The following link opens a new window which contains interactive demonstrations on statics:
Introduction
The purpose of these interactive demonstrations is to help you develop a thorough understanding of basic principles of structural behavior, and to provide you with tools and knowledge that will help you to design structures that are efficient and elegant.
Before you begin, you should have some familiarity with the rudiments of graphic statics. These can be learned from: 
Zalewski, and Allen. Shaping Structures: Statics. New York, John Wiley and Sons. 1998. ISBN 0471169684, and from the companion CD-ROM lessons in: Iano, Joseph. Graphic Statics. New York: John Wiley and Sons. 1998. ISBN 047128338X.
The Origins of These Demonstrations
These interactive demonstrations were conceived and programmed by Simon Greenwold. When Simon was a graduate student in architecture at MIT, he took a beginning structures class in which he learned graphic statics from the textbook by Zalewski and Allen entitled Shaping Structures: Statics. Drawing on his previous experiences as an undergraduate math major, teacher of high school geometry, and computer programmer, he created the first version of these demos as a tool for presenting his final project in the class. Subsequently, while doing graduate work in MIT’s Media Lab, he completely reworked, expanded, and enhanced the demos, working closely with Waclaw Zalewski and Edward Allen, to produce the product linked to above.