Evening star., 1922-02-12
CONCRETE SHIP BUILDER
& BLAMES THEA7ER ROOF
co., p. W. Anderson Believes Construction
Of Slab Was Faulty-Says Some OF
reinforcement Out of Place.
of cinders spread over the hot tar coat

of cinders spread over the hot tar coat
ing.
Weakened by Ceiling.
The ceiling of the theater was
suspended on steel straps from the
roof beams and trusses and from
various points along the center OF
the concrete roof slabs. which added
very materially to the load to be sup
ported by these thin concrete slabs.
The slabs We're further weakened Dy
chiseling into same after they had
been completed so as to reach the rem
forcing steel wires upon which to hang
the straps supporting the ceiling. as
shown in figure 8:
Having in mind the detalis OF
ten feet wide between oenters. Of
supports. the readers attention is
again directed to Figure 1. and
particularly that part which shows
the angle at which the supporting
beams entered the supporting walls.
sides. and how the main wire mesh
reinforcing rods had to be cut
,liagonally adjacent to these walls.
1t may be added. for the beneht OF
the engineer. that this reinforcement
had no anchorage whatsoever in the
side walls.
Figure is an enlargement of that
part of the roof slab bounded by
truss TIP and beams Bis to BIS
and the adjacent outside walls. TINS
drawing is intended to show the
location Of the reinforcing steel In
the concrete roof slabs. and attention
is also directed to the condition of
roof slab between beams B-21 and
B-22, near and at the junction with
the west and north walls. The
engineer will readily appreciate the
weakness at this point. and 1t Is the
writer's firm belief that cracks in the
w" which extended rapidly in three
directions indicated by lines extend
ing to points "X.'' ''Y'' and ~" The
slab then parted along the line
"W"-"Z." the eastern half swinging
about beam B-22 as q hinge, some.
what as indicated in Figure :, ana
then parting somewhere over the
center or eastern top edge of this
beam, thence falling through the
ceiling below, which had probably
already sagged and cracked, due to
the failure Of the supporting strap
connected to the center OF TINS
broken slab. much the same as indi-
Gated by this latter figure. The
western half Of this roof slab would
move in a similar manner. and the
two halves would have the tendency
to pull beams B-21 and B-22 toward
each other and out of their seats IN
the diagonal supporting hollow tie
walls.
Marks Give Evidence.
Evidence of the failure Of this con-
crete slab as herein outlined is borne
out by marks on the western ana
northern tile walls, which are CIR.
cular in curvature. with beams b-ll
and B-22 as their approximate centers
respectively. Failure of this slab
would weaken slabs between beams
B-22 and B-23 and slabs between
beams B-20 and B-21 to the point OF
failure, and they. in turn. wouid also
tend to push beams B-21 and BIZ out
of their seats and toward each other.
The tile walls bear evidence of the
movement of these beams IN this dl-
,rection from their point OF support,
and it is also evident that this move
ment took place after the greater por-
ton Of their load was removed. SINCE
the supporting plate under beam B-2l.
which is still in place, shows no signs
Of scoring under the sliding move
ment.
AS soon as beams B-21 and B-22
were unseated their free ends would
fall with buckling strain on russ
T-12, as evidenced by the method OF
fastening shown in figure 4. 1t Will
also be noted that beams 'B-21 and
B-l9-c were fastened to truss T-12
by the same bolts, hence when these
bolts failed. due to the action OF beam
B-2l. the north end of B-19-c would
also be allowed to fall. Similar ac-
ton occurred at beam B-22 and
B-1S-b and at other beam intersec-
tions at their truss supports in rapid
succession. The unusual strain set
up on truss T-12 by the falling of
beams B-21 and B-22 would be suff-
cient to disturb it's equilibrium, and
the wreckage bears evidence of this
truss having been tipped toward the
stage, or in a northerly direction, be-
of the center portion of this truss
caused a turning moment on truss
TIL about it's l beam support in the
west wall. causing the top of this
truss to move in an easterly direction
until it was rolled or slipped from
it's support. thus causing the collapse
of the entire roof structure.
More Rapid Than Eye.
1t will be appreciated that each of
the successive steps in this failure
would be more rapid than the human
eye could follow, but there would be
a sufficient time interval between the
appearance of a crack in the ceiling
below letter "W' in figure for the
human eye to conceive of failure
at this point before the final collapse
occurred.
The actual strength Of the con-
crete roof slab. which the writer has
failure, is most problematical for
SPECIAL NOTICES.