To convert from grams to kilograms: 1 kilogram = 1,000 grams

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1 Tips for Making Measurements When you design a structure, it s useful to collect and record quantitative data as evidence for your evaluation. You can use the tips below for making quantitative measurements. Measuring Mass Measuring Loads Measuring Strength Measuring Displacement Measuring Horizontal Stiffness Measuring mass You can use the spring scale to approximately measure the mass of the structure (in grams) or the weight (in Newtons). The pennies comprise almost all of the mass. Place the pennies in a plastic bag and hang it from the spring scale. To convert from grams to kilograms: 1 kilogram = 1,000 grams To review the difference between mass and weight, read the Everyday Mass/Weight Confusion article. Measuring loads Buildings must be strong enough to support design loads which are stated in the building specifications, or in design codes. Measure both vertical and horizontal loads. Vertical loads: Buildings are built to support downward forces; their own weight (dead load) and other transient weights ( live load ).

2 To apply a vertical load to the model, place a plastic container containing pennies on top of the structure. Use the spring scale to weigh the pennies: Place the pennies in a plastic bag and hang it from the spring scale. Read the weight in Newtons. Example: Vertical design load for the wood frame and masonry house For the wood frame in Sessions 6 and 7, the design specifications require that the structure supports 200 pennies, representing the dead and live loads of the floors above. 200 pennies have a mass of about 550 g, exerting a downward force of about 5.4 newtons, or about 1.2 lbs. Vertical design load = 5.4 newtons Horizontal loads: Earthquakes and wind exert horizontal forces on the structure. Earthquake engineers estimate that the horizontal force that will act on a building during an earthquake is proportional to its weight, typically 1/10th of its weight. The horizontal force can act in any horizontal direction: front to back, or side to side, or any direction in between. To apply a horizontal load to the model, use the spring scale to pull the model in a horizontal direction. Read the magnitude of the force in Newtons on the spring scale.

3 Example: Horizontal design load for the wood frame and masonry house For the structures in Sessions 6 and 7, most of the model s weight is the pennies. Since 200 pennies weigh 5.4 newtons, the horizontal design load is just over.54 newtons. Horizontal design load = 0.54 newtons. Measuring strength An ultimate strength test involves destroying your model! The ultimate strength is the maximum load that the model supports before it fails. Vertical strength: To find the ultimate strength of the your model for vertical loads, keep adding pennies to the plastic container until the model collapses. Record the weight of pennies which cause collapse.

4 Horizontal strength: To find the ultimate strength of the your model for horizontal loads, attach the spring scale to the model and pull in a horizontal direction until the model collapses. Record the force on the spring scale just before collapse. Measuring displacement Horizontal displacement: Use a ruler to measure the horizontal distance (in centimeters) between the base and the top of the building. Measuring horizontal stiffness The foam building in the videos of Session 4 is very flexible and moves a lot without breaking when it is shaken. (You can imagine all of the furnishing, plumbing lines, and electric wiring, as well as the inhabitants being destroyed in the motion.) Your model, on the other hand, is probably quite stiff, and moves just a little.

5 You can measure the horizontal stiffness (k) by finding how much horizontal force (f) is required to cause a certain horizontal displacement (x) in a structure. Mathematically, this is expressed by the formula: Stiffness = force/displacement k = f/x 1 meter = 100 centimeters 1 kilogram = 1000 grams