US2590478A

US2590478A - Apparatus and method for molding prestressed concrete structural members

Info

Publication number: US2590478A
Application number: US165620A
Authority: US
Inventors: Weinberg Victor
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-09-13
Filing date: 1950-06-02
Publication date: 1952-03-25
Anticipated expiration: 1969-03-25

Description

V. WEINBERG APPARATUS AND METHOD FOR MOLDING PRESTRESS CONCRETE STRUCTURAL MEMBERS Filed June 2, 1950 2 SHEETS-SEEM l Q M Q Q N Riv ,6 6 4. T if W L Y. D ha 6 m m, 3 U -1 b v A: S J X a m M m e h w w m w Qflllll q n N\ TlNlllrwllllvuo A Q Q A y,

Marci: 25, 1952 v. WEINBERG 2,590,478

APPARATUS AND METHOD FOR MOLDING PRESTRESSED CONCRETE STRUCTURAL MEMBERS 2 SHEETS-SHEET 2 Filed June 2, 1950 Patented Mar. 25, 1952 UNITED STATES APPARATUS AND METHOD FOR MOLDING PRESTRESSED CONCRETE MEMBERS STRUCTURAL Victor Weinberg, Paris, France Application June 2, 1950, Serial No. 165,620 In France September 13, 1946 8 Claims.

The present invention is a continuation in part application of my co-pending specification Ser. No. 773,136 filed September 10, 1947, now abandoned.

My invention has for its object a novel and improved system for the casting of structural members made of preliminary stressed concrete, of any type whatever. According to my invention, the mold or molds are tensioned and suspended inside a rigid frame and on the other hand said mold or molds are made rigid with a number of intermediary reinforcing members that do not extend throughout the length of the prestressed member or members, said reinforcing members being tensioned through a tractional stress exerted on the mold or molds. The tensioning of these reinforcing members is then performed automatically in unison with the mold.

This novel system is of particular advantage for the molding of prestressed posts or beams having a varying transversal cross-section and including stretched reinforcing members that do not extend throughout the length of posts or beams, in other words, that stop at those points for which calculation shows that reinforcing members are useless beyond such points by reason of the reduction of the bending momentum and are even objectionable by reason of the exaggerated compression provided inthe concrete through the presence of such supplementary reinforcing memhers.

I have illus trated in accompanying drawings a preferred embodiment of an arrangement according to my invention.

In said drawings:

Fig. 1 is a diagrammatic view of an arrangement according to the invention.

Fig. 2 is a perspective showing of a plant executed in conformity with the diagram of Fig. 1 and adapted for the casting of prestressed concrete posts of 1a varying cross-section.

Fig. 3 is a plan view of a similar industrial plant in accordance with the diagram of Fig. 1 and the perspective view of Fig. 2, adapted for the execution of a similar post.

Fig. 4 is a cross-sectional view through the longitudinal axis of symmetry of Fig. 3.

In the various figures:

I designates the outer rigid frame or tensioning frame constituted by shaped iron members.

2 designates the actual mold constituted by thin steel sheets.

3 designates continuous reinforcing wires.

4 and 5 designate intermediary shorter reinforcing wires.

6 and IE1 designate tie rods for attaching the mold to the frame I at either end-thereof, i. e. at X and Y, the arrows 11-5 of Fig. 1 showing the direction of the tensional stresses.

1a and lb designate the anchoring means securing one end of the intermediary reinforcing members to the actual mold 2, said anchoring means being constituted e. g. by steel tubes round which said reinforcing members form loops and that are secured in their turn to the mold through a pin.

a and 9 designate the tie rods for attaching to the frame I traction-transmitting cross members or straps I I and I2 carrying the corresponding ends of the reinforcing members 3, the arrows 'y--6 of Fig. 1 illustrating the direction of the tensional reac ions exerted on the reinforcing members or wires.

The ends of the intermediary reinforcing wires 45 that are not attached to the mold are also secured to the corresponding cross member II that is rigid with the frame through the tie rod 8 and associated adjusting nut l3.

Id, I5 and I6 designate further nuts or the like stops used for securing or looking the various tie rods when the associated parts have been properly tensioned.

Furthermore, in Figs. 2 to 4, I1 designates jacks carried by the frame and adapted to exert tractional stresses while I3 designates the cross member to which said stresses are applied and Lastly I9 and 20 designate nuts or the like abutments through which the cross member I8 acts on the tie rods 9 and I0.

The operation of the arrangement illustrated is as follows:

The continuous wires 3 held between the cross members II-I2 are mounted independently of the mold 2 and may, there-fore, be stretched separately e. g. through the agency of the jacks I'l illustrated in Fig. 2; the action of the jacks on the cross-member I8 and tie rod 9 produces a shifting, towards the head end Y of the arrangement, of the cross member I2, carrying the looped ends of the reinforcing wires; on the other hand, the cross member II at the foot end of the arrangement is connected with the frame I through the tie rod 3 and is locked on said frame through a nut or the like securing member l3. The tractional stresses may be exerted on the cross-member I2 either mechanically, say through the jacks I! or manually e. g. through action on the nut I5 fitted over the tie rod 9. After the reinforcing wires 3 have received the desired elongation, they are rigidly secured to the frame I through a screwing home of the locking nut I5 or the like member over the tie rod 9.

This being performed, the same jacks are used for exerting a tractional stress on the mold 2 through the agency of the tie rods at the head end of the arrangement, the tie rods 6 holding the mold at the foot end of the arrangement not being yet locked by the nut M. This tractional stress provides [for a gradual tensioning of the section of the mold comprised between its head facing the side Y and the anchoring means lb together with the tensioning of the intermediary tensioning wires 4 and between said anchoring means and the stationary cross-member l l The foot end of the mold facing the side X moves freely away from said left hand side X towards the right hand side Y until the nuts I4 or the like stops on the tie rods [4 engage the frame I; obviously, from this moment onwards, the mold section comprised between lb and the foot end facing X is also tensioned under the action of the tractional stresses exerted on its head end.

The location of the nuts I4 on the tie rods 6 is adjusted in a manner such that they abut against the frame only at the moment at which the reinforcing wires 4 and 5 have acquired the almost complete desired elongation and consequently the desired prestressing.

Furthermore, if the reinforcing members 4 and 5 should acquire, as is generally the case, a final tensioning that is identical with that of the reinforcing members 3, in other words, if their total elongation is different for a same unitary elongation, the reinforcing wires 5 that are the shortest, should be given a length such that they extend before the tensioning beyond the anchoring points lb by a predetermined length. Supposing a is the total elongation to be given to the wires 4, and b that to be given to the wires 5, a is larger than D for a same elongation per unit of length. At the beginning of the tensioning operation i. e. at the moment at which the wires 4 engages the anchoring means la under the action of the tractional stresses exerted on them through the mold, the wires 5 will still extend beyond their anchoring point lb by a length (1-1;. As soon as the wires 4 have been stretched by a length equal to this difference which corresponds to a displacement by an equal amount of the mold from the left hand side X towards the right hand side Y, the mold, being at the moment considered tensioned between its head at Y and the point la and submitted to no tensioning between said point la and the foot end X, the anchoring means lb should abut in their turn against the loop formed by the reinforcing wires 5 and as the tractional stress continues being executed at the head end of the mold, said wires 5 are submitted in their turn to elongation. Simultaneously, the mold section comprised between 1a and lb also begins being tensioned. It is easy to ascertain that if said traction is continued until the anchorage lb begins moving towards Y, the wires 5 and 4 will have received a total elongation equal respectively to b and to a; care should be taken to adjust the position of the nuts l4 so that they may be located at a distance of the frame that is slightly less than the total shifting elongation a. Consequently, towards the end of the stressing, the mold is looked through its foot end by said nuts l4 and is consequently also stretched between the point of attachment with the tie rods 6 up to a point in register with the anchorages lb. The complete tensioning of the mold 2 and wires 4 and 5 is then at an end and the locking nuts l5 are tightened against the frame I so as to transfer onto the latter the tension of the mold and of the reinforcing wires to be considered.

In the actual plant illustrated in Figs, 2, 3 and 4, the operation is similar to that disclosed with reference to Fig. l: the tractional stress is exerted by symmetrical jacks ll acting on the transversal cross member I8. During the preliminary stretching of the continuous reinforcing wires 3, the nut I9 is locked while the nuts 20 are in contradistinction unscrewed to move away from the cross-member IS. The jacks I! being now actuated, this shifts the cross-member l8 towards the right hand side Y by the necessary amount that is equal to the elongation it is desired to give the wires 3. The nut !5 on the tie rod 9 is then locked in order to transfer the tension of the wires 3 onto the frame I following which the jacks may be returned into their inoperative position. The nuts 20 are then looked and the nut I9 is moved away from the cross member. A further action of the jacks will then shift the cross-member l8 towards the right hand side at Y whereby the mold 2 is carried along through the tie rods 10. This produces a tensioning of the mold 2 and of the wires attached at la and lb in the same manner as disclosed hereinabove. This operation being at an end, the nuts 56 are locked also as described hereinabove and the jack I! are released,

The first of the two successive operations described does not affect the mold as the continuous reinforcing wires 3 are secured to the frame and are not secured to the mold. In the second operation, on the contrary, the mold is shifted from the position A, A to the position B, B, the shifting by AB at one end being however slightly greater than the shifting AB at the other end as the former is the sum of the shifting AB' and of the elastic elongation of the mold produced through its tensioning.

The method of which an embodiment has been described is applicable to a system of molds or of a series of molds arranged in parallelism with reference to one another inside a single frame and the tensioning operations described that have been disclosed hereinabove may then, if desired, be executed simultaneously for two or more molds or series of parallel molds.

On the other hand, the method remains of interest with however a simplified sequence of operative steps when the structural members of prestressed concrete to be molded are not provided with intermediary reinforcing wires such as 4 and 5. The traction exerted on the mold has then for its sole object to tension the latter.

I have found by experience that the method according to the invention shows numerous advantages such as follows:

The tensioning of the mold increases to a considerable extent the intensity of the vibrations that may be applied to said mold, chiefly when the vibration is executed at a high frequency, say at a rhythm of 6,000 to 9,000 per minute, As a matter of fact, when the mold stretched in accordance with the invention is provided with one or more vibrators secured through any known means, it is found, provided the tensioning stress applied is properly adjusted, that the intensity of the vibration is substantially improved which leads to a better settling of the concrete when compared with the results obtained with an ordinary mold.

The fact that the prestressing reinforcing wires are anchor'ed to a rigid frame independently of heretofore.

The tensioning of the intermediary reinforcing members in structural members of prestressed concrete that was heretofore difficult to obtain in practice, is provided very simply in accordance with the present invention.

What I claimis:

1. An arrangement for molding prestressed concrete structural members comprising an engated rigid frame, at least onemold lying inside the frame, two cross-members lying inside the frame near the ends of the mold, between which reinforcing members are adapted to be laid, means for rigidly connecting one of said crossmembers to the adjacent end of the frame, means for tensioning the other cross-member to stretch the reinforcing members between the two crossmembers, means for tensioning the mold through action thereon in the vicinity of said other crossmember and means associated with the end of the mold adjacent the first cross-member and including an abutment cooperating with the first mentioned end of the frame to form a resistance to the tensioning of the mold.

2. An arrangement for molding prestressed concrete structural members comprising an elongated rigid frame, at least one mold lying inside the frame, two cross members lying inside the frame near the ends of the mold and between which reinforcing members are adapted to be laid, means for rigidly connecting one of said cross-members to the adjacent end of the frame, means for tensioning the other cross-member to stretch the reinforcing members between the two cross-members, at least one anchoring member rigid with the mold and adapted to hold one end of intermediary reinforcing members the other end of which is anchored to the cross-member that is rigidly connected with the frame, means for tensioning the mold and associated intermediary reinforcing members through action thereon in the vicinity of said other cross-memher and means associated with the end of the mold adjacent the first cross-member and ineluding an abutment cooperating with the first mentioned end of the frame for forming a resistance to the tensioning of the mold.

3. an arrangement for molding prestressed concrete structural members comprising an elon gated rigid frame; at least one mold lying inside the frame, two, cross-members lying insidethe frame near the ends of the mold and between which reinforcing members are adapted to be laid, means for rigidly and adjustably connecting one of said cross-members to the adjacent end of the frame, means for tensioning the other crossmember to stretch the reinforcing members between the two cross-members, means for tensioning. the mold through action thereon in the vicinity of said other cross-member and means associated with the end of the mold adjacent the first cross-member and including an abutment cooperating with the first mentioned end of the frame for forming a resistance to the tensioning of the mold.

4. An arrangement for molding prestressed concrete structural members comprising an elongated rigid frame, at least one mold lying inside the frame, two cross-members lying inside the frame near the ends of the mold and between which reinforcing members are adapted to be laid, means for rigidly connecting one of said cross-members to the adjacent end of the frame, a cross-beam on the outside of the end of the frame furthest removed from the end that is secured to a cross-member, a series 'of'tie-rods rigidly connected with the other cross-member nearest said cross -beam, a second series of tierods rigidly connected with the end of the mold nearest the cross-beam, means for selectively connecting the cross-beam with either of the series of tie-rods and jacks fittedbe'tween the 'crcss-beam'and the nearest end of the frame to urge the cross-beam away from the latter to provide for the longitudinal stressing 'movement of the rein-forcing members and of the mold according to the tie-rod ser'ies that is secured to the cross-beam.

5. A method for 'fnblding prestressed concrete structural members in a mold located inside a stationary frame consisting in laying reinforcing members between two transversal cross-members located near the ends of the frame and one of which is rigid with the frame, tensioning said reinforcing members through action on the other cross-member and tensioning the mold through the end opposed to the cross-member that is rigid with the frame and casting the concrete over the reinforcing members in said mold.

6. A method for molding prestressed concrete structural members in a mold located inside a stationary frame consisting in laying reinforcing members between two transversal cross-members located near the ends of the frame and one of which is rigid with the frame, laying auxiliary reinforcing members between predetermined points of the mold and the cross-member that is rigid with the frame, tensioning said first mentioned reinforcing members through action on the other cross-member and tensioning the mold through the end opposed to the cross-member that is rigid with the frame to stretch first the auxiliary reinforcing members and the portion of the mold lying between them and the end of the mold to which the tensioning is applied, securing the other end of the mold to the frame and continuing the tensioning of the entire mold together with the auxiliary reinforcing members and casting the concrete over the reinforcing members in said mold.

'7; A method for fitting the reinforcements inside a mold with a view to molding therein prestressed concrete structural members in a mold located inside a stationary frame consisting in laying reinforcing members between two transversal cross-members located near the ends of the frame and one of which is rigid with the frame, laying auxiliary reinforcing members between predetermined points of the mold and the cross-member that is rigid with the frame, tensioning said first mentioned reinforcing members through action on the other cross-member and tensioning the mold through the end opposed to the cross-member that is rigid with the frame to stretch first the auxiliary reinforcing members and the portion of the mold lying between them and the end of the mold to which the tensioning is applied, securing the other end of the mold to the frame and continuing the tensioning of the entire mold together with the auxiliary reinforcing members, the shorter auxiliary reinforcing members being engaged originally on the corresponding anchoring points with some clearance to provide an idle relative travel of these shorter auxiliary reinforcing members during the beginning of the tensioning of the longer aux-. iliary reinforcing members and mold.

8. A method for molding prestressed concrete structural members in a mold located inside a stationary frame consisting in laying reinforcing members between two transversal cross-members located near the ends of the frame and one of which is rigid with the frame, inserting tensioning devices between the front end of the frame near the other cross-member and a cross-beam to the front thereof, transiently connecting said cross-beam with the said front cross-member, tensioning the reinforcing members through operation of the tensioning means on the crossbeam, connecting the front cross-member with the frame, disconnecting the cross-beam with reference to the front cross-member, connecting again on the cross-beam to stretch first the aux iliary reinforcing members and the portion of the mold lying between them and the end of the mold to which the tensioning is applied, securing the other end of the mold to the frame and continuing the tensioning of the entire mold together with the auxiliary reinforcing members and disconnecting the mold with reference to the cross-beam and connecting its front end to the frame.

VICTOR WEINBERG.

REFERENCES CITED FOREIGN PATENTS Country Date Germany June 16, 1933 Number