Improvements in the Manufacture or Construction of Joists, Girders, and the like.
Year: 1892

page_text: Date of Application, 11th Aug., 1892
Complete Specification Left, 4th May, 1893-Accepted, 17th June, 1893
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture or Construction of Joists, Girders,
and the like.
A communication by FRANÇOIS HENNEBIQUE, of Chaussée de Ninove, Brussels, in
the Kingdom of Belgium, Engineer.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for
Foreign Patent Solicitors, 6, Lord Street, Liverpool and 6 Bank Street,
Manchester, both in the County of Lancaster and 323, High Holborn in the
County of Middlesex, Civil Engineer, do hereby declare the nature of this
invention to be as follows:-
This invention has for its object the manufacture of joists having extraordinary
advantages over the metallic girders at present employed in that, whilst they are.
much lighter in weight, they have a much greater resistance, and, further, are
considerably cheaper. The invention is based on the peculiar and carefully
determined combination of the characteristic properties of two substances of
entirely different natures, which, while being suitably united, give, from certain
points of view, results impossible to be obtained by means of any one of these
substances of equal weight and of any form.
These considerations have led to the invention of an improved arrangement of
joists of iron or steel and cement, because these two substances possess qualities of
reverse effect which, judiciously superposed, allow the desired result to be attained
in joists, that is to say, the greatest possible resistance to bending.
But the preponderating quality of iron is its great resistance to the effects of
tension, whilst the preponderating quality of cement consists in the resistance it
affords to the effects of compression.
From these observations, the result is that if a girder be constructed of a bar of
iron entirely coated with a layer of cement, to which the iron will thus form a core,
a support is obtained of which the resistance to bending will be equal to the
resistance to tension of the iron plus the resistance to compression of the layer of
cement above the bar of iron. In fact the iron will only feel the effect of the
strain by the amount by which the resistance which the cement opposes to com-
pression is exceeded, aud only when the cement is crushed. But this moment is
delayed to the extreme limit by the resistance of the bar to which the cement
adheres on all sides. It may therefore be said that the two resistances are literally
added together and thus it is possible to construct very light girders offering
resistances hitherto unknown.
The law of construction of this kind of joist being thus found in the addition and
combination of two high resistances inherent in the two substances in presence of
one another, and acting in a contrary direction, it only remains to determine the
proportions of iron and cement which are to be used in the manufacture of girders
for resisting a given amount of bending. In calculating these proportions, the
employment of useless quantities of cement is especially to be avoided. On this
point it may be remarked that it has been already stated that the part of the
cement, the resistance of which to compression is of use, is that which is situated
above the bar of iron, the portion of cement below this latter having evidently no
action in that direction. As a result, therefore, the bar must not be inserted in
the centre of the joist but in its lower part so that all the layer of useful cement is
situated above it and may then be calculated exactly in proportion to the resistance
to tension of the iron bar.
This being granted, it is only a question of selecting the form of juist which is

page_text: most advantageous in practice, seeing that it may be employed in any kind of
building and especially for ceilings, supports, lattice work girders, etcetera.
Figure 1 of the accompanying drawing shows a section of the rectangular cement
joist P with an iron bar B. This form is less theoretical than that shown in
Figure 2, the thickness of cement being not so necessary immediately at the sides
of the bar B as above it, which militates in favour of the trapezoidal section, which
is preferably adopted in practice, especially as it further presents special advantages
in the construction of ceiling supports in which it imitates more or less the arch
between two consecutive rafters. It is of course understood that the joists may
be covered in any suitable manner with wood or other suitable materials allowing
any desired ornamentatious to be attached thereto. Thus Figure 3 represents a
section of a simple set of joists with flooring on asphalt and visible joists, whilst,
Figure 4 is a set of joists with flooring on sleepers, the joists being fitted with bars
of wood by means of clasps which bars receive the ceiling laths.
Figures 5 and 6 represent in transverse and longitudinal section long joists in
which suitable anchors A of sheet metal support the bar B from point to point.
The arrangement of these anchors or hold fasts is particularly advantageous for
diminishing the effect of the tearing action which is exerted when the joists bend
on the intermediate parts of the iron bar B which causes at these points the cement
to spring when the tearing effect has reached a certain degree and thus break the
joist at this limit because a force other than that of compression destroys the
cement.
But the limit of resistance of the joist is greatly extended when these other
forces are removed, and the cement remains merely exposed to the effect of com-
pression alone. This diminution of the effect of the tearing force exerted on the
iron bar is obtained precisely by the use of these holdfasts or anchors, and the iron
bar thus remains absolutely immovable and secured in its place in the cement which
is now solely subjected to the effects of compression. In addition to their fastening
in the cement, the anchors A which clasp the bar B may be fixed at their upper
ends to a little wood binding joist K such as shown in Figure 6. This binding
joist fixed in and surrounded by the cement then directly supports the flooring and
forms thus a further improvement in the arrangement.
Figure 7 shows the view in perspective of a ceiling with visible joists and floor
on asphalt, all the parts being broken off to clearly show the arrangement.
Figure 8 is a similar view of a set of joists with ceiling on laths and flooring cn
asphalt or sleepers.
Figure 9 shows a set of joists for industrial purposes with a monolithic
pavement.
Figure 10 represents a main girder on the same system supporting two sets of
joists.
By examining these figures, it may be ascertained how small a quantity of iron
is employed in the girder of this system of combined iron and cement which is of
great importance as regards weight and price. It may also be remarked that such
a ceiling is absolutely safe from fire which cannot reach the iron protected by a
sufficiently thick covering of Portland cement, the peculiar immunity of which in
the case of conflagrations is well known.
Further, visible joists of an artistic form which are so difficult to obtain with
other kinds of rafters are very desirable from an architectural point of view.
In certain cases, the set of joists formed in the manner herein before described
may be covered with sheets of steel T fitted conformably to the section of the joists
and then covering the whole extent of the ceiling as is shown in Figure 11.
These
covering plates may be connected with one another either in the axis of the joists
or in the centre of the. parts between them. The result of this arrangement of
plates T is that they may form themselves the beams if they are suitably con-
structed. In this case, the trough formed by the plate receives the transverse
anchors A in the upper part, and the shank or bar of iron B'exposed to the force
of the tension may be arranged at the bottom of the trough either externally or

page_text: internally; the troughs are then filled with cement to form the part for receiving
the effects of compression which is thus intimately connected with the bar exposed
to the tension. This latter may also be soldered to the bottom of the trough as
shown in Figure 12, and it may be of any suitable form. The edges of the troughs
are constructed of plates, the breadth of half of the space between the joists, which
when connected together form the direct support for the flooring. This arrange-
ment of sets of joists may also be employed with advantage in girders of rectangular
section as shown in Figure 13.
The girders made on the above described plan in all their forms of construction
may evidently also serve for any other industrial applications, such as for instance
the construction of bridges, viaducts, etcetera; they may assume any form or curve
required, whilst always preserving the same qualities of resistance.
Dated this 10th day of August 1802
WM. P. THOMPSON & Co.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Manufacture or Construction of Joists, Girders,
and the like.
A communication by FRANÇOIS HENNEBIQUE, of Chaussée de Ninove, Brussels,
in the Kingdom of Belgium, Engineer.
I, WILLIAM PHILLIPS THOMPSON F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6 Lord Street, Liverpool, and 6, Bank Street Manchester, both
in the County of Lancaster, and 323 High Holborn, in the County of Middlesex,
Civil Engineer, 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 has for its object the manufacture of joists, girders and the like
having extraordinary advantages over the metallic girders at present employed in
that, whilst they are much lighter in weight, they have a much greater resistance,
and, further, are considerably cheaper. The invention is based on the peculiar and
carefully determined combination of the characteristic properties of two substances
of entirely different natures, which, while being suitably united, give, from certain
points of view, results impossible to be obtained by means of any one of these
substances of equal weight and of any form.
These considerations have led to the invention of an improved arrangement of
joists, girders and the like of iron or steel and cement, because these two substances
possess qualities of opposite effect, which, judiciously superposed, allow the desired
result to be attained in joists, girders and the like, that is to say, the greatest
possible resistance to bending.
But the preponderating quality of iron is its great resistance to the effects of
tension, whilst the preponderating quality of cement consists in the resistance it
affords to the effects of compression.
From these observations, the result is that if a girder be constructed of a bar of
iron entirely coated with a layer of cement, to which the iron will thus form a core,
a support is obtained of which the resistance to bending will be equal to the
resistance to tension of the iron plus the resistance to compression of the layer of
censent above the bar of iron. In fact the iron will only feel the effect of the
strain by the amount by which the resistance which the cement opposes to com-
But this moment is
pression is exceeded, and only when the cement is crushed.
delayed to the extreme limit by the resistance of the bar to which the cement
adheres on all sides. It may therefore be said that the two resistances are literally
added together and thus it is possible to construct very light girders possessing a
capacity of resistance hitherto unknown.
The law of construction of this kind of joist being thus found in the addition and

page_text: combination of two high resistances inherent in the two substances in presence of
one another, and acting in a contrary direction, it only remains to determine the
proportions of iron and cement which are to be used in the manufacture of girders
for resisting a given amount of bending. In calculating these proportions, the
employment of useless quantities of cement is especially to be avoided. On this
point it may be remarked that it has been already stated that the part of the
cement, the resistance of which to compression is of use, is that which is situated
above the bar of iron, the portion of cement below this latter having evidently no
action in that direction. As a result, therefore, the bar must not be inserted in the
centre of the joist but in its lower part so that all the layer of useful cement is
situated above it and may then be calculated exactly in proportion to the resistance
to tension of the iron bar.
This being granted, it is only a question of selecting, the form of joist, girder or
the like which is most advantageous in practice, secing that it may be employed in
any kind of building and especially for ceilings, supports, lattice work girders,
etcetera.
Figure 1 of the drawing filed with the Provisional Specification shows a section
of the rectangular cement joist P with an iron bar B. This form is less theoretical
than that shown in Figure 2, the thickness of cement being not so necessary
immediately at the sides of the bar B as above it, which militates in favour of the
trapezoidal section, which is preferably adopted in practice, especially as it further
presents special advantages in the construction of ceiling supports in which it
imitates more or less the arch between two consecutive rafters. It is of course
understood that the joists may be covered in any suitable manner with wood or
other suitable materials allowing any desired ornamentations to be attached thereto.
Thus Figure 3 represents a section of a simple set of joists with flooring on
asphalt and visible joists, whilst, Figure 4 is a set of joists with flooring on sleepers,
the joists being fitted with bars of wood by means of clasps, which bars receive the
ceiling laths.
Figures 5 and 6 represent in transverse and longitudinal section long joists in
which suitable anchors A of sheet metal support the bar B from point to point.
The arrangement of these anchors or holdfasts is particularly advantageous for
diminishing the effect of the tearing action which is exerted when the joists bend
on the intermediate parts of the iron bar B which causes the cement to spring at
these points when the tearing effect has reached a certain degree and thus break
the joist at this limit because a force other than that of compression destroys the
cement.
But the limit of resistance of the joist is greatly extended when these other
forces are removed, and the cement remains merely exposed to the effect of com-
pression alone. This diminution of the effect of the tearing force exerted on the
iron bar is obtained precisely by the use of these holdfasts or anchors, and the iron
bar thus remains absolutely immovable and secured in its place in the cement which
is now solely subjected to the effects of compression. In addition to their fastening
in the cement, the anchors A which clasp the bar B may be fixed at their upper
ends to a little wood binding joist K such as shown in Figure 6. This binding
joist fixed in and surrounded by the cement then directly supports the flooring and
forms thus a further improvement in the arrangement.
It will be self understood that the section and form of the suspension anchors or
stirrups A, Figures 5, 6 and 6^, as well as the manner in which they are attached
to the bars, may be different to what is shown in the drawing, the principle of this
part of the invention consisting in the suspension itself of these anchors, which
form with the cement the complete and indissoluble union of the lines of tension
whilst allowing of there being applied in the construction of the armed cement
girder thus formed, the forms and methods of calculation employed for lattice work
girders. These stirrups, of whatever form or section they may be, are placed at
intervals according to calculation, and in all joists constructed according to this
invention and of which they form an essential part.

page_text: Figure 7 shows the view in perspective of a ceiling with visible joists and
floor on asphalt, all the parts being broken off to clearly show the arrangement.
Figure 8 is a similar view of a set of joists with ceiling on laths and flooring on
asphalt or sleepers.
Figure 9 shows a set of joists for industrial purposes with a monolithic pavement.
Figure 10 represents a main girder on the same system supporting two sets
of joists.
By examining these figures, it may be ascertained how small a quantity of iron
is employed in the girder of this system of combined iron and cement which is
of great importance as regards weight and price. It may also be remarked that
such a ceiling is absolutely safe from fire which cannot reach the iron protected
by a sufficiently thick covering of Portland cement, the peculiar immunity of which
in the case of conflagrations is well known.
Further, visible joists of an artistic form which are so difficult to obtain with
other kinds of joists are very desirable from an architectural point of view.
In certain cases, the set of joists formed in the manner hereinbefore described
may be covered with sheets of steel T, fitted conformably to the section of the
joists and then covering the whole extent of the ceiling as is shown in Figure 11.
These covering plates may be connected with one another either in the axis of the
joists or in the centre of the parts between them. The result of this arrangement
of plates T is that they themselves may form the beams if they are suitably
constructed. In this case, the trough formed by the plate receives the transverse
anchors A in the upper part, and the shank or bar of iron B exposed to the
force of the tension may be arranged at the bottom of the trough either externally
or internally; the troughs are then filled with cement to form the part for
receiving the effects of compression which is thus intimately connected with the
bar exposed to the tension. This latter may also be soldered to the bottom of
the trough as shown in Figure 12, and it may be of any suitable form. The edges
of the troughs are constructed of plates, the breadth of half of the space between
the joists, which, when connected together, form the direct support for the flooring.
This arrangement of sets of joists may also be employed with advantage in girders
of rectangular section as shown in Figure 13.
The girders made on the above described plan in all their forms of construction
may evidently also serve for any other industrial applications, such as for instance
the construction of bridges, viaducts, etcetera; they may assume any form or curve
required, whilst always preserving the same qualities of resistance.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, 1 declare that what I claim is-
1. In the manufacture or construction of joists, girders and the like, the
assemblage of two appropriate materials, such as iron and cement, or any other
metal and agglomerant, in such manuer that the resistance which one of these
materials (the iron) offers to tension is added to the resistance which the other
material (the cement) offers to compression, the two forces being exerted in a
contrary direction and contributing thus to the formation of girders or the like
having great resistance whilst at the same time being extremely light.
2. In the manufacture or construction of joists, girders and the like on the
principle specified in Claim 1, the combination of two substances in such manner
that the one which is subject to the tensional strains is entirely covered, coated by
and held in the lower part of the substance on which the effects of compression are
to be exerted and the upper part only of which becomes of use, that is to say, the
part above the iron.
3. The use of iron in the form of round, square, bent or other bars and of
cement of a trapezoidal section as being the most practical arrangement, substan-
tially as herein before described and shown on the sheet of drawings and for the
objects specified.

page_text: 4. The construction of rafters or girders by forming troughs of sheet metal to
which is connected, in any suitable manner, the bar which is subject to tensional
strains, whilst the trough itself contains the substance which undergoes the
effect of compression, substantially as hereinbefore described and shown on the
drawing.
5. For retaining the bars B fixed in the cement, the use of anchors or ties, A,
surrounding the bar and being simply fitted in the cement, or even fixed by their
upper extremities to a wooden joist fixed for this purpose on or in the cement
substantially as described.
6. The use of anchors or suspension stirrups, A, of any suitable form or section,
these anchors forming with the cement a complete and indissoluble union of the
lines of tension and allowing of there being applied to the strengthened cement
joist, thus formed, the formulæ and methods of calculation for lattice work girders,
such anchors or supports of whatever form or section they may be, being placed at
intervals determined by calculation and in all the girders of the system hereinbefore
described of which they form an essential part.
Dated this 3rd day of Max 1802
WM. P. THOMPSON & Co.,
Agents for the Applicant.