Modeling Structural Elements

Modeling Structural Elements

Overview

In this lesson, you will explore how to add the elements to the building model that provide the structural framework for the building.

You will start by adding a dimensional framework of levels and grids to the architectural model, and then add placeholders for structural elements that impact the architectural design (such as columns). They will then copy essential elements from the architectural model to a Revit structural model and place the key structural framing elements such as foundations, floors, shear walls, columns, beams, and joists.

The endpoint of the lesson will be a structural model that can be used for structural analysis and shared with the other members of the design team.

Linking an Architectural Model and Copying Shared Elements

Link the preliminary architectural model to your new structural model and use the Copy/Monitor tool to copy shared elements:

  • Dimensional framework—levels and grids
  • Placeholder elements—walls, floors, and columns placed in the architectural model
Adding placeholder columns to the architectural model at grid intersections
Adding placeholder columns to the architectural model at grid intersections
Modeling Concrete Columns, Beams, and Floor Slabs

Model the concrete columns, beams, and floors slabs on the first floor and lower level of the project using the Structural Column, Beam, and Floor tools. These elements will provide the basis for detailed structural design and structural analysis to confirm the sizes of all members.

You can place structural elements in any view, so select a view that makes your work task easier:

Use plan views for elements that are placed below or through the cut plane (for example, columns).

  • Use reflected ceiling plan views for elements that are placed above the cut plan (for example, beams).
  • Use 2D or 3D section views for elements that are difficult to select in plan views (for example, floors).
  • Use 3D views with the Snap in Place option for elements whose ends snap to other objects (for example, beams).

In addition, be sure that the view’s level of detail, view range, and visibility graphics overrides are set in a way that makes the structural elements visible.

Modeling Wood Columns, Beams, and Beam Systems

Model the wood columns, beams, and beam systems on the upper levels of the project using similar techniques, but with a few variations:

  • Use the Align tool to line up the outside faces of the wood columns in the exterior walls with the edge of the floor slab (and the outside face of the concrete columns) below.
  • Use the Beam System tool to create a regularly spaced system of joist elements to span between the wood beams and support the upper floors and roof.

Since levels 2 through 4 are very similar, you can use shortcuts to simplify your work. After placing the wood structural elements on one level, copy them to the clipboard and use the Paste Align tool to copy them to similar locations on other levels.

Modeling Structural Walls and Foundations

Add structural walls (for example, shear walls that resist lateral forces) to the structural model using the Wall tool. For this design, you will place:

  • Concrete shear walls at the lower level and level 1 to work with the concrete framing at those levels
  • Plywood shear walls at levels 2 through 4 above
  • Retaining walls at the edges of the lower level

You can also add foundation elements to transfer the loads from the structural framing to the ground:

  • Foundation slabs to transfer distributed loads
  • Wall foundations to transfer continuous wall loads
  • Isolated foundations to transfer concentrated column loads

Be sure to set the Placement Plane option to accurately place your foundation elements at the proper level. In addition, make certain that the view’s level of detail, view range, and visibility graphics overrides are set in way that makes the new elements visible.

Learning Objectives

After completing this lesson, you will be able to:

  • Understand the importance of copying the dimensional framework to facilitate structural systems modeling.
  • Understand and apply the concepts and techniques of modeling structural framing of differing material types—concrete and wood.
  • Appreciate the advantages and tradeoffs of modeling elements in 2D or 3D views.
Tutorials
Linking an Architectural Model and Copying Shared Elements

In this tutorial, you will learn how to:

  • Link an architectural model to a structural model.
  • Set the options for copying shared elements.
  • Select and filter the objects to be copied.
  • Create working views of the structural model that facilitates modeling.
Copying shared elements from a linked model
Copying shared elements from a linked model
Video Tutorial

Practice Exercise
  • Open the model for this exercise in Revit and link it to the architectural model of the building (from the Linked Files folder).
  • Copy the north-south grids from the linked model into the Revit Structure host project.
  • Also create a new 3D view and name it 3D Structural Frame.
3D Structural Frame View
3D Structural Frame View

Modeling Concrete Columns, Beams, and Floor Slabs

In this tutorial, you will learn how to:

  • Adjust the grids and column locations to better serve the interior layout and structural integrity of building.
  • Specify and placing concrete columns and beams in plan views and with 3D snapping.
  • Specify the structure and materials for concrete floor slabs.
Moving columns by adjusting the grid locations
Moving columns by adjusting the grid locations
Video Tutorial

Practice Exercise
  • Place 10" (0.25 m) square concrete structural columns at interior grid intersections on level 1 and the lower level.
  • Create a new concrete structural framing type for 12" x 24" (0.30 m x 0.61 m) concrete beams and place these beams at the top of the structural columns on level 1 to support the level 2 floor slab.
  • Unhide the floor slab at level 2 and change its type to be a 6" (0.15 m) concrete slab.
Concrete beams placed at the top of level 1 columns
Concrete beams placed at the top of level 1 columns

Modeling Wood Columns, Beams, and Floors

In this tutorial, you will learn how to:

  • Choose, place, and align wood columns relative to other model elements.
  • Specify the wood beam types and place them in plan views and with 3D snapping.
  • Create beam systems of regularly spaced beams and joists.
  • Specify the structure and materials for wood structural floors and place identical instances at many levels at once.
Copying wood structural elements to a similar position on another level
Copying wood structural elements to a similar position on another level
Video Tutorial

Practice Exercise
  • Place 6 x 6 (0.15 m x 0.15 m) wood columns at the grid intersections on the right side of level 2 (along grids C and D) and align edge columns to the outer boundary of the floor slab.
  • Place5 x 22 (0.13 m x 0.57 m) Glulam beams of southern pine along grids C and D to support the floor level above. Use an offset -0.75" (19 mm) to place these beams below the plywood subfloor at Level 2.
  • Create a beam system of 16" (0.40 m) TJL wood open web joists to span between the beams at grids C and D. Use an offset of -0.75" (19 mm) to also place these joists below the plywood subfloor. The joists should be center justified and spaced at a fixed distance of 2’ (0.61 m).
  • Create a similar beam system using 14" (0.36 m) TJL wood open web joists to span between the beams at grids B and C.
  • Copy the wood structural elements that you created in this exercise to similar locations on levels 3 and 4.
  • Select the floor at level 4 and change it to the plywood floor type.
Sketching the boundary for a beam system of open web joists
Sketching the boundary for a beam system of open web joists

Assessment
Linking and Architectural Model and Copying Shared Elements
What are the advantages and disadvantages of linking to a Revit model versus sharing a single project file?

Through linking, you maintain manageable file sizes and help protect against inadvertent changes being made by team members to our designs.

Sharing a single file for smaller projects and within smaller collocated teams can cut down on the coordination work of using separate linked files. Coordination, instead, can be achieved by using worksets, which guards against unwanted edits to your portion of the design.

How does linking to models affect the performance of a host model?

As the file size increases, the performance of the host model may diminish.

Is the information displayed in a linked model refreshed automatically?

When you open a host model, the linked models are refreshed. Otherwise, we have to reload links from the Manage Links dialog box.

Why does the Copy\/Monitor tool limit the types of elements that can be copied and monitored? What do these elements have in common?

It limits you to copying the elements that are essential for coordination between the different models. It limits these types so that you do not unnecessarily copy in elements that will not be needed and, thus, burden the model and degrade performance.

What are the advantages and disadvantages of copying shared building elements as generic types versus copying the original types?

Copying elements as generic types makes it easier to identify the copied versions versus the ones that you have changed to accurate types in your modeling process.

Modeling Concrete Columns, Beams, and Floor Slabs
Can you rotate columns as you place them?

Yes; by pressing the space bar, you rotate through the available options.

What are the advantages and disadvantages of placing a column by specifying its depth versus specifying its height?

It will change the level with which the column is associated.

What are the advantages and disadvantages of placing columns in 3D views?

3D views can be used for placing columns at grid locations or when snapping to other points. But plan view should be used when accurate placement is required and snap points are not available. One advantage of placing elements in 3D view is that you can immediately see and verify the results.

Which 2D view is best for placing beams at the top of the level 1 columns?

A reflected ceiling plan view that allows you to see the placement plane from below.

Modeling Wood Columns, Beams, and Floors
What is the difference between the nominal dimensions for wooden elements and the actual dimensions? Is it the same for all sizes?

The nominal dimensions of a piece of lumber, such as 2x4 or 2x6, are always somewhat larger than the actual, or dressed, dimensions.The nominal dimension is the next highest integer value from the dimension specified. For example, 1.5 x 3.5 inch (38 x 89 mm) members are referred to as 2x4s.

Why is it better to align the outside faces of the wood columns to the edge of the floor versus leaving them centered on the grid intersections?

Because the face of the columns on all levels should be flush with the exterior face of the wall, so that the columns will align with the wall framing and not protrude into the finished space.

Why are beams placed in one direction and a beam system of smaller joist elements placed in the other direction?

The beam system of joists is supported by the beams running in the orthogonal direction at their ends. For that reason, the beams must be bigger in order to carry the cumulative loads from the joists.

Why is the elevation of the beam start and end offsets and the beam systems lowered to match the thickness of the structural floor?

The beams are dropped in order to represent the actual construction conditions. Wood beams are typically located below and support the structural floor, but do not intersect with it.

Modeling Structural Walls and Foundations
What are the key differences between structural walls and basic wall types?

Structural walls have extra properties, such as its structural type (shear, bearing, and so on) and others that enable analytical modeling.

What determines whether a wall requires a wall foundation?

Walls that carry loads from above require wall foundations in order to transfer those loads to the soil. Interior partition walls and nonbearing walls do not require wall foundations.

Are isolated foundations needed to support columns that are embedded in retaining walls?

Typically not, since those retaining walls will have wall foundations.

Are isolated foundations needed to support columns that are embedded in retaining walls?

Typically not, since those retaining walls will have wall foundations.

Why are isolated foundations needed under the interior columns? Would the slab foundation not provide enough support?

The interior columns are transmitting point loads that are the accumulated from the loads above and, thus, require an isolated foundation to transfer the loads and avoid punching through slab.

Key Terms

The following key terms were used in this lesson:

Shear Wall

A rigid vertical diaphragm that transfer lateral forces (caused by wind, earthquakes, or settlement) to the foundation elements in a direction parallel to their planes. Examples include reinforced concrete walls, plywood shear panels, and vertical trusses.

Joist

Light horizontal framing members that support a floor or ceiling. They typically span between walls or between larger beams or girders.

Beam System

A collection of beam elements that are typically placed in a regularly spaced pattern.

Floor Slab

A structural slab, often made of concrete, used as a floor on grade or below grade.

Isolated Foundation

A foundation element used to transfer structural point loads to the ground. Isolated foundations are typically placed beneath column elements.

Wall Foundation

A foundation element used to transfer structural wall loads to the ground. Wall foundations are typically placed beneath foundation wall and retaining wall elements.