The Detroit times. [volume] (Detroit, Mich.) 1903-1920, 1911-02-21


an approved concrete mixture. re-
shape, so that the steel and Iron
Will take up all tension stresses.
and assist In the resistance 10 com
Sec. 2. PERMITS AND DRAW
INGS. Complete drawings. speci-
flcations and details OF all rein
forced concrete construction. show
Ing the size and position OF all re-
inforctng members, shall be filed
with the Department OF Buildings
before a permit 10 construct such
work shall be issued. For all
buildings. strain sheets must be
submitted with the drawings and
The live loads in pounds per
square foot for which the different
members are designed, shall be
marked on each and every moor
plan OF the drawings submitted.
Sec. 3. METHOD OF CALCULA-
TON. In calculating the strength
of reinforced and plain concrete,
used for walls. columns, beams.
ing. the thickness OF the concrete
only shall be used exclusive OF any
plasterlng or floor ballast.
Reinforced concrete slabs. beams
and sirders. shall be designed in
SYMPTOMS:
(a) The accepted theory OF fiex-
ure shall be applied to all MEM
bers resisting bending.
CO. The steel shall take all the
tension stresses.
tc) The ratio OF the modulus OF
elasticity OF concrete TO that OF
steel shall be 10 Is.
td) The modulus OF elasticity
shall remain constant at all work
ing stresses.
(e) The stress strain curve OF
concrete In compression shall be
considered az straight line.
sT Sec; AL ,v,,osIIs UNIT
Ing stresses. based on figuring full
live and dead loads, shall be used:
(a) The allowable unit stress
for plain steel bars shall not be
more than forty-ive (45T) per cent
OF the commercial elastic limit and
in no case greater than $1,000
pounds per square inch.
OBJ Deformed high carbon steel
bars rolled from billets shall not
be more than forty-five (45%) per
cent OF the commercial elastic limit
and In no case greater than $4,000
pounds per square inch.
(c) All other steel reinforcing
bars rolled from billets which pro-
vide compound. tensile and sheer
members, shall not be more than
forty-iive (4596) per cent OF the
commercial elastic limit, and in no
square inch.
(d) The allowable unit stress In
extreme fibre OF concrete I'm COM
preston. shall be six hundred and
nfty (obO) pounds per square inch.
(e) The allowable unit stress
upon concrete In direct compress
sion, shall be four hundred and
nifty (460) pounds per square inch.
Cd The allowable unit shear
ing stress upon concrete shall be
forty (40) pounds per square inch.
hn Of conepsts t ,,se sSsl
be forty t4O pounds per square
Sec. s. COLUMNS. (a) For Col
umns reinforced with longitudinal
than twelve Q2) times the least al
ameter OF the bars. the safe load
shall be computed as follows;
Safe load Tin pounds)=5oo Ac+
Ac==net cross section Of columns
In square inches.
As=cross section Of longitudinal
reinforcement In square inches.
OBJ For columns reinforced with
longitudinal steel, and with spirally
wound hopping. provided. at least
one % per cent OF hopping Is used.
Safe load I'm pounds)=s6o (Ao-t
15As).
Ac=net cross section OF concrete
enclosed In hopping.
As=net cross section of longitudin-
al reinforcement.
Where columns are subject to loads
OF known eccentricity. the combined
stresses In the extreme fibre due to
direct compression and the bending
moment shall not exceed the maxi
mum compression stress allowed In
m
The above stresses apply only 20
columns In which the ratio OF the
unsupported length to least side or
diameter does not exceed fifteen
15).
All columns shall have at least
one ID per cent. OF longitudinal re-
enforcement. whether the same 10
used In the calculations or not.
Proper provision shall be made for
transmitting the stresses at the
spices in the column rods. and in
buildings over four 90 stories In
height, proper connection must be
made between the lower and the up
per ends OF the column rods.
In no case shall any column be
less than ten Qo) inches In It's
Sec. 6. BENDING MOMENTS
AND CONTINUOUS ACTION. The
bending moment for slabs and beams
with a uniformly distributed load,
when not continuous over supports.
shall be taken at " WI.
When the slabs and beams are
continuous over both supports. the
bending moment for uniformly dis
tributed load shall be taken at not
less than one-tenth WI.
Where slabs and beams are con-
tinuous over one (D support only,
the bending moment for a uniformly
distributed load, shall be taken az
not less than One-ninth WI
In the case OF square panels, REIN
forced In both directions and con-
tlnuous over all supports. the bend
ing moment OF the slab for q uni
WI.
w=Load in pounds.
LELength Of span In feet.
Length OF span shall always be
understood to be the clear distance
between the supports.
Sec. z. STEEL OVER SUP
PORTS. In all cases where reduce
ton in the bending moment is al
lowed on account OF the continuous
action. sufficient reinforcement must
be introduced In the top OF the slab
or beam over the supports. to take
a bending moment equal to the DIFF
ference between that allowed and
that given for non-continuous MEM
bers.
TO BE TREATED AS "T" BEAMS.
IL the Orders. beams and slabs are
poured In one ID continuous opera
ton, then the Orders and beams
may be treated as TT" beams, with
a portion OF the slab as a fiange. In
no case shall the flange be of a
greater width than the distance be-
tween adjacent beams, or be as
sumed TO extend TO distance on
each side Of the beam, greater than
three ca times the thickness OF the
slab.
In all cases where the shearing
stress along the plane OF junction
or the rib and hange n excessive,
the beam must be reinforced by