Morris tribune. [volume] (Morris, Minn.) 1880-2000, 1897-04-07
THE ST. LOUIS TORNADO.
Enormous Pressure Exerted by Wind
An Architects Views.

The st. Louis tornado Of May,
1896, is the subject of an elaborate
paper by Mr.. Julius Baier in a recent
number of the Proceedings of the
American Society Of Civil Engi-
neers." Mr.. Baier, who is civil
engineer making speciality of the
iron and steel work in high buildings,
has made careful study of the de-
struction caused by the tornado, for
the purpose Of determining the pres
sure it exerted on brick structures.
The general deductions from his IN
vestigation are as follows: The ex-
treme force of the wind was general
ly confined to upper stories and roofs,
and the intensity of this force must
have been extremely variable, not
only as exerted on adjacent proper
ties, but on single building. There
was very general evidence OF the de-
structive force being exerted from
the inside. In the case of the st.
Louis bridge, the author Of the paper
estimates that for distance of $50
feet at the center Of the structure the
wind must have exerted a lifting
pressure Of over 43 pounds per square
foot. At the east end the wind must
have exerted a force equivalent to
uniform static pressure OF at least
60 pounds per square foot over an
area at least $50 feet long by Is feet
high. 1t is regarded as more prob
able, however, that the area Of de-
structive pressure was more than Is
feet high, and that the pressure was
not uniform, but maximum near
the center and less at the sides In
the case of the brick chimney Of
the Union Depot electric railway, Mr..
Baier estimates that the wind must
have exerted in this locality. "a force
equivalent to static pressure of IS
to 81 pounds per square foot over an
area Of at least "A feet wide by ITO
feet high. It is considered probable
that the pressure was not uniform,
but greater near the top. 1t is also
possible that the chimney was over
turned either by successive gusts Of
wind recurring at intervals COZ e
spending to the oscillations Of the
chimney, or by one sudden and in
tense blast. In the former case the
actual pressure Of the wind might
be much less, while in the latter it
would be much more than the
amounts mentioned. The largest
and heaviest single object moved by
the tornado was the Valley grain
elevator, standing on the east shore
of the river, on the south line Of the
path of the storm. Mr. Baier calcu-
lates the. force exerted must have
amounted to at least 16 to 20 pounds
per square foot over an area
300 feet long and Ito feet
high. All this is cited for its bear
ing on the construction Of the mod
ern high office building. The IRON
framework of such building gives it
its strength, and consequently. pAust
be relied upon to resist wind pres
sure. The skeleton framework used
in early buildings Of this class is
simplaan arrangement of metal col
umnssand beams, depending for its
efficiency on exterior walls and par
titions to hold it in position, just
as the muscles hold the bones of the
skeleton in place The word cage
is term particularly descriptive of
that type of construction represented
by the most advanced practice,
framework Of columns and beams
spliced at the joints, riveted at the
connections and stiffened by an eff
ficient bracing which makes it per-
fectly safe against any external force,
leaving the thin and light exterior
walls with no duty except that of
providing protection and ornamental
ton for the building The effect of
an extremely high wind pressure on
an office building of this general class
must depend largely on the extent
to which its framework partakes of
the nature of the skeleton or cage
types Of construction. Mr.. Baier
concludes that the chief justification
Of much that seems bold or ques-
tionable in the construction of some
high buildings lies in the fact that
as yet none have failed. If the safe
ty Of such great structures is to be
determined entirely by the logic of
the fitness of the survivor based on
a brief and favorable experience,
rather than by a rigid analysis by
tried and accepted principles OF en-
cheering designs, it may ultimately
lead to some very deplorable results"