Truss Designs and Materials

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Truss Designs Trusses For ultimate strength and to fit within the client’s criteria, a truss design will be used for the observation deck. Not only does a trussed cantilever better strength than a suspension design it also ensures that there are no obstructions to the view above the deck. This will give sightseers 360-degree views of the breathtaking scenery around them. Truss girders are an efficient and economical structural system where the material is fully utilised. For short to medium spans, it is more economical to use a parallel chord truss such as a Warren, Pratt or Howe truss as these designs minimise the cost of fabrication and erection. However for short spans, a Warren truss is more appropriate as it is more economical as it uses fewer materials than a Howe or Pratt truss. For aesthetic purposes, it is ideal to have an even number of bays on a Pratt or Warren design to avoid a central bay with cross diagonals. Compressive Members A compressive member, or strut, is a component of a structure that undergoes “pushing” forces when under load. This “pushing” or “squeezing” force is constant throughout the member; both ends experience the same force. When designing a compressive member on a truss, some knowledge about how different members act when under a load needs to be understood to get the ultimate strength out of the design. When a load is placed onto a compressive member, it is stronger in one plane compared to another and is just as likely to buckle in plane or out of plane. To account for this, a compressive member should be designed to be as short as possible with additional bracing considered to prevent any buckling. Tension Members A tension member is a component of a structure that undergoes “pulling” forces when under load. Just like a compressive member, this force is constant throughout the member with both ends experience the same force. These members should be as compact as possible to allow for the “stretching” forces that they undergo. A tension member should be kept as light as possible while still be structurally strong to keep overall costs down for the structure. Warren Truss Patented by James Warren in 1848, theWarren truss is the most popular and recognisable truss bridge design in the world. This design uses equilateral triangles to spread loads, minimising forces to only compression and tension. As a load moves across a Warren truss bridge, centre members can swap between compression and tension depending on the position of the load. With minimal components, this design requires fewer materials than others, making it the most economical for short spans. Materials Balsa Wood When it comes to light, strong materials for constructing the scaled model, there is no better economically viable material like Balsa Wood. Being quite a dense timber, Balsa is the only timber in the world that is both a hard wood and a soft wood due to its properties. With a range of dens
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