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Preliminaries
Create a cover sheet for your assignment to include the following information;
• Assignment Number
• Name
• Due date (refer to the Assignment Schedule in Course Spec)
• Date submitted
Number of hours spent on studying for and completing the assignment for:
• Task 1
• Task 2
• Task 3 Do not submit this task but do record hours
Brief list of things that you learnt from this assignment
• Task 1
• Task 2
•Task 3 Do not submit this task but do say what you have learnt from chapter 3
Brief list of things that you remain uncertain about
• Task 1
• Task 2
• Task 3 Do not submit this task but do note any things you are uncertain about
Note that the last three items (hours, what you learnt and what you are uncertain about) are an essential part of the assignment. The last two force you to reflect for a moment and think- what was this really all about?
You need to have enough evidence to show that the modelling/solution is your own work. Show all theoretical calculations, otherwise marks will be deducted.
Task 1 – Relevant to Chapter 1 Weighting 10%
There should be nothing complicated in this task – but you should expect some frustration in getting used to Strand7 if you have not used it before. The task asks you to demonstrate that you can follow the model building instructions in chapter 1.4 to recreate the model that forms the basis of the investigation and discussion in this chapter and to plot bending moments and extract deflection results from this model.
Read through chapter 1 of the Study Book. Set up a Strand7 finite element model of the beam B1, B2, B3 (including all load cases and combinations) as shown on page 2 – WITH THE FOLLOWING CHANGE – change the beam spans from 5000, 7000, 6000 to 6500, 8500, 7500. To set up the model use the method as defined in chapter 1.4.
As with all tasks for this course you are required to set up models in Strand and then copy an image from the model to the pasteboard and then paste this image into a word document that you will then send to me with any appropriate annotation and / or discussion. There are three useful copying methods. Ctrl + Printscreen copies the entire screen but without any overlaying windows. Alt +
Printscreen copies only the active window and is useful for copying overlaying windows. Finally and generally most usefully, from the Strand7 top menu item Edit, select Copy Graphics. This will copy just the graphic model without the borders. Ctrl + V or Edit Paste may then be used to paste your image to the word document.
There are several ways in which you can enhance the readability of graphics copied from Strand7 and it is expected that you will explore and make use of these. The Strand7 default settings are generally OK for viewing on screen but for producing a finished document suitable for printing you should consider the following options:
Within Strand7;
• Right click on screen / View Options / and click on Screen Preview. This allows you to change the color of the background screen from black to white. Particularly for documents that will be printed the white background is preferable if for no other reason than it saves on ink.
• Right click on screen / View Options / Numbers. You will probably find that the default setting is Scientific or Fixed with 4 or 6 decimals. This generally leaves a lot of unnecessary zeros cluttering up the display. Generally this should be changed to Engineering with only 2 decimals for greater clarity and conformity with engineering conventions. Note that you can have different number formats in the “pre processing” and “post processing” environments.
• In the post processing environment, right click on screen / rainbow icon / Settings / Legend / Font. You will probably find that the default is set to Arial size 8. This is generally too small and you should change this to Arial Narrow Size 10.
• There are numerous other ways of modifying the effectiveness of the graphics display
Deliverables:
It is expected that you will provide all appropriate titles and discussion to your word document.
1 Once you have created your model reproduce the view shown at the bottom of page 5 and copy to your word document. (To make the beams show as solid rather than as a line you may need to (in Strand7) – right click on screen / click on Entity display / Click on the beam icon / Click on Solid). (10 marks)
2 Create the envelope bending moment diagram as described on page 9 and copy this to your word document. For clarity change the Entity display from Solid to Line and show only the beams. Use the ‘microscope’ if necessary to find the value of the maximum positive and negative moments at all significant points along the beam length. (Envelopes in Strand7 are more complicated than you may be used to and you may need to refer to the Strand7 Help files to assist you with this.) Can you explain the significance of these load cases? What is the information you are extracting using these load cases and why?
Use the method recorded on page 3 to undertake an approximate analysis of the beam (using the modified spans). Create a table in your word document comparing the results of your analysis to those of your approximate analysis. (45 marks)
3 Follow the instructions at the bottom of page 9 to subdivide the beams adding a node at the centre of each. Analyse the model. Select the load case Fd.ef.incremental and use the Displacement Scale icon to change the scale of the deflected shape to a reasonable value. Copy this screen to your word document. Use the microscope to determine the deflections along the length of the beam for this load case.Using the method defined on page 5 undertake an approximate analysis for deflections. Create a table in your word document comparing the results of your analysis to those of you approximate analysis and comment. (30 marks)
4 Write a brief paragraph discussing the results of your investigation including overall comparison of your results to those in the text and to those obtained by approximate analysis techniques.
(15 marks)
Feel free to add any further information to your word document to more effectively record your investigation.
Task 2 – Relevant to Chapter 2 Weighting 10%
You should find this chapter and the associated Task 2 to be fairly straightforward and hopefully interesting as it introduces plate modelling that is likely to be new to at least some of you. This chapter is equally applicable to both structural and mechanical engineers.
Do not take this chapter cheap – there are a lot of important issues developed in it. Perhaps most important is the statement on page 16 ‘always think long and hard about restraint modelling’. Most ‘errors’ associated with finite element modelling are concerned with incorrect modelling of restraints. (This can affect SpaceGass models in just the same way.) Incorrect restraints may give rise either to models that will not solve or to models that give sometimes drastically non conservative results.
The second major topic developed in this chapter relates to the naming conventions associated with bending moments and stresses developed in plate elements. The naming convention for bending moments is quite different to that used with beam elements and in addition you need to understand your way around the shear stress tauxy, tauyz and tauzx. Plate element analysis is further developed in chapters 5, 6 and 7.
Deliverables:
1 Pages 15 to 19 describe the mechanics of building a plate element model of a simply supported slab. Follow these instructions to build your own model of this slab together with the three load cases WITH THE FOLLOWING CHANGE – change the slab span from 5000 to 6000 and the slab width from 3000 to 2000. Thickness of the slab is 250 mm.
(10 marks)
2 Analyse your model and view the deflected shape. Reproduce figure 2.5 and cut and paste to a word document. (10 marks)
3 Change to a plan view and create a contour plot of deflections for load cases 1 and 2. Check the maximum predicted deflection for these load cases and compare to your manually calculated result. Copy a deflection contour diagram to your word document and comment on the values. (20 marks)
4 Change to a contour plot of the bending stresses caused by load case 1, copy to word document and record the maximum predicted value. Compare to your manually predicted value. (20 marks)
5 Reproduce the graph at the top of page 26, copy to Word and comment on the significance of the Area under the curve. (10 marks)
6 Reproduce the graph at the bottom right of page 26 copy to Word and comment on the significance of the Area under the curve. (10 marks)
7 Record the maximum deflection due to the point load (without mesh refinement). Undertake mesh refinement as described on pages 27 to 29 and copy a view of the resulting mesh to Word. Reanalyse, record the value of the maximum deflection for point load and comment.
(20 marks)