US Contractor: Quantity Takeoff
This article is a guide for producing concrete quantity take-offs from Tekla Structures models. To do so, the sections below provide insight into methodologies and workflows. This guide will also provide insight into what Tekla can produce for quantity estimates, the basic workflow to achieve these results, considerations to keep in mind, as well as document-related settings and reports associated with this work task.
Please note that the material contained within this guide is available in the US Environment using either the Imperial Cast-in-place or Rebar Detailing roles. Any images created for this article utilize that configuration and a basic model created using the CIP-Rebar Detailing model template.
The rest of this introduction will provide an overview on what to expect with quantity take-offs in Tekla Structures before moving how to how it works and any considerations.
Introduction
Quantity Takeoff vs. Estimate
For the context of this guide and using Tekla Structures for accurate quantities, quantity take-off is defined as follows:
A quantity takeoff in this context is not an estimate but is used to help create one. An estimate includes cost coding and pricing schemes associated with the categorization of concrete parts and related materials. Tekla Structures can produce a breakdown of these materials, sorted by Phase or Building Hierarchy, and listed out by object type and material grade. This output (see Example Image 1) is created as an Excel file that can be used to transpose the data to another workbook or program for the integration of cost to create the estimate.
Why use Tekla Structures?
Using Tekla Structures for quantity takeoffs provides a level of accuracy that is difficult to achieve elsewhere. Creating a model for quantity takeoff benefits from a 3D representation to better understand the project, and remove human error in the calculation of quantities.
The model can then be leveraged through the lifecycle of the project once the job has been awarded. Models can also be used for constructability review, project planning and management, sequencing, detailing, documentation, and providing status on construction from the field.
The Correct Report for the Task
The US Environment offers many report templates that provide concrete quantities. These reports all have a unique way of breaking down and reporting the information from the model. However, one of two reports should be utilized when modeling for concrete quantity takeoffs. When reporting is discussed in this guide, it is with the two report templates in mind:
- 310 CIP Takeoff - by Phase
- 310 CIP Takeoff - By Hierarchy
Both of these reports are available in Tekla Structures 2023 SP8 and going forward. They will be found in the Report tool from the Drawings and Reports ribbon utilizing the Cast-in-Place and Rebar Detailing roles.
Example Image 1
How Quantities Work in Tekla Structures
When an object is created in Tekla Structures, such as a concrete pad footing, its physical properties are immediately known by the software based on the criteria specified by the user. For example, after creating an 84”x84”x36” pad footing the user can immediately inquire about the properties using the custom inquiry tool and see the name, profile, length, volume, and so on. See Example Image 2.
If we move this idea forward and model the entire foundation system within Tekla, we can inquire about any of these objects as needed. However, doing so in this fashion requires a great deal of time to aggregate results. That is why the Reports function is used to accomplish the same task but for the entire model or specified portions, all at once.
Creating a model allows us to quickly aggregate the physical properties (data) in a report. The effort is spent modeling, and reporting quantiles using a predefined template allows to creation of robust quantity reports with simple steps.
More detail on the workflow process is below and further details on available report templates can be found later in this article.
Example Image 2
Surface Area vs. Contact Area
Tekla Structures can quickly report the overall surface area of an object. Additionally, it can also report a specified plane or face of an object. The latter includes surface area for the top, bottom, or all sides. This can be useful information but these surface area fields of a concrete part may not be specific enough in the context of quantity takeoffs.
Often it is the “contact area” that is the desired surface area output. This is an applied understanding of the properties of a concrete object. It requires human interpretation and is circumstantial or conditional to a given type of object. For example, the contact area of a grade or tie beam would only be the surface area of the two lateral sides. But for an elevated beam, the bottom surface area would also be required in addition to both lateral sides.
Tekla Structures can provide the contact area of a part, but it is not a single attribute that can be reported. It requires one of two methods to calculate this contact area. Report templates 310 CIP Takeoff - by Phase and 310 CIP Takeoff - By Hierarchy provide contact areas based on object type using specific attributes in formulas.
Additionally, Tekla also has tools such as the Form Face Creator for defining the contact area of unique concrete shapes. Both of these methods are discussed in this article under the Reporting of Quantities and Additional Considerations, respectively.
Modeling for QTO: General Process
The general process for modeling concrete structures for concrete takeoff is fairly straightforward. Begin by modeling the concrete on the lowest elevation or area of the structure and proceed with these general steps. Repeat these steps for each concrete part, you model.
One example of this could be to model all foundations and foundation wall geometry first with cuts and openings. Then go back and add all embed plates and anchorage. Then finally add reinforcement (if applicable). Then repeat for the next area or elevation. When creating your first models, keep the areas you model at one time smaller and more manageable.
The basic workflow is as follows:
- Establish the Model Organization and Level of Development (LOD) for the model.*
- Model the concrete shapes to create the structure.
- Model the reinforcement (if applicable).
- Repeat for each section/area/elevation of the structure.
- Run the quantity report as required.
*Note: See Major considerations for more information on Project / Model Organization and Level of Development (LOD).
Major Considerations
This section provides context to key considerations when modeling in Tekla. Take the time to review each and become familiar with the resources provided. These points should help produce accurate and consistent results in your modeling efforts. Additional considerations and best practices for concrete quantity takeoffs are also provided further in this article.
Training and Resources
There is a level of assumed understanding on the users' behalf when providing the workflow in this article. New users, or existing users unfamiliar with concrete or reinforcement need to have access to training materials related to the tasks mentioned in this article. There are several learning paths for online or instructor-led courses for concrete and rebar.
These learning paths are documented on our US Contractor: User Resources page, under Section 3. Tekla Resources & Learning. It is encouraged that users undertake one of these learning paths related to the area of modeling they wish to learn or strengthen when first adopting Tekla Models for concrete quantity takeoffs.
In addition, if users have specific questions or wish to inquire about a certain area not fully covered in the training, they may search this Tekla User Assistance webpage for answers, visit the Tekla Forums, or reach out to our US Support Team. Information on how to use each of these resources can also be found on the US Contractor: User Resources page, under Section 4. Assistance and Feedback.
Project/Model Organization
Organizing a BIM model is generally a good practice. This applies to modeling efforts for quantity takeoffs as well. Inherently, most takeoffs compartmentalize the building or structure into phases or a hierarchy. Tekla Structures provides the ability to do this as well. Organizing your model can be leveraged in the reporting of quantities. Report template 310 CIP Takeoff - by Phase and 310 CIP Takeoff - By Hierarchy will break down objects based on their respective structure if they have been applied. The following provides more insight into using Phases or Building Hierarchy to compartmentalize your Tekla model project:
Building Hierarchy
Building Hierarchy allows you to define a traditional location breakdown structure of your project/models. It has a default hierarchy structure: project → site → building → level → space. A level is a horizontal plane at a specified elevation within a building. Spaces are volumes that provide for certain functions within a building.
By defining the boundaries of the hierarchy, objects will automatically be associated with them, so long as the center of gravity exists within the specified building/level/space. You can add levels and spaces to the model by either importing them from a reference model or creating them directly in your model. In the Cast-in-place and Rebar Detailing roles for the US Environment, the building hierarchy tools are found on the Manage Ribbon.
If you are utilizing building hierarchy and wish to report the quantity takeoff with this breakdown, utilize the report 310 CIP Takeoff - By Hierarchy.
You can find instructions on how to use building hierarchy with your models on Tekla User Assistance:
- Article: Building hierarchy - create and manage levels and spaces
- Article: Building Hierarchy
Phases
Phases are used to logically group objects. Each phase consists of a number, a name, as well a few other attributes. Phases can be created via the Phase Manager found on the Manage Ribbon.
Users can create phases to place objects and name these phases appropriately. If your company typically thinks of the phases of their projects, the phase manager will allow you to create phases flexibly and then select the objects and add them to the desired phase. Keep in mind that only one object can be assigned to a single phase at any time.
If you are utilizing Phase and wish to report the quantity takeoff with this breakdown, utilize the report 310 CIP Takeoff - By Phase. Note that this report allows you to omit any phase you wish from the report output by populating the word “Exclude” or “X” in the Comment field inside the Phase Manager (Example Image 3).
For more information on using phases for your Tekla model projects see the following resources:
- Article: Phase Manager
- Video: Tekla Structures: Phases and Phase Management
- Warehouse Download: Phase Creator
Example Image 3
Level of Development
Level of Development (LOD) can best be understood as a reference to the reliability of your model. It’s the degree to which an element’s geometry and attached (non-graphic) information have been applied. When using BIM models for material quantity takeoff, the Level of Development is a factor companies must decide on to produce adequate and reliable results. The higher the Level of Development, the more your project team members can rely on your model.
LOD levels range from 100 to 500. The BIMForum created the Level of Development Specification. These levels can be used as guidelines, to set expectations and to make estimates about the workload. The higher the required LOD, the more time and effort you’ll likely need to spend on Tekla models. Here’s what the different LODs mean:
LOD 100 - Conceptual design
At this level, elements are not represented geometrically: the exact location, shape, or size of an element cannot be derived from the model. Instead, elements are represented with symbols or another generic representation.
LOD 200 - Design development
According to the BIMForum specification, elements at LOD 200 are represented with generic placeholders. The approximate size and shape of elements and systems are shown. At this level, your team will get an idea of the shape and configuration of the concrete. However, it’s not possible to make any claims about the exact volumes as most openings may be omitted.
LOD 300 - Documentation
At this point, the model includes information about the size, shape, location, orientation, and quantity of the elements - and this information can be measured directly from the model. It’s not necessary to look up the dimensions in notes or call-outs. Measurements can be derived directly from the geometry. At LOD 300, a project origin has been defined and the location of elements is accurate concerning this origin.
LOD 350 - Model coordination
For modeling and coordination, LOD 350 is often required. At this level, parts that are needed for coordination with other building systems are included in the model. This means that interfaces with other building systems are graphically represented and supports and connections are included. For example, at this stage, you will include general reinforcement, embedments, and small openings.
LOD 400 - Ready for construction
At this level, specific system information is included and elements are modeled with the necessary level of detail and accuracy for the construction or fabrication of the components. Graphic and non-graphic information is included that will guide the fabrication, construction, and work execution processes. At this point, prefabrication sheets and cutting lists can be derived from the model, and components can be ordered. A model at this LOD level is ready for construction and fabrication.
LOD 500 - Field verified
If your model will be used for facilities management, you will most likely be asked to model your systems at LOD 500. This level means that the elements in the model have been verified in the field. The dimensions, location, quantity, and orientation of the elements have been checked in the actual building after completion. As-built models fit in this category. Note that this does not mean that the systems have been modeled at a higher level of information or with more detail. At LOD 500, a model can look the same as a model at LOD 400. The difference is that at LOD 500, the model has been verified on-site - and therefore has a higher level of reliability.
LOD Considerations for QTO
As mentioned above the higher the LOD the more time it takes to model. But there is a trade-off to modeling to a low LOD for takeoffs: the accuracy of quantities. The less detail in the model, the less accurate your takeoff will be. Using BIM models for takeoffs is a balancing act between the time involved and the level of accuracy desired.
LOD 300 is the level at which most companies model when performing quantity takeoffs. It provides a high enough accuracy to be reliable without extending the estimation process. With that said, some companies prefer to model less or more detail, aiming for LOD 200 or LOD 350 respectively.
In the end, your company will need to determine the desired LOD for the quantity takeoff process. This is something that should be done at the start of adopting BIM models for QTO so you achieve your desired results.
Refer to the BIMForum’s Specification for additional detail and insight into LOD.
Using Part Presets & Reports
When creating concrete objects in Tekla, use the tools found on the Concrete ribbon first. Ensure to have your property pane open on the right-hand side. This provides you access to the parameters that you can change to get the shape you need.
Whenever possible it is recommended to use the part presets that are saved for each tool from the top dropdown menu. Each tool/object type has predefined settings you can load to populate important information. For example, the beam tool has presets for beams, corbels, joists, and even curbing. These presets also auto-populate many fields reducing the time to create concrete parts.
Generally presets save time in the modeling process and allow for adjustments on only what is needed, such as the profile. However, the other key benefit is that using these presets will ensure that your objects will be recognized for use later in the workflow. This applies to selecting objects, reporting, drawing creation, and other tasks. It also ensures that you and other members of your team are modeling consistently. If you need to create your own presets, start with an existing one and save it with a new name, then adjust the settings as needed. Finally, save again to update your preset.
For quantity takeoff, consistency is important. The presets for concrete parts use specific fields to ensure the report template recognizes the concrete correctly and provides the correct data. Specifically, this refers to the prefix field found in the Properties pane of a concrete part under the Cast Unit header, as highlighted in Example Image 4. The specific attribute name for this field is CAST_UNIT_PREFIX, should you need to refer to it when modifying or creating additional templates.
Each concrete object type uses a particular prefix that corresponds with the type of contact area that needs to be reported. Users need to use the correct preset when creating concrete objects so they are reported correctly.
For example, an elevated slab uses the prefix “ES”. Any concrete object, regardless of shape or tool used to create it, will be reported as an elevated slab if the prefix is “ES”. The contact area therefore is the result of the surface area of the bottom and all lateral sides of the object. If the prefix is set to “S”, this is recognized as a Slab on Grade, and the contact area will only report the surface area of the lateral sides.
A full list of concrete object categories, required prefixes, and how contact area is calculated for each can be found further in this guide under the section Reporting of Quantities.
The key takeaway is to understand that utilizing the presets in Tekla structures will apply the correct prefix for you.
Example Image 4
Approaches to Modeling CIP Concrete
Start Broad, Add Detail
When modeling concrete the best approach is to start broad and then add detail. This statement is true for almost all modeling in Tekla, especially for concrete. For example, if modeling a wall with a step and openings, first model the basic wall. Its size should be the overall height, length, and thickness, and omit any steps or contours.
Once the wall is in place you can proceed to alter its geometry to add any steps or holes. This is done by adding cuts or adjusting the geometry with Direct Modification. Once you do, proceed to the next element such as adding any anchors or embed plates. If you intend to model the reinforcement as well, that should be done last.
Model as You Construct
When modeling concrete structures it is always best to model in the same fashion you would construct the structure. That is to say, begin with the lowest elevation first and work your way upwards. Most often this is your foundation. If that is outside the scope of work, proceed with the lowest part of the structure you need to model.
Model one area or elevation at a time. Add all the detail that is required for that specific area and move on to the next. The benefit of this is it requires less switching of views to achieve your current task, which saves time. It also keeps what you are modeling more visible. With nothing above you, you don't have to worry as much about view extents and clip planes. It simply helps keep things organized and visible.
Once you get more proficient in modeling, you want to consider modeling objects or structures that are adjacent to or touching your scope of work. Doing so allows you to better coordinate and compensate for their presence.
Using the "Correct" Approach
There is often more than one way to do a specific task in Tekla. Modeling certain types of parts or groups of parts can vary from user to user. Sometimes one approach provides a benefit over another. But more often than not it is a matter of preference. Knowing this or wondering if you are using the “correct” approach can often cause indecision or frustration for new users.
What users should keep in mind is that the result is what matters. So long as your parts or model are accurate, how exactly you go there is not quite as important. Finding those preferred or the most efficient methods is accomplished by “doing” or formalized training. As you continue to create more models, you will refine your approach, seek out alternative methods, and in some cases even compare notes with other users.
Focus on getting the model completed and to the level of accuracy you need. Rely on the tools in the ribbon. Feel free to explore the tools found in the Applications & Components side pane, but do not let them bog you down. If something doesn't work the way you intend, move on to an approach you know works. If you are unsure what this is then make a quick check with the Instructor, or look it up in the TUA. If all else fails, our support team can help you through it.
Complex Concrete Shapes
Depending on the scope and nature of your project, concrete can have some pretty complex shapes. For new users, this can be a point of contention. The tools in the ribbon do not appear to be able to create some complex shapes in one fell swoop.
The reality is a little bit different. We can lean on what is discussed in the “Start Broad, Add Detail” section of this page for some insight. Users can create complex concrete shapes by adding them together.
The basic example of a thickened edge on a slab can provide some insight. The slab and edge would be modeled separately, using the polybeam tool to form the thickened edge. It would be placed after the slab has been modeled. As modeled, these two elements are separate. They can be combined into one solid object using "Attach to part" or by Pours.
The benefit of the thickened edge and slab remaining separate is that you can quantify independently. The length of the thickened edge in reports will show up as its own line item. Now if you need these two as one object, you can use the “Attach to part” command found on the edit ribbon. This will combine the objects and when inquiring about the volume, it will be the total of the two items that have been combined.
The drawback to this is that you will need to explode this part merge to edit it. It is because of this drawback that this method is only recommended sparingly. Once you've become familiar with pours and how they work you can then decide how to combine your concrete most efficiently.
Reporting of Quantities
Reports allow you to view, use, and share information from the model. They use templates that dictate the format of information to be produced. Reports provide a fast and consistent way to quantify or review the objects in the model. If users are new to reporting in Tekla Structures, first refer to the following resources before continuing with the rest of this section:
- See the Reporting & Documentation found in Section 3. Tekla Learning and Resources on the US Contractor: User Resources page.
- Video: Creating reports
- Video: Types of reports
- Video: Reporting quantities
Additionally, this section provides technical details on how report templates achieve their results. If you are new to Tekla Structures, this information may seem targeted for an intermediate to advanced skill level. In time, as you become more proficient with the software, these concepts will come more into focus. For the time being, focus on understanding what the output of the report is so you can align your expectations with the results.
The Report Contents
As mentioned in the introduction, two reports are available with concrete quantity takeoffs specifically in mind. They are 310 CIP Takeoff - by Phase and 310 CIP Takeoff - By Hierarchy, which produce a Microsoft Excel-based report and can be found in the Report Tool found on the Drawing and Reports Ribbon.
These are two versions of the same report that break down the model data either by building hierarchy or by phase, as explained in the previous Major Considerations section of this article. However aside from the difference in report breakdown, they provide the same information in the same manner.
Example Image 5
The report provides the following general blocks of information, refer to Example Image 5 for correlation.
- The Report Title and Header
The report title is static and can only be changed in the Template Editor. The Project Name and Project Number are populated by the fields of the same name found in the Tekla Menu → Project Properties. The date and time stamps are populated based on your Windows settings at the time the report is created.
- The Project Summary
The summary provides an overall view of the totals per level. The level is defined by phase or building hierarchy depending on which report is created and what you have established in your model. The last line provides a total of all levels, in the project or of what was selected before running the report. If no phases are added or a building hierarchy is established, the report outputs this section as follows:- 310 CIP Takeoff - by Phase places everything in the model on Phase 1.
- 310 CIP Takeoff - by Building Hierarchy provide a single line with the total quantity results listed as “PROJ-NAME” Summary, where “PROJ-NAME is replaced with anything populated in the Project Name field in the Project Properties.
The project summary provides the name of the level, the Top Elevation or Phase Name (depending on the report template), as well as the sum values for contact area, concrete volume, and rebar weight per level. Note that for rebar, you must the model using the rebar tools otherwise this field displays a zero value (”0.00”).
- Report Breakdown Section Start by Phase or Building Hierarchy
This section begins with the breakdown of each level reported. The header provides the same information reported in the Project Summary section above. The quantity information is then provided for the concrete object type (4) and any attached reinforcement (5). This repeats until all unique object types are reported and the section ends with a summary (6).
This breakdown of levels will repeat until all levels (entire model or only selected objects) have been reported. The report sorts the levels in ascending order. That means lowest to highest elevation for Building Hierarchy or sequentially for Phase starting with the lowest phase number (ex. 1, 2, 3, etc.).
- Concrete Information
Concrete objects are reported by Name and then material. Each combination of this will report as its block and the number of elements that meet that criteria will be listed as line items below and then summarized with a sub-total. Complete documentation on which attributes for each of the columns for this block can be found directly below under Concrete Information: Expanded.
- Rebar information per concrete element
If reinforcement has been modeled and is correctly attached to the concrete part/cast unit. the report parses out the reinforcement into two blocks: Straight Bar and Bent Bar. The provides the Grade, Size, Shape, Name, and Weight (lb) for each line as we as a subtotal. If no rebar has been modeled or is not attached, then the value will be zero (0.00). The bar is sorted by grade, then size in ascending order.
- Report Breakdown Section End w/ summary
This block provides a summary at the end of the breakdown section for ease of use. The same fields and calculations are used here as in the project summary at the beginning of the report.
Concrete Information: Expanded
Example Image 6
Refer to Example Image 6 for a correlation of the data fields and their descriptions.
- Mark
This field provides the Mark Number of the object. Assigning the mark number can be done in one of two ways:- By performing numbering via the Number tool found on the Drawings & Reports Ribbon.
- By populating the Design Group Mark field in the properties pane when selecting the concrete object.
The report will always report the Design Group Mark if it is populated, even if numbering has also been performed. If the design group mark is not populated the contents of the Cast Unit Mark will populate instead. If the number has not been performed and no value is in the design group mark, a generic mark placeholder is shown. The format of this placeholder is the cast unit prefix, the number 0, and a question mark in parentheses.
The attributes used in the report are CAST_UNIT_POS for the mark number generated by the numbering tool and DESIGN_GROUP_MARK for the field found in the properties pane for a concrete object. The report uses the following formula for the cast unit row in the template to report which value is based on the logic provided above:
- Profile
This field reports the profile used from the Profile Catalog. This includes basic dimensions populated in the Profile field for standard concrete shapes. For example, 24”X24” for a square column of D24 for a 24” diameter round column. The attribute used in the report is PROFILE. - Quantity (varies)
This quantity unit type varies by concrete object type and reflects industry standards when quantifying each respective type. Refer to Table A in Report Template Data for specific quantity data per element type. - Contact Area (sf)
The contact area varies by concrete object type and reflects industry standards when quantifying each respective type. Refer to Table B in Report Template Data for specific quantity data per element type. - Volume (cy)
Provides the sum volume of the concrete parts in cubic yards. Note that volumes removed by cuts to the concrete object are accounted for. - Rebar Weight (lb)
Provides the sum weight of rebar that is modeled and attached to the concrete parts in pounds. For more information on attaching rebar, see How Tekla Structures automatically attaches rebar set bars to concrete parts and Attach a reinforcement object to a concrete part.
Report Template Data
Table A: Quantity Data per Object Type
Function | Common Tool | Quantity | Unit | Attribute |
---|---|---|---|---|
FND Beam | Strip Footing
|
Length | lf | LENGTH |
Step Footing | Length | lf | WIDTH * | |
FND Pads | Number | ea | NUMBER | |
Beams | Beam | Length | lf | LENGTH |
Tie Beams | Beam | Length | lf | LENGTH |
Slab on Grade | Slab | Top Surface Area | sf | AREA_FORM_TOP_GLOBAL |
Elevated Slabs | Slab | Top Surface Area | sf | AREA_FORM_TOP_GLOBAL |
Columns | Column | Number | ea | NUMBER |
Tie Columns | Column | Number | ea | NUMBER |
Walls | Panel | Length | lf |
*Note: Step footings created with the Stepped Footing have the start and end points perpendicular to the strip footing. Reporting on LENGTH would give an incorrect result. WIDTH is used as it provides the length of the lateral side of the step concrete object. For this reason, this report also quantifies step footings independently from any other foundation element type.
Table B: Contact Area Calculation per Object Type
Object Type | Prefix | Contact Area Calculation |
---|---|---|
FND Beam | GB, SF |
Calculates both lateral sides: GetValue("AREA_PROJECTION_XY_NET")*2 |
Step Footing | ST |
Calculates both lateral sides: GetValue("AREA_PROJECTION_YZ_NET")*2 |
FND Pads | DP, F, FT, P, PC |
Calculates both lateral sides: GetValue("AREA_FORM_SIDE") |
Beams | B, CBL, HNC |
Calculates bottom and both lateral sides: GetValue("MAINPART.AREA_PROJECTION_XZ_NET") + (GetValue("MAINPART.AREA_PROJECTION_XY_NET")*2) |
Tie Beams | TB |
Calculates both lateral sides: GetValue("MAINPART.AREA_PROJECTION_XY_NET")*2 |
Slab on Grade | S |
Calculates all lateral sides: GetValue("AREA_FORM_SIDE_GLOBAL") |
Elevated Slabs | ES |
Calculates bottom and all lateral sides: GetValue("AREA_FORM_SIDE_GLOBAL") + GetValue("AREA_FORM_BOTTOM") |
Columns | C, CC |
Calculates all lateral sides: GetValue("AREA_FORM_SIDE_GLOBAL") |
Tie Columns | TC |
Calculates the two larger lateral sides: if (GetValue("AREA_PROJECTION_XY_NET")) >= GetValue("AREA_PROJECTION_XZ_NET") then |
Walls | W |
Calculates both lateral sides: GetValue("AREA_PROJECTION_XY_NET")*2 |
*Note: This tool is a component located in the Applications & Components side pane.
Additional Considerations
Unique Contact Area Conditions
Occasionally unique shapes of concrete or special conditions will require additional attention to obtain accurate contact area outside the reports. For shapes that require human input instead of the formulas outlined above, Tekla Structures can address them with the tool Form Face Creator. The Form Face creator can be downloaded from the Tekla Warehouse and then installed for each user. There are two versions of the tool, one for Parts and one for Pours. You may download both if you wish but for quantity takeoffs you will focus on using the one for Parts.
The Form Face Creator is a tool that can automatically apply an object type called a Surface to one or more faces of a concrete part. This can be done to one or multiple pieces of concrete at a time. The tool comes with several presets for common concrete conditions and users can provide labels for surfaces created, choose distinct colors for said surface, and define other settings as well.
It is recommended to use the presets provided as a starting point to ensure the name of the surface condition matches your requirements to ensure easy identification in reporting. The Form Face Creator tool’s functions and features are documented on our TUA: Form Face Creator (for parts) and also has a demonstration video.
If you have unique concrete shapes, verify the quantity on the report. If the contact area reported does not encompass all of the contact area required, the workflow is to utilize the Form Face Creator. Once you have applied the surfaces with the tool you can run the report 340 Form Face QTO or refer to the Organizer under the Surfaces category on the right. You can then adjust the output of your report as needed with the quantity from the Form Face QTO report.
Examples of conditions where the Form Face Creator is often used would be soffits or beams with unique cuts or singular concrete masses that have irregular or sloped geometry. Depending on the level of granularity of unique shapes you wish to define, the Form Face Creator should be considered during the quantification process. Please note that surfaces are a unique object type and are not included in concrete reports, such as the quantity reports discussed in this guide. Surfaces will need to be quantified independently.
Best Practices: Concrete Parts
Note: Any custom components or applications mentioned, are found under the “Concrete” header of the Applications & Components side pane in one of the sub-directories. You can also simply search for the name of the component at the top to find it.
General
- Use Direct Modification to update and edit objects. Direct Modification allows users to interact directly with the concrete shapes and properties of other object types. Using this feature can help reduce clicks and data input associated with changing objects via the properties pane alone.
- Ensure the Contextual Toolbar is visible, especially when using Direct Modification. It provides quick access to key attributes to adjust and modify objects you select.
- Utilize view extents, clip planes, and work area to minimize onscreen clutter or visible objects.
- Understand and apply filters to isolate objects in the view or during selection. Filtering is used throughout Tekla and using it, even on a basic level, can help expedite efficient use of the software. If you are unfamiliar with filters, a two-part video series is available on their use:
Beams
- The beam tool on the concrete ribbon provides additional beam types by clicking the dropdown under the icon. For beams that have corners or complex paths, utilize the Polybeam.
- If a beam is on an angle, you can use the grips with direct modification to drag one end up. You can also select one grip by clicking it and then move it with move linear for precise adjustments.
- The beam tool is often excellent at creating cutting parts for use with the Part cut command. This is most common in creating cuts through walls for openings.
- Fitting beam ends to other concrete parts can be accomplished by the Fit Part End tool on the Edit Ribbon. There is also the Fit beams and column component in the Applications and Components side pane.
Columns
- The column tool creates both rectangular and round columns. For a round column utilize the prefix D and the diameter of the column in the profile. Example: A profile of “D24” creates a 24” diameter round column.
- When creating columns ensure to adjust the top and bottom elevations in the under “position” in the properties pane. This will ensure it is at the correct location in space.
Embedments and Hardware
- The Embed Creator component is excellent for creating embed plates with anchorage.
- Anchor bolts can be modeled manually but several components create accurate anchorage quickly. Use the search term “anchor” in the Applications & Components.
- To create a pipe sleeve in a wall or slab, model a steel beam perpendicular to the concrete. Use the profile catalog to select one of the Pipe profiles found under “Circular hollow sections”. Ensure to use the profile that best represents the sleeve.
- The pipe sleeve can be used as a cutting part to create a hole in a concrete part. the cut will be the entire diameter of the sleeve, not just its wall thickness.
Foundations
- Do not overlap continuous footings with pad footings as this will create inaccuracy in quantities.
- For large equipment pads or mats, use the Slab Tool instead of the pad footing tool.
Slabs and Flatwork
- You can create a simple slope on slabs by using a Part Corner Chamfer. You do so by selecting the handle at the corner of a slab. You can adjust the distance of the part from the top or bottom of the slab. Add a value to the Dz1 (top) and Dz2 (bottom) fields to execute.
- Consider using the Floor Layout Tool in the Concrete Ribbon to create slabs that contain several layers.
- Utilize the Concrete Stair Tool for creating cast-in-place stairs.
Step Footings
- By default, the Stepped Footing tool copies the properties of the first footing you select to input it and applies to the step itself. This can cause issues as the Step footings created with the Stepped Footing have the start and end points perpendicular to the strip footing. Reporting on LENGTH would give an incorrect result. WIDTH is used as it provides the length of the lateral side of the step concrete object. For this reason, the reports in this guide report quantify step footings independently from any other foundation element type.
- To create step footings, model the entire run of continuous footing first.
- Utilize the Spilt tool on the Edit Ribbon to separate the footing at the correct locations.
- Then use the Move Linear command to adjust each segment in elevation.
- Finally, utilize the Step Footing Tool in the Applications & Components side pane to connect each step. Double-click the tools icon to adjust the slope of the step.
- Utilize the following component preset to start applying step footings that will be itemized by the reports in this guide: Cip_Est_StepFtg.
Walls
- When working with walls and adding details, cuts, or embedments, it is best to work at an elevated view. You can open the view that is along that wall’s gridline so that you are looking at it in elevation.
- If you do not have a view that provides this you can create one by using the New View → Using Two Points command found on the View Ribbon.
- Consider using the Wall Layout Tool from the Panel drop-down on the Concrete Ribbon. This tool uses direct modification to make it easy to create sandwich walls or walls with steps. In addition, you can also easily add openings and seams to walls using the contextual toolbar.
- Make use of the Geometry Detailing Strip to add wall edge thickenings, recess patterns, wall corbels, mock joints, and facade protrusions.
Best Practices: Reinforcement
To quantify reinforcement, it must be modeled. The reports mentioned in this guide rely on the reinforcement objects to report the accurate weight and breakdown data for each concrete part. Without the reinforcement modeled, the rebar weight values will report as zero (0.00) and the rebar breakdown will not show.
When it comes to modeling rebar in Tekla, the first to understand is how important the concrete in your model is. Concrete acts as a container of sorts in which we will place the reinforcement. Users can leverage how the concrete is organized to report on or create drawings of reinforcement. The key takeaway from this should be that accurate concrete is the first step in modeling accurate rebar.
Rebar Modeling Method General Guidance
- Rebar components are ideal for the beginning stages of rebar modeling such as pre-construction, initial rebar placement, and Estimation.
- Rebar components may be limited in scope as they are designed to apply to a specific type of structure.
- Rebar components may require further editing outside the component. If manual edits are required, first explode the component before doing so.
- Rebar sets utilize concrete geometry to provide a general shape. Additional detail needs to be added by the user by applying modifiers. These modifications are located in a contextual ribbon after selecting a rebar set. They include end details, splitters, and so on.
- When working with Rebar Sets, ensure that Direct Modification is turned. You can find it to the left of the selection filter dropdown on the bottom selection type toolbar.
- Rebar Tutorials for rebar sets are available and can be found here: Tekla Structures Rebar Fundamentals.
Putting It All Together
The information in this guide speaks to considerations in modeling for quantity takeoff as well as how specific Tekla resources work. This section aims to do just that by elaborating on each step and tying it back to the topics above. The goal is to provide an overall understanding of how to apply the concepts above.
1. Establish the Model Organization and LOD for the model.
In this first step, you will create your new, blank model. Ensure to name it appropriately and save it at the correct location per your company’s standards. Here is where you take the time to define the project information found in the File → Project Properties menu. Additionally, you will want to modify the default grid or create a new one so it reflects the project to be modeled. You will also want to review the Model Options and make sure that they reflect your project's needs.
Models created with the CIP-Rebar Detailing Template should be adequate for most users. If you have your model template, these options should be inline with your company's needs but it is good practice to review them nonetheless before getting started. For example, the Rebar Set settings for default clear cover thickness is something that may need to be adjusted on a project-by-project basis, if you intend to model the rebar for the upcoming project.
The next key step is directly from the previous section Major Considerations. Here you will decide how you will organize your model. This will be done using either Phases or the Building Hierarchy and therefore will dictate which report template you will utilize for your quantity takeoff. You will also need to choose the level of development (LOD) you will be modeling for.
Remember that this helps establish consistency in your model and therefore your quantity results. Make sure that this information is effectively communicated to any team members who may be contributing to the modeling effort.
A note on sharing the modeling effort.
If you intend to share the modeling tasks with another team member, you will want to share the model using Tekla Model Sharing. By doing so you will create the initial baseline for your shared model. Working with Tekla Model Sharing can speed up the model creation process. Ensure that all team members who are contributing are invited with Editing permissions.
If splitting the workload amongst two or more team members, it is a good practice to come up with a division of responsibility for your modeling efforts. That is to say who will be modeling what parts of the project? You can divide this how you see fit, such as by level, elevation, or commodity type (concrete vs. rebar). The important part is to define the responsibilities of each member contributing to avoid duplicate work efforts and wasted time. For additional best practices using model sharing, see our article Best practices in Tekla Model Sharing.
2. Model the concrete shapes to create the structure.
When beginning your modeling efforts, make sure to keep in mind the advice given in the section Approaches to Modeling CIP Concrete. This guide promotes modeling as you construct and only model a portion of the model to completion before moving on to the next. If you are using model sharing, areas or levels of the project can be modeled by team members in tandem.
The specifics of modeling concrete for a given project are often unique to that project, so it is difficult to give step-by-step processes. Generally speaking, when modeling concrete you do so by creating Parts. Depending on the tool used the input method for a part may be different. For a pad footing or column, it is a single click. Beams and walls need two or more points to form a path. Slabs are created by tracing the boundary. Further properties of a part are specified in the properties pane. This includes the profile or dimensions of the concrete part as well as its material and position. Refer to the section Additional Considerations above. There are tips and tricks for most concrete shape/element types that can provide some assistance or guidance on adding these elements to your model.
A note on using references in the modeling process.
References can be extremely useful in creating models and speeding up your process. References come in two general types: 2D and 3D. Two-dimensional references are usually documents such as vector PDFs or .dwg files. These can be inserted into Tekla and used as an overlay to snap to while creating objects. Although 2D references will not create the model for you, having them present reduces the time to transpose what is in the document into a model.
3D references are most commonly in the form of an IFC file. This is a software-agnostic BIM format that can be produced and viewed by various authoring software, such as Tekla Structures. IFC files may contain information and geometry for concrete, structural steel, MEP, and much more. If you are provided an IFC, you can reference these into Tekla Structures to account for during your modeling process. Having pipe runs and HVAC present can ensure the concrete geometry you create is accurate, providing more reliable quantities. On occasion, you may be provided an IFC file with the concrete already modeled. You can review the quantity information of the IFC right in Tekla’s Organizer or even convert it to native Tekla objects and then use it with one of the 310 CIP Quantity Takeoff reports.
Remember to trust but verify any external references provided to you. Spot-checking and reviewing the accuracy of these documents and files and correcting errors you find. If not done, you are adopting the errors of the previous model author and compromising the accuracy of your takeoff.
For more information on working with 2D references, see Working with PDF References. For tips regarding IFC files and converting them, refer to Introduction to Working with IFC Files and Converting Existing Geometries.
3. Model the reinforcement (if applicable).
Tekla users who focus on cast-in-place concrete vary on whether they model the reinforcement. This is usually dependent on their companies’ capabilities, services they offer, as well as project scope and responsibility. Therefore when it comes to quantity takeoffs, modeling the reinforcement is done on a company-by-company basis. For those who wish to quantify the reinforcement, they will need to model it. This is done after the concrete shapes have been created.
Rebar can be placed and configured through a couple of different methods in Tekla structures. The most effective way to model rebar would be the tools found in the Rebar Ribbon. These tools give users the fidelity to model an entire structure efficiently. The tools first conform the bar's general shape to the concrete. Then the detail is added to finalize the configuration. These details include end conditions, splicing, cranking, or couplers.
Another method would be to take advantage of the rebar components in our Application & Components side pane. These components are geared towards specific purposes or concrete shapes. There are specific tools for columns, beams, continuous footings, openings, and additional bars. These components intend to take the manual application of the rebar tools out of the equation. Instead, use the dialog box to assist in defining the configuration. Albeit sacrificing a little control over speed.
Both methods are viable and provide a vast toolbox for modeling reinforcement. With that said, it is recommended that users learn the tools in the ribbon first. Or at the very least in tandem with using other rebar components. The reason for this is that the components use the rebar tools and apply them via dialog boxes. Understanding how the rebar tools work also provides an understanding of how the components work. So it is beneficial for users to start with the rebar tools when learning to model reinforcement.
4. Repeat for each section/area/elevation of the structure.
Approaching your modeling tasks systematically provides users with the ability to keep a limited scope that can be verified before moving on. When creating BIM models, errors made in the early stages of the modeling process can have trickling effects as the model is further developed. It is for this reason that it is recommended to model your project in stages. This can be aligned with your Project/Model Organization structure. It can also be further divided to keep modeling tasks and scopes more manageable.
The idea is that this article's guidance is a process that can be applied to each section of your project as you continue modeling, as well as the project as a whole. The 5 steps in the QTO General Process would be applied to first the foundations, then any basement structural elements, then the first-floor elevation, and so on until the structure is complete. Note that you do not have to run the quantity report at each section you complete, though you can aid in verifying that things look correct from a quantity standpoint as well as a model visual standpoint.
Inserting checks and balances in your modeling process, whether for quantity takeoff or full detailing, is the best practice for creating and utilizing BIM.
5. Run the quantity report as required.
The benefit of creating a model for quantity takeoff is the ability to report on a model's information accurately and quickly. Reporting can be done at any stage of the model process. The two reports for quantity takeoff output to Microsoft Excel and by default are saved to the model folder. Each time the report is run, the user is asked if they wish to overwrite this file. You can also choose to save these report outputs at another location, giving them a unique name if it is required to keep records or traceability.
The report will be up to date on the current state of the model at the time it was created. This is also dependent if the report is run on the entire model or just selected objects. It is encouraged to use the reporting feature as your model to verify your progress. Tips and best practices for reporting can be found on our US Contractor: User Resources page, under Section 3. Tekla Resources & Learning. As a reminder, the following two reports are intended to be used with this guide. Note that other report templates that provide quantities will not provide the contact area data.
- 310 CIP Takeoff - by Phase
- 310 CIP Takeoff - by Building Hierarchy
It should be mentioned that the above report templates are there to facilitate modeling for quantity takeoff immediately after installing the software and proceeding through an applicable learning path. Any report template provided with Tekla Structures can be modified and changed via the template editor. Often companies using Tekla for QTO or a variety of tasks customize existing templates to further suit their needs or create new ones for other purposes.
Doing so is a task that requires an intermediate skill level with Tekla Structures. We do offer resources on using and customizing reports and other kinds of templates. Hyperlinks to these resources can be found directly on our US Contractor: User Resources page, under Section 3. Tekla Resources & Learning.