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# Bridge constructions

Presentation about the masterpiece "Bridge constructions" by Sander Boelaars and Stijn Riemen, performed february 2013
by

## Stijn Riemen

on 4 February 2013

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#### Transcript of Bridge constructions

Bridge constructions Sander Boelaars
Stijn Riemen Akashi Kaikyo Bridge Suspension bridge Pont du Gard Arch bridge Forth Bridge Cantilever bridge Sydney Harbour Bridge Truss-arch bridge Erasmus Bridge Cable-stayed bridge load distribution: upside of the beam is under compression
compression is a pushing force
downside of the beam is under tension
tension is a stretching force Truss bridges truss functions as a beam, with a more economical use of materials
forces only act at the nodes, therefore only tension and compression in the members
compression in upper chord, tension in lower chord Calculations on trusses Warren truss equilateral triangles
60° angles
50 N load suspended from node C Static determinability when a structure is statically determinate it can be analysed using the equations of equilibrium (Newton's Third Law)
a structure is statically determinate when 2n = m+3
n is the number of nodes, m is the number of members
there are 9 nodes and 15 members
2x9 = 15+3 so the truss is statically determinate Normal forces 50 N load suspended from node C
force is equally distributed because truss is symmetrical in C
supporting points A and E take on equal amounts of the applied load
weight of structure itself is neglected
results in a 25 N normal force in both nodes A and E Node A Node I All kinds of bridge types Beam bridge simplest type of bridges
oldest type, occurs naturally
beam, log, plank of wood, slab of stone are all beam bridges Beam bridges load-bearing structure is a truss
truss consists out of triangular elements
members and nodes Basic truss types Spaghetti bridge design How much force is the material used able to withstand? Measuring tension Measuring compression Results: spaghetti can withstand 0,29 N compression on average
spaghetti can withstand 27,96 N tension approximately + we decided to use 20 strands of spaghetti bundled together for use in the members under compression, these members can withstand 20x0,29 = 5,8 N
under a load of 50 N from node C the maximum compression in a member is 58 N, but in our bridge the members will only be able to withstand a maximum of 5,8 N, using ratios the maximum load on node C for our bridge will be 5 N our truss bridge consists out of two trusses held together by lateral bracings
each truss can carry 5,0 N
together they can carry 10,0 N
10,0 N converted is approx. 1 kg Held 1374 grams Conclusion the bridge was able to carry more than we calculated
probably due to inaccuracies in measuring compression, spaghetti is stronger than we measured Thank you