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

an approved concrete mixture. re-
inforccd BY steel or iron OF any
shape. 80 that the steel and iron
VIII take up all tension stresses.
and assist in the resistance 20 COM
Sec. 2. Permits AND DRAW
INbS. Complete drawings, speci-
ncations and details OF all rein
forced concrete construction. show
ing the size and position OF all re-
with the Department OF Buildings
before n 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. g. METHOD OF CALcULA-
TION. In calculating the strength
or reinforced and plain concrete.
used for walls. columns. beams.
floor construction or for hreproof-
ing. the thickness OF the concrete
only shall be used exclusive OF any
plastering OF floor ballast
Reinforced concrete slabs. beams
and sirders. shall be designed In
accordance with the Following as
(a1 The accepted theory of fiex-
ure shall be applied to all mem
bers resisting bending.
lb) The steel shall take all the
tension stresses.
(c) The ratio OF the modulus OF
elasticity concreta-to- that Of
steel shall be 10 Is.
ld) The modulus or elasticity
shall remain constant at all work.
ing stresses.
(e) The stress strain curve OF
concrete in compression shall be
considered az straight line.
Sec; Z; ALLOWABLE 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 (45Ss) per cent
OF the commercial elastic limit and
In no case greater than 5000
pounds per square inch.
(b) Deformed high carbon steel
bars rolled from billets shall not
be more than forty-hve (45gS) 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-ilve (46So) per cent OF the
commercial elastic limit, and In no
case greater than 10000 pounds per
square inch.
GAP The allowable unit stress in
extreme fibre Of concrete in COM
preston, shall be six hundred and
hfty (0bO) pounds per square inch.
(e) The allowable unit stress
upon concrete In direct compress
sion. shall be four hundred and
nfty f5o) pounds per square inch.
I'D The allowable unit shear
Ing stress unnn ahall
forty (4O) pounds per square inch.
CD The allowable adhesive
strength OF concrete to steel shall
be forty (4o) pounds per square
Sec. s. COLUMNS. (a) For Col
umns reinforced with longitudinal
bars tied at intervals not greater
than twelve Q2) times the least d.
ameter OF the bars. the safe load
shall be computed as follows,
16As).
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 Q) per cent or hopping 10 used.
the safe load shall be computed as
follows:
Safe load lin pounds)=s5o (Act
15As).
Ac=net cross section OF concrete
enclosed In hopping.
As-net cross section OF longitudin-
nj reinforcement.
Where columns are subject to loads
OF known eccentricity, the combined
stresses In the extreme fibre due to
moment shall not exceed the maxi
mum compression stress allowed In
slabs and beams.
The above stresses apply only to
columns In which the ratio OF the
unsupported length to least side or
diameter does not exceed fifteen
All columns shall have at least
one % 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 ut the
spices In the column rods. and In
buildings over four (D stories In
height, a 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 lO inches In It's
smallest dimension.
Sec 9. 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 u WI.
When the slabs and beams are
continuous over both supports. the
bending moment for a uniformly dis
tributed load shall be taken at not
less than one-tenth WI.
Where slabs and beams are con-
tinuous over one % support only.
the bending moment for a uniformly
distributed load. shall be taken at
not less than one-ninth WI.
In the case OF square panels, REIN
forced In both directions and con-
tinuous over all supports. the bend
Ing moment OF the slab for a uni
formly distributed load shall be taxi
en- at not less than one-twentieth
WI.
W=Load in pounds.
L=Length OF span In feet.
Length OF span shall always be
understood to be the clear distance
between the supports.
Sec. q. STEEL OVER SUP
PORTS. In all cases where reduc-
ton In the bending moment In 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.
Sec. 8. BEAMS AND GIRDERs
TO BE TREATED AS 'T'' BEAMS.
III the Orders. beams and slabs are
poured in one % continuous opera
ton, then the Orders and beams
may be treated as ct" 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 a distance on
each side OF the beam, greater than
three CD times the thickness OF the
slab.
In all cases where the shearing
stress along the plane OF Junction
OF the rib and fiange 10 excessive,
the beam must be reinforced by
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