Bridges

The Challenge:
- Design and construct a bridge using only the provided 1/4" x 1/4" lumber and wood glue that can safely span a 12-inch gap. The bridge must adhere to specific size constraints and will be tested for its structural efficiency. The efficiency will be a ration of bridge weight in ounces/how many lbs the bridge holds.
Constraints:
- Bridge must span gap that is 12 inches wide.
- Bridge must be 16 inches long.
- Bridge cannot be taller than 4 inches.
- Bridge cannot be wider than 3 inches.
- Each group will be allotted 20 linear feet of 1/4"x 1/4" lumber to build.
  - Any material used beyond their allotted amount will results penalty points.
- Various joint types are allowed and encouraged.
- Paper gussets should be used. (no wood gussets)
- Groups of 3 max! Pairs encouraged.

- Efficiency Ratio = (Maximum Load Held) / (Weight of the Bridge) :
  - This means a higher number is better, indicating the bridge held many times its own weight.
- Here's the calculation:
  - Step 1: Convert Bridge Weight to Pounds
    - Since 1 pound = 16 ounces, you will divide the bridge's weight in ounces by 16. This gives you how many pounds your bridge weighs!
  - Step 2: Calculate the Efficiency Ratio
    - Now that both are in pounds, you can divide.
    - Efficiency Ratio = Maximum Load Held (POUNDS)/ Weight of the Bridge (POUNDS)
  - Example: Let's say a bridge weighs 5 ounces and held 40 pounds.
    - Convert Bridge Weight:
      - 5 ounces/16 ounces = 0.3125 pounds
    - Calculate Efficiency Ratio:
      - Efficiency Ratio = 40 pounds/0.3125 pounds = 128. So, an efficiency ratio of 128 means the bridge held 128 times its own weight.

Vocabulary:

beam – a horizontal supporting member
bridge – a structure that spans a gap
buckle – to bend under compression
column – a major vertical support of a structure
compression – the tendency to push, squash, or squeeze a material
constraint - limit
efficiency – the strength-to-weight ratio
force – the capacity to do work or cause physical change; energy, strength, or active power
joint – a place where two or more things come together and are united
lamination – the act of layering a structure
load – the overall force to which a structure is subjected in supporting a weight or mass or in resisting externally applied forces; the amount of weight or mass supported by the lift of an airplane or airplane wing
mass – the amount of matter within an object
model – a small object, usually built to scale, that represents in detail another, often larger, object
modification – a change in design, hypothesis, or prototype
racking – a type of stress that distorts a square or rectangle, causing it to become a parallelogram
rigid – stiff or not easily bent
roadbed – the foundation of a road
scale – a system of proportion
side grain – the grain of wood as seen from the side of the wooden strip
side view – a view from the side of something
sketch – a drawing, usually freehand, that provides a quick illustration of an object or process
span – the measure of the distance between supports
substructure – the structure of a bridge that extends below the roadbed
superstructure – the structure of a bridge that extends above the roadbed
tension – the force pulling a material apart
timber – the wood used as a building material
tower – a tall structure that acts like a cantilever beam
truss – a rigid framework, as of wooden beams or metal bars, designed to support a structure such as a bridge

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