diff --git a/src/bonsai/bonsai/core/structural.py b/src/bonsai/bonsai/core/structural.py
index af092e1034..bae45ada33 100644
--- a/src/bonsai/bonsai/core/structural.py
+++ b/src/bonsai/bonsai/core/structural.py
@@ -43,7 +43,7 @@ def assign_structural_analysis_model(
         ifc.run(
             "structural.assign_structural_analysis_model",
             **{
-                "product": ifc.get().by_id(product_.BIMObjectProperties.ifc_definition_id),
+                "products": [ifc.get().by_id(product_.BIMObjectProperties.ifc_definition_id)],
                 "structural_analysis_model": ifc.get().by_id(structural_analysis_model),
             },
         )
@@ -110,7 +110,7 @@ def unassign_structural_analysis_model(
         ifc.run(
             "structural.unassign_structural_analysis_model",
             **{
-                "product": ifc.get().by_id(product_.BIMObjectProperties.ifc_definition_id),
+                "products": [ifc.get().by_id(product_.BIMObjectProperties.ifc_definition_id)],
                 "structural_analysis_model": ifc.get().by_id(structural_analysis_model),
             },
         )
diff --git a/src/ifcopenshell-python/ifcopenshell/api/structural/assign_structural_analysis_model.py b/src/ifcopenshell-python/ifcopenshell/api/structural/assign_structural_analysis_model.py
index dd96f543b2..dfae40d862 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/structural/assign_structural_analysis_model.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/structural/assign_structural_analysis_model.py
@@ -17,43 +17,22 @@
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
 import ifcopenshell
+import ifcopenshell.api.group
 import ifcopenshell.api.owner
 import ifcopenshell.guid
+from typing import Union
 
 
 def assign_structural_analysis_model(
     file: ifcopenshell.file,
-    product: ifcopenshell.entity_instance,
+    products: list[ifcopenshell.entity_instance],
     structural_analysis_model: ifcopenshell.entity_instance,
-) -> ifcopenshell.entity_instance:
+) -> Union[ifcopenshell.entity_instance, None]:
     """Assigns a load or structural member to an analysis model
 
-    :param product: The structural element that is part of the analysis.
-    :type product: ifcopenshell.entity_instance
+    :param products: The structural elements that is part of the analysis.
     :param structural_analysis_model: The IfcStructuralAnalysisModel that
         the structural element is related to.
-    :type structural_analysis_model: ifcopenshell.entity_instance
     :return: The IfcRelAssignsToGroup relationship
-    :rtype: ifcopenshell.entity_instance
     """
-    settings = {
-        "product": product,
-        "structural_analysis_model": structural_analysis_model,
-    }
-
-    if not settings["structural_analysis_model"].IsGroupedBy:
-        return file.create_entity(
-            "IfcRelAssignsToGroup",
-            **{
-                "GlobalId": ifcopenshell.guid.new(),
-                "OwnerHistory": ifcopenshell.api.owner.create_owner_history(file),
-                "RelatedObjects": [settings["product"]],
-                "RelatingGroup": settings["structural_analysis_model"],
-            }
-        )
-    rel = settings["structural_analysis_model"].IsGroupedBy[0]
-    related_objects = set(rel.RelatedObjects) or set()
-    related_objects.add(settings["product"])
-    rel.RelatedObjects = list(related_objects)
-    ifcopenshell.api.owner.update_owner_history(file, **{"element": rel})
-    return rel
+    return ifcopenshell.api.group.assign_group(file, products, structural_analysis_model)
diff --git a/src/ifcopenshell-python/ifcopenshell/api/structural/unassign_structural_analysis_model.py b/src/ifcopenshell-python/ifcopenshell/api/structural/unassign_structural_analysis_model.py
index 6fd53aa80d..2053e7d075 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/structural/unassign_structural_analysis_model.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/structural/unassign_structural_analysis_model.py
@@ -17,40 +17,21 @@
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
 import ifcopenshell
+import ifcopenshell.api.group
 import ifcopenshell.api.owner
 import ifcopenshell.util.element
 
 
 def unassign_structural_analysis_model(
     file: ifcopenshell.file,
-    product: ifcopenshell.entity_instance,
+    products: list[ifcopenshell.entity_instance],
     structural_analysis_model: ifcopenshell.entity_instance,
 ) -> None:
     """Removes a relationship between a structural element and the analysis model
 
-    :param product: The structural element that is part of the analysis.
-    :type product: ifcopenshell.entity_instance
+    :param products: The structural elements that is part of the analysis.
     :param structural_analysis_model: The IfcStructuralAnalysisModel that
         the structural element is related to.
-    :type structural_analysis_model: ifcopenshell.entity_instance
     :return: None
-    :rtype: None
     """
-    settings = {
-        "product": product,
-        "structural_analysis_model": structural_analysis_model,
-    }
-
-    if not settings["structural_analysis_model"].IsGroupedBy:
-        return
-    rel = settings["structural_analysis_model"].IsGroupedBy[0]
-    related_objects = set(rel.RelatedObjects) or set()
-    related_objects.remove(settings["product"])
-    if len(related_objects):
-        rel.RelatedObjects = list(related_objects)
-        ifcopenshell.api.owner.update_owner_history(file, **{"element": rel})
-    else:
-        history = rel.OwnerHistory
-        file.remove(rel)
-        if history:
-            ifcopenshell.util.element.remove_deep2(file, history)
+    ifcopenshell.api.group.unassign_group(file, products, structural_analysis_model)
diff --git a/src/ifcopenshell-python/test/api/structural/test_assign_structural_analysis_model.py b/src/ifcopenshell-python/test/api/structural/test_assign_structural_analysis_model.py
index 4e8cbb0f00..da09c38674 100644
--- a/src/ifcopenshell-python/test/api/structural/test_assign_structural_analysis_model.py
+++ b/src/ifcopenshell-python/test/api/structural/test_assign_structural_analysis_model.py
@@ -29,12 +29,13 @@ class TestAssignStructuralAnalysisModel(test.bootstrap.IFC4):
         )
         rel = ifcopenshell.api.structural.assign_structural_analysis_model(
             self.file,
-            product=product,
+            products=[product],
             structural_analysis_model=subject,
         )
+        assert rel
         assert rel.is_a("IfcRelAssignsToGroup")
         assert rel.RelatingGroup == subject
-        assert product in rel.RelatedObjects
+        assert rel.RelatedObjects == (product,)
 
 
 class TestAssignStructuralAnalysisModelIFC2X3(test.bootstrap.IFC2X3, TestAssignStructuralAnalysisModel):
diff --git a/src/ifcopenshell-python/test/api/structural/test_unassign_structural_analysis_model.py b/src/ifcopenshell-python/test/api/structural/test_unassign_structural_analysis_model.py
index e43fe1eaa0..c80842b7ad 100644
--- a/src/ifcopenshell-python/test/api/structural/test_unassign_structural_analysis_model.py
+++ b/src/ifcopenshell-python/test/api/structural/test_unassign_structural_analysis_model.py
@@ -29,12 +29,12 @@ class TestUnassignStructuralAnalysisModel(test.bootstrap.IFC4):
         )
         ifcopenshell.api.structural.assign_structural_analysis_model(
             self.file,
-            product=product,
+            products=[product],
             structural_analysis_model=subject,
         )
         ifcopenshell.api.structural.unassign_structural_analysis_model(
             self.file,
-            product=product,
+            products=[product],
             structural_analysis_model=subject,
         )
         models = self.file.by_type("IfcStructuralAnalysisModel")