Jacob S Height Engineer
     Most normal buildings are made of bricks and mortar.  These materials wouldn't be strong enough to hold up a skyscraper.  The biggest breakthrough in the building of skyscrapers was when iron and steel became available in massive quantities.  Another important aspect of skyscrapers are the beams.  Most beams are designed to bend and the flexibility makes the building resist winds and other elements better.  Most beams are made of steel.  The most widely used beam shape is the "I-beam". 

     Skyscrapers are held up by numerous things.  The first support system is the base.  A substructure is put underground to help support the weight.  Next are a bunch on vertical columns, usually made of steel.  Each floor then gets steel girders which are attached to the vertical columns.  Finally, the walls and floors are built onto the steel skeleton.

     There are three main cities skyscrapers are built: Chicago, New York, and Hong Kong.  Every skyscraper-to-be must be designed specifically to withstand any winds, weather, or other elements it might have to face.

 
InterviewI interviewed Brenda, a pharmacist who was the general contractor when her house was being built.   She had a few good points to make sure we included.  Triangles are the strongest structure.  Also, most structures are based around a center beam on which the weight is focused.  Corrugation is also really strong; we ended up using corrugation. 
Our structure met the height and weight requirements.  It was about 9.5" tall and held the minimum of 45 lbs.  The maximum held in our class was not ours, but ours did hold 360 pounds.  Our design was relatively simple.  We had a corrugated circle inside a corrugated triangle.  I think the fact that we had a large base helped to distribute the weight more evenly.  Our structure also had some weaknesses.  One major weakness was the fact that our structures top was slanted.  As you can see in the picture, that made all the weights to slide off one side.  Some of the corrugation wasn't even and caused the structure to be less strong in one part than another.   If I could make another structure I would make sure to make the top straight and have a grid system or even more than one level to help the weight not be focused on a weak spot.reflections
   
Sites Used:

http://science.howstuffworks.com/skyscraper.htm