Properties of Plank wood & bridge question

In summary, the group is tasked with proposing designs for a plank bridge over a river. The material's strength properties, specifically for wood, are needed but have not been found. It is suggested to consult the Forest Products Laboratory website for this information. Additionally, the practicality of a 2-3km long wooden bridge without supports is questioned and it is recommended to look into Michael Ashby's book on Materials Selection for guidance on selecting a suitable material for the project.
  • #1
Ngineer
64
1
Hello everybody,

For a group project, we are supposed to propose several designes for a plank bridge over a river.

I've tried to find this material's (plank wood) strength properties, or a stress-strain diagram to no avail. Do you know where I can find it?

Also, is it reasonable for a wooden bridge to be 2-3km long? Do we need supports over the river to make it safe and practical?

Your help is greatly appreciated!

Thanks
 
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  • #3
Ngineer said:
Also, is it reasonable for a wooden bridge to be 2-3km long? Do we need supports over the river to make it safe and practical?

?

This is what a bridge just over 2km long might look like ...

http://inbarton.110mb.com/bridgecurve.jpg [Broken]http://inbarton.110mb.com/bridgeair.jpg [Broken]
 
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  • #4
First things first. If you have decided your construction will be based on wood, you can find the approximate material properties in Michael Ashby's book on Materials Selection (https://www.amazon.com/dp/1856176630/?tag=pfamazon01-20).

The properties you are looking for are the following: Flexural strength, buckling strength and tensile strength for a 'wood-like' material. Also, it is literally impossible that you can build a 2-3 km structure out of a single plank of wood that is supported only at the ends - if it somehow escapes bending under its own weight it will still easily be swayed by winds. Maybe I am giving you more complicated advice than you need, so just look up Ashby's book first. It deals with several nice examples regarding how to select a material for specific objectives.
 
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  • #5
If your plank has a large enough area moment of inertia you could use one plank and not have excessive swaying... but good luck finding a tree that size...
 

1. What is the density of plank wood?

The density of plank wood can vary depending on the type of wood used, but on average it ranges from 0.4 to 0.8 grams per cubic centimeter.

2. How strong is plank wood?

The strength of plank wood also varies depending on the type of wood and its condition, but it is generally known to be a strong and durable material.

3. What factors affect the properties of plank wood?

The properties of plank wood can be affected by several factors, including the type of wood, the age and condition of the wood, and the environment in which it is used.

4. How does moisture affect plank wood?

Moisture can significantly impact the properties of plank wood. Too much moisture can cause the wood to swell and warp, while too little can cause it to shrink and crack.

5. What are the main considerations for building a bridge with plank wood?

When building a bridge with plank wood, it is important to consider the type and condition of the wood, the weight and load that the bridge will need to support, and the environmental conditions in which the bridge will be located.

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