US2917901A

US2917901A - Load carrying structure

Info

Publication number: US2917901A
Application number: US499967A
Authority: US
Inventors: Lackner Erich
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-04-07
Filing date: 1955-04-07
Publication date: 1959-12-22
Anticipated expiration: 1976-12-22

Description

Dec. 22, 1959 E. LACKNER 2,917,901

LOAD CARRYING STRUCTURE Filed April '1, 1955 2 Sheets-Sheet 1 fm en-fof: 4

Eric/7 Lac he Dec. 22, 1959 E. LACKNER LOAD CARRYING STRUCTURE Filed April '7, 1955 2 Sheets-Sheet 2 Erich LqcKnel and building time.

United States Patent lice The present invention relates to a load carrying structure, and more specifically to a load carrying structure in the form of a plate resting on the ground and made of individual sections some of which are pre-stressed.

One object of the present invention is to build such a load carrying structure with a minimum plate thickness and with a minimum of necessary reinforcement.

A further object of the present invention is to build such a load structure which requires a minimum of excavation.

An additional object of the present invention is to build I such a construction especially adapted for carrying a concentrated load whereby the deformation of the structure by said load is held to a minimum.

Another object of the present invention is to build such a structure with a minimum expense of building material With the above objects in view, the present invention mainly consists of a load carrying structure comprising the following elements, namely, plate means engaging tile ground and composed of a plurality of interconnected sections, and stressing means independently stressing at least one of the sections, without transferring the stressing force from the one section to another section, for reducing the maximum moment and deformation created by the load on the one section, so that the plate means may be thinner than if it were made in one piece and unstressed.

The stressing means are preferably made in form of anchor rods connected at one end to at least one of the plate sections and extending therefrom in substantially prependicular direction into the ground. Anchor heels are preferably connected to the other end of said stress rods to transfer the stresses created in the rods into the ground on which the structure rests. The individual sections from which the plate means are formed are preferably interconnected by separate sealing blocks.

By subdividing the bottom plate of the structure in a plurality of sections and by stressing at least one of the said sections independently fro-m the other ones by the mentioned stress anchors and interconnecting the sections after at least one of the same is prestressed, a very favorable overall bending moment can be created in the bottom plate of the structure and secure adherence of the structure to the ground with a resulting small deformation of the complete structure can be obtained. The subdivision and the arrangement of the stress anchors in at least one of said sections can be made in such a way that the structure is especially adapted to receive a concentrated load, whereby the stresses created by the stress anchors produce moments in said section they are attached to, which counteract the moments created by the concentrated load and the other forces acting in said section. In this way, it is possible to reduce the thickness of theplate considerably and to obtain a great saving of building material and building time.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be- 2,917,901 Patented Dec. 22, 1959 best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which: I

Fig. ,1 is a transverse cross section through onemodification of the load carrying structure illustrating the same in a schematic way;

Fig. 1a is a partial cross section of a modification of the structure shown in Fig. 1;

Fig. 2 shows a bending moment curve schematically illustrating the bending moment created in the structure when a concentrated load is applied along the center line of the bottom plate of the structure and stress anchors are not used;

Fig. 3 shows a bending moment curve illustrating the bending moment in the center section of the structure before this center section is connected to the side sections and when this center section is stressed by the stress means;

Fig. 4 shows a bending moment curve obtained by superimposing the bending moment curve of Fig. 2 with v the bending moment curve of Fig. 3;

Fig. 5 is a transverse cross section through another modification of the load carrying structure illustrating the same in a schematic way;

Fig. 5a is a partial cross section of a modification of the structure shown in Fig. 5;

Fig. 6 shows a bending moment curve similar to 2,--

but illustrating the bending moment created in the second modification;

' Fig. 7 shows a bending moment curve similar to Fig. v3, but also applied to the second modification;

Fig. 8 shows a bending moment curve obtained by superimposing the bending moment curves of Figs. 6 and 7; and

Fig. 9 is a cross sectional view of a construction detail only schematically illustrated in Figs.'1 and 5.

Referring now to the drawings, and especially to Fig. 1 which illustrates a cross section through a load carrying structure especially used for drydocks, gate chambers, or foundation troughs for tall buildings. The structure consists of a trough-shaped body having side walls 22 and a bottom wall composed of a plurality of sections and as shown in Fig. l of a middle section 1 and two side sections 2. The end faces of the sections are preferably V-shaped and the sections are interconnected to each other by forming a V-shaped groove in one of the sections and a V-shaped projection on the other section, as shown at 3 in Fig. 1 or the plate sections may be interconnected to each other by forming the side faces of both sections with a V-groove and interposing between two adjacent V- grooves a separate sealing block 4, as shown in Fig. la. Though only one block is shown in Fig. In, it has to be understood that such sealing blocks 4 are provided on both sides of the middle section 1. The plate sections, side walls and sealing blocks are made of concrete or reinforced concrete.

Connected to the center section 1 are stress anchors 8, made from rods or cables of high alloy steel, which are connected at points 10 to the center section and reach from there in a direction vertical to the plate deep into the ground on which the plate rests. The other end of these stress anchors 8 is preferably provided with anchor heels 9 schematically illustrated in Fig. l to securely anchor the rods or cables 8 deep in the ground.

In building the bottom plate of this structure the stress anchors with their anchor heels are first put into the ground. The center section 1 is then poured on the ground, the stress anchors are then connected to the center section and after-the concrete of the center section has been properly hardened, this center section is stressed by means of the stress anchors to create in this center section bending moments adapted to counteract the bending moments resulting from the various loads acting on said center section when the structure is used. Afterwards the adjacent side sections are constructed and joined to the center section and finally the complete structure is finished.

The structure which is set into excavated ground is subjected to deadweight forces and buoyancy fo'rces resulting from the ground water surrounding the structure. The ground water level is indicated by the marker 11 in Fig. 1, the size and direction of the buoyancy forces acting on the structure is indicated by the vector 12, the size and direction of the deadweight forces is indicated by the vector 13, and the size and direction of the resulting force is indicated by the vector 14.

Fig; 2 shows a bending moment curve illustrating the bending moment created in such a structure, which is made: in the ordinary manner without stress anchors, when a concentrated load is applied along the center line of the bottom plate of the structure. The location and size ofsuch a load, for instance of a ship resting with its keel on the center line of a drydock is schematically illustrated by the vector 15 of Fig. 2. The combination of this ship load and the forces created by the aforementioned deadweight loads and buoyancy forces create in the-bottom plate of the structure, when stress anchors are not provided, an overall bending moment which is illustrated by the curve 16, which indicates a-maximum bending moment 17 in the center of the plate. Such a maximum bending moment would require acertain plate thicknessand/or a certain amount of reinforcement within the plate to prevent an undue deformation of the plate which could lead to cracking or destruction of the same. Such a bending moment could be favorably influenced by increasing the excavation depth and thus creating greater buoyancy forces.

In order to reduce this necessary plate thickness and/ or the necessary amount of plate reinforcement and/or the excavation depth, the platemade according to the present invention is subdivided in sections and in the case of a concentrated load acting substantially along the center line of the middle section stress anchors, as abovedescribed, are provided in this middle section and this middle section is pro-stressed by means of these stress anchors before it is connected to the side sections of the plate. These stressed anchor means will transmit forces, schematically illustrated by the vectors 18 in Fig. 3, to this'middle section so that a moment curve 19 will result.

When such a pre-stressed center section is now combined with the remaining side sections 2 and the side walls 22 of the structure and this structure is subjected to a main load schematically indicated by the vector 15 in Fig. 2 a combined moment curve 20 will result which is schematically illustrated in Fig. 4. It can be clearly seen from this figure that the resulting maximum bending moment 21 is considerably smaller than the bending moment 17 (Fig. 2) which latter bending moment would be created in a structure not made according to the present invention.

Though Fig. 1 shows only two stress anchors 8 it has to be. understood that this figure illustrates only a cross section through the structure and the actual structure is, provided with two rows of stress anchors respectively located in planes through the lines 8 and parallel to the longitudinal axis of the structure.

Instead of two rows of stress anchors it is also possible to, arrange a plurality of stress anchors in four or more parallel rows on the center section 1, arranged in such a way so as to produce a bending moment curve substantially as shown in Fig. 3.

The structure schematically illustrated in Fig. l sho'ws a. drydock and in such a structure the main load is concentrated substantially along, the center lines of the bottom plate. It has to be clearly understood that the same construction principle can be applied to bottom plates of other structures in which the main load is concentrated at different locations. In such construction the subdivision of the bottom plate in sections and the arrangement of the stress anchors in these sections has, of course, to be made according to the size and location of the main loads. Stress anchors could, for instance, be provided on the side sections and the center section could be free of any such stress means. It has to be understood that in this case too, the sections provided with the stress anchors have to be made first and pre-stressed as mentioned above and the remaining sections be joined afterwards to these pre-stressed sections.

in some structures it may be advisable to stress one of the sections first, interconnect the remaining sections afterwards and stress then the thus formed complete bottom plate by additional stress anchor.

In the drydock construction as illustrated in Fig.

1 the stress anchors 8 are preferably provided in the center section in two parallel rows outside of and symmetrically to the center line of the center section along which the concentrated load acts. The side sections 2 preferably protrude beyond the side walls 22 as shown at 23 in Fig. 1. In this case the load of the material pressing on the top face of the projections 23 reduces or counteracts the buoyancy forces acting on the side sections 2 to a desired degree and the tilting moment created on the side walls 22 by the ground pressing against the side walls is counteracted by the moment of they ground forces acting on the top face of the projections 23. This arrangement of side sections projecting beyond. thev side walls 22 contributes therefore to a possible reduction of the plate thickness.

Fig. 5' illustrates a modification of the just-described structure. Instead of joining the center section 1 with the side sections 2, directly by means of abutting V- grooves and V-projections or sealing blocks which abut directly on V-grooved side faces of these sections, linkage means are provided at the location where two adjacent plate sections or plate sections and sealing blocks are joined. These linkage means consist of some compressible material, for instance heavy layers of corrugated cardboard or the like interposed between joining faces. To locate this material properly the V-shaped groove formed in one of the adjacent sections is preferably stepped so that only a very small center portion of this V-shaped groove will be in direct engagement with the V-shaped projection formed on the other of the adjacent sections and the. compressible. material will be interposed in the spaces respectively created at the outer ends of the joint. In this way, a hinge connection is formed between the center section and the adjacent side section, which allows for a very small rotational movement of these sections about the apex of the V-projection. Such a construction is schematically illustrated in Fig. 5. A similar construction is illustrated schematically in Fig. 5a where the center section is joined to the side section by means of a separate sealing block 6'. The same compressible material 7 is in this case, in the same manner as described above, interposed between the sealing block 6 and thetwo sections respectively joined by this sealing block. Though Fig. 5a shows only one sealing block 6, it has to be understood that such sealing blocks 6 are provided at both sides of the middle section 1.

Figs. 6, 7 and 8 show similar as do Figs. 2, 3 and 4' the moment curves for this modification.

Inorder'to adapt the stress force created by the stress anchors in the center section to differentloads applied to the center section and thereby to create a favorable maximum bending moment in the structure, means are preferably provided, especially in a structure in which the middle section is hinged to the outside sections, to change the stress forces created in the stress anchors. For this purpose, the connecting end of the stress anchors is coBStructed as illustrated in Fig. 9'. The upper end ofthe cable 8 is provided with a cable-head 25 having an outside thread. A nut 26 .is threaded onto this outside thread of the cable head and this nut rests on a steel plate 27. 'This steel plate is preferably resting on a lead plate 28 which, in turn, rests on a hard mortar plate 29. The cable head 25 and the adjusting nut 26 are enclosed by a sheet metalcasing 30 which as a removable cover 31.

This structure as described above is arranged in a cavity 32 provided in the bottom surface of the center section 1 having bigger overall dimensions than the easing 30. The space between the casing 30 and walls of the cavity 32 is filled with concrete. The cavity is closed on the top by means of a hard asphalt cover 33.

In order to adjust the stress force created in the stress anchor 8, the covers 33 and31 are removed and the nut 26 is turned by means of a socket wrench so that the position of the cable head -25 is adjusted with relation to the abutting plate 27 and the stress forces in the cable S are either reduced or increased. In order to facilitate the tensioning of the stress anchor 8 the same is preferably encased in a layer of bitumen 24.' M It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of load carrying structures differing from the types described above.

While the invention has been illustrated and described as embodied in a load carrying structure comprising plate means engaging the ground and composed of a plurality of interconnected sections at least one of which is prestressed, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can be applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. A load carrying structure comprising, in combination, plate means bedded over its entire bottom face on the ground and composed of a plurality of movably interconnected sections, at least one of said sections adapted to carry a main load acting on said section along a given area and creating a bending moment in said section; and stressing means acting in a direction substantially normal to said plate means, being connected to said section outside said area and independently stressing at least said one section in a direction toward the ground, for producing a moment counteracting the moment produced by the main load and reducing the deformation created by the load on said one section, wherebythe stresses created in said one section are not transferred to said other sections so that said plate means may be thinner than if it were made in one piece and unstressed.

2. A load carrying structure comprising, in combination, plate means bedded over its entire bottom face on the ground and composed of a plurality of movably interconnected sections, at least one of said sections ada ted to carry a main load acting on said section along a given area and creating a bending moment in said section; and stressing anchor means connected to at least said one section outside said area and extending therefrom in substantially perpendicular direction into the ground for independently stressing said section in a direction toward the ground, for producing a moment counteracting the moment produced by the main load and reducing the deformation created by the load on said one section, whereby the stressescreated' in said one section are not 6 transferred to said other sections so that said plate means may be thinner than if it were made in one piece and unstressed.

3. A load carrying structure comprising, in combination, plate means bedded over its entire bottom face on the ground and composed of a plurality of movably interconnected sections, at least one of said sections adapted from in substantially perpendicular direction into the ground for independently stressing said section in a direction toward the ground, for producing a moment counteracting the moment produced by the mainload and reducing the deformation created by the load on said one section, whereby the stresses created in said one section are not transferred to said other sections so, that said plate means may be thinner than if it, were made in one piece and unstressed; and anchor heel means connected to the other end of said stressing anchor means for transferring the stresses created in said stressing anchor means into the ground. I

4. A load carrying structure as defined in claim 1 .in which the plurality of movably interconnected sections have side faces and in which the side faces of adjacent sections being respectively formed with V-grooves and V-shaped projections for movably interconnecting said sections.

5. A load carrying structure as defined in claim 1 in which the plurality of movably interconnected sections have side facesformed with V-grooves; and including sealing blocks having side faces matching said V-grooves and arranged between adjacent sections for movably interconnecting the same.

6. A load carrying structure as defined in claim 1 in which the plurality of movably interconnected sections have side faces and in which the side faces of adjacent sections being respectively formed with V-grooves and V-shaped projections for interconnecting said sections; and including linkage means formed from compressible material and interposed between said V-grooves and said V-snaped projections of ad acent sections for interconnecting said sections in a hinged manner.

7. A load carrying structure as defined in claim 5; and including linkage means formed from compressible material and interposed between said V-grooves of said sections and said matching side faces of said sealingblocks for interconnecting said sections and said sealing blocks in a hinged manner.

8. In a trough-shaped building structure for carrying a main load substantially along the center line of the bottom of the structure, in combination, bottom plate means bedded over its entire bottom face on the ground and composed of a center section and side sections adjacent both sides of the center section and movably interconnected to the same; and stressing means acting in a direction substantially normal to said plate means, being connected to said center section outside and substantially symmetrical to said line along which the main load engages said center section and spaced from both sides of said center section for stressing said center section in a direction toward the ground for reducing the maximum moment and deformation created by the load on said center section, whereby the stresses created in said center section are not transferred to said side sections so that said plate means may be thinner than if it were made in one piece and unstressed.

9. In a trough-shaped building structure for carrying a main load substantially along the center line of the bottom of the structure, in combination, bottom plate means bedded over its entire bottom face on the ground and composed of a center section and side sections adjacent both sides of the center section and movably'inter connected to the same; and stressing anchor means connected. to said center section outside and substantially symmetrical to said line along which the mainload engages said center section and spaced from both sides of said center section and extending from said center section in substantially perpendicular direction into the ground for stressing said center section in a direction toward the ground for reducing the maximum moment and deformation created by the load on said center section, whereby the stresses created in said center section are not transferred to said side sections so that said plate means may be thinner than if it were made in one piece and un stressed.

10. In a trough-shaped building structure for carrying amain load substantially along the center line of the bot tom of the structure, in combination, bottom plate means elastically bedded over its entire bottom faceon the ground andv composed of a center section and side sections adjacent both sides of the center section, said center section and said side sections formed with V-grooves; sealing blocks having side faces matching said V-grooves and arranged between said center sectfon and said side sections; linkage means formed from compressible material and interposed between said V-grooves of said sections and said matching side faces of said sealing blocks for interconnecting said sections and said sealing blocks in a hinged manner; stressing anchor means connected to said center section outside and substantially symmetrically to said line along which the main load engages said center section and spaced from both sides of said center section and extending from said center section in substantially perpendicular direction into the ground for stressing said center section in a direction towards the ground without transferring the stressing force from said section to said side sections, for reducing the maximum moment and deformation created by the load on said center section so that said plate means may be thinner than if it were made in one piece and unstressed; and adjusting means operatively connected to said stressing anchor means for adjusting the stress in the same according to the magnitude of the main load acting on said center section.

11. In a trough-shaped building structure for carrying a main load substantially along the center line of the bottom of the structure, in combination, bottom plate means elastically bedded over its entire bottom face on the ground and composed of a center section and side sections adjacent both sides of the center section, said center section and said side sections formed with V-grooves; sealing blocks having side faces matching said V-grooves and arranged between said center section and said side sections; linkage means formed from compressible material and interposed between said V-grooves of said sections and said matching side faces of said sealing blocks for interconnecting said sections and said sealing blocks in a hinged manner; stressing anchor means connected at one end to said center section outside and substantially symmetrically to said line along which the main load engages said center section and spaced from both sides of said center section and extending from said center section in substantially perpendicular direction into the ground for stressing said center section in a direction toward the ground without transferring the stressing force from said section to said side sections, for reducing the maximum moment and deformation created by the load on said center section so that said plate means may be thinner than if it were made in one piece and unstressed; anchor heel means connected to the other end of said stressing anchor means for transferring the stresses created in said stressing anchor means into the ground; and adjusting means operatively connected to said stressing anchor means for adjusting the stress in the same according to the magnitude of the main load acting on said center section.

12. In a trough-shaped load carrying building structure having side walls, in combination, bottom plate means bedded over its entire bottom face on the groundand composed of a center section and side sections adjacent both sides of the center section and movably interconnected tothe same; sections protruding beyond the side. walls of the structure into the ground integrally madeand in line with said side sections; andv stressing means acting in a direction substantially normal to said plate, means, being connected to said center section: spaced from beta sides and toe center line of said center section and substantially symmetrical to the center line thereoffor stressing said center section in a direction toward the ground for reducing the maximum moment and deformation created by said stressing means on said center section, whereby the stresses created in said center section are not transferred to said side sectionsso that said plate means may be thinner than if it were made in one piece and unstressed.

13. In a trough-shaped building structure having side walls and made for carrying a. main. load substantially along the center line of the bottom of the structure, in combination, bottom plate means elastically bedded over its entire bottom face on the ground and composed of a center section and side sections adjacent both sides of said center section, said center section and said side sections formed with V-groovesand said. side. sections pro.- truding beyond the side walls of the. structure, into the ground; sealing blocks having side faces matching said V-grooves and arranged between said center section and said side sections; linkage means formed fromcompressible material and interposed. between said V-grooves of said sections and said matching side faces: of said sealing blocks for interconnecting said sections and said sealing blocks in a hinged manner; stressing anchor means connected at one end respectively to said center section outside and substantially symmetrically to said line along which the main load engages said center section and spaced from both sides of said center section for stressing said center section in a direction toward the ground without transferring the stressing force from said section to said side sections for reducing the maximum moment and deformation created by the load on said center section so that said plate means may be thinner than if it were made in one piece and unstressed; anchor heel means connected to the other end of said stressing anchor means fortransferring the stresses created by said stressing anchor means into the ground; and adjusting means operatively connected to said one end of said stressing anchor means for adjusting the stress in said adjusting anchor means according to the magnitude of the main load acting on said center section.

14. A process for making a supporting structure comprising the steps of placing a first plate section against the ground; first stressing said section tocreate in the same bending moments opposed to bending moments created in said section when a given load is applied to the same; connecting additional plate sections to said first plate section after said first plate. section has been stressed to form a complete plate therewith, whereby the force of said first stressing is limited to said first plate section; and stressing said complete plate to create a favorable moment distribution in said plate when a given load is applied.

References Cited in the file of this patent UNITED STATES. PATENTS 1,129,677 Holland Feb. 23, 19 15 1,961,986 Schneider June 5, 1934 2,384,616. Harris Sept. 11, 1945 FOREIGN PATENTS 61.976 Netherlands Nov. 15', 1948 485,545 Canada Aug. 12, 1952 1,028,862 France n Man. 4,. 1.9 53 746,5 89 Great Britain Max. 1 4, 195.6