CALCULATING TRUSSES

Calculating Trusses

Calculating Trusses

A truss is a complicated and potentially frustrating statics problem to solve. The more members a truss contains, the longer it takes to solve. It can be overwhelming to attempt to solve these trusses via the method of joints.  Using the method of sections, this process can be sped up a great deal, but it requires a good deal of thought to figure out where to begin, and how to proceed. A way around this is to utilized the power of computers to assist in the computation of the method of joints.  Since this method is a fairly straight forward and mindless task, the computer can perform these masses of computations quicker and more accurately (and with less frustration) than a person.  Therefore, it would be useful if there where a computer program to perform these operations for you.

The method my program will use for determining the forces in a truss member is as follows:

I. The program will receive input from the user regarding the various components of the truss, such as A. the coordinates of the vertices B. the loads at those vertices C. which vertices are connected to one another by various members.

II. The program will then use the input data to determine the loads in each of these members. A simple example of a truss that this program will evaluate is the one shown at left.  It consists of several vertices, one of which is a hinge (vertex C, exerting forces only in the X and Y direction) and another which is set on rollers (vertex B, exerting forces only in the Y direction) as shown in the free body diagram below.

The Program This program will utilize the method of joints to determine the forces present in its various members.  Actually writing the code to accomplish this is somewhat difficult. First, we find a vertex that is connected to only two other vertices. Next, we solve for the components of force in this vertex.  It is usually easiest to start with the vertex on the roller, since there is only one force component to worry about, besides the forces applied by the two other members connected to it.  We are specifically looking for a the one of the components (either the i or j) in the member to equal zero while the same component isn't zero in the other unknown member. ...