Introduction to Structural Mechanics
In an effort to compete with film and TV, theatrical stage scenery has been growing larger, more complicated and more ambitions year after year. This trend began with Broadway shows such as Les Misérables and The Phantom of the Opera and continues today. This trend has been expanding from the commercial markets to regional theatres across the country. In order to meet the needs of these large scale and often non-traditional physical productions technical directors and theatre technicians need to understand the forces at work on structural members and be able to determine what is necessary to resist those forces. In the past scenery would often constructed using tried and true methods, or engineered using the ―trial and error‖ or the ―that should hold it up…‖ method. This is becoming less and less practical, economical and safe. In the world of scenic construction there are certain things that are more or less standard. For example, platforms built from lumber will usually use either 2 x 4 or 1 x 6 in the construction and covered using ¾‖ plywood. You probably would then attach six legs of some sort, two on each end and two centered along the platform‘s long side. Why do you build it this way? Because that is how you were taught to build platforms. It works. It always has and it always will. But what if the platform could only be two inches thick? What if it also had to span ten feet without support in the middle? What if it is a production of The Fat Boys Learn to Dance and all six of them do a kick line on the platform for the finale?! You could tell the designer and director that their artistic vision is impossible and there must be legs in the center or the platform must be thicker or you could calculate what materials you would need to use to make this artistic moment a reality. Sarcasm aside, there should be no doubt that a technical director, scenic carpenter or theatrical technician must have a good working knowledge of simple structural mechanics. There are many books on the subject of engineering but most of them are directed at students of Engineering, not the theatrical technician. It is the author‘s attempt here to compress a very lengthy and detailed subject into a simplified and manageable form, useful to the theatrical technician. This is not an easy task and involves simplifying or, in some cases, omitting much of the information. For example, it is rare that we will need to account for snow loads or have to account for seismic occurrences when designing indoor scenery, therefore this text will not discuss such matters. Many professional engineers would resolutely object to such a text as this and they do have a point. This text cannot even begin to cover the actual complexities involved in even apparently simple structural cases. Since a chain is only as strong as its weakest link, even a slight mathematical error or error in logic could produce disastrous results. They feel that a little knowledge is a dangerous thing. What must be remembered at all times is that mastering the material covered in this book does not make one a structural engineer. That would require many years of school, concentrating solely on such matters. What mastering this material does give is a tool to provide reassurance that one‘s methods and materials are sufficiently strong so as to provide for safe scenery. Anyone experienced in scenic construction already has a feel for the forces at work in a structure, but these mathematical
tools give some substance to your ‗‖gut reaction‖. One should never throw away standard scenic construction methods simply because your numbers say there is sufficient strength in one‘s new choice of material. As the theatrical world expands into more and more elaborate construction it is becoming necessary to be able to dissect a particular system to determine what forces are at work and how those forces will affect the material the scenery...
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