Much of the strength of built structures comes from the interplay of forces acting within the structure itself, rather than simply from the strength of the materials used.
© Construction Photography
The study of forces within a framework is an important part of an engineer’s training. Any framework can be broken down into component struts or girders, and the simplest of these is usually called a beam - a horizontal girder that carries various vertical loads.
Beams and girders are essential tools in the construction industry, be they made from oak, steel or prestressed concrete.
All doorways and windows require wooden or steel/concrete lintel beams to carry the weight of the structure above. Tall buildings are still built around a steel-girder lattice, and modern suspension bridges are simply suspended hollow-box girders with additional internal girder reinforcement.
In order to design such weight-bearing structures, an understanding of how the beam deals with these weights is essential. Fortunately, the calculations concerned are not complex, as you will discover for yourself.
Girder skeleton of an unfinished structure.