Evening star. [volume] (Washington, D.C.) 1854-1972, 1931-03-08

principles but even then only II the structure
IL Of the limited dimensions permitted by Jap
anese building regulations. An American once
building must have steel frame. but should
also have reinforced concrete walls and parti-
tons.
Enough Of ruins They weary by their mo-
nOtony. We need constructive research that
we may construct better and understandingiy.
Constructive vibration research requires arta-
Hcial earthquakes under strict control We
make them ct Stanford University at our
pleasure, under the control Of Prof. Lydik
jacobsen and the direction of Dean Theodore
Hoover Of the Engineering School. We limit
their activity, however, to q shaking table and
the particular model that may be bolted TO 1t.
The table is q massive affair of steel beams,
large enough to carry a full-sized wall or the
four walls Of small room or q big box
filled with sand tank fun of water or a
model Of a skyscraper. We have worked it
with each one OF these to test-some structure
or to experiment on movements Of wet or dry
ground or to measure the impact Of water
against dam or TO photograph with movie"
camera the swaying Of a tall building.
To produce an earthquake effect we may
strike the table pianissimo or crashingly with
a half ton pendulum that drives it against pow
erful springs. Or we may run a hywheel which
carries an eccentric weight and is firmly at-
tacted 70 the table By this device We can
continue the vibration indefinitely with any
desired 1OTce, ana any numDer OF CO-duo-ATO
movements q minute.
But to shake is only half the task. We must
know what the earthquake does To accom-
plish this Prof. Jacobsen, whose ingenuity as
an earthquake trainer seems inexhaustible, has
devised delicate recording apparatus, which
enables him to determine what the distortion
Of the model has been at any time during an
experiment and what stress has been set up
in the structure.
EXPERIMENTS with the shaking table have
been in progress at Stanford for about
three years. in small way because the avail
able funds are limited and also because re-
search proceeds most surely if not hurried in
the early stages. Some preliminary results
have, however, been published for engineers,
and an embarrassing number Of promising leads
Of investigation Is opening up. Among them
is one that is of special interest to builders Of
@Woolworth" Chrysler and Empire towers and OF
the innunaerable small fry among skyscrapers.
I can best illustrate 1t by describing the
Great Six of Baalbek, in SYRIA group OF six
columns supporting fragment Of heavy entab-
lature. They formed the portal Of the temple
Of Jupiter which Theodosius the Great, with
Christian fury, destroyed so far as lay IN his
power. Walls and columns fell at his COM
mand, but the Great Six defied him and they
have continued TO defy all attempts TO over
throw them, even by severe earthquakes. Six
teen hundred years have passed, but there they
stand, united by the heavy entabiature and
indeed preserved by it.
They are so feet tan and the massive rem
Iant they support is the weight Of an In
verted pendulum. It swings to and fro on them
with O long, slow motion, swinging more slowly
than the earth moves under them In an earth
quake.
Thus, as the columns swing toward the point
where they might be overthrow, the returning
movement of the ground brings their base UNI
der them. Upon their reverse swing the same
check acts again. They have never been swung
far enough to fan because they are stopped