ENGIN2203 Structural Analysis Assessment :

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Federation University Australia

School of Science, Engineering and Information Technology ENGIN2203 Structural Analysis

Analysis Assignment 2

INTRODUCTION

This ENGIN2203 Structural Analysis Assessment exercise involves the use of Space Gass to investigate several issues of a structural nature. The objective of this exercise is to enhance your understanding of structural behaviour, as well as develop a basic competency in the use of an industry-standard structural analysis computer program. This assignment consists of two parts.

PART A is an individual task. All steps of the task including the submission and peer assessment processes are completed on Moodle. (10 marks)

PART B is a group task, continuing from the Analysis Assignment 1. (10 marks)

Please note that you need to upload 3 files in the Moodle submission link by the due date:

1. Complete the workshop peer assessment activity and make relevant submissions on Moodle according to the timelines. Link to activity: https://moodle.federation.edu.au/mod/workshop/view.php?id=6274795

2)    Complete report file for B (in a single Pdf file)

• produce and upload the SPACE GASS file for part B (in .SG format).

ASSESSMENT

The following issues will be considered in arriving at the final mark:

• Neatness of presentation of the written/typed work and quality of diagrams
  • Correctness of manual calculations, computer modelling and output results
  • The extent to which all appropriate calculations, diagrams, etc, are shown and the instructions given in the assignment brief are followed.
  • Readability and scale of the diagrams (i.e. printed from SPACE GASS).
  • All requested results from SPACE GASS should be presented in the report.
  • Timely completion of relevant tasks.

Due: End of week 11 – Sun, Oct 23, 2022 – 17:00

PART A: Analysis of indeterminate beam Submission phase (deadline: 9 Oct 2022) – 3 marks:

A two-span continuous beam is provided in the workshop activity. Use the slope- deflection method to manually analyse the beam and determine the full bending moment diagram as outlined in the workshop activity. Some of the input parameters are obtained based on your student ID so each student is assigned a different beam for analysis.

You will be asked to upload the full workings and diagram results of your manually analysed beam in the form of a pdf file.

Assessment phase (deadline: 23 Oct 2022) – 4 marks:

Once the manual calculation phase is complete, the peer ENGIN2203 Structural Analysis Assessment phase will become available in which you will be assigned the workings of another student and will be asked to assess their workings using Space Gass software. You will be asked to provide detailed feedback on the manual calculations and bending moment diagram and submit a screen shot of the bending moment diagram you obtained from Space Gass.

1. Do the joint bending moments and the maximum sagging bending moment values within 5% of the software results? If not, what is the error?
2. Are the reaction force values within 5% of the Space Gass results? If not, what is the error?
3. Does the overall shape of the bending moment diagram (drawn on the tension side) match with the software results? If not, what is the error?
4. To make sure you haven’t made any errors in your Space Gass simulations, go through steps (i) to (vii) of “Checking the results from structural programs” in the lecture slides of Topic 7. Provide an observation for each of these steps and justify that you have created your model correctly.

Feedback phase (deadline: 23 Oct 2022) – 2 marks:

In the “Overall feedback” section, upload an image of the analysed beam displaying the bending moment values at joints as well as the Maximum sagging values. Also, upload your Space Gass file for evidence of your assessment.

Reflection (deadline: 9 Oct 2022) – 1 mark:

At the end of this activity, you are encouraged to spend some time reflecting on your workings and the feedback you received. How well do your manually calculated joint bending moments compare with the computer results? Can you spot your errors (if any)?

Finally, provide your reflection on this activity, did you find it engaging? Would you prefer to see more of such assessment types in future?

PART B: Portal Frame Model

INTRODUCTION

This exercise continuesENGIN2203 Structural Analysis Assessment 1 to apply the wind loading on a typical steel portal frame building, using SPACE GASS program. You need to use the group inputs and results of your calculations from Assignment 1. Please make sure you address the feedback provided to you in the previous assignment and provide a small summary of changes.

The diagram of the portal frame was given in Assignment 1. The portal frames are pinned- base, with the usual rigid connections at the eaves and the ridge. There is no haunch in the structure.

In a normal portal frame building design, a substantial number of wind loading scenarios (internal and external wind loads) would be considered. For this exercise, however, a small subset of load cases will be investigated.

REQUIREMENTS

For the portal framed structure, and based on the dead load + wind load cases described below, the following is required:

Determine the following maximum design actions, derived from Load Cases 4 to 7, for the first internal portal frame in from the end of the building and specify which load case has resulted in this maximum value:

• Maximum uplift on the footing (kN);
• Maximum hogging moment at the ridge (kNm);
• Maximum sagging moment at the rafter-column connection (kNm).

In addition to these answers, the following is to be included in the submission

• All calculations involved in determining the loadings and any corrections (from Assignment 1);
• A fully dimensioned diagram of the model, showing member and node numbering and section sizes;
• Fully detailed diagrams showing the loadings used for the three load cases LC1, LC2 and LC3;
• The bending moment diagrams determined for load cases LC4, LC5, LC6 and LC7.

Note that the various diagrams should be produced by SPACE GASS.

FURTHER INFORMATION

i)      Load Cases to Analyse

The following load cases should be input into SPACE GASS:

• LC 1: Un-factored DL
  • LC 2:  The total UDL (kN/m) from external wind pressures, due to wind

coming from direction ‘A’

• LC 3:  The total UDL (kN/m) from external wind pressures, due to wind

coming from direction ‘B’

• LC 4: 0.9 x LC1 + LC2
  • LC 5: 0.9 x LC1 + LC3
  • LC 6: 1.2 x LC1 + LC2
  • LC 7: 1.2 x LC1 + LC3

Use the information provided in Assignment 1 for the required loads. Note that:

• The 0.9 factor applied to the dead loading in LC4 and LC5 and 1.2 factor in LC6 and LC7 are in accordance with AS1170.0 Cl. 4.2.2 . The 0.9 factor applies when the dead loading and the wind loading are in opposite directions. If they are in the same direction, then the worst case would be given by the dead load exceeding our estimate, and hence it is factored up by using the familiar 1.2 ultimate load factor. However, if the dead load opposes the wind, then the worst case would be if the dead loading actually turned out to be less than estimated, resulting in a larger nett uplift effect. To allow for this possibility, we hence factor down the dead load by the 0.9 factor.
  • Wind loadings are not factored up because they may already be regarded as ultimate loads. When we select the average recurrence interval R for determination of the regional wind speed VR (AS1170.2 Cl. 3.2) and then undertake strength limit state design of members for the actions generated by these wind loads, an optimum design would have the structure on the point of collapse under these wind loads. Hence, they are the ultimate loads.

ii)  Creating the Model in SPACE GASS

Created the 2-D portal frame manually, by ‘constructing’ the nodes and members of the first internal portal frame in from the end of the building and apply the relevant loads accordingly.

SUPPLEMENTARY NOTES

PART B)

• All the dead and wind loads are distributed loads, so the loading data is input via the Datasheet in the ‘Member Distributed Forces’ option from the ‘Loads’ drop- down menu.

The loads have to be applied to the structure member-by-member, although the ‘generate’ option may be used when a significant number of members is involved. Say, for example, a particular load case LC4 involved three vertical members, 7, 8, and 9 carrying UDL loading as shown below:

The part of the Member Distributed Forces datasheet relating to this load case would appear as follows:

Note the following important points:

• Every loaded member has its own line in the datasheet, but because each line is specified as Load Case 4 the loads are all applied simultaneously in this load case.
  • Member 9 has 2 lines in the datasheet, because for part of its length it carries a 5 kN/m UDL and for the remainder of its length the UDL is 8 kN/m. The two loads applied simultaneously to the one member are referred to as Sub Loads 1 and 2. If you try to apply more than one load to a particular member in a given load case without giving them different sub load numbers, Space Gass will ask if you want to overwrite the load already input.
  • Dead and live loads are normally most conveniently input using the Global axis system, as these loads are normally vertical and thus aligned with the Global Y axis (they would be –Y loads). The choice is either Global-Inclined or Global-Projected:
    • If Global-Inclined is used (normal case), then when you specify a UDL of, say, 4 kN/m, the meter length is measured along the axis of the member. For dead loadings, this would be the normal situation.
    • If Global-Projected is used, the metre length would be taken as measured perpendicular to the direction of the load. For example, this would be applicable if there was a vertical UDL was being applied to a sloping member, where the UDL was specified as 4kN/m, in which the metre was measured horizontally.
  • Wind loads are normally most conveniently input using the Local axis system, because wind pressures are perpendicular to the building surfaces and hence if the loads are input as either +y or –y loads in the Local axis system, they will be perpendicular to the members.
  • The location of the start and finish of a UDL on a member may be specified either in terms of actual distances in ‘m’ from the start of the member, or in terms of a % of the member length.
  • In the above example, the Global axis system was selected for input of the loads. If the Local system had been used, then the loads would have been input as –y loads. Either is fine. Probably member loads are most commonly input in the Local axis system, and concentrated loads are always input in the Global axis system.
• The Self Weight option is accessed via the ‘Loads’ drop-down menu. Simply type 1 under ‘Case’ and -1 under ‘Y Acceleration (g’s)’. That is, for Load case 1, member weights are calculated allowing for one ‘g’ of acceleration in the downwards direction. You wouldn’t do this for any of the other load cases if you are going to later combine them with Load Case 1, as to do so would result in double-counting of member self-weights.

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