General Workflow Bridge Design

Project Work - Step by Step

The general workflow sequence inside SOFiSTiK using SSD and SOFiPLUS is recommended as follows:

  • Prepare all project data for input into the software
  • Create a new SSD project file
    • Define project name
    • Select design code
    • Select system
  • Define materials
  • Define standard cross sections
  • Define prestressing systems
  • System and load generation within SOFiPLUS
    • Define a bridge axis
      • Define horizontal alignment
      • Define vertical alignment
      • Define placements
      • Define secondary axis if necessary
      • Define variables for cross sections
    • Define bridge cross sections with the Cross Section Editor inside SOFiPLUS
    • Define bridge geometry using the predefined axis geometry
    • Define tendon geometry and tendons
    • Define actions and load cases with Loadcase Manager
    • Define all loads such as additional dead weight, settlement and temperature loads
    • Mesh system
  • Linear Analysis of already defined loads
  • Generate envelopes from traffic loads with SSD Task “Traffic Loader”
  • Define construction stages and start automatic analysis within CSM
  • Define combinations and superpositions with CSM DESI
    • Intermediate Superpositioning (all variable actions/ loadcases) of inner forces related to the total cross section (final stage).
    • Final-Superpositioning (Dead load, superimposed dead load, prestress, creep&shrinkage&relaxation, envelopes of variable loads) of inner forces related to the partial cross sections.
  • Design Code Checks * ULS Design for required reinforcement, bearing capacity calculation and other ultimate cases. * SLS Design: Serviceability checks (fibre stress checks, crack width check, displacements of the structure, fatigue, dynamics etc.)
  • Generate Report
  • Save project files

For practical examples and further information about the detailed input please see the available bridge tutorials.

Start New SSD Project

To start a new project please open the SSD and go to menu “File” > “New Project”. Now the “System Information” dialogue opens. Please define project title, project name and project directory first.


We recommend to use a local directory for your project files to speed up communication between program and data base. Later on you can zip and save your project data on a company server.


Now select the code. First select the country flag and then the code. In case you like to use the pure Eurocode without any national annex use the European flag. For further Information about available design checks please read the manuals AQB and BEMESS chapter NORM.



If you leave the “System Information” dialogue with “OK” the selected country code is fixed and saved inside the data base. You may NOT change the code later on.

With the orientation of the dead load you define the global coordinate system. We are using a red arrow for the x-direction, a green arrow for the y-direction and a blue arrow for the z-direction. These colours will be used in all our program modules.

Working with SOFiPLUS you have two major options:
  • working with structural elements (automatic mesh generation)
  • working with finite elements (manual meshing)


You must select one option to generate your system. A mix of both methods is not allowed in the graphical input, but can be done with script language inside TEDDY.


If you leave the “System Information” dialogue with “OK” the global coordinate direction is fixed and saved inside the data base. You may NOT change the direction later on.


For bridge design we recommend to use a 3d system.

Material Definition

Inside the SSD task-tree the task “Materials” is one of the default settings.


Simply use the right mouse click function to generate as many new materials as necessary.



In case you have different construction stages in your cross section (e.g. composite section), it is necessary to define separate materials for every stage even if the material properties are the same for both parts.


Extra material constants may be defined for any type of material (AQUA:MEXT record). Please refer to AQUA manual for more details:


Cross Section Definition

Inside the SSD task-tree the task “Cross Sections” is one of the default settings.

../../_images/cross-section_tree.png ../../_images/cross-section-add.png

Few options are available:

  • Cross-section-values
  • Plate
  • Rectangle
  • T-Beam section
  • Circle / annular section
  • Tube
  • Cable section
  • Rolled steel


Simply use the right mouse click function to generate as many standard cross sections as necessary. Specific bridge cross sections will be generated later via SOFiPLUS - Cross Section Editor.


Prestressing System

Please add a new SSD-task “Prestressing Systems” to your project. With a right mouse click on this task you open the context menu. Select the option “New” and generate a new prestressing system. You may select one of several system out of the available library.


Alternatively it is possible to use self defined prestressing systems. In that case create a new prestressing system and select “User defined”.


System Generation within SOFiPLUS

Open SOFiPLUS from the SSD task “SOFiPLUS(-X) GUI Model creation”.


It may be useful to collect and write down all necessary project data before starting with the system generation. E.g.:

  • bridge geometry information including axes information
  • cross section geometry
  • construction sequence including influence on cross sections and bridge structure
  • concept for element group numbering. All elements such as beams, quads, springs, couplings are organised in groups.

Inside the SOFiPLUS window all necessary commands are organised in a Sidebar on the left side. Tab “System” repeats the options from SSD to define materials, cross sections and prestressing systems. You also find the command to define new geometric axes.


Define Bridge Axis

First we define a new bridge axis. Go to sidebar > tab “System” and use the right mouse click on the command “Geometric Axes”. From the possible commands we use the option “New Axis..”.


Now define a new name for your axis.


There are only 4 letters and/or numbers allowed for the axis name.


Confirm the name with “OK” and you will get into the first dialogue, where you define the horizontal alignment of the new bridge axis. Most important is to understand the concept of stations along the axis. Just imagine you start walking along the axis for 15.0 m and you started at station 10.0 m. Now you stop at station 25.0 m = 10.0 +15.0 m . For further description please see the SOFiPLUS manual.



We recommend to define your axis longer than your real bridge length. Usually an extension of 10.0 m at the beginning and > 10.0 m at the end of the bridge is sufficient. This is necessary to add bridge elements later on, because you are not allowed to use negative station values.

After the horizontal alignment you define the vertical alignment. Usually you can use the information from the bridge layout drawing.


A very important option is to define variables along the bridge axis. These variables can be used for the cross sections generation later on. The idea is to define a master cross section with all necessary variables inside. During the meshing process the program will use cross section and variable information to generate all necessary interpolated cross sections for the final finite element mesh.


You are not allowed to use variable for material numbers inside the cross section. It is also not possible to use variables for the area of longitudinal reinforcement along the bridge axis.


A next important step is to define placements along the bridge axis. Placements represent special points along the bridge axis to define supports, construction points, beginning and end of a bridge structure. We will use these placements later on for an easy and fast system generation with structural lines and structural areas. They are also very important for the influence line evaluation later on. Support placements will be used together with the cross members editor later on to generate support elements and align them automatically with the placements and the axis.


The last setting during the axis generation is the option to define secondary axes. Secondary axes can be used for grid structures to define the positions of multiple beams parallel to the bridge axis, or also for shell bridges to define the boundary of the bridge including the position where the shell thickness changes.


At the moment the secondary axis are always parallel to the main bridge axis. It is only possible to define a constant offset in y and z direction.


Define Cross Sections

Besides the standard cross sections, we already defined inside the SSD, we will now define more complex bridge cross sections. This will be done within the Cross Section Editor inside SOFiPLUS. First go to the “System” tab and use the right mouse click on “Cross Sections” . We want to define a new solid cross section for reinforced concrete.


Define Bridge Geometry

Whether you will use beam or shell elements, defining the bridge geometry follows the same principles based on an existing bridge axis. Go to the tab “Structural Elements” and select a command “Line” or “Area”. Use the right mouse click to open the context menu and select the command “SEGment on geometric axis”. Now click on the axis in your drawing area. The next context menu opens. Select the command “Between all placements”. The program will automatically generate structural elements between all predefined placements.

../../_images/segment-on-axis.png ../../_images/between-all-placements.png

For more detailed information please see the different bridge tutorials.

Define Tendons

The tendon geometry and the tendons will be defined graphically inside SOFiPLUS. There are two general options to define tendons inside SOFiPLUS.

  • with “PT Editor” based on bridge axis
  • with “Tendon (Draw)” command based on existing AutoCAD spline or line objects.


In case you do have multiple beams you should use secondary axes to define the beam elements and also to define the tendon geometry.

For new bridges the “PT Editor” is the most useful command, we recommend to use. Simply go to the sidebar tab “Prestressing” and select the command “PT Editor (Developed Geometry)”. Please be careful according to the elements you are using inside your system. In case of beam elements you must use the command below the title “Beam PT: Create and Modify”.


In the next step you must select a geometric axis as a reference.


Inside the upcoming dialogue all settings for the tendon geometry and the tendons are defined according to the selected bridge axis. The general principle is to define one tendon geometry and use this geometry to define multiple tendons if necessary with different start and end stations for every single tendon. The tendon geometry is a spatial spline defined by several Geometry Points. Inside the table of Geometry Points you may edit every setting. Alternatively you may select multiple points and change the settings of all selected points inside the Properties field.


Clicking on the “Edit Tendons” button you get into the Tendon definition dialogue. The first tendon is already set inside the table. With the button “Draw Tendon” you may define new tendons with variable start and end stations. Important is to define a load case for the static determinant tendon forces and moments. Usually we recommend to have the necessary loadcases defined before you start defining the tendons. Nevertheless it is also possible to generate a new load case right from this dialogue. In case you define a load case (LC0) the static determinate forces and moments are saved separately inside this load case. Usually this input is not necessary. The CSM procedure described later will automatically take care of the two parts of the prestressing forces and moments.


After defining all tendons you see a list of all tendons in the sidebar. In case you want to define new tendons, which are parallel to your already defined tendons, you should use a command “Clone...” from the context menu. Simply use the right mouse click on one of your tendons. The cloned tendons have a fixed offset in y- and z-direction related to the connected bridge axis.

../../_images/tendon-07.png ../../_images/tendon-05.png

In case you want to edit the tendon properties simply double click on the tendons listed in the sidebar.


Editing the cloned tendon geometry is not possible.

Now the tendon generation process is finished.

Define Actions and Load Cases

Before defining any loads it is necessary to define actions and loadcases. This is done with the “Loadcase Manager”. Simply go to tab “Loads” and click on “Loadcase Manager” We recommend the following list of actions. All these actions are defined inside SOFiPLUS > Loadcase Manager tab “Actions”.

Description Action PART SUPP
Self weight G_1 G PERM always
Additional Dead load G_2 G PERM always
Temperature T Q EXCL exclusive
Settlement F Q COND conditional
Traffic load TS L_T Q_1 Load Group 1 EXCL exclusive
Traffic loads UDL L_U Q_1 Load Group 1 EXCL exclusive
Prestressing P P PERM always


Action for Creep and Shrinkage will be defined later on inside the construction stage manager CSM

We recommend the following list of load cases. All these load cases are defined inside SOFiPLUS > Loadcase Manager tab “Loadcases”.

Basic Loads

LC Number Description Action
1 self-weight structure NONE
2 additional dead load (e.g asphalt) NONE
51-5X settlement in in every support axis, e.g. 10 mm F
81-82 uniform temperature load NONE
83-84 temperature difference NONE
91-98 temperature combinations delta TN + wm*delta TM and wn*delta TN + delta TM T


  • The loadcases 1 and 2, self weight and additional dead load, will be used later on inside the construction stage manager (CSM). Processing the construction stages the load cases will be connected automatically to the corresponding action types. Connecting LC 1 and 2 to action “NONE” will secure, that they will not be used twice in manually defined combination later on.
  • According to the code a combination of temperature loads is necessary. This will be done in a separate user task .

Traffic Loads

LC Number Description Action
120x load train e.g. LM1 with 300 kN axle load NONE
2xx envelope from “Traffic Loader”, TS Load Group 1 L_T
3xx envelope from “Traffic Loader”, UDL Load Group 1 L_U

Define Loads

Defining loads you may follow two general principles:

  • Element Loads
  • Free Loads

Element loads are directly related to a structural point, line or area. In case the geometric properties of these elements changes, the load changes as well. As we are defining our bridge system according to a bridge axis we also want our loads to follow the axis in case we change the axis parameters of our bridge. For that reason we recommend to use “Element Loads” for bridge design.

The “Free Loads” are based on the geometric input. Later on during the meshing process the loads will be connected to existing elements. In case no element can be found also no loads will be applied.


If any load is not fully applied to the elements, there will be a warning:


Mesh System

To start the meshing process click on the export button on top left of the sidebar.


The export dialogue contains two tabs: “Common” and “Text Output”. Usually the default settings are sufficient and you simply click “OK” to start the automatic mesh generation. The settings inside the tab “Text Output” control the amount of output. The standard rule in SOFiSTiK is, that the maximum amount of output is based on the settings before any calculation. Later on it is possible to reduce (or increase again) the existing output in Reportbrowser. But you cannot increase a non-existing output without a new calculation.

../../_images/sofp-export-01.png ../../_images/sofp-export-02.png

Now the input is finished and we can go back to the SSD window. Usually you may close the SOFiPLUS window.

Linear Analysis

Before we start analysing all existing load cases, we have to create combined temperature loads.

Combination of Temperature Loads

Temperature loads will be combined according the requirement of the code later on in the SSD project with a task “User Text”, because this is very easy to do numerically.

The input sequence is printed below:

+prog sofiload
head Temperature Load Combinations

LC 91 TYPE T TITL 'T summer posdt TN+wm*dT' ; COPY 81           ; COPY 83 FACT 0.75
LC 92 TYPE T TITL 'T summer negdt TN+wm*dT' ; COPY 81           ; COPY 84 FACT 0.75
LC 93 TYPE T TITL 'T winter posdt TN+wm*dT' ; COPY 82           ; COPY 83 FACT 0.75
LC 94 TYPE T TITL 'T winter negdt TN+wm*dT' ; COPY 82           ; COPY 84 FACT 0.75
LC 95 TYPE T TITL 'T summer posdt wn*TN+dT' ; COPY 81 FACT 0.35 ; COPY 83
LC 96 TYPE T TITL 'T summer negdt wn*TN+dT' ; COPY 81 FACT 0.35 ; COPY 84
LC 97 TYPE T TITL 'T winter posdt wn*TN+dT' ; COPY 82 FACT 0.35 ; COPY 83
LC 98 TYPE T TITL 'T winter negdt wn*TN+dT' ; COPY 82 FACT 0.35 ; COPY 84


Task “Linear Analysis”

For the linear analysis we add the task “Linear Analysis” to our project file. When opening this task all available load cases within the database are selected for analysis. As we do have self weight, additional dead load and the single temperature loads in our database, but we don’t want to have them used in our project we change the selection manually.


In every SSD task there is a tab “Graphical Output”. These pictures are designed for a simple 2d slab project. Therefore we recommend to switch of all standard graphics. We will generate our own graphics in a separate task “Interactive Graphic”.


Traffic Loads

The evaluation of traffic loads is done with the influence line method using the SSD task “Traffic Loader”. Please insert the task “Traffic Loader” into your project and open it. Inside the dialogue there are 5 tabs.


  • To run this task it is absolutely necessary to have a full stiffness matrix available inside the data base. For that reason run the task “Linear Analysis” always before running the task “Traffic Loader”.
  • In case you have a pile foundation inside your project, please note, that the influence line method (module ELLA) cannot produce any bedding results. As a workaround we recommend to use real beam elements and model the bedding with single spring elements.

Inside the first tab - Lanes - you define the lanes, where the traffic passes over your bridge. Select the bridge axis and a section type “EC”. The program will automatically define all necessary lanes.



  • The bridge axis used for the traffic loads must be located above all bridge elements. In case of an inclined bridge deck, you must define a new axis above the complete bridge deck to apply all traffic loads correctly.
  • This task works perfect for paralle lanes. In case of non parallel lanes a numerical text based input is necessary.

Inside the second tab - Load Trains - you define the load trains. Simply click on the button “Add loadtrain...” and select the necessary loadtrains out of the library of load trains. For bridge projects according to the Eurocode you need a loadtrain LM1 300, LM1 200 and LM1 100. Of course you may define also the fatigue load models


Inside the third tab - Calculation - you select all elements you want to have results for. There are only results for beams, nodes, quads and springs available. Simply click on the button “New” to add additional elements. Elements you don’t want will be deleted with a click on button “Delete”. The load case numbers listed here are fixed and will be added to a base loadcase number later on in tab number 4-load groups


Inside the forth tab - Load Groups - you define the different load goups and evaluation cases. Also you define base load case number, which has at least 3 digits. A load group contains all loads according to the load group definition inside the Eurocode. Usually we define a load group for the tandem axle loads (TS), for the uniform distributed loads (UDL) and also for the horizontal loads. The evaluation cases contain the different load positions in combination with the lanes. Internally the program creates an envelope of all cases. To make sure the results will be used correctly in the further project work, all result load cases are saved in the correct actions.


An action can be seen as a container with loadcases saved inside this container. Therefore all loadcases of one container have the same properties. Later on we simply use all loadcases out of one container by calling the action itself.


Inside the fifth tab - Plots - you define the amount of graphical output. Usually the influence lines are plotted for all elements. Otherwise you fill in the element number you want, or select the elements via ANIMATOR selection. We recommend to select only a few elements. This will speed up the analysis and reduces the amount of output.


After all settings are clear you close the dialogue. When closing the dialogue the task is processed automatically, because the option “Process immediately” is active per default setting. After the analysis the envelopes can be plotted using a task “Interactive Graphic”.

Construction Stages

With the construction stage manager we are able to analyse the whole building process. This process will effect the forces and moments inside our structure and cannot be neglected. When having prestressed or composite structures the CSM is mandatory.

Before adding the SSD task “Construction Stage Manager (CSM)” from our task library, you should set up a time line with all necessary incidents. Construction stages are defined inside cross sections and also inside the tendon geometry and layout already made in SOFiPLUS. All elements of your structural system are organised in groups. This is important as you may activate and also deactivate single groups of elements at any time during the construction process.


Usually there are different incidents between two major stages like prestressing, grouting, temporary loads, creep and shrinkage. For that reason it is useful to increase the stage number by 10. This enables you also to add new stages in between, without renumbering everything.

Recommended Stage Numbers:

  • 10th: a new group of elements is active
  • 11th: prestressing, static determinate part
  • 12th: prestressing, static indeterminate part
  • 13th: grouting (optional)
  • 14th: new loads, e.g. formwork
  • 15th: up to 4 creep and shrinkage steps (15,16,17,18)
  • 19th: for precamber analysis or activation of self weight from cross section stage

The first construction stage should start with stage number 10.

If all the predefinion work is finished you may insert the CSM task and open it. Inside this dialogue the first three tabs are the most important ones.

The first table contains a list of all construction stages. This describes the timeline of all incidents of our structure. Only the creep and shrinkage stages have a time duration.


The second table defines the properties and activation stages of all element groups.


The third table defines the properties and activation stages of load cases during the construction process.


Tab four and five are dealing with control parameters and the amount of output. For the first application the default settings are good. If you close the input with the “OK” button the option “Process immediately” is active and the whole process starts.

Important to know is the fact, that all the results are saved again in a serie of load cases. The numbering follows a very clear concept.


Overview of loadcases used by CSM:

CSM Construction stages:

LC Number Description
3970- 3997 Comparison loadcases - cast in one (CTRL cast)
4000- 4999 Total CS displacements and forces without pre-stress losses from C+S
5000- 5999 Difference displacements and forces -> CSM DESI with safety factors
6000- 6999 AQB inner stresses from creep and shrinkage including pre-stress losses -> CSM DESI
7000- 7999 Sum stress results (real stresses) of the AQB−LCST−evaluation incl. pre-stress losses from C+S
15000- 15999 Primary part effect of prestress separated in construction stages
16000- 16999 Secondary effect of prestress in construction stages using more than 1000 stages:
40000-49999 Total CS displacements and forces
50000-59999 Difference displacements and forces
60000-69999 AQB inner stresses from creep and shrinkage
70000-79999 AQB-LCST result stresses (real stresses)

For CSM new segments with CTRL CANT 3:

LC Number Description
180000-189999 help load cases for analysis of restraint

For CSM precamber analysis (CAMB)

LC Number Description
140000-149999 Total CS displacements without CAMB modification

For CSM Equation System usage

LC Number Description
1999 CSM_Combination loadcase (CTRL LCEQ)

For CSM DESI Design usage

LC Number Description
1001-1099 AQB check print
1101-1199 SLS rare (characteristic) superposition and design
1201-1299 SLS nonfrequent superposition and design
1301-1399 SLS frequent superposition and design
1401-1499 SLS permanent superposition and design
1701-1799 SLS construction design rare (characteristic)
1801-1899 SLS construction design permanent
1901-1998 1.0 superposition
2101-2199 ULS design
2201-2299 ULS construction design
2501-2599 Accidential
2601-2699 Earthquake
2801-2899 Fatigue LM3 with pk-inf and pk-sup prestress
2901-2999 Fatigue simplified LM1 with pk-inf and pk-sup prestress
9001-9499 Superposition with pk-inf and pk-sup prestress


In case of more than 1000 construction stages, the number of the result load cases is increased by a factor of 10 to 40000-49999 and so on.

Combinations and Superpositioning

For the design process a combination in ULS and SLS state of all loads is necessary. For prestressed, post tensioned or composite beam bridges it is necessary to have the combinations from all loads acting on the final bridge construction separate. The final combinations is done in the beam design program AQB. The module CSM is able to generate all necessary combinations.

To apply the automatic generation of all necessary combinations add a task “Text Editor (TEDDY)” inside your project.


Use the right mouse click function on the new “Text Editor (TEDDY)” task and select the option “Rename”. Please define a new name for this task, e.g. “CSM Desi MAX”

Here you list all variable actions you want to be used inside the combinations. Additionally you assign every action to the necessary design checks.

According to the German code it is necessary to have two different actions for settlements which will be used for different design checks:

  • possible settlement SF will be used for ULS design check
  • probable settlement ZF will be used for SLS design check

The input sequence is printed below:

+prog csm $Combinations
head  Combinations
!*!Label Select variable actions
     T     ULS,SLS
     F     ULS,SLS
     L_T   ULS,SLS
     L_U   ULS,SLS

!*!Label request combinations only

!*!Label  define extension for new data file
CTRL FILE 'maxi'

+apply $(name)_maxi.dat

Design Checks

According to the code selected at the beginning of the project several design checks are necessary. Again the module CSM is able to generate all necessary design checks automatically.

To apply the automatic generated design checks add a task “Text Editor (TEDDY)” inside your project.


Use the right mouse click function on the new “Text Editor (TEDDY)” task and select the option “Rename”. Please define a new name for this task, e.g. “CSM Desi ULS,SLS”

The input sequence is printed below:

+prog csm $Design Checks
head  Design Checks
!*!Label Selection of code design checks
$DESI ULTI,Deco  $ make only ULS design and decompression check
DESI STAN  $ make all available design checks according selected code


+apply $(name)_desi.dat


Using CSM module a new file $(name)_desi.dat is generated automatically. You may have a look into this file to see the general settings. If you like you may generate a new task “Text Editor (TEDDY)” in your project. Now you may simply copy the corresponding input lines from the $(name)_desi.dat into your new task. This is a very easy method to generate a new task with a specific design check. Doing this, you may change all settings according to your needs.


Generate Report

In SSD every single task produces a report file project.plb. For a graphical visualisation of all results we recommend to add several tasks “Interactive Graphic”. You may move these tasks at any place inside your task-tree. Usually it is helpful to have system plots, plots with the resulting forces and moments and finally some plots with the design results.


In every task “Interactive Graphic” you may define as many pictures you want. Lots of pictures may slow down the performance. Therefore we recommend to use multiple tasks for graphical results.

There is an option to generate a complete documentation file. Goto SSD menu “SOFiSTiK > Report Browser > All Reports” or use the icon shown in the following picture.


Inside the complete document you may insert a table of contents. This can be done inside the Report Browser menu “Document > Insert Table of Contents”, see picture below.


To have a secure output file we recommend to print the final document to a pdf file. This can be done easily with the print function from the report browser. Open the report browser and go to menu “File” > “Export to PDF”


Save Project Files

After the project is finished, all calculations are done and a final report was generated, you should save your project on a company server. For that reason we recommend to pack your project files together in one file. Simply go to SSD menu “File” > “Archive” or use the button with the zip-symbol. Alternatively you may click directly on the Zip symbol in the tool bar.



To reproduce a project only the files project.sofistik and project.dwg are necessary.