Expert: Veto Varma - 3/3/2007

Question
Hey there. My name's Anie and I'm taking a class in Environmental Science. We are studying earthquakes and we have the option of presenting something in relation to the class. My group would like to show the class earthquakes and its effects on buildings. We're using wooden sticks and our teacher has an apparatus for "earthquakes" he built a while ago. So, if you can, what is the easiest but strongest design or structure for an earthquake resistant skyscraper but in smaller scale and wooden? We want to make it with a square base and about 3 stories. We propose it to be around 45 cm tall with each story about 15 cm, and the base 22.5 x 22.5 cm. We want no solid walls either. We researched cross bracing, etc. but there are so many designs to choose from!! Any of your help would be much appreciated! Thanks in advance!

Anie

Answer
Hello Anie,

You are on right track. Wooden stick, three storey model will be ideal to show the effects of earthquake on a building. Here are couple of suggestions.

a. To show the effects of bracing and ductility design I propose to use Cross bracing, also called X bracing, on all stories only on two sides. You should have stick model where you can attach the bracing very easily. Buildings designed without X brace have moment connections, i.e. connections resist all the rotation and makes building rigid. X brace saves some cost and easier design. you can highlight these things in you model.

b. You can put the same stick model on little rubber pads, and shake it and show the effects. This is called base isolation concept, whereby reducing the eartquake energy transfer to building and saving in the design. For more information on this concept you can visit University of California, Berkeley website.

Hope this helps.

Regards
Veto