EMS5CAE – Computer Aided Engineering ANSYS
(2020)
Individual Assignment
Civil Engineering
Due Date: Friday, 8 May 2020
Analysis of an Overcrossing Truss Bridge
1 Outline
Pedestrian/Bicycle overcrossings represent one of the most crucial elements of a
communities non-motorised transportation network. They are the critical links joining
the areas separated by a variety of “ba
iers” like rail lines, rivers or highways. A truss
idge is a type of overcrossing where the connected elements of the
idge form
triangular units. Trusses are rigid and transfer loads from single point to a wider area.
While designing the elements of a
idge factors like cost, design life, loads,
deflections, dynamic behaviour, material etc. have to be analysed to ensure the safety
and reliability of the structure.
On a shared
idge, there are three main types of loads to be considered during
analysis –
Dead load: Weight of deck, Weight of any railing/supports, self-weight of
the structure.
Live Load: Pedestrians, Cyclist, Wind.
Moving Load: Loading of a moving service vehicle
For this task, we will consider only a dead and live load.
2 Objectives and Specifications
The aim of this project is to conduct a finite element based structural, modal and
harmonic response analysis on a truss
idge. The members of the system must be
investigated for multiple cases to ensure the safety and performance of this system.
The structure supplied to each student has been made from 10 mm solid bar. This
needs to be changed to a more appropriate I-beam cross section. Each student should
select and model two (2) different sections to compare and discuss the effect of each
cross section – remember to use your engineering judgment when writing the
discussion, i.e., the thickest and heaviest member might give you the least deflection
and co
esponding frequency response, but are you over-engineering? Use the data in
Figure 1 to select your two different I-beams. Also select a thickness of the deck that
is appropriate – remember you as the engineer needs to justify this. A
idge with a
500 mm deck might not deflect at all, but does this make logical sense?
This means you will need to use SpaceClaim to model two cross sections with an
a
itrary length, say 100 mm, then save this on your local drive, see Figure 2. Then,
using SpaceClaim, extract the beams and mid-surface of the deck, share topology and
move the deck mid-surface so that it aligns with the central axis of the beams. By
selecting all the beams, you can assign different profiles in the Beams section of
SpaceClaim, under the Prepare tab.
You will need to use three analysis systems in ANSYS. The first is a Static
Structural, then drag in a Modal system on the solution cell of the Static Structural,
Finally, drag a Harmonic Response onto the Modal solution cell. Your analysis should
look like Figure 3.
Figure 1. List of beam dimensions
Figure 2. Beam example
Figure 3. ANSYS Analysis
Once in ANSYS, you will need to set-up your analysis. Use Structural Steel as the
material for the beams and Oak Hardwood for the deck. For your mesh, select an
element size that that provides less than 32K nodes, and represents your model
sufficiently. Justify your selection.
Ensure you have created connections of the
idge frame to the deck. Again, use
your engineering judgment and discuss what type of connection you have used and
how this represents the physical problem you are solving.
For the boundary conditions, you will need to apply a standard earth gravity, a
5 kPa pressure on the deck and fixed supports at the 4 corner nodes of the truss frame,
Figure 4 and Figure 5. For your analysis setting in static structural, keep all defaults
ut discuss the use of Large Deflection; what does it mean and do you need to use it?
The modal analysis setting just needs to include 12 modes in total. The Harmonic
esponse needs to have the pressure applied as per the Static Structural, but you
analysis setting for the Harmonic repose should include the setting shown in Figure 6.
For the post-processing, show and discuss your results in terms of deformations,
stresses and strains for the static structural, mode frequencies and shapes for the modal,
and frequency response and total deformation for the harmonic analysis.
Refer the to standard for the allowable deflection and discuss this with regard to
your results, Figure 4. Also, use the information from your static structural and modal
analysis to ensure your deflection is acceptable as per Figure 5.
Figure 4. Deflection Standard
Figure 5. Static deflection limits for
idges with walkways.
Compare the results from the two different beam profiles, discuss how these
changed the results, and what the pros and cons are for the different profiles. You can
also discuss aspects related to costs, construction and logistics of building the
idge –
not just the FEA results. Remember, you need to discuss your results, don’t just past
in a picture and state the values. Relate them to the physical model.
Figure 6. Pressure load surface
Figure 7. Fixed supports
Figure 8.
3 Technical Report Layout
Before starting your report, please make sure you complete the academic integrity
module. Each submitted piece of work will checked for plagiarism, and if your report
has been found to
each the academic integrity guidelines, you will be refe
ed to the
academic integrity committee for a hearing.
If you are not sure about something relating to academic integrity, please discuss
your concerns with the teaching staff as we can guide and help you with any queries
efore submitting the assignment.
The report can be laid out as follows:
• Use size 12 font for the body text, and format section and titles accordingly.
• Font can be Timed New Roman, Cali
i or similar.
• Use spell check and read your assignment before submitting.
• Reference figures and other sources of information. Use a referencing tool such
as Zotero https:
www.zotero.org/
• Use the numeric IEEE style type.
• MAX 2000 words! Be concise!
To ensure your submission fits the page/word count ranges, make certain to count
words in the body using your word processor and then add in the equivalent word
counts for your tables and images. References do not count towards the wordcount.
Figures and tables are counted by the amount of words they replace. A good rule of
thumb is 50 words per image (picture, graph, spectrum, etc.). Figures with two images
(e.g. 1A and 1B) are counted as 100 words. Three images amount to 150 words and so
on. Brief tables are counted as 100 words each, while longer or wider tables can be up
to one full page (200 words). Make sure you include only highly relevant images and
emove non-essential images to help your manuscript be more reader-friendly while
fitting within the page/word limits.
A Technical Report can contain the following sections:
Section Details
Title page Title of the report. Student details including name, ID, date and subject,
the main text word count.
Summary A summary of the whole report including important features, results and
conclusions
Contents Numbers and lists all section and subsection headings with page
numbers
Introduction States the objectives of the report and comments on the way the topic of
the report is to be treated. Leads straight into the report itself. Must not
e a copy of the introduction in this handout.
The sections which
make up the body
of the report
Divided into numbered and headed sections. These sections separate the
different main ideas in a logical order
Conclusions A short, logical summing up of the theme(s) developed in the main text
References Details of published sources using the IEEE style.
Acknowledgements List of people who helped you research or prepare the report, including
your proof-readers
Appendices (if
appropriate)
Any further material which is essential for full understanding of your
eport (e.g. large-scale diagrams, computer code, raw data,
specifications) but not required by a casual reade
Systéme International (SI) units are to be used. Non-SI measurements can be
included, but they should follow the SI measurement in parentheses. An example is
2.54 cm (1.00 inch).
4 Marking
A marking ru
ic will be provided separately on the LMS.
1 Outline
2 Objectives and Specifications
3 Technical Report Layout
4 Marking