Improvements in Concrete-and-iron Beams or Beams Composed of similar Materials.
Year: 1892

page_text: Date of Application, 25th Jan., 1892
Complete Specification Left, 6th Apr., 1892-Accepted, 7th May,
1892
PROVISIONAL SPECIFICATION.
Improvements in Concrete-and-iron Beams or Beams Composed of
similar Materials.
I, FREDERICK GEORGE EDWARDS, of 120 Leighton Road, Kentish Town,
London, Builder's Assistant, do hereby declare the nature of this invention to be as
follows:-
This invention relates to improvements in the first part of the invention described
in my Specification of Letters Patent No. 2941, A.D. 1891, the said part consisting
of concrete-and-iron beams or beams composed of similar materials.
Heretofore it has been necessary when these concrete-and-iron beams have to be
built into walls and other structures to curve the rods upwards at the ends to resist
the tensile stresses due to fixing. I now prevent the ends being fixed by forming
them of a quadrantal shape over the bearings, the quadrant being struck from the
intersection of the underside of the beam with the inner side of the bearing. The
extra strength and stiffness due to fixing are thereby lost, but the construction is
simplified. This is especially useful for landings and lintels as they can be built
into walls with a length of bearing not exceeding their depth but otherwise a
bearing not less than one-fourth or one-fifth of the span is required. Although a
quadrantal end is described as the best form, a differently curved or an inclined end
may be used.
I also improve the arrangement of the rods in deep beams where two or more
series are used one above the other by bending the upper series of rods downwards
between the spaces of those in the lower series at the centre of the beam where
the tensile stresses are greatest. The tensile strength of the upper series of
rods is thus used to greater advantage while the resistance of the beam to
horizontal shearing is not materially reduced. A third series of rods may be bent
downwards at the centre to lie on top of the lower series. This arrangement is
more suitable for beams not fixed at the ends, that is to say, in beams where the
position of the greatest direct stresses does not correspond with that of the greatest
shearing stresses. In other cases, where the position of the greatest direct and
shearing stresses coincide, the second series of rods should simply be bent down-
wards to lie ou top of the first series.
In beams supported at the ends with uniformly distributed loads the intensity of
the shearing stresses at the ends of the rods (when embedded horiz. tally) is
double that with a corresponding cential load although the total amount of
shearing stress is the same. I have row discovered that by simply curving the
rods upwards at the ends the shearing stresses may be more uniformly distributed
over the length of the rods or shifted towards the middle, while at the same time
Horizontal rods can
the inclining of the rods increases their hold on the concrete.
also be secured by slightly corrugating them for about one-fourth of their length at
each end the corrugations preferably increasing in depth at the extreme ends.
Rivet or other heads may be formed on the ends of the rods for the same purpose.
Beams thus constructed are adapted for a central or distributed load and by means
of these improvements larger sized rods can be held by the concrete than would
otherwise be the case.
The ends of the rods may be bent upwards at right angles over the bearings to
increase the resistance of the concrete to horizontal shearing. This is especially
useful in the case of loads concentrated near the ends of the beam.
In place of the strip of nailing concrete extending through the length of the
beams it is preferable in some cases to use small detached blocks inserted in

page_text: convenient parts of the beam. This is more applicable for the lintels and railway
sleepers.
The railway sleepers described in the Specification of Letters Patent before
referred to are cheapened by dispensing with the rods at the top and curving some
of the rods upwards from the bottom at the middle to take their place.
Fire-resisting floors may be formed by placing rectangular concrete-and-iron
beams side by side, the underside being protected by plastering or other well-known
fire-resisting materials. For long spans these beams may rest on larger concrete-
and-iron beams or girders. It is sometimes convenient to use the beams in narrow
widths with rebated joints especially for corridors and landings.
Dated this 23rd day of January 1892.
FRED. G. EDWARDS.
COMPLETE SPECIFICATION.
Improvements in Concrete-and iron Beams or Beams Composed of
similar Materials.
I, FREDERICK GEORGE EDWARDS, of 120 Leighton Road, Kentish Town,
London, Builder's Assistant do hereby declare the nature of this invention and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
This invention relates to improvements in the first part of the invention described
in my Specification of Letters Patent No. 2941 A.D. 1891, the said part consisting
of concrete-and-iron beams or beams composed of similar materials. It was there
shown and proved by experiments that by embedding rods of sufficiently small
diameter in the underside, concrete beams could be made to fail under a breaking
load by crushing at the top instead of suddenly breaking across, thereby very
largely increasing their strength and also causing a considerable deflection before
fracture.
Heretofore it has been necessary when these concrete-and-iron beams have to be
built into walls and other structures to curve the rods upwards at the ends a
(Fig. 1) to resist the tensile stresses due to fixing. I now prevent the ends being
fixed by forming them of a quadrantal shape over the bearings, the quadrant being
struck from the intersection (Fig. 2) of the underside of the beam with the inner
side of the bearing. The extra strength and stiffness due to fixing are thereby
lost, but the construction is simplified and the beams can be built into walls with a
length of bearing not exceeding their depth. Although a quadrantal end is
described as the best form, a differently curved or an inclined end may sometimes
be used.
I also improve the arrangement of the rods in deep beams where two or more
series are used one above the other as shown by Figs. 2 and 3 by bending the
second series of rods B downwards between the spaces of those in the first series A
at the centre of the beam where the tensile stresses are greatest. The tensile
strength of the second series of rods is thus used to greater advantage while the
resistance of the beam to horizontal shearing is not materially reduced. A third
series of rods C may be bent downwards at the centre to lie on top of the first and
second series. This arrangement is more suitable for beams not fixed at the ends,
that is to say, in beams where the position of the greatest direct stresses does not
correspond with that of the greatest shearing stresses. In other cases, where the
positions of the greatest direct and shearing stresses coincide, the second series of
rods would be brought closer to the first series at those points as is the case with
the rods A and B in Fig. 1 and also in the railway sleeper (Fig. 13).
In concrete-and-iron beams supported at the ends with uniformly distributed
loads the intensity of the shearing stresses at the ends of the rods (when embedded
horizontally) is greater than with a corresponding central load and would be
double were it not that the concrete towards the ends of the beams relieves the

page_text: rods of a portion of their tensile stresses. Should the rods draw out at one end
the concrete would be exposed to undue tension and the beams would break at
some point not far from the bearing. The total amount of shearing stress along
the whole length of the rods is about the same however the load is applied and I
have now discovered that by simply curving the rods upwards at the ends the
shearing stresses due to a uniformly distributed load may be more uniformly
distributed over the length of the rods while at the same time the inclining of the
rods increases their hold on the concrete. The correct curvature D E (Fig. 4) to
equalize the shearing stresses due to uniformly distributed loads is deduced from
the following equation:-
Let M₁
Let M
Moment of central load at any point distant from the centre.
Moment of corresponding distributed load at any point distant a
from the centre.
Let c =
=
Half the length of the beam in inches.
Let W = Breaking load at centre.
Let 10 =
Corresponding distributed load per inch run of beam.
221
Let= C=
Distance of any point from the centre of the beam.
If the distance d (Fig. 4) of a horizontal rod below the neutral axis y of a
beam be called unity the required distance of the rod D E below the same axis to
equalize the shearing stresses due to a distributed load would be equal to
every noint
M₁
at
M₂
= 1;
y at the centre of the beam
or 6 at = or 57 and at =
Therefore the depth below the neutral axis
at the distance = or 8; at c =
€
5.
An inspection of the diagram (Fig. 4) for half a beam shows that this curve
does not greatly differ from a straight line from D to E which will be sufficiently
accurate for many purposes. A greater inclination of the rods tends to shift the
shearing stresses towards the centre but in that case they are uniformly distributed
by slight tensile stresses induced in the rods and corresponding compressive
stresses in the concrete. A. central load applied to a beam with the rods curved for
a distributed load as in Fig. 4 would also tend to produce a greater intensity of
shearing stress at the centre and in this case also the same remark applies.
One effect of curving the rods upwards at the ends is to leave a greater
proportion of the tensile stresses to be resisted by the concrete, making it necessary
to embed horizontal rods also. When horizontal rods are combined with the
curved rods the shearing stresses on the surfaces of the former are rather
concentrated towards the ends and these may be secured by corrugating them for
say, one-fourth of their length at each end, the corrugations preferably increasing
in depth at the extreme ends as shown at the ends of the rods A (Fig. 2). I
found by experimenting with wires of 1" diameter that small corrugations were
sufficient to more than quadruple the hold on the concrete. Rivet heads or collars
of sufficient size formed at or near the ends of the rods would evidently answer the
same purpose.

page_text: The curved rods may also be corrugated if considered desirable. The corru-
gations tend to increase the resistance of the beam to horizontal shearing and the
ends of some of the rods may be bent upwards as shown at e (Fig. 2) for the same
purpose. The latter may be useful in the case of heavy loads concentrated near
the ends of the beam. In fixed beams the ends f (Fig. 1) of the rods which are
curved upwards may be corrugated with the corrugations preferably increasing in
depth at the extreme ends, to reduce the necessary length of hearing. When the
load is to be distributed the upper series of rods 13 may remain at the top of the
beam as shown at B. Cantilevers would have the rods embedded at the top and
these may be similarly corrugated at the fixed end of the beam.
In beams of relatively small depth as for instance, in stair treads, landings, or
corridor floors, it is generally sufficient to embed horizontal rods, for two reasons:
firstly, the tensile stresses resisted by the concrete tend to distribute the shearing
stresses on the surface of the rods uniformly and secondly, a sufficient length is
obtained to hold rods of a useful size. These rods may be corrugated at the ends
if desired. Fig. 5 is a diagram showing the probable distribution of the direct
stresses in such a beam due to a distributed load and also the corresponding
shearing stresses, supposing the iron as is usually the case to be sufficiently
ductile. The hatched portion represents the stresses on the concrete and the
trapezium g h k represents the distribution of the shearing stresses on one half
the surface of the iron rods.
In place of the strip of nailing concrete extending through the length of the
beams as described in the Specification of Letters Patent before referred to it is
preferable in some cases to use small detached blocks inserted in convenient
parts of the beam.
Fig. 2 is a half elevation of a 4" x 4" lintel for a 4' 0" span with quadrantal
ends and with twelve rods embedded in the underside in three series, the lower
series A of five rods being corrugated for one-fourth the length at each end, the
second series B of four corrugated at the extreme ends, and the third series C of
three turned up at the ends to increase the resistance of the beam to horizontal
shearing. For internal lintels blocks of nailing concrete may be inserted on one
side which is also roughened for plastering. Fig. 3 is a central section of the same
lintel.
"
Fig. 6 is a central section of a 44* × 6* lintel with ten rods, and Fig. 7 of a
4"x7" lintel with nine 3 rods suitable for larger spans.
Bressummers would
be similarly constructed.
Figs. 8, 9, 10, and 11 show sections of beams in narrow widths with rebated
joints which are especially suitable for corridor floors, landings, and similar uses.
For relatively large spans, say 24 times the depth, the rods would all be
horizontal, but for short spans to carry correspondingly heavy loads each alternate
rod may be curved upwards and the others corrugated at the ends as previously
described. The latter arrangement besides giving the rods a more secure hold
also increases the resistance of the beams to horizontal shearing. Fig. 8 is a
2" x 9" beam with eighteen rods; Fig. 9 a 24" x 9" beam with thirteen "rods;
Fig. 10 a 3" x 9" beam with ten rods; and Fig. 11 a 4" x 9" beam with
nine rods. Perhaps it will be more convenient to make the smaller beams
in greater widths. The beams would be supported on corbels or formed with
quadrantal ends. Butt instead of rebated joints may be used and the underside
may be roughened for plastering.
11
When the beams are formed in situ for corridor floors and the like they may be
made of unlimited width but it is preferable to form joints at intervals to
prevent cracking by expansion and contraction. Considering the great cost
of boarding and strutting required for temporary support it will probably be found
that narrow beams which can be easily lifted about will be cheaper.
Fig. 12 is a section through a floor formed with concrete-and-iron beams D
4" thick resting on larger transverse concrete-and-iron beams E E' placed S' 0"
apart. The underside of the floor may be plastered or otherwise ceiled. For

page_text: ordinary dwelling-house floors the 4" beams D would be much stronger than
necessary if composed of the best quality of concrete with the full amount of iron
rod inserted as previously described. It is therefore proposed in such cases to
construct these particular beams with one part of Portland cement to four parts
of coke breeze, the iron rods being correspondingly reduced in sectional area.
The rods, on account of their reduced surface for the adhesion of the cement
should be laid in a bottom layer of stronger material, say: one of cement to two
of coke breeze. These beams would have to be stocked some time before use to
acquire sufficient strength and to get thoroughly dry. Floor boards or sleeper
fillets to receive flooring could then be nailed to them directly they are laid in
position. The transverse beams E E¹ would sometimes be moulded in situ because
of their weight and would generally be made of the strongest quality of concrete
with the corresponding amount of iron rod inserted. A useful size for the rods is
about diameter per foot of span. The beam E' is shown rebated to receive
the floor beams D. If built into walls they would be formed with quadrantal
ends or other means employed to prevent fixing. For very large spans concrete-
and-iron girders as described in the third part of my Specification of Letters
Patent No. 2941 A.D. 1891, may be used in place of the transverse beams or in
combination with them. When used in combination the transverse beams would
rest on top of the girders or in their perforations which may be made in suitable
positions and of suitable shape to receive them.
Flat roofs and bridges may be constructed in a similar manner and cemented or
asphalted over to render them watertight.
Fig. 13 shows a half elevation and Fig. 14 a section of a concrete-and-iron
railway sleeper 9' 0" x 10" x 4" with seventeen "rods embedded in two series, the
lower series A. of eleven being entirely in the underside and the upper series B
of six curving upwards to resist the tensile stresses in the top of the sleeper in the
centre. The upper series of rods are preferably reduced in number to increase
the resistance of the sleeper to horizontal shearing at the point immediately
beneath the rail at a where these stresses are at a maximum. The ends of the
rods are shown corrugated to increase their hold on the concrete. Four concrete
nailing blocks are shown which are intended to receive the spikes for fixing the
rail chairs and are surrounded by rings embedded to prevent splitting. The
spikes should be parallel sided. This method of attachment will accord with
existing practice but the concussion caused by driving the spikes may be found
injurious to the sleeper and perhaps a better method of fixing will be by bolts;
holes being formed through the sleeper for the purpose and the holes in the chair
rails slotted so that the chair can be wedged up to the rail before the bolts are
finally tightened.
Fig. 15 is a diagram showing the distribution of the direct and shearing
stresses in such a sleeper supposing the ballast of the permanent way to be
uniformly compressible. Any variation in this respect would only increase or
alter the direct stresses at the centre of the sleeper against which there is ample
provision. The straight lines wsst indicate the shearing stresses and the
parabolas cue the direct stresses.
The concrete-and-iron sleepers will probably be found as flexible as creosoted
timber, they will not crush under the rail chairs as timber is so liable to do, will
add to the stability of a railway for fast traffic, and if made of proper materials
will be indestructible.
The experiments described in my former Specification were made with beams
composed with equal parts of Portland cement and coke breeze but it is
apparent that any good concrete with the interstices filled up with cement
would hold rods equally as large. For instance: the concretes now so largely
used composed with an aggregate of crushed granite should answer although
containing a much smaller proportion of cement. Slag cement which is said to
have superior adhesive power may be even better for the purpose than the ordinary
Portland.

page_text: The iron rods increase the transverse strength of concrete beams in most cases
about eight times and the deflection in a still larger proportion, in one particular
instance about fourteen times. The resistance to impact is probably increased in
where A =
the ultimate deflection of a concrete-and-iron
the proportion: 8
beam and A. the ultimate deflection of a similar concrete beam.
1
It will thus be seen that a concrete-and-iron beam 2" thick say for a corridor
floor will be twice as strong as a similar concrete bean 4" thick; and as the
quantity of iron inserted is generally less than fourteen pounds per cubic foot with
no more expensive labour than bending or corrugating, it will be cheaper.
Concrete beams again, although strong enough to carry a large dead weight
carefully applied, are on account of their small deflection easily broken with a
comparatively small falling weight.
The iron rods being under a simple tensile stress will not twist and break up the
concrete under great heat as is the case with iron girders embedded in fireproof
floors. Therefore floors constructed as previously described with the beams
composed with coke breeze or other refractory aggregate will form a safe
structure which if protected by fireproof slabs or plastering, or any of the
well-known applications of asbestos, silicate cotton, or other materials, from actual
contact with fire and water, would support those refractory but weak materials
through a very severe fire. The actual condition, safe or otherwise of the beams
would also be known as a very considerable deflection would become apparent
before they finally failed. Portland cement (set) and iron expand and contract
practically the same under similar changes of temperature.
The modulus of rupture of Portland cement beams of rectangular section is eighty
per cent. greater than the resistance of the Portland cement to tension; and as the
congrats and ivan haame ave strongan than canavots haams in the mitin.
it follows that the modulus of rupture of concrete-and-iron beams of rectangular
section is eighty per cent, greater than the resistance of the concrete to compression.
Considering the cheapness of concrete it will therefore in most cases be most
economical to use beams of rectangular section.
The best qualities of bar iron elongate about 24 times as much as plate iron
before rupture and are rather too ductile to obtain the best results with concrete-
and-iron beams. By cold rolling, the tensile strength may be increased 50 per cent.
and the ductility reduced 60 per cent., making the bars just suitable for the purposes:
but the polished surface thereby acquired may be found to decrease the hold of the
concrete and the cost may be too great. Probably the best results are to be
obtained with mild steel which can be readily obtained of the required ductility.
When it is considered that bars are 20 per cent. stronger than plates, that the
tensile strength can be still increased by 50 per cent. on reducing the ductility
60 per cent. with advantage to the beam, and that the number of small rods reduces
the effect of a flaw to a minimum, rendering them safe with a small factor of
safety, it will be seen that this is an exceedingly economical mode of employing
iron or steel for constructional purposes.
Concrete-and-iron beams will not deteriorate but increase in strength with
age and if the concrete is composed of proper materials it will itself be proof
against all atmospheric influences and will also preserve the iron from rusting.
concrete-and-iron" is intended to include all beams similarly
The term
constructed.
Having now particularly described and ascertained the nature of my said invention,
and in what manner the same is to be performed, I declare that what I claim is :
1. Forming quadrantal or similar ends to concrete-and-iron beams to prevent
fixing as described with reference to Fig. 2.

page_text: 2. The improved arrangement of rods in series as described with reference to
Fig. 2.
3. Curving or inclining the rods upwards at the ends to distribute the shearing
stresses more uniformly and to increase the hold on the concrete as described with
reference to Figs. 2 and 4.
4. Corrugating the ends of the rods to increase their hold on the concrete as
described with reference to Figs. 1 and 2.
5. Forming rivet heads or collars at or near the ends of the rods instead of
corrugating the ends as described with reference to Fig. 2.
6. The improved concrete-and-iron lintels and bressummers as described with
reference to Figs. 1, 2, 3, 6, and 7.
7. The concrete-and-iron beams with rebated joints as described with reference
to Figs. 8, 9, 10, and 11.
8. The method of forming floors, roofs, bridges, and similar structures with
concrete-and-iron beams as described with reference to Fig. 12.
9. The improved concrete-and-iron railway sleepers as described with reference
to Figs. 13 and 14.
Dated this 6th do. of i 1905
FRED. G. EDWARDS.