Passage V

A structural beam, such as one used in construction, will deflect (bend) when a sufficiently large force is applied perpendicular to the beam’s length. Three studies of 12 trials each were performed on the deflection of 2 straight structural beams—a concrete beam and a steel beam—that had identical dimensions.

In each trial, 2 supports were separated by a distance L, measured in centimeters (cm), and a beam was centered on top of the supports. A force, F, measured in kilonewtons (kN), was then applied to the center of the beam, and the maximum deflection of the beam, d, was measured in millimeters (mm). See the apparatus diagram.

Study 1

Twelve trials were performed in which L was varied and F was 1 kN. In the first 6 trials, the concrete beam was tested in the H configuration. In the last 6 trials, the concrete beam was tested in the I configuration. Figure 1 shows the results of these trials.

Study 2

In 12 trials, the procedures of Study 1 were repeated, except that the steel beam was tested. Figure 2 shows the results of these trials.

Study 3

Twelve trials were performed in which L was 100 cm and F was varied. In the first 6 trials, the concrete beam was tested in the I configuration. In the last 6 trials, the steel beam was tested in the I configuration. Figure 3 shows the results of these trials.