EXPERIMENT: 3
THE EFFECT OF THE CROSS-SECTION SHAPE ON THE STRENGTH OF BEAMS
In this chapter I have written about the experiments and the results on the effects of the cross-section shape on the strength of beams.
3.1 Purpose
To establish which cross-section shape will hold the most load.
3.2 Hypothesis
I think the folded plate will hold the most load because
it's more layered. I think if there's more layered, it'll be able
to with-stand more.
3.3 Variables
Dependent Variable: Failure Load (N)
Independent Variable: Cross-section shape of a beam
Controlled Variables: Total Material, length
3.4 Materials
15 card board pieces which are 400mm x 240mm x 550mm.
2 supports (level desks to put cardboard beam on)
Data sheet
1 Extensometer Scale
1 Fish Scale
3.5 Making of the Test Specimens
For this part of the experiment, I decided to experiment
on five different types of beams. These five types of beams would
have five different shape. The shapes are: 1) folded plate, 2)
square, 3) circle, 4) triangle, and 5) inverted triangle. I
folded each cardboard piece, so that all the sides were equal. I
then connected the cardboard using duct tape. For this
experiment, I had a total of fifteen specimens (there were three
of each type). The planned cross-section shapes are shown on Figure 3.1.(A). All of the actual test specimens are shown on Figure 3.1.(B). After making the specimens, each specimen was assigned
a label. For example specimen S-3 means, it is a square, and it
is the third test of this type. After labelling the specimens,
you must measure the dimensions of each beam and record it on the
data sheet.
3.6 The Test Set-up
Figure
3.2 shows the planned test
set-up. Figure
3.2, the supports, specimen,
scale, and clear span are shown. The clear span is the distance
between each support. Figure 3.3
shows the actual test set-up. Before you start experimenting, you
must first prepare the specimen. Mark the centre of the specimen
and the support points on the specimen. This will help with the
correct placing of the specimen. Put the scale onto the centre of
the specimen. Using the support points on the specimen, mark the
support points with the supports. On the data, write the initial
reading on the scale.
3.7 The Test Procedure
Now that everything is set-up you can start the
experiment.
3.8 Behaviour of Specimens During
Testing
As you experiment, you have to observe how the specimen
reacts. You should notice that before experimenting, the
specimens all have shape. When you begin to apply load on the
specimen, the specimen will begin to flatten. At the end of the
experiment, you should notice that the beam is flat, and it has
lost its shape.
3.9 The Results
All the results for the shape experiment are shown on Table 3.1. The first column in this table identifies each
specimen by its name. The second column shows the failure load
for the first beam of each type. The third column shows the
failure load for the second beam of each type. The fourth column
shows the failure load for the third beam of each type. The
results for each type of beam should be around the same failure
loads for each test. However, some results are different may be
because that certain specimen may have had some weaknesses, such
as parts peeling off. The last column of the table shows the
average results for each type of beam. The average is found by
adding the three failure load results of each type together, and
dividing the total by three.
3.10 Conclusions
Looking at the final data, which are shown in Table 3.1, I would say that the shape does affect the failure
load of beams.
3.11 Accept/Reject Hypothesis
I accept my hypothesis because the shape does affect the
strength of beams.