September 1 2021
Roof truss, like other similar structures, are devices used for transmitting loads from the wrong place to the right ones. They serve the function of taking the weight of the roof and transferring or distributing it out into the load-bearing walls of the house. What really makes the truss unique from other structures is its clever and very efficient design the way it carries the load. This is due to two major factors - geometry and laws of statics.
How Geometry Works
Just imagine having a set of flat sticks where you make holes at the end of each one so that you can connect it with bolts. If you connect three of these sticks, you make a triangle which stays rigid even if you don’t tighten the bolts so much. However, if you get four sticks and make them into a square, you won’t be able to turn it into a rhombus when you push on it regardless how much you tighten it.
Unlike the triangle, the rigidity of a square depends on the strength of the bolts and to make the square really rigid, you have to make a diagonal brace to make two triangles within the square. Triangles have this excellent inherent rigidity as its geometric property. They have the highest order polygons. You can even add rigidity to it by adding or making more triangles around it. This is the fundamental truth about a roof truss.
The Laws of Statics
Basically, the laws of statics state that if a body or a structure is loaded at two points only, the resulting forces at these points are equal, opposite, and act along the line between them. Applying this to a roof truss, this means that the resultant forces on the truss members are axial, or acting along the axis of the member, placing them in either pure compression or tension. Depending on their angles and the distribution of the loads, the truss members may be in tension or compression. But overall, they are designed in a perfect equation and balance, thus producing rigid, strong, and durable truss.