FAQ’s ABI

What are the units in MKS for stay forces in Viewer and tabular output?
The stay force in Viewer is shown as kN and kg in the text report.  Moments and other values are similar between graphical and tabular output. 

Can stress diagrams been viewed for moving load combinations and envelopes in ADAPT-ABI 2009?
Yes, when you go to Post-construction phases of results and select any combination, case or envelope including moving loads, you need to turn on the “Max” or “Min” tab in order to view the stress diagrams.

Can steel sections be modeled in ADAPT-ABI 2009?
ADAPT-ABI allows you to model generic material properties in which the modulus and name can be defined as below:

GENERIC PROPERTIES N=1
1 ES=2040000

Note that the properties do not include the unit weight of the generic material so the user will have to manually apply this loading to the structure.

Will results from ABI v4.5 be overwritten when I run the same .inp file in ABI 2009?
No, you must save the .inp file produced in v4.5 to a new location and generate a new .inp file in v2009 prior to execution.  The new output file will be saved in the new directory and should match the graphical output from the “View Results” tab.

Why are changes made to my .INP file not reflected in my latest analysis for ABI2009?
After completing the graphical modeling of a structure using the GUI in ADAPT-ABI, the user has the option to make further changes to the input file in text format.  Once saved, the changes made to the input file will be reflected in the analysis and results.  If you then open the model and re-generate the input file, the changes previously made will be reset and not included since the newly created input file is generated from the data from the graphical input.

What is the proper way to model hinges at the tops of piers in ADAPT-ABI?
Node hinges should be installed at the same step (day) as piers and supports.  The node hinges should initially be set to R=3,3,3.  This is essentially “Follow the Master” for X/Z translation and Y rotation.  The hinges can then be modified to a roller or other condition in the appropriate step.  This can be accomplished by simply clicking on that step and then changing the hinge properties.  If hinges at pier tops are not modeled this way, you may receive an instability error in analysis (i.e. non-convergence) since the nodes that are located at the same position, as is the case with all hinges (the program creates two nodes at same location).  In this scenerio the hinges are not connected by an element or restraint. 

Also, at the location of hinges the program will automatically create fixed restraints (3,3,3) that connects the girder with the bearing location.  In this scenerio, where nodes of the restraint and hinge are matching, the restraints are not necessary since  a common master node is shared between a restraint and node hinge.  This will lead to an erroneous solution.  To overcome this, you can:

  1. manually modify the input file by deleting the restraint line at the appropriate step, or
  2. create a small offset between the top of pier and bottom of girder.  In this case, the program correctly accounts for restraints and node hinges.

This video, ABI2009 Hinge Modeling (save as .wmv extension) shows how to properly model node hinges at tops of piers.

ADAPT-ABI?
In ADAPT-ABI, the user may specify the restraints or the program creates them automatically. In locations where several nodes occur (i.e. connections), the program may have difficulty in correctly assigning restraints between piers and cells. 

To delete, modify or replace an automatically generated restraint, go to the developed view to delete an existing restraint, modify an existing restraint or add a new restraint.  You can double click on any restraint to bring up the properties box for editing.

 As an example you can allow Z Translation and Y Rotation free while X Translation will follow the master, resembling R=3,0,0. The following are possible restraints:

R = 3,0,0; X translation follows master, Y rotation free, Z translation free.
R = 3,0,3; X translation follows master, Y rotation free, Z translation follows master.
R = 3,3,3; Y translation, Y rotation and Z translation follow master.
R = 0,3,3; X translation free, Y rotation and Z translation follow master.
R = 0,0,3; X translation free, Y rotation free and Z translation follows master.
R = 0,0,0; X translation, Y rotation and Z translation free.

 Other cases are not allowed when the nodes are not located at same location. As an example “11 R=0,3,0 M10” is intended for a hinge, thus  a nodal hinge should be created in lieu of a restraint. Similarly, “50 R=3,3,0 M49” is possible when you use a nodal hinge. Double clicking on “Add Node Hinge”  will allow for the same input functionality as a Restraint.

What is the key advantage of ADAPT-ABI over other structural analysis software?
Unlike general structural analysis software which mainly focus on the completed bridge behavior, ADAPT-ABI models the material properties, time-dependent factors of creep, shrinkage, relaxation in prestressing, elongation of tendons, aging of concrete and provides information for geometry control during construction (for example  the  pre-camber required during construction of a balanced cantilever bridge to counteracting the short-/long-term deflection), in addition to some post-construction design force envelope calculations like influence line, bending moment and shear force diagrams.

As the loadings during construction phases often causing more severe force resultants for critical structural elements, ADAPT-ABI helps bridge engineer to get a better overview and thorough understanding of the design force envelop and behavior of a bridge throughout its entire life span.

What are the types of bridge that ADAPT-ABI handles?
Geometry wise:
– Simply Supported Single Span Bridge
– Simply Supported Continuous Span Bridge
– Continuous Span Bridge with Post-Tensioning over Supports Only
– Continuous Bridge with Post-Tensioning over Entire Length of the Bridge Frame
– Spliced Girder
– Monolithic Deck and Pier
– Bridge Curved in Plan and / or Elevation
– Box-Girder Bridges
– Arch Bridges
– Cable-supported bridges
– Road/Rail Over Bridges (Flyover)

Construction Methodology wise:
– Balanced Cantilever Construction
– Cast-in-place Construction
– Precast Construction
– Incrementally Launched Method
– Span-by-span Construction
– Precast-prestressed girder bridges with field splicing and topping slab
– Bridge rehabilitation with external post-tensioning
– Composite Construction

Apart from construction stages analysis, what type of post-construction analysis ADAPT-ABI can perform?
ADAPT-ABI can calculate the gravity resultant forces due to dead, live and moving loads, and provide graphical diagrams of influence lines and force (moment, shear, torsion*) envelopes.

Apart from day-wise responses during construction program generates the response for all user defined load cases, total construction loadings, PT, Hyperstatic, Long Term (including Creep, Shrinkage & Relaxation) and all moving loads with their envelop.

From ABI v5 onwards Torsional forces are calculated in using simplified assumptions by Witecki. Recently version of the program can generate Seismic Loading using co-efficient method.

Presently I am using Spreadsheet and In-house tools to handle bridge projects. Can you please describe merits and demerits of ADAPT-ABI in comparison to our existing solution?
Often spreadsheet solutions as well as in-house tools are used to analyze and design their bridge geometry. While these solutions quickly produce initial solutions for simple structures, these mostly have following disadvantages:
– May not handle construction stages, requires lot of documentation
– May not produce Moving load result envelope
– Elongation report generation may not be possible
– May produce conservative results for even simpler projects
– Camber calculation is difficult
– Requires up-front investment in model generation

On the other hand though using ABI user needs to idealize the model like any other finite element software, for mostly medium size bridges it offers following advantages:
– Produces initial as well as optimized designs
– Simple procedure supports quick and reliable design times
– Excellent design (training) tool for beginners as well as experts
– Camber calculation even for CIP method is accurate and easy
– Simpler and quicker Moving load analysis and Elongation report

What are the main differences between v 4.xx and v 2009 (v5) of ADAPT-ABI?
ADAPT-ABI version 5 is a major release to ease the pain of old ADAPT-ABI version 4.x users. In ver. 4.x, users were required to complete the modeling entirely in textual command input. While all the technical features of ver 4.5 are supported, version 5 now provides an intuitive 3D graphical user input interface that allows users to create, modify and view model and results in 3D.

Along with many new features and enhancements of existing capabilities, new version of ABI can open older version of INP and MOV file for processing. Moreover the program can now import DWG or DXF files to generate cross sections, bridge alignments and other important components.

Does ADAPT-ABI generate moving load as per IRC or BS5400-Part II or EC requirements?
ADAPT-ABI has a general moving load generator that allows user to define any type of truck/vehicle loading patterns. Once the patterns are defined and saved into a library file, they can be used to “run” through the travel paths to obtain the influence lines as well as design force envelops.

Therefore, even though there is no default BS5400 Pt 2 vehicle loadings pre-defined, user are free to create and enhance the moving load library to cater the loading requirements of specific design code that they are using.

Does ADAPT-ABI design post-tensioned members (like beams/girder)?

In ADAPT-ABI, users are required to input and specify the tendon shape and stressing forces, and let the program calculate the results which include pre-camber, tendon losses, elongation, and others. ADAPT-ABI doesn’t design any structural component.

However, to figure out the right shape and post-tensioning forces to be applied, the calculation can be performed easily in ADAPT-PT PLUS program to the desired allowable stress limits.

I want to model a CIP deck on top of precast girder. How I can model that in ABI?

Also explain the composite analysis feature in ABI and how I can view combined result in result viewer?

Please follow the steps below to complete the intended operations:
– Model the deck and assign offset 500 mm in Z direction.
– Model the girder and assign its properties.
– Model the Loading -25 kN/m and assign offset 500 mm in Z direction.
– Create Mesh with Composite option.
– Create days 1, 28, 35 and 40.
– Cast Girder on Day 1 and activate self-weight.
– Install Girder and supports in Day 28.
– Install Deck on Day 35.
– Activate UDL on Day 40.
– Generate INP and Execute.

View Bending Moment on Day 40. Two diagram will be shown, one in the Girder and second on the deck.

Click on Select Composite Elements icon from the relevant toolbar.

You may download the model composite. Please rename the extension from .DOC to .ABI to open it in ADAPT-ABI.

I have a curved deck of radius 90 m and total length of 77.32 m. How can I model such deck with ease in ADAPT-ABI?

Please follow the steps below to complete the intended operations:

Draw a reference line and ensure its ends are (0,0,0) and (75,0,0).
Specify the Span as ‘Ramped Arc’ with Radius 90 m.
Model the deck, support and apply self-weight.
Solve the structure.
 

You may download the model Arch_Deck. Please rename the extension from .DOC to .ABI to open it in ADAPT ABI.

I want to model a deck resting on a arch. The deck is 100 m long including two tapered part of 15 m on both side. Deck is 12 m wide with a thickness of 925 mm at the middle and 3.5 m thickness near abutments. The arch is a box section of 4 m X 3 m with a wall thickness of 500 mm. Please explain how I can model this using ADAPT-ABI.

You may download the model 2RefLines. Please rename the extension from .DOC to .ABI to open it in ADAPT-ABI.

It is recommended to create two reference line, one for the deck and the second for the arch. Then select any one of these and go to developed view. Create the girder (snap both ends).

Return back to normal view. You may wish to use copy command to select the same section on the other reference line and use its property box to assign the correct reference line and section.


Now select the deck and open its property box. Use define sub-segment command to create three segment of 15 m, 70 m and 15 m. Apply it using green tick mark.

Go to Location tab to assign proper cross sections for each sub-segments.

You may download the modified model 2RefLines_2. Please rename the extension from .DOC to .ABI to open it in ADAPT-ABI.

One simple bridge is resting over two piers. While left support is fixed, right support is intended to be a roller one. The installation activities specified in ABI are as follows:
Day 10 – Pier
Day 20 – Pier Segments
Day 30 – Middle Segments

However during analysis program is showing “SOLUTION DID NOT CONVERGE” and couldn’t generate the results.
– What is the reason?
– Is there any workaround?

Though the completed bridge geometry has no stability issue, observe the structure at day 20. Right part of the structure is resting upon a fixed support, but left part is resting on a roller support. Since there is no connectivity between these two parts, left part can float indefinitely in horizontal direction.
In reality some temporary gadget or equipments are used to hold left part in position till the bridge is complete. Hence during construction left support would behave like a hinged or mostly at fixed one.

You may download the model T01_E. Please rename the extension from .DOC to .ABI to open it in ADAPT-ABI.

Initially assign both the supports as fixed. Create one step on day 30 to change support behavior from fixed to roller once entire deck is constructed.

You may download the modified model T01_S. Please rename the extension from .DOC to .ABI to open it in ADAPT-ABI.

I have modeled one 3 span beam in STAAD. Model parameters are: Spans = 6 m + 10 m + 6 m; Cross Section = 500 mm X 500 mm; Material = Concrete Member; Load = 5 kN/m throughout.
However when the same model is created in ABI, Bending Moments are not matching with STAAD results. Why there is such variations?

Please make a note that whenever one wish to match result between two programs, all parameters related to analysis must be same.
Moreover unlike STAAD, ABI considers time dependents parameters like Creep, Shrinkage etc. Hence for comparison, one needs to make sure effect due to such parameters are neutralised.
Also make sure the beam is meshed with adequate numbers of elements.

Nevertheless match ‘E’ value of concrete with that in STAAD model.

Finally note that STAAD consider support along centroid of the section, by default. However ABI places supports at the top of the deck.

  
You may download the model 3Span_E. Please rename the extension from .DOC to .ABI to open it in ADAPT-ABI.

 Set ultimate Creep and Shrinkage values as zero. Mesh this structure with 0.5 m cell size in ABI. As you might be aware STAAD splits a beam in 12 sub-segments internally. Input ‘E’ value of concrete as 21718 N/mm2.
Either move the deck or the support to restrain the deck along centroid. It will also bring the load along centroid of the member as in STAAD.

You may download the modified model 3Span_S. Please rename the extension from .DOC to .ABI to open it in ADAPT-ABI.

I have used traveler for a balance cantilever model. All segments and supports are installed on intended days. Movement and removal for both the travelers are also specified from their respective property boxes. However after analysis no traveler is being shown in the result viewer. Am I missing something? Also clarify while specifying traveler movement how I should specify the cell numbers?