Column Buckling

Objective
To investigate the concept of column buckling.

Definition and Theory
Buckling is defined as an instance of lateral bending or bowing of the column shape due to a compressive load on a column. There are three basic types of column failures. One, a compressive material failure, i.e., the material cracks or crumbles. This type of column failure usually happens to columns that are very short and fat. Two, a buckling failure, i.e., lateral bending or bowing of the column shape. This type of column failure usually happens to columns that are very long and skinny. Three, a combination of both compressive and buckling failures. This type of column failure occurs when length and width of a column is in between a short and fat and long and skinny column. (P) is the compressive load that causes buckling to occur. Buckling for this experiment is defined when the lateral change from a straight line to the curve is equal to the ratio (D) is equal to (L) / (H) = 24; record the load at this point. We are using this ratio to so we can compare column buckling of various lengths. As the length decreases, the horizontal distance (H) decreases.

Procedure

• Calculate the buckling ration, the H distance as defined above, for each column length in the data table (see below).
• Use a 1/8" x 1/4" piece of balsa wood as the compressive test member. Be sure to place the strong axis (the 1/4" dimension) is in the vertical position. This will insure the compressive member buckles in the weak, horizontal, direction first.
• Starting with the 36" long compressive member, load the pennies on the end of the cable until buckling occurs. Record the information in the table. Do this for each length as shown in the data table. Remember to keep the cable on a 45� angle.
• Graph the relationship between Column Length and Load on the graph provided
• Answer the questions in the lab.