Paper presented in IABSE 2008 in Chicago

1. BIM and advanced post-tensioning design methods
Jyrki JAUHIAINEN Jyrki Jauhiainen, born 1973,
Head of Department, received his civil engineering
Advanced Concrete Space for a degree from the University of
Structures Oulu, Finland.
portrait
Civil Engineer , M.Sc. 32 x 48 mm
Finnmap Consulting Oy
Helsinki, Finland
Jyrki.Jauhiainen@finnmapcons.fi
Summary
The goal of this paper is to describe one process for developing advanced design techniques for
post-tensioned concrete structures. The integration between finite element calculation softwares and
different 3D modelling softwares has become more and more important in everyday engineering
work. The design of the post-tensioned structures has been a well specialized field in construction
business. Different 3D and FEM programmes have been developed in order to enhance the
effectiveness of design process. Yet, no practical solution for BIM and post-tension design has been
presented. The methods and results of BIM; its advantages, problems encountered, solutions and
future prospects will be presented in this paper. The author presents observations gathered during
this hectic development process.
Keywords: post-tensioning; anchors; slabs; beams; BIM; FEM; advanced design methods; VBC
1. Introduction
All data needed for the design, construction, use and maintenance of buildings is easier to manage –
quickly, in real time, graphically and in digital form – when using the help of a product model.
With the help of the product model you can exchange and manage a huge quantity of information
more reliably and efficiently than before.
The design of post-tensioned concrete structures is a specialized field in construction business.
Structural engineer provides the calculations while draftsmen are preparing drawings and site
personnel are executing the actual work. As a result of this, customer will receive durable and good
product, concrete structure by means of reliable and cost-effective plans as well as state of the art
site production. The increasing use of BIM technology has forced us to take a closer look on this
procedure as a whole, how to maximize the effectiveness and how to minimize errors and miss-
information. And of most importance, how to maximize the benefits for our customer.
Linking the design and drafting capabilities of various software gives the engineer a completely
new set of tools. The design process can be accessed in each phase and the iterative nature of
prestressed structure design will show its strength.

2. 2. Requirements
After earlier mentioned input data processing, the
engineer has normally conducted structural
calculations manually or by using in-house
developed spreadsheets. If results were shown to
be not satisfying, the input data had to be
modified.[1] In our project we wanted to enhance
the effectiveness of this phase. Post-tensioning
calculation is an iterative process and by
combining the experience of the engineer with
computer calculation power, iteration can be
made faster and more effective. Our idea was to
create/write a link between input source, static
software and BIM environment so that all
information could be transferred as automatically
as possible and yet the engineer would have
possibilities to intervene and control the process.
One crucial point for us was of course that this
Fig 1 Created data link between BIM and FEM data transfer should work in both directions, a bi-
directional data transfer. Of an importance was to
notice that if changes in dimensions occurred,
these also needed to be included directly in BIM environment.[2] Accordingly also update in input
data source had to be done.
3. Discussion, Conclusions and Acknowledgements
This developed new tool and way of working has already proven its effectiveness in everyday
design work. Both time consumption and numbers of design errors have been decreased. The
quality of design has improved. It enables faster information flow from designer to draftsmen or
modeller and it also opens possibilities for further development within BIM.
Virtual building concept
In the future the VBC Virtual Building Concept will become an everyday issue for engineers.[3]
The tools developed will offer a powerful way to implement also post-tensioned structures as a vital
part of the whole construction process. VBC model can also contain information of structures life-
cycle design. Tendons can be measured after laying them on site and this information can be stored
in the model and used later for repairs or new openings etc. The VBC can work as data storage for
everybody involved in the project, including future users.
4. References
[1] AALAMI, BIJAN, Guidelines for the design of Post-tensioned Floors, Concrete International,
March 2003
[2] CHUCK EASTMAN, PAUL TEICHOLZ, RAFAEL SACKS, KATHLEEN LISTON BIM
Handbook: A Guide to Building Information Modeling for Owners, Managers, Designers,
Engineers and Contractors, 2008
[3] CONFEDERATION OF FINNISH CONSTRUCTION INDUSTRIES, ProIt, Product Model
Data in the Construction Business, 2006

3. BIM and advanced post-tensioning design methods
Jyrki JAUHIAINEN Jyrki Jauhiainen, born 1973,
Head of Department, received his civil engineering
Advanced Concrete degree from the University of
Structures
Space for a Oulu, Finland.
Civil Engineer , M.Sc. portrait
Finnmap Consulting Oy 32 x 48 mm
Helsinki, Finland
Jyrki.Jauhiainen@finnmapcons.fi
Summary
The goal of this paper is to describe one process for developing advanced design techniques for
post-tensioned concrete structures. The integration between finite element calculation softwares and
different 3D modelling softwares has become more and more important in everyday engineering
work. The design of the post-tensioned structures has been a well specialized field in construction
business. Different 3D and FEM programmes have been developed in order to enhance the
effectiveness of design process. Yet, no practical solution for BIM and post-tension design has been
presented. The methods and results of BIM; its advantages, problems encountered, solutions and
future prospects will be presented in this paper. The author presents observations gathered during
this hectic development process.
Keywords: post-tensioning; anchors; slabs; beams; BIM; FEM; advanced design methods; VBC
1. Introduction
All data needed for the design, construction, use and maintenance of buildings is easier to manage –
quickly, in real time, graphically and in digital form – when using the help of a product model.
With the help of the product model you can exchange and manage a huge quantity of information
more reliably and efficiently than before.
The design of post-tensioned concrete structures is a specialized field in construction business.
Structural engineer provides the calculations while draftsmen are preparing drawings and site
personnel are executing the actual work. As a result of this, customer will receive durable and good
product, concrete structure by means of reliable and cost-effective plans as well as state of the art
site production. The increasing use of BIM technology has forced us to take a closer look on this
procedure as a whole, how to maximize the effectiveness and how to minimize errors and miss-
information. And of most importance, how to maximize the benefits for our customer.
Traditionally more advanced calculation methods have been considered to be separate software
from drafting tools. Like various FEM tools and CAD based drafting tools. But we wanted to find
out a way to link FEM programmes with our modelling tools and make this link usable for group of
programmes, not just one particular.
Linking the design and drafting capabilities of various software gives the engineer a completely
new set of tools. The design process can be accessed in each phase and the iterative nature of
prestressed structure design will show its strength. As shown on Figure 1. The BIM design path can
be edited or accessed in various phases.

4. INPUT DATA
STRUCTURAL
CALCULATION
DRAFTING BIM
CAD 3D
OUTPUT OUTPUT
DRAWINGS, LISTS DRAWINGS, LISTS, MODEL
Fig. 1: PT design workflow
Product model-based data management in a construction project connects the information needed
for design, product manufacturing, construction, and the use and maintenance of the building.
Product modelling transforms building design from traditional line-drawing to 3-D design
combined with other product information. Design is done with the help of product structures and
components. The spatial model contains information about the spaces, their location, area, and other
desired characteristics of the spaces. Product structures such as walls and slabs contain information
about, for example, materials, measurements, thermal insulation, strength and environmental
qualities. When the schedules are linked with product structures, the result is 4-D design.
b) More automated data transfer through manual editing in Excel etc. The results are taken
automatically from FEM programme and post-processed in Excel. The tendon coordinates are then
manually transferred to BIM software.
c) Fully automated data processing between calculation and modelling software, editing is done in
BIM environment. This involves the use of tender model as a source of input for calculation. All
editing is done either in FEM environment or in BIM environment. The connection works in both
directions.
After carefully examining these alternatives, we decided to go further with the alternative c. It is
most advantageous and completes our needs for BIM. It will also produce most added value for the
project and for the customer.
2.2 Requirements
Basically post-tensioning projects consist of few major parts [1]. Fist can be described as input data
processing. Engineer traditionally receives input data – developed by means of CAD- or pdf-file -
for calculation from client or other designer. The engineer uses this information stated in these
documents as the basis for ones calculations and takes into account also other design requirements.
Now, however, we desired to use geometrical model, modelled already at tender phase of the
project as input data source. This geometrical data could include also loading, material information
etc, vital information for PT designs.

5. 0.6
f ( x) 0.3
0
0 0.15 0.3
x
2
f ( x) := a a22⋅ x + b 2⋅ x + c2
0.4
f ( x)
0.2
0
2 4 6 8
x
2
f ( x) := aa33⋅ x + b 3⋅ x + c 3
0.4
f ( x)
0.2
0
10 12 14 16
x
Fig. 2: Yesterday: Manual calculation by Excel or MathCAD sheets
After earlier mentioned input data processing, the
engineer has normally conducted structural
calculations manually or by using in-house
developed spreadsheets. If results were shown to
be not satisfying, the input data had to be
modified. In our project we wanted to enhance
the effectiveness of this phase. Post-tensioning
calculation is an iterative process and by
combining the experience of the engineer with
computer calculation power, iteration can be
made faster and more effective. Our idea was to
create/write a link between input source, static
software and BIM environment so that all
information could be transferred as automatically
as possible and yet the engineer would have
possibilities to intervene and control the process.
One crucial point for us was of course that this
Fig 3 Created data link between BIM and FEM data transfer should work in both directions, a bi-
directional data transfer. Of an importance was to
notice that if changes in dimensions occurred,
these also needed to be included directly in BIM environment. Accordingly also update in input
data source had to be done.
The programme we wrote automatically reads the needed tendon information from calculation
software. After this, the engineer can define anchors and required reinforcement etc. The BIM
software will model the tendons with designed heights and other parameters. The modelled tendon
will have some user defined parameters such as elongation, tendon ID, material features. This
information can be used to produce traditional tendon lists with elongations and all the information
needed for the quantity engineer and for the site traditionally or Virtual Building Concept, the site

6. and manufacturer can obtain this information automatically.
Fig. 4: Geometrical model
3. Problems encountered
3.1 Software
The development of an in-house, non-commercial solution faces many problems. First and not least
is the programmes capability to communicate with other types of programmes. Application
Programming Interfaces (API) enables, if released for users, writing codes to switch information.
Our requirements were naturally to transfer adequate amount of tendon and geometrical information
from calculation software to the used BIM software. To meet our demand, we had to develop as
open system as possible to be able to use various programmes, and not to limit only one software
provider. [2]
However, we encountered some problems, described below. Some programmes are partly not ready
yet for use. They are still in beta-testing phase or there simply is no suitable software available. The
use of these programmes can be more challenging than normal CAD based programmes. The user
interface might be unfamiliar and new. Cost for software licences can be substantial. More
advanced FEM programmes, which can handle tendon design to some level, are expensive. The
choice of programme for structural engineer is limited at least for now. At some special areas,
traditional 2D design can still prove to be more efficient, not forgetting paper and pencil. Quality
printouts may be a problem if not taken into account. Resources must be focused more in the
beginning of the projects. This is very important point and to be considered by all parties involved
in the project. Although these obstacles created a problem, we did find a way to overcome these.
The application interface should be kept as simple as possible and yet it should provide to engineer
adequate level of control of the data transfer procedure.
4. Benefits
4.1 Designer
The use of advanced BIM tools both in design and calculation operations can greatly decrease
errors made by design team by allowing the use of conflict detection where the computer actually
informs team members about parts of the building in conflict or clashing, and through detailed

7. computer visualization of each part in relation to the total building [3]. It improves design, avoids
spatial interferences, and reduces RFIs (requests for information). The new tools also make design
work faster and more cost effective. The information which designing engineer creates with various
calculation software can now easily and error free manner be transferred for modellers use. Enhance
and speed up design by generating more precise information and by reducing design errors, by
improving the plans compatibility and by promoting collaboration between various designers. Total
execution time for whole project will actualize only after all parties have implemented BIM
techniques and test period has been successful. For smaller only PT projects and for PT parts of
larger projects, this technique is already a powerful tool.
4.2 Customer
The benefits for customer are following:
Of most importance is that total time used for design can be decreased when all parties use the same
model - BIM – simultaneously. One other big benefit refers to BIM requiring update of information
for all parties; the information will in this way always be accurate. Customer service will be
improved by generating useful information to support decision-making and by visualizing and
comparing alternatives functionally and in terms of costs. The cross-checking of designs is easy and
fast, mistakes can located easily; model check. The complexity and challenging features of the
project can be easily visualized, efficiency in tender phase.
Fig. 5: Present information flow Fig. 6: Future information flow
The flexibility of designs will be enhanced and documents will be updated automatically. The
control of design information in large projects can be optimized. Using BIM will give the
competitive advantage and time schedule in 4D. The whole construction sequence can be modelled
and material flows can easily be controlled. Overall information flow will be better.
4.3 Site
From the sites point of view, modelling offers some clear advantages and of course in the future
even more possibilities. It enables the transfer to completely paperless site. The site personnel can
quickly check directly from the model all the information needed to execute their work.

8. Fig. 7: Connecting design with execution
All geometrical data can be transferred directly from the model without any manual editing.
Material lists and structural dimensions can be produced automatically. And in the model all
reinforcement is shown in 3D as it would appear on site and collision risks can be detected and
avoided in time. This will save time and costs on site. To improve construction work quality and
productivity by generating more practically usable information for production planning, cost
management and scheduling, and the manufacture and procurement of building products are also
our goals. This technique also - if not guarantees - but makes it easier to check HVAC and other
installations before noticing costly collision with structures on site.
Fig. 8: Tendon plan (CAD) Fig. 9: Finite element model, tendons (FEM)
5. Discussion, Conclusions and Acknowledgements
This developed new tool and way of working has already proven its effectiveness in everyday
design work. Both time consumption and numbers of design errors have been decreased. The

9. quality of design has improved. It enables faster information flow from designer to draftsmen or
modeller and it also opens possibilities for further development within BIM.
The site and customer can also take a closer look on model in earlier stage and procurement can be
started in earlier stage. Demanding structures can be visible to all parties of the project and all have
access to same information.
Virtual building concept
In the future the VBC Virtual Building Concept will become an everyday issue for engineers. The
tools developed will offer a powerful way to implement also post-tensioned structures as a vital part
of the whole construction process. VBC model can also contain information of structures life-cycle
design. Tendons can be measured after laying them on site and this information can be stored in the
model and used later for repairs or new openings etc. The VBC can work as data storage for
everybody involved in the project, including future users.
6. References
[1] AALAMI, BIJAN, Guidelines for the design of Post-tensioned Floors, Concrete International,
March 2003
[2] CHUCK EASTMAN, PAUL TEICHOLZ, RAFAEL SACKS, KATHLEEN LISTON BIM
Handbook: A Guide to Building Information Modeling for Owners, Managers, Designers,
Engineers and Contractors, 2008
[3] CONFEDERATION OF FINNISH CONSTRUCTION INDUSTRIES, ProIt, Product Model
Data in the Construction Business, 2006