Assignment 1B Truss Building Claire Gabriel 584657 Constructing Environements Semester 2/12
Over all the design is efficient and fulfills its goals. Using a common roof truss the weight is evenly spread. Small amounts of plasticine secure the design but do not put to much weight on the design which is vital when working with light materials. The design is very secure in the middle and the truss system means that the weight is evenly spread across the design. We choose this truss because it is simplistic and most effective.
Above an diagram of a common roof truss
Left A The completed design, you can clearly see the common truss design. The two major beams are created from ice cream sicks which are slightly stronger to hold the main weight. B The plasticine is lightly placed to join the pasta together. C The creating of the truss. D The middle section of the design is a double layer of pasta crossed over to secure the entire design with plasticine above, in between and bellow to secure the design. Bellow the corner joins sit over the entire cup to gain maximum support.
Design and Performance
Above After sketching a brief diagram and choosing our truss. We began by creating an initial support system of a cross. We used double thickness of pasta for extra strength. Then we built three trusses and attached them to the design (figure 2). As we were attaching them we found the supporting design could not hold the new three new trusses been added. In attempt to secure it we had more plasticine to the joints creating more weight which resulted in the structure not being able to stand up (figure 3).
After the design colapsed, we concluded that the truss is efficient our construction was not. As a result we simplified the design using less plasticine and using it more efficiently. We also used ice cream sticks in the truss to hold the design more securely. We attempted to use them else where but found that the weight was to much to warrant there use. Overall we learnt that the simpler and cleaner the more efficient the design.
Bellow Comparisons of other groups designs. (Figure 1) There design used the same truss as ours, it is smaller in diameter and length and also higher. There design was also very efficient. (Figure 2) opted for a double pyramid design. (Figure 3) was a successful design that was nearly finished at the time. It was the largest in the class and was a complex truss that I am not sure would stay together when placed on the cups it would have been interesting to see the completion of the design.
Right Free Body Diagram demonstrating how the weight is applied across the truss.
HA pinned support
roller support RC
On comparison to the elephant shelter the truss system was allot more versatile to work with. - As the blocks were so bulky they we difficult to create a more efficient design. However I was able to create a more efficient design using the truss system.
Bellow The designs from the elephant shelter designs created with MDF blocks.
- The blocks had more weight and created a more sturdy design. But I think both designs could have with standard similar forces as the pasta was actually joined together. - A combination of the MDF blocks and the pasta, plasticine truss support could have been most efficient. For example if the plasticine was used to support the bricks it could have more support the bricks.
Comparison of Structure and Materials
In the evolution of building there have been two great developments since the use of timber and stone in creating shelter. The truss was invented in Europe in the middle ages (Olson, 2003). The top end of the beam is normally in compression and the bottom edge in tension. These stresses reach a maximum near the middle of the beamâ€™s span and for every doubling of span the strength of the beam must increase four times. Our truss design was formed with the triangles. The triangle forms a stable shape on comparison to a square or rectangle which joints are rigid and not as stable from corner to corner. The Truss that we choose (the common truss or the king truss) successfully balances out the applied loads and is structurally efficient. This type of truss was one of the first truss system invented and is often used in housing. The shape of the roof also provides efficient drainage. When experimenting with our design we realized the main challenges we had to over come was balancing out the weight of the plasticine on the select pasta. When we started building we did not consider this and created a design that was to large and heavy for the truss to support and it subseAbove Example of common roof truss used in quently collapsed. After revaluationing the design we decided it was house design. not the truss it was the method of building that was causing us problems we realized we could create the same design with half the materiWe also included to ice cream sticks as the main beams as they were supporting the most weight. This design was very effceint and also visully more appealing it demonstrated the efficentcy and strengh that a truss could provide even if it is made out of pasta, ice creams sticks and cups.
Reflection and Critique
Texts: Gauld, B 1995, Introduction to Building Structures, 3rd Edition, Structures for Archiects, Longman Scientific and Technical, England Forbes, P 2005, Origami for Engineers, Egineered from Nature, Fourth Estate, London Websites Truss systems, Banners, viewed 29th of August 2012 http://timber-trusses.com/images/banners/pdf/Trusses-how_they_work.pdf Images Class photographs authors own Truss systems, House Truss, viewed 29th of August http://www.mitek.com.au/Default.aspxc Common Truss, Timber Trusses, viewed 28th of August 2012, ttp://timber-trusses. com/images/banners/pdf/Trusses-how_they_work.pdf