12-100 Introduction to Civil and Environmental Engineering
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Testing of wood specimens
Submission of plank calculations
February 11, 5:00 P.M.
Submission of preliminary report
February 13, 2:30 P.M.
Testing of planks
Construction of cardboard structures
Testing of cardboard structures
Presentation of oral report
Submission of final report
February 25, 5:00 PM
This project involves structures that bridge a horizontal span to support a load, and in doing so the
major elements of structural mechanics will be introduced.
Essentially, most bridges can be
, structural members capable of resisting internal
simplest type of beam is a plank, and this project starts with the study of wood planks.
The strength of a plank or beam, meaning the load it will carry before it fails, was another of the
great problems of antiquity and the renaissance.
It was understood that the load at failure would
depend upon the span length, the size of the beam in cross-section, and the beam material itself.
How can one predict (calculate) the load at which failure will occur?
The answer that we use as
modern engineers was developed between the 17
centuries, and is summarized by the
principles of force vectors, free body diagrams, reactions on structures, internal bending
moments, theory of elasticity, and stresses induced by bending.
In our lectures and homework
exercizes you will learn those principles, as well as relevant principles of statistics, and you will
use them to answer the engineering questions surrounding the wood planks in this project.
This project involves a series of three experiments.
Your group will receive a set of six wood
specimens and one wood plank.
In the first experiment, on September 20, your group will test the
six wood specimens to obtain the failure stress of the wood.
From that information you will
calculate pertinent statistics concerning the expected performance of your wood plank.
second experiment, on September 27, your wood plank will be tested as a bridge, at which time it
will either fail or survive.
Between September 20 and 28 you will also design and construct a
cardboard structure as a substitute for the wood plank; in the third experiment, on September 29,
your cardboard structure will be tested as a bridge, at which time it will either fail or survive.
The Bridge, its Location, its Span, and its Loading
The floor in the Tung Au lab contains a hatch that opens to reveal a frightening drop.
and the cardboard structures must span 48 inches across that opening, and are intended to support
your instructor, who weighs 180 lb, as he steps over the abyss.