Comparision - bridge comparison PDF

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Design 1 It is based on a camel back truss bridge design. Camel back truss is a variation of the Parker truss that has a polygonal upper chord of exactly five slopes. This provides some saving of material with the greatest depth of truss where it is most required, at the center of the span. Despite it having the least maximum stress N/mm2 it has the highest total weight and load handle ratio. Which makes it the most efficient among the rest of the design. Furthermore its load is evenly distributed throughout the bridge and it has the highest deform factor so the load distributed more evenly. Moreover it is the cheapest to build but its one of the more complicated bridge to put together. Based on data all the beams are used efficiently towards the overall structure. Also because it was the cheapest and we can use the budget to invest in a variety of materials for a stronger structure. Design 2 It is based on a variation of a Pratt design. It is the more expensive version of the Pratt bridge compared to design 4. Plus it’s less efficient than design 4 as well as it has the lowest total weight and load handle ratio among all the design. Further more the way it spreads out the forces when under load. The longer, angled truss members are under tension. The shorter, vertical members are under compression. This gives a slight advantage over the efficiency of design 3. It’s one of the more difficult design to put together but its easier than design 1. Like design 4 is not advantageous if the load is not vertical but its perfect for mix load application and it not efficient beyond 76m in length. Design 3 Its based on a Howe bridge design. Howe truss bridge consisting of chords, verticals, and diagonals whose vertical members are in tension and whose diagonal members are in compression. Based on the group data it is the strongest among all the design having the most max stress among all the design. But it the most expensive among all the design too. Its doesn’t distribute force as efficient as the Pratt design but it is one of the easier design to put together. Thus it places comparatively lesser stress on top and bottom chord members hence those members are designed with slightly lighter build. Overall it a strong structure but it isn’t as efficient as design 1&4.

Design 4 It is based on a Pratt bridge design.What makes it so good, and gives it an advantage over the Howe truss, is how it spreads out the forces when under load. The longer, angled truss members are under tension. The shorter, vertical members are under

compression. Furthermore it’s a very simple design so it’s easy to put together and if there’s any changes to the design it wouldn’t be very time consuming. It also has a high deform factor so load distribute better. Thus it has the highest maximum stress among the rest of the design but its not as efficient as design 1. Plus its not as advantageous if the load is not vertical but its perfect for mix load application. Also Pratt bridge is only efficient up to 76m in length after that it becomes less efficient which is not ideal for a 100m bridge. Design 5 It’s based on a warren bridge design. The truss utilizes Newton’s laws of motion especially statics that forms an important part of the laws. The straight components meet at pin joints and the components of the truss will be involved in tension or compression. Moreover the structure is strong due to the use of triangles. The triangles are ridged which contributes to the strength of the structure. The span which is the distance between the end points has been found to be greater than with other designs. Furthermore the load is evenly distributed through out the bridge due to all triangles in the bridge is equal and it’s a simple design which can easily be put together but there’s some beam which were unnecessary as they don’t contribute at all to the overall structure which consider as a waste. Also It is easy to fabricate, assemble and inspect because of simple design.

Reference https://www.quora.com/Which-bridge-is-stronger-the-Howe-truss-or-the-Warrentruss-1 https://www.machines4u.com.au/mag/4-types-of-truss-bridges-which-is-worth-theweight/ https://skyciv.com/docs/tutorials/truss-tutorials/types-of-truss-structures/ https://en.wikipedia.org/wiki/Truss_bridge https://bridgehunter.com/category/tag/camelback-truss https://www.ncdot.gov/initiatives-policies/Transportation/bridges/historicbridges/bridge-types/Pages/truss.aspx...