IL25157A

IL25157A - Composite and prestressed steel-concrete beams and their manufacturing process

Info

Publication number: IL25157A
Application number: IL25157A
Authority: IL
Original assignee: Birguer A
Priority date: 1965-05-21
Filing date: 1966-02-11
Publication date: 1970-02-19
Also published as: BE664243A; US3368016A; BE789655R; ES317020A1

Description

nm Composite and prestressed beams and their manufacturing process ALEXANDRE Ci 24042 In the erection of buildings and cases are sometimes met in over a considerable span of the the height of the beam must be reduced to a Armoured and prestressed concrete elements not solve this on account of the fact that their ratio which 1 and h are respectively the span and the height of the is On the other the beam dealt with in the present invention and described makes it possible to reach limiting values of of the order of twice what is possible with under the same For this the process for making such beam substantially consists in starting with a cated concrete beam which may comprise in its zone ded to be compressed by outside at least one unstressed metal in applying to this beam a first prestress in fastening to the beam in in the zone thereof intended for being subjected to another side tensile at least element by means of fastening elements of high tensile strength and in between the metal and the a layer of adhesive material in applying in a preferential way onto the composite material which has thus been a second In one of the composite and prestressed beam consists of a ted concrete beam onto which is fastened a nonstressed metal flat on the side where the flange will be sed by outside This flat may be fastened to the hard concrete by means of bolts of high elastic limit and by inserting of a layer of or other adhesive material between the metal flat and crete These bolts must be able to withstand the skimming stresses existing between the metal flat and the remainder of the section skimming or grazing stress being the effort which tends to separate the concrete from the On the other these bolts must prevent buckling of the flat in the zone where the latter is strongly it is for this although the skimming effort may be negligible at this that the bolts after not be spaced too far The bolts of high elastic limit subject the tact surface between the steel and the concrete to a prestress which provides the connection by The presence of the layer of provides a ficient of friction which is considerably higher than that which would be obtained without this layer of The flat can also be attached to the concrete flange by means of studs fastened into said metal These studs shall be provided with a kind of head or hook in order to ensure a mutual grip between the and the Aforesaid studs withstand the skimming or grazing stresses and avoid buckling of the metal flat under The latter shall be placed on the crete flange immediately after the flange has been in order that the studs should readily penetrate into the There is a third system for this metal The latter is then replaced by two or several parts into which the studs are and they are placed on the in order that the concrete might be cast between the various This process also has the further advantage of making it possible to tie some stressing cables between two or several also be imagined to replace aforesaid flats by heavy nonstressed bars embedded into the concrete but in most cases there will hardly be enough space for lodging the number of bars which would be required to replace an outside The first prestress is either to the crete when the metal flat is fastened by means of studs of high tensile or compound section formed by the concrete section and the steel section fastened to the flange which is to be compressed by side The nonstressed metal flat is then fastened to the concrete flange which will be drawn by action of the outside stresses by means of bolts of high tensile of a layer of being inserted between this flat and the concrete or by another means which will make it possible to carry out this system of connection with or without mortar These bolts must only have to the skimming effort existing between the flat and the remainder of the sidering that in this the flat is being The second prestress is then applied on the plete section with upper and lower After the first the concrete flange which will drawn under the effect of outside stresses is strongly Afther fastening of the the loss of stress in the concrete by creep is recovered in the which fact is quite considering this flat will subsequently be subjected to heavy ten sile The bean is it has either protruding bars for the upper or holes through which prestressing cables can be passed for the Compared to concrete beams which are merely prestre this beam offers an additional safety against the formation of on account of the presence of the drawn metal Under the action of there will be no increase of stress In at this the concrete is only very weakly stressed and will not need to seek release on the On the other the compressed metal flat will undergo a considerable increase of stresses because at this point the concrete undergoes a very strong sion and will seek release by transferring part thereof to the This phenomenon results from tests ch have been made on a prestressed compound beam at the laboratory of the Ghent ExOerience has shown that the creep ceases much faster than for a concrete beam has simply been and also that the creep is much By way of appended figure 1 illustrates a with partial perspective view of a beam conforming to the present insufficientOCRQuality

Claims

In this figure 1, 1 refers to a prefabricated concrete beam; 2_ and 3_ to the metal flats fastened by means of their studs _^-5_ to the flange of the beam before hardening; 6_ to the elements of first prestress; 1_ to the elements of second prestress; 8_ to the metal flat; _9 to the layer of cement-mortar inserted between flat 8_ and the face of beam _1; 1_0 to the bolts of high tensile . strength for fastening the flat _8 to the flange of the concrete beam. All these elements are again illustrated in '.the embodiment of figure 2 which is moreover completed by concrete fillings 1_1~1_2. and by cross-bars or cross-cables 1_3_ for subsequent application of a transversal prestress . It is evident that the process according to the present invention can be applied to beams or similar elements of various shapes and dimensions, together with any appropriate additional feature. 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. A process for making composite steel-concrete beams, characterized by the fact that it substantially consists in starting with a prefabricated concrete beam which may comprise in its zone intended to be compressed by outside stresses, at least one unstressed metal element; in applying to this beam a first prestress; in fastening to the beam in question, in the zone thereof intended for being subjected to outside tensile stresses, another mexai at least nonstressed' element by means of fastening elements of high tensile strength and in inserting, between the metal and the concrete, a layer of adhesive material and, finally, in applying in a preferential ' way onto the composite material which has thus been realized, a second prestress.

2. A process for making composite steel-concrete beams, characterized by the fact that it consists in performing the following operations onto a prefabricated concrete beam having at least one nonstressed metal flat in the end of its zone intended to be compressed by outer stresses, viz.: in subjecting this beam to a first prestress; in fastening to the beam, in the end of its zone intended to be subjected to traction by outer stresse another at least -one- nonstressed metal flat by means of bolts of high tensile strength and by inserting, between the metal and the concrete, a layer of an adhesive material and, finally, in subjecting the compound steel-concrete structure which has thus been obtained, to a second prestress.

3. A process according to claim 1, characterized by the fact that it consists, starting from a prefabricated concrete- beam, in applying to the latter a first prestress, in fastening to the upper and lower faces of said beam, nonstressed metal flats by means of bolts with a high tensile strength and inserting a layer of adhesive material between said flats and the concrete flanges and, finally, in applying the second prestress to the resulting steel-concrete composite structure.

4. A process according to claim 1, characterized by elements in the form of the fact that the metal' flats provided with studs are fastened to the concrete beam in the zone intended to be put under compression by outside stresses, before the concrete has hardened, by means of aforesaid studs.

5. A process according to et^im-i—or claim 4, characterized by the fact that in the zone of the concrete beam intended for being put under compression by outside stresses, two or more than two spaced flats have been provided. r

6. A process according to claim Zt-err 5, characterized by the fact that the nonstressed metal flats carrying the fastening studs are placed onto the shuttering; the beam is cast through the spaces between these flats.

7. A process according, to claim 1, characterized by the fact that the metal elements fastened to the zone intended to be put under compression by outer stresses, consist of a certain number of heavy nonstressed metal bars embedded in the- concrete flange.

8. A process according to one of the preceding claims, characterized by the fact that the beam acts as support for an upper slab by means of protruding bars.

9. A process according to one of the claims 2 to 7, characterized by the fact that the beam acts as support for an upper slab subjected to a transverse prestress.

10. A process according to one of the preceding claims, characterized by the fact that the beam may be subjected to the second prestress, either after an upper slab has been cast , or after having had to hear part or the whole of the fixed loads.

11. A process according to one of the preceding claims, characterized by the fact that the beam comprises one or several bolts of high tensile strength, which bolts go right through the section for being fastened onto the upper and lower flats.

12. A process according to one of the preceding claims characterized by the fact that the fastening by means of bolts with high tensile strength can be replaced. by any other bonding means either with or without layer of cement-mortar.

13. Any beam obtained by applying the process according to one or several of the preceding claims and having any approp a T-shape, -a—doti-e—T—shape a rectangular shape. -or—even--arr--sh-a^^it--- eitatctiyfe—rft&yfe-jra-er-w -vap-iefeie--ifte*4:-i-e..

14. A process for making composite and prestressed steel-concrete beams, and beams obtained thereby, substantially as described above and illustrated by the appended drawings. Dated this 10th day of February, 1966