This week I experimented with the
two cross section types, bar and tube. I found tube to be more cost effective.
Also I tested the three types of metals, CS, HSS, and QTS. I found HSS to be
the most cost effective, it was much cheaper than QTS and only slightly more
than CS but much stronger. I also came to the conclusion that condensed bridges
are less expensive and perform better to less tension on such long piece that
would have to be thicken to hold that same weight, so short and thin is better
thick and long. With WPBD it was easy to make changes, test, and find the data
on how to adjust from there. One thing I learned is that an easy way to be cost
effective it to make some few important areas just a bit stronger will allow
you to reduce many other areas allowing the bridge to still hold but still
reduce the cost. Last I did some research into how trusses designs work.
My research of truss bridges has
shed light on to why they are made with triangles and what the more common
styles that are used, many have more of an X crossing rather than a crossing
that goes to the left or right like /|/| / or \|\|\ . Also I learned that while
truss bridges are very effective over short to medium spans, arch bridges seem
to be more efficient and hold more weight when compared to the truss, so
trusses that have an arch shape or angled on top tend to be better. In my
research I found that many trusses are top trusses rather than bottom trusses,
the reason being that the weight gets distributed downward and out to the ends
better that way. These mean that the middle where the load is farthest from the
distribution point at the ends and at the ends are the areas that undergo the
most force and undergo it for most of the time meaning that these areas must be
more enforced than the rest of the bridge.
What were going to do this week
is to compare our bridge data and try to combine the best aspects of each and
make them work together as best as possible. This week will mostly be a lot of analysis
and much more testing in WPBD to see what can still be improved before we move
to models .
My three questions will be:
What are the pros and cons of a
truss bridge to other short to medium length bridges?
What is the strongest load design
for a truss, normal or arched? Truss on top, bottom, or both?
When bridges fail what is the
most common reason why and what is the area that fails?
-
Kyle Hayes
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