48321 ENGINEERING MECHANICS
Mar 13,23Question:
Background:
48321 ENGINEERING MECHANICS
Spring 2020 ASSIGNMENT 1: Free body diagram Report
No more than 4 pages in length
This assignment is due by COB Friday 28th Aug 2020
- Identify an existing structure & its’ support/s. (2 mark) (please identify one simple structure near or within your house)
- Take a photo and/or do a detailed drawing of your chosen structure and its’ support/s. (3 marks)
- Draw a Free Body Diagram of your chosen structure – show the loads and boundary reactions where they act, the likely direction of these forces, and for loads – whether you expect them to be concentrated or distributed, permanent (dead) , imposed (live), wind Include an assessment of how the support/s should be modelled i.e. pin, roller, surface contact etc. Justify your decision (15 marks).
- Based on the FBD, estimate/calculate the load on the structure and the boundary reactions. (3 marks. Note if the FBD is statically determinate, you can do calculation; If the FBD is statically indeterminate, you can make )
- Describe your chosen structure including the following:
- The nature and location of the overall structure
- The materials used
- Your guess/estimate of the age of the structure
- Any other interesting information. (2 marks)
ASSIGNMENT 1 Marking Guide
| Mark out of | ||
| 1 | Identify a support of an existing structure. | 2 |
| 2 | Take a photo or do a detailed drawing of your chosen support. | 3 |
| 3 | Draw a Free Body Diagram of your chosen support – you will not | 2
3 3 3 4 |
| know the magnitude of loads or consequently reactions, but I | ||
| expect you to show where they act, the likely direction of these | ||
| forces, and for loads – whether you expect them to be | ||
| concentrated or distributed, permanent (dead) , imposed (live), | ||
| wind etc. | ||
| a. The rigid body in the FBD is appropriate for the structure | ||
| shown in the photo/drawing. | ||
| b. The FBD includes all the loads that could be expected to act | ||
| on the structure. | ||
| c. The nature of the load is shown appropriately i.e. | ||
| concentrated or distributed load, permanent, imposed, wind | ||
| etc. | ||
| d. The types of support/s are appropriately justified. | ||
| e. Appropriate reaction forces are shown at each support. | ||
| 4 | Estimate/calculate the load on the structure and the boundary reactions | 3 |
| 5 | Describe your chosen support/connection/detail including the following:
· The nature and location of the overall structure · The materials used · Your guess/estimate of the age of the structure · Any other interesting information. This description should be no more than one A4 page. |
2 |
Total out of 25
Mark = 0 if cut and pasted from web, or copied from another student.
Answer:
Introduction
FREE BODY DIAGRAM REPORT
- Identify an existing structure & its’ support/s. (2 mark)
(please identify one simple structure near or within your house)
IDENTIFYING THE STRUCTURE
Whenever we look around in a park to sit, we find a structure called “bench”. Even on roads and street corners we find this structure. They are of different shapes, size and materials. A bench is one of the most common structures used for sitting.
Generally in the parks, we find a very simply concrete bench structure. It is basically a beam with a definite length. The beam is simply supported at the two ends. The support are stron enough to bear the uniformly distributed weight of the beam. The beam serves as a platform where people can sit, or stuffs can be put on.
One such common bench structure identified is shown in the image.
- Take a photo and/or do a detailed drawing of your chosen structure and its’ support/s. (3marks)
IMAGES OF THE STRUCTURE
- Draw a Free Body Diagram of your chosen structure – show the loads and boundary reactions where they act, the likely direction of these forces, and for loads – whether you expect them to be concentrated or distributed, permanent (dead) , imposed (live), wind etc. Include an assessment of how the support/s should be modelled i.e. pin, roller, surface contact etc. Justify your decision (15 marks).
FREE BODY DIAGRAM OF THE STRUCTURE
Free body diagram includes all the forces that acts on the structure. As the identitied structure is a simple bench, hence it has two forces-
The complete free body diagram is shown below:
Here, the load is uniformly distributed and acting in downward direction(say, with a magnitude of W Newton/meter. And the support has surface contact, so the reaction forces are in upward direction at both the support; A and B. Also, as the structure is symmetrical, so each support bears half of the total weight of the structure.
- Based on the FBD, estimate/calculate the load on the structure and the boundary reactions. (3 marks. Note if the FBD is statically determinate, you can do calculation; If the FBD is statically indeterminate, you can make estimation.)
ANALYSIS OF THE FREE BODY DIAGRAM
The length of the bench is 2 meters.
Assuming that the weight of the structure is 1000 lb per meter. (as we cannot exactly measure the weight of the fixed bench, so estimated value is taken).Then,
Total load(L)= 1000*2= 2000 lb
So, total load is 2000 lb. Now this 2000 lb has to be beared by the two support equally.
FA(force at support A)= FB(force at support B)= L/2= 2000/2= 1000 lb.
Thus, the reaction forces at both the support is 1000 lb.
- Describe your chosen structure
DESCRIPTION OF THE STRUCTURE
- The structure is a civil engineering structure located at the James Park, Queensland. The bench is fully rectilinear with a span of 2 meters and a height of 0.5 meters. The structure is rigidly fixed on the plain ground and is also symmetrical in nature.
- The structure is fully made up of reinforced concrete. The top surface has a wooden plank over the beam, so as to provide comfort while sitting on it.
- The structure is very tough and long lasting. It seems some what around 3 years old structure.
- The interesting part of the structure is that you can place whatever you like on the structure to sit upon comfortably.
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