STRUCTURAL STEEL AND STEEL-FRAME BUILDINGS. 143 
FOUNDATIONS. 
It is believed that every building whose foundations were well and 
strongly established — upon deep piling, as the Union Ferry Building 
and the Merchants' Exchange; with reenforced-concrete slab, as the 
Call Building; upon separate concrete piers or grillages resting upon 
good beds having a uniform load per square foot, as the Union Sav- 
ings Bank in Oakland; or upon any other type of excellent founda- 
tion — escaped injury by the earthquake to the foundations themselves, 
nor did the superstructure owe any damage to inefficiency in those 
foundations. 
The central portion of California was subjected to a severe earth- 
quake in 1868, and has, on a number of occasions since, been slightly 
shaken by earthquake shocks, but many architects and engineers, and 
the people generally, had become so accustomed to these slight move- 
ments of the earth's crust that little attention was paid to them, and, 
so far as the writer can learn, architects had believed that in estab- 
lishing solid foundations for high steel buildings, with good anchor- 
age and bracing, adequate to take care of extreme wind force, they 
had sufficiently guarded against the effects of any earthquake vibra- 
tions which might occur. As a matter of fact, the provisions thus 
made seem to have been ample and safe so far as any disturbance of 
the foundations or any lack of support of the superstructure has 
been detected. Notwithstanding the severe vibrations these tall 
buildings have been called upon to endure, they have remained plumb 
and very slightly damaged by the earthquake. 
STRUCTURAL-STEEL FRAMES EXPOSED TO VIBRATORY MOTION. 
As stated by A. O. Leuschner, secretary of the California earth- 
quake commission, and also by Professor Omori, the distinguished 
seismologist of Japan, the vibratory motion in Berkeley and in San 
Francisco was approximately 3 inches in a horizontal direction and 
about 1 inch vertically, the time of the first oscillation being one sec- 
ond. This is understood to be the vibration on very hard soil or 
solid rock. Where the soil was softer and less coherent the waves 
became longer and the movement slower. 
This vibratory motion had a tendenc}^ to move the foundation of 
a high building and the basement immediately in connection with 
it forward and back, and perhaps to move some of its columns in 
opposite directions, although this is not certain. At any rate, it 
apparently had the effect, owing to the inertia of the mass of the 
upper part of the building, of bringing a maximum bending moment 
to bear on the frame at some point between the basement and the top 
