ex_20_insert_node.py

@@ -5,7 +5,7 @@
 ss.add_element([10, 0])
 ss.add_support_hinged(1)
 ss.add_support_hinged(2)
-ss.q_load(-1, 1)
+ss.q_load([-1, -3], 1)
 ss.insert_node(1, factor=0.3)
 ss.point_load(3, Fy=-10)
 ss.insert_node(3, [5, 5])

anastruct/fem/system.py

@@ -664,6 +664,9 @@ def insert_node(
         elif factor is None and location is not None:
             assert location is not None
             location_vertex = Vertex(location)
+            length1 = (location_vertex - element_to_split.vertex_1).modulus()
+            length2 = (element_to_split.vertex_2 - location_vertex).modulus()
+            factor = length1 / (length1 + length2)
         else:
             raise FEMException(
                 "Invalid parameters",
@@ -713,18 +716,26 @@ def insert_node(
 
         # Copy the q-loads from the old element to the new elements
         if element_id_to_split in self.loads_q:
+            q_load_start = element_to_split.q_load[0]
+            q_load_end = element_to_split.q_load[1]
+            q_perp_load_start = element_to_split.q_perp_load[0]
+            q_perp_load_end = element_to_split.q_perp_load[1]
+            location_q_load = factor * (q_load_end - q_load_start) + q_load_start
+            location_q_perp_load = (
+                factor * (q_perp_load_end - q_perp_load_start) + q_perp_load_start
+            )
             assert element_to_split.q_angle is not None
             self.q_load(
-                q=element_to_split.q_load,
+                q=[-q_load_start, -location_q_load],
                 element_id=element_id1,
-                rotation=np.degrees(np.pi + element_to_split.q_angle),
-                q_perp=element_to_split.q_perp_load,
+                rotation=np.degrees(element_to_split.q_angle),
+                q_perp=[q_perp_load_start, location_q_perp_load],
             )
             self.q_load(
-                q=element_to_split.q_load,
+                q=[-location_q_load, -q_load_end],
                 element_id=element_id2,
-                rotation=np.degrees(np.pi + element_to_split.q_angle),
-                q_perp=element_to_split.q_perp_load,
+                rotation=np.degrees(element_to_split.q_angle),
+                q_perp=[location_q_perp_load, q_perp_load_end],
             )
 
         # Remove the old element from everywhere it's referenced

tests/test_e2e.py

@@ -302,9 +302,9 @@ def it_retains_supports_and_loads(SS_20):
             assert SS_20.supports_hinged == [SS_20.node_map[1], SS_20.node_map[2]]
             assert SS_20.loads_point == {3: (0, 10)}
             assert list(SS_20.loads_q.keys()) == [2, 4, 5]
-            assert SS_20.element_map[2].q_load == (-1, -1)
-            assert SS_20.element_map[4].q_load == (1, 1)
-            assert SS_20.element_map[5].q_load == (1, 1)
+            assert SS_20.element_map[2].q_load == approx((1, 1.6))
+            assert SS_20.element_map[4].q_load == approx((1.6, 2.205258))
+            assert SS_20.element_map[5].q_load == approx((2.205258, 3))
 
     def context_find_node_id():
         @pspec_context("find_node_id() function using Example 8")