Use size 12 font for the body text, and format section and titles accordingly. • Font can be Timed New Roman, Calibri 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!
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 “barriers” like rail lines, rivers or highways. A truss bridge is a type of overcrossing where the connected elements of the bridge form triangular units. Trusses are rigid and transfer loads from single point to a wider area. While designing the elements of a bridge 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 bridge, 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 bridge. 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 corresponding 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 bridge 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 arbitrary 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 bridge 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 but 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 response 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 bridges 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 bridge – 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 breach the academic integrity guidelines, you will be referred 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 before 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, Calibri 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 remove 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 be 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 report (e.g. large-scale diagrams, computer code, raw data, specifications) but not required by a casual reader 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 rubric will be provided separately on the LMS. 1 Outline 2 Objectives and Specifications 3 Technical Report Layout 4 Marking