US2948995A - Connections between reinforced, precast concrete structures and method of making same - Google Patents

Description

Aug. 16, 1960 v M. H. R. coGAN 2,948,995

CONNECTIONS EETwEEN EETNEOECEO, PEE-CAST CONCRETE STRUCTURES ANO METHOD OE MAKING SAME 5 Sheets-Sheet l Filed Feb. 24. 1953 NvENToz:

MYLEs n.12. COGAN EN ws ATTORNEY.

Aug. 16, 1960 M.' H. R. coGAN 2,948,995

CONNECTIONS BETWEEN REINFORCED, PRECAST CONCRETE STRUCTURES AND METHOD 0E MAKING SAME 5 Sheets-Sheet 2 Filed Feb. 24, 1953 INVENTOR- FIC-1. C:

MYLES H. E. COC-AAN f- MAM N5 ATTORNEY Aug. 16, 1960 M. H. R. coGAN 2,948,995

CONNECTIONS BETWEEN REINF'ORCED, PRE-'CAST CONCRETE STRUCTURES AND METHOD oF MAKING SAME |NVENTOR: MYLE5 H.R..COC1AN HE ATTORNEY M. H. R. coGAN 2,948,995

PRE-CAST CONCRETE AKING SAME 5 Sheets-Shevec` 4 nvenlror Mqee HR. Clown EL; m His M'fomeq CONNECTIONS BETWEEN REINF'ORCED,

STRUCTURES AND METHOD OF' M Aug. 16, 1960 Filed Feb. 24, 1953 Aug. 16, 1960 M. H. R. coGAN 2,948,995

CONNECTIONS BETWEEN REINFORCED, PRE-CAST CONCRETE STRUCTURES AND METHOD OF MAKING SAME Filed Feb. 24. 195s 5 sheets-sheet 5 HG. 15. I

los i lOB 5' Mes H- dn EL) His AJH-meg CONNECTIONS BETWEEN REINFORCED, -PRE- CAST CONCRETE STRUCTURES AND METHOD F MAKING SAW Myles H. R. Cogan, Houston, Tex., assignor to Shell gli Company, New York, N .Y., a corporation of Delaare Filed Feb. 24, 1953, Ser. No. 338,293

20 Claims. (Cl. Sil- 179) This invention relates to connections between metalreinforced, separately cast concrete structures, e.g., between a pre-cast superstructure that has one or more metal reinforcing rods and the support therefor, such as a foundation, column or girder having similar rods, and to a method of making such connections, viz., of erecting a superstructure on a support, etc. The structures may, for example, be parts of a building, such as walls, columns, glrders, beams or floor slabs, or may be poles or stanchions for supporting cables, pipes, power lines or the like, columns for elevated roadways or foundations.

Reinforced concrete structures of the type indicated above are frequently o-f such size or shape as to make it impracticable or uneconomical to cast two or more of them integrally. Thus, it is common to cast a supported structure separately from the support or foundation therefor and to erect or cast the latter as a separate structure at the site of erection and subsequently attach the pre-cast supported structure. This is usually accomplished by ailixing mating brackets or bed plates to the pre-cast supported structure and to the supporting structure and connecting the brackets or plates of the two structures by bolting or the like. Such brackets or plates must be precisely leveled to the supporting structure or shims or the like must be employed to position the supported pre-cast structure in the desired, predetermined location and this necessitates some care in the installation of the support and/ or the making of the connection. Moreover, to develop the -desired tensile stress in the reinforcing rods of the structure entirely to the juxtaposed parts of the two structures it is necessary to bond the rods to the brackets or bed plates, which further adds to the cost, especially when precise positioning is required. Y

It has not heretofore been feasible to join such separately cast structures by merely welding or otherwise connecting projecting reinforcing rods between two spacedV structures and then filling the gap between the structures with fresh concrete or grout and permitting the latter to set for the reason that the latter shrinks during hardening,

whereby the full strength in compression of the iilling material is not developed over the full area of the juxtaposed parts of the structures. This causes non-uniform application of compressive stresses at the connection when the latter is subjected to loading. This is particularly objectionable and causes high localized compressive stresses when the connection is subjected to bending moments, eg., when a column connected thereby is subjected to a horizontal force applied at some distance above the connection or when a beam having a cantilever connection is loaded. Moreover, in such a connection the metal reinforcing rods are not always adequately loaded to the juxtaposed ends of the structures, preventing early` of the rods;

development of the full tensile strengths further, this makes it impracticable to pre-stress the rods at the connection, such pre-stressing being desirable in` certain installations.

Itis an object of this invention to provide an improved Patented Aug. 16, 1960 ice connection between separately cast metal-reinforced structures and an improved method of making the same wherein the metal reinforcing rods are connected to develop tensile stress across the connection for anchoring the two parts together, and wherein the full compressive strength of the lling material is developed over the cross sectional area of the juxtaposed parts of the structures which does not require the use of bed plates, brackets, or the like. Ancillary thereto, it is an object to provide an improved connection and method of the type indicated wherein the reinforcing rods may, if desired, be prestressed at the connection.

A specific object is to connect a pre-cast, metal-reinforced concrete structure such as a column or the like on a support, such as a foundation, to achieve a secure anchoring of the structure to the support against tilting and afford substantially uniform `distribution of compressive stresses over the cross sectional area of the connection without the use of bed plates or the like.

A further object is to provide an improved connection and method of erection of the type described that is more economical and is simply applied in practice to a variety of pre-cast structures.

Still another object is to provide a connection and method of erection whereby the exact location of the pre-cast structure in relation to the support can be adjusted, within limits, to fit the former into the desired conformation to other elements of a composite structure, such as a row of similar structures, a house having several pre-cast walls, or to an elevated roadway supported thereby, obviating the need for extremely precise location of the foundations.

Other objects of the invention will become apparent from the following description. j

In summary, according to the invention separately cast concrete structures (for convenience sometimes referred to as the supporting and supported structures, respectively)` have initially exposed surfaces adapted to lie in opposed and spaced relation in the completed, composite structure, and each structure has embedded therein one or more metal reinforcing rods that project from the said exposed surfaces. The supported'structure is positioned in relation to the supporting structure with the said surfaces thereof in opposed and spaced relation and brought to the precise desired relative position, eg., by orientation and leveling, and held in such position. The reinforcing rods, which are preferably located in their respective structures inY similar geometric patterns so as to be substantially in alignment when the structures have the desired relative positions, are then firmly connected together, preferably by welding or by clamps, so as to bond each of the rods of the supported structure to one or more rods of the supporting structure to insure the transmission of tensile stress between connected rods. The intervening Space or gap between the exposed surfaces is then filled with a suitable load-sustaining filling material that includes a fresh hydraulic cementitious aggregate of the nonshrinking type which hardens to form a firm? mass (expanding cementitious aggregates being included' among non-shrinking aggregates) to enclose or embed the connected reinforcing rods and cover the exposed surfaces and substantially parallel to one another; in the case of a column or wall mounted above a foundation, or a'girder supported above a column or wall, the rods are substantially vertical and these surfaces are horizontal; however, in some embodiments, e.g., when a beam is xed to a column, girder or wall, the surfaces may be horizontal, vertical or at some other inclination, and when two oor slabs are united the surfaces are usually vertical. The supported structure may be held in the desired position in relation to the supporting structure by any suitable means such as a derrick, crane, temporary tower, scaffolding, a leveling jack that may support the structure during orientation and leveling, or the like, or a combination thereof. The connection between the rods that project from the several structures is advantageously such as to permit loading of the rods throughout their lengths to the full tensile strengths thereof. For this reason it is preferred, when welding is employed, to make the rods long enough to overlap throughout the major part of the intervening space between the said exposed surfaces, and to weld the overlapping rods substantially along the full distance of the lap, e.g., for about 6-12 inches in the case of quarter-inch rods and proportional distance for rods of other diameters. Overlapping, though preferred, is not essential, and a separate tie member may be used to connect non-overlapping rods or to strengthen a connection wherein an insufiicient overlap occurs.

Considering the filling material in greater detail, it is well known that mortars, grouts, and concrete aggregates, herein generically referred to as hydraulic cementitious aggregates, when made from usual construction material shrink upon setting. Were such an aggregate employed alone to fill the intervening space between the exposed surfaces of the juxtaposed structures to be connected, the filling material would, after hardening, no longer fill the space completely and bear uniformlyV against the said surfaces; instead, only parts of the filling material would make Contact and, in extreme cases, an actual small gap may result. This prevents a uniform distribution of compressive stresses over the cross sectional area of the surface, and may result in progressive failure, particularly when the connection is subjected to a bending moment. Since the reinforcing rods are in such case either slack or actually in compression (c g., when the supported structure s resting on a supporting structure beneath it) they do not function to anchor the supported structure securely to the suporting structure, and an undesirably large relative motion between the structures may result from the application of a force of a given magnitude to the supported structure. For example, when the supported structure is a column resting on a foundation and a tilting force applied to the column, a definite tilting movement would occur in the column before the rods at the side of the column from which the force acts are sufficiently stressed to counteract the resulting bending moment.

Now, according to the invention, this diliiculty is overcome by using for at least a part of the load-sustaining filling material a special hydraulic cementitious aggregate, 'known per se, which is non-shrinking, i.e., which at least maintains its volume during setting and hardens to form a firm mass. Such an aggregate may have the property of maintaining its volume substantially unchanged during setting, but preferably is of the expanding type, whereby the reinforcing rods are placed under slight or considerable tension during the setting. The welded or otherwise connected rods may be optionally loaded slightly in tension prior to filling the intervening space by adjustment of the leveling device, or by other means exerting a force tending to separate the said surfaces, but this is not necessary, particularly in the latter case. It is preferred to employ the non-shrinking cementitious aggregate only for ya part of the load-sustaining material, as by filling up the greater part of the aforementioned intervening space with solids or ordinary concrete (which may be of the shrinking type) leaving a smaller space into which the nonshrinking aggregate is tamped after the previously emplaced concrete has hardened. By this preferred method the expansion of the latter aggregate can cause only a small tensioning of the reinforcing rods, insufficient to destroy the bond of the latter to their respective structures or to the major part of the load-sustaining material. This feature is useful in that it permits the use of aggregate that is definitely of the expanding type without a very precise control of the amount of expansion, because mixtures that do not either expand or contract or those that expand to accurately specified limits are more didicult to use in practical construction work. In certain instances, as where the said exposed surfaces are vertical, this preferred method involves the inconvenience of placing a vertical spacer board adjoining one of the exposed surfaces to fill part of the gap while the remaining, major part of the gap is filled with ordinary concrete and subsequently removing the spacerboard and filling the resulting thin gap -with expanding aggregate; in this case recourse may be had to an alternate method, wherein the entire gap is filled with an aggregate of the same composition, the content of the expanding cement or expanding ingredient thereof being more carefully controlled to avoid excessive expansion.

ln the resulting structure the welded rods are preferably under tensile stress while the load-sustaining material between the surfaces of the support and the pre-cast structure is under compressive stress. This load-sustaining material is a body of cohesive aggregate, i.e., hardened cementitious aggregate, extending continuously between the said surfaces. In other words, the filling material is thus loaded without interposing a wedge, screw or the like.

The invention will be described in greater detail with reference to the accompanying drawings forming a part of this specification and illustrating certain preferred embodiments, wherein:

Figure 1 is an exploded elevation view showing the elements used for making the connection;

Figure 2 is a horizontal sectional view taken on line 2-2 of Figure l;

Figure 3 is an isometric view of the completed structure;

Figures 4-7 are vertical sectional views through a foundation and lower part of a column showing successive stages of the method of erection;

Figure 8 is a vertical sectional View taken on line 8--8 of Figure 9 showing a modied connection applied for connecting a beam to a wall;

Figure 9 is an elevation of the connection according to Figure 8;

Figure 10 is a sectional view through a further modification showing a beam connected to a vertical surface of a wall or column;

Figure 11 is an elevation view showing an alternate connection between reinforcing rods;

Figure 12 is a sectional view taken on line 12--12 of Figure 13 showing a further application of the invention for joining concrete floor slabs that are cast separate from supporting columns;

Figure 13 is a sectional view taken on line 13--13 of Figure l2;

Figure 14 is a sectional view of a modified construction wherein the floor slabs are cast integrally with the beams `and the invention is applied for joining adjacent slabs;

Figure 15 is a sectional view showing the invention applied to connecting a floor beam to a girder taken on line l5-15 of Figure 17;

Figure 16 is a sectional view taken on line 16--16 of Figure 15; and

Figure 17 is a fragmentary plan view, on a reduced scale, of the construction according to Figures 15 and 16.

The invention will 'be illustrated in Figures 1-7 by way of example as applied to the erection of a double stanchion for supporting pipes and the use of an internal leveling device' will be shown; however, it will be' understood that other types of structures, as previously indicated, and other types of leveling devices, such as externally applied jacks or towers, fall within the scope of the invention.

Referring to the drawings, Figures 1 3, 10 and 11 are concrete foundations which may be bell-bottom footings located entirely beneath the ground level 12 having at, upper exposed, horizontal surfaces 13. A double stanchion 14 has a pair of columns 1S and 16, each of which has a lower, exposed, horizontal terminal surface 17 The stanchion is prefabricated of concrete prior to erection and has suitable metal reinforcing rods of which only the rods 1S are shown. These rods are embedded in the concrete and project downwardly beneath the surface 17. Any suitable number, e.g., four, of such projecting rods arranged as a rectangle may be used on each column.

Each footing has a corresponding number of, viz., four, vertical reinforcing rods 19 rmly embedded therein and projecting upwardly beyond the surface 13 at locations to be substantially in alignment with correspoding rods 18, i.e., in juxtaposition thereto, when the corresponding column is placed in position above the footing as indicated in Figures l and 4-7. The proper relationship of the reinforcing rods 18 and 19 can be obtained by the use of wooden templates that position the rods prior to and during the casting of the concrete. A plurality of shorter vertical reinforcing rods 20 are optionally, although preferably, embedded in each footing so as to project upwardly `above the upper ends of the rods 19 at positions outside of the rectangle defined by the rods 19 and laterally beyond the columns 15 and 16, as shown in Figure 2. A suitable leveling device may, if desired, be embedded in each footing; thus, a hollow tube 21 may be embedded at the central axis and project upwardly above the surface 13. The leveling device further includes an externally threaded tube 22 adapted to'have a sliding t within the tube 21 and having an enlarged bearing plate 23 at the top. A nut 24 is threaded on to the tube 22 and is wide enough to engage the upper edge of the tube 21; it may be provided with lugs 25 for receiving a spanner wrench.

To make the connection the stanchion 14 is erected to position the columns 15 and 16 over the footings 10 and 11 by means of a suitable derrick (not shown) with the surfaces 13 and 17 in opposition and in vertically spaced relation so as to leave .an intervening space of convenient height, such as twelve inches. The subsequent operations will be described with reference to Figures 4-7 in which only one of the footings on `columns is shown, it being understood that both connections are made simultaneously and in the same manner. As shown in Figure 4, the stanchion is rst placed on the plate 23 so as to be supported thereby, and is leveled by adjusting the nut 24 to bring the surface 17 to the desired elevation; leveling of a stanchion in a direction transverse to the vertical plane joining the two footings is also effected, using an external support, not shown. When the stanchionV is properly positioned each rod 18 is next to a corresponding rod 19; `if necessary, these rods are bent slightly to bring them into contact.

The contacting rods are then welded continuously as i indicated at 26. It will be noted that the reinforcing rods 20 extend above the surface 17. It is advantageous to make the cross sectional area of the weld equal to that of one reinforcing bar.

Referring to Figure 5, an annular reinforcing tieV rod 27 is attached to the welded vertical rods and a` second annular reinforcing tie rod 28 is attached to the lower portions of the rods 20. These annular reinforcing rods, although preferred, are optional. v

A form 29 is then built around the rods and concrete 30 is poured into it to a level A slightly below the surface 17, thereby leaving a free space which may suitably have a height of one to several inches.

Referring to Figure 6, when the concretel 30` is dryv and has completed substantially all of the shrinkage that accompanies setting, a hydraulic cementitious aggregate of the type that does not shrink upon setting, such as dry grout 31, is placed into the space immediately beneath the surface 17. It is preferable to roughen the upper surface of the concrete 30 and the surface 17 prior to introducing the grout. By dry grout is means a fresh mixture of line aggregate and hydraulic cement containing only enough water to permit setting but insuicient to form a plastic mix. The cement should consist of or contain ingredients that prevent shrinkage upon setting or which, preferably, cause a slight degree of expansion upon setting. Such ingredients are metallic aggregates having the quality of expanding in volume during the setting and curing stages, forming a void-filling staple ingredient that is insoluble in water. They may contain iron particles or iron in the ferrous form which oxidize during setting, and may include an alkali to cause oxidation. An example of such an ingredient is Embeco described in The Action of Embeco in Concrete and Mortars, published by The Master Builders Company, Cleveland, Ohio, 1935. The grout should be tamped and hammered to pack it carefully and to ll all voids. The ce-v though the preferred use of two bodies of lilling materiall 30 and 31 was described it is evident that the expanding or non-shrinking aggregate 31 may in some instances be used to fill the entire space between the surfaces 13 and 17. If desired, the welded rods can be tensioned slightly prior to lling the space between the surfaces 13 and 17, e.g., by turning the nut 24 on the leveling jack. This is particularly advantageous when the grout is of the type that does not either shrink or contract appreciably during setting, and may be used to form a pre-stressed connection.

Referring to Figure 7, after the concrete or grout 31 has set for about ten hours a third annular reinforcing tie rod 32 may be attached to the rods 20 near their upper ends. The form is then extended by adding a section 33 and concrete 34 is poured around the edges of the concrete 31 and the lower side portions of the column 15 to form a protective shroud for the grout. After setting, the forms are stripped resulting in a structure having the appearance indicated in Figure 3.

Any difference in color between the dry grout 31 and the surrounding concrete areas can be remedied by applying a suitable cement wash to the surfaces concerned after the grout is thoroughly dry; this makes the application of the protective shroud 34 unnecessary in many cases.

Referring to Figures 8 and 9, a reinforced concrete the lower exposed supporting surface 45 of the beam. f

The reinforcing rods 41 project upwardly from the surface 44 to a height slightly below that of the surface 45.

The beam 43 has a plurality, e.g., four, reinforcing rods 46 embedded therein and projecting vertically downwardly from the surface 45, there being one rod 46 opposite each rod 4l. Some of these rods may, if desired, be

integral with the lower longitudinal reinforcing rods 47 of the beam, while others may be inclined as shown at 46a to transmit shear, and extend hoizontally to their ends, indicated at 4Gb. They may, if desired, be fixed to the upper reinforcing rods 47a.

In making the connection the pre-cast beam 43 is placed into the notch 42 and supported and leveled precisely,

both longitudinally and transversely, with the surfaces 44 and 45 in spaced relation to leave an intervening space; the leveling device in this case may be an external jack, indicated diganimatically at 48. Each rod 4l is then welded to a corresponding rod 46, as indicated at 49, and a layer of concrete 50 is cast to fill the major part of the intervening space. When this concrete has set and completed its shrinkage, the upper and lower surfaces of the remaining space are roughened and a layer of non-shrinking aggregate, such as dry grout l,- which is preferably of the expanding type, is t-amped into this space and permitted to set to form a firm mass. It is evident that suitable forms, as previously described, as well as reinforcing rods may be used for the concrete 50 and aggregate 51. In this case, however, a cement wash would be preferred to the concrete shroud. The space between sides of the beam 43 within the notch 42 may be grouted, using grout similar to the grout 51 or ordinary grout.

Referring to Figure l0, there is shown a connection to a wall 66 that provides a vertical surface 6l., and may extend above the top of the horizontal vbearn 62 to be supported thereby. This embodiment illustrates the application of the invention to the case wherein the exposed surfaces are vertical and the connected reinforcing bars are horizontal.

The wall 66 has embedded therein horizontally projecting metal rods 63 which are firmly bonded to the wall, e.g., welded to the upright metal reinforcing rods 64 of the wall and/ or provided with large heads 65; the rods 63 may be made integral with the upright rods 64 and curved in the manner previously described for the bars 46 and 47 in Figure 8. The projecting rods 63 are arranged in a geometric pattern similar to that of the longitudinal reinforcing rods 66 of the beam, the latter rods projecting horizontally beyond the vertical, initially exposed terminal surface 67 of the beam; thus, four rods '63 and four rods 66, situated at the corners of a rectangle, may be used. The wall further has a shoulder or haunch 68 cast integrally therewith and provided with metal reinforcing rods 69 and 70. The beam 62 may have reinforcing rods 71 with inclined portions, as shown, to improve transmission of shear.

In making the connection the beam may be supported in various Ways: according to one method it is supported and leveled precisely by means of a jack 4S, independently of the haunch 68, leaving a small gap between the latter and the beam. The surfaces 61 and 67 of the wall and beam are thereby placed in opposed and horizontally spaced relation. Each horizontally projecting rod 63 is then welded to a corresponding horizontally projecting rod 66, as indicated at 72. The intervening space between the surfaces 6l and 67 `and the space between the haunch and the bottom of the beam are then lled with fresh dry grout 73 of the non-shrinking type and, preferably, of the expanding type, which hardens into a rm mass, the grout being well tamped into position and retained by suitable forms, not shown. The grout, when of the expanding type, mayv cause a rise in the height of the beam but this is negligibly small because the layer of grout beneath the beam is quite thin. Expansion of the grout places the rods 63 and 66 under tension. Since the entire space between the surfaces 61 and 67 is, in this embodiment, filled with grouut of the same composition, it is desirable to control the amount of the expanding ingredient of the grout to avoid excessive expansion such as would tension the rods sufficiently to destroy their bonds to the wall and beam.

According to another method, the beam 6'2 may be placed directly on the haunch 68 without the leveling jack; the other operations are as described above, except that no grout is placed beneath the beam. With this method it is not possible to adjust the exact height of the beam independently of the haunch.

As was stated above, the projecting rods of the several juxtaposed structures may be connected by means other than welding. An alternative means suitable 'for use in areas wherein welding is not permissible, is disclosed in Figure l1, showing separately cast structures 75 and 76, having projecting reinforcing rods 77 and 78, respectively. When these structures are placed in the desired relative positions, the rods are secured by means of clamps 79 and 80, each comprisinga U-bolt S1, a wire rope clip 82 and a pair of nuts, of which only the nut rS3 is visible in the drawing. The invention may also be applied to connecting separately cast concrete slabs which may or may not have integral supporting beams.

Referring to Figures 12 and 13, which show the application of the invention to the joining of floor slabs that are separate from their supporting beams 43 that may be disposed in parallel relation `and supported in any manner, eg., in notches in walls such as the Wall 49 as previously described for Figures 8 and 9, by welding the terminal, vertical parts of the horizontal reinforcing rods 47 and 47a of the beams at 49' .to vertical rods of the wall and filling the interval with concrete 50 and expanding grout 5l. In addition to the horizontal reinforcing rods 47 and 47a the beams have embedded therein upright stirrups 84 that extend above the beams at the center line and have their upper, horizontal traverses spaced above the beam by 'a distance less than the thickness of the floor slab to be supported. The floor slabs 85, 85a and 85h, are cast separately from the beams and wall and have widths great enough to span the interval between adjacent beams 43 but less than the center-to-center distance between such beams, so as to leave horizontal intervals between the vertical marginal surfaces of each pair of juxtaposed slabs resting on the same beam. The floor slabs carry suitable horizontal metal reinforcing rods S6 at a suitable level, eg., about a third of thi-ckness above the bottom. Reinforcement may also be provided at a higher level as indicated at 87 by providing additional reinforcing rods or by` bending some of the rods 86 up near the lateral margins. At least some of these rods project horizontally beyond the marginal surfaces of the slabs for distances suflicient to provide overlap between opposed rods on the juxtaposed slabs.

In assembling Ithe slabs, the latter are first placed on the beams 43 with the margins in supporting engagement thereon and the stirrups 84 are connected to the reinforcing rods 86, preferably by welding. lThe opposed reinforcing rods l86 and 87 of the juxtaposed slabs are then connected, eg., by welding as indicated at 8S. Dry grout of the non-shrinking type, preferably the expanding type, is then tamped into the interval between the slabs as shown at 89 and allowed to set to form4 a firm mass thereby effectively loading the bars 86 and 37. The completed connection is able to transmit bending moment, i.e., the upper rods 87 are loaded in tension and the lower part of the grout 89 is loaded in compression;

1 for this reason the connection between the lower reinforcing rods 86 could be omitted under certain design loading conditions. At the center of the span between beams the slabs are, of course, subjected to a bending moment inthe opposite sense, and inflection points occur between the 'center and the margins of the slab. It 'may be stated, however, that the invention is not strictly limited to cases wherein the reinforcing rods 86 and 87 are provided at different levels; in Vsome `floor slabs, rods are provided only at one level, sometimes near the mid-level, and the connection according to the invention is also applicable to joining such slabs.

Referring to Figure 14, showing the invention applied to the joining of separate floor slabs that are cast integral to the beams, the floor slabs 90 project laterally to both sides of their beam portions 91, the latter being supported in any manner, eg., Vin the wall 40 as described above for the beams 43. The combined beams and 'licor slabs carry suitable longitudinal reinforcing bars, of which only the rods 92 are shown, and Vtransverse reinforcing bars 93 that are preferably below the mid-level of the slab and may extend downwardly into the beam portions and anchored therein, as shown. The structures may be further reinforced with reinforcing bars 94 at a higher level above the beam portions for transmitting shear and to strengthen the structure for cantilever loading. The bars 93 project beyond the vertical marginal surfaces 95 of the slabs and the beam portions are mounted in spaced relation so that the vertical surfaces 95 of juxtaposed slabs are spaced apart, with the bars 93 of the respective slabs overlapping.

For connecting the floor slabs the projecting opposed bars 93 of the juxtaposed slabs are first firmly connected, e.g., by welding as shown at 96. The gap between the surfaces 95 is then filled with non-shrinking, preferably expanding, grout as indicated at 97, a suitable form (not shown) being provided. When the grout hardens to form a firm mass the interval between the surfaces 95 is filled completely and, when expanding grout is used, the rods 93 may be loaded slightly in tension. The conjoined slabs are thereby adapted to be subjected to a bending moment such that the upper part of the slab is in compression.

Referring to Figures 15-17, a reinforced concrete girder 100 is used to support the intermediate parts of a series of parallel, separately cast, reinforced concrete beams 101, 102, it being understood that the beams are additionally supported by walls or by other girders, not shown, extending parallel to the girder 100. The girder 100 may be supported in any suitable manner on columns or the like, e.g., on haunches 103 projecting from a wall 104. Separately pre-cast `reinforced concrete floor slabs 10S, 107, extend between adjacent beams or between the wall 104 and a floor beam The beams have central tongues or ridges 101a, 102a, extending the full lengths of the beams and shoulders 101b, 102b, on both sides of the ridges for supporting the slabs. Similarly, the wall 104 has a tongue or ridge 104e: at the outer side thereof, leaving a supporting shoulder 104b. The slabs rest on these shoulders and are positioned by the ridges; they have suitable metal reinforcing rods 108, 109, extending across the span and parallel to the beams, respectively. The point of novelty in this construction resides in the connection between the girder and beams.

The girder 100 has the upper part thereof notched as indicated at 110, Figure 15, at each crossing of a beam while each beam 101, 102, etc., has the lower par-t thereof notched as indicated at 111, Figure 16, at each girder. Vertical thrust is thus transmitted through the plane of contact 112 between the bases of the notches. As seen in Figure 15, the notches 110 need not be made subs-tantially longer (along the length of the girder) than the width of the beam, and they are usually made only large enough to permit the beams to be inserted without binding into aligned notches on a number of girders. The notches 111 on the beams are, however, longer (along the length of the beam) than the width of the girder. The depths of these notches are such that the shoulder 10117 of each beam is at about the level of the top ofv the girder. The girder carries suitable metal reinforcing rods, such as longitudinal rods 113 and 114. Beneath each notch the girder has transverse metal reinforcing rods 115 embedded therein and projecting laterally beyond both sides of the girder, the overall lengths of the rods 115 being slightly less than.- the total width of the notches 111 in the beams. These rods 115 may be fixed, e.g., welded, to the rods 113.. `The beams carry longitudinal'reinforcing rods 116 and 117, the latter being at the level of the notches 111 and almost in alignment with the rods 115 so as to be in touching, side-'byside relation. As shown in Figure 16, the rods 117 project into the notch 111 so as to overlap lthe rods 115. Some of the rods` 117 may be bent up over thel notch,

10 as indicated at '117m The rods 116 and 117 may be connected by looped rods 118.

In assembling the structure, the girders are first emplaced and the beams-101, 102, `are tted with the notches in interlocking relation and the projecting rods in overlapping relation to the projectingrods 117.

' The overlapping rods are then firmly connected, eg., by

welding as shown at v1119. Dry grout of the nonshrinking or, preferably, `of the expanding type is then tamped into the space between the beam and girder surrounding the connected rods to fill the notch 111 and allowed to set to form a firm mass. A suitable form, not shown, may be provided for this operation. The notch 110 may be similarly filled with grout. The floor slabs 105-107 are then placed on the beams and-wall, secured by any conventional or suitable means, such as hold-down bolts (not shown), and the spaces between the slabs and the ridges are lled with grout, as indicated at 121. The slabs may, of course, be attached by the arrangement shown in Figures 12 and 13, in which case the beams would have at upper surfaces. The grout |'120, when hardened, effectively loads the lower portions of the beams in compression, thereby better adapting the beams for sustaining loads that subject it to bending moments at the girders in which the lower parts of the beams are loaded in compression.

I claim as my invention:

l. Method of making a connection betweenl two separately cast concrete structures each of which has ernbedded therein metal reinforcing rods projecting outwardly from a surface thereof, comprising the steps of: positioning the said pre-cast structures with the said surfaces thereof in opposite and spaced relation so as to leave a free intervening space; firmly securing each rod projecting from one of the structures to a rod projecting from the other structure to form for each rod a connection adapted to transmit tensile stress; thereafter maintaining the interval between said surfaces so as to hold the connected rods tautly and lling the said intervening space completely between the said surfaces with a load-sustaining material that consists essentially of a hydraulic cementitious aggregate of the type that contains expanding cement in amount at least to maintain its volume against shrinking during setting and hardens to form a firm, essentially non-plastic mass; and allowing the said hydraulic cementitious aggregate to set, whereby the portions of said connected rods between said surfaces are secured tautly after setting.

2. Method according to claim 1 wherein said surfaces are positioned to effect an overlap between the oppositely projecting rods over the major part of the distance between said surfaces and the rods are secured by welding along substantially the full length of the overlap.

3. Method according to claim 1 wherein the step of lling the intervening space includes the following oper-- ations: lling the major part of said space with concrete that hardens to form a firm, essentially non-plastic mass and leaving a small clearance immediately adjacent one of said surfaces; allowing said concrete to set; and thereafter tamping a dry grout into said small clearance, said dry grout consisting essentially of the hydraulic cementitious aggregate defined in the said claim.

4. In combination with the steps of the method according to claim 3, the step of placing a concrete shroud about the grout. Y

5. In combination with the steps of the method according to claim 1, the step of moving said pre-cast structures slightly apart after securing the rods and prior to lling the intervening space with the load-sustaining material to apply tension to the connected rods, and maintaining said tension until after the said hydraulic cementitious aggregate has set.

6. Method of making a connection between two separately cast concrete structures each of which has embedded therein metal reinforcing rods projecting outwardly from a surface thereof, comprising the steps of: positioning the said pre-cast structures with the said surfaces thereof in opposite and spaced relation so as to leave a free intervening space; firmly securing each rod projecting from one of the structures to a rod projecting from the other structure to form for each rod a connection adapted to transmit tensile stress; and thereafter filling the said intervening space completely between the said surfaces with a load-sustaining material that includes a hydraulic cementitious aggregate of the type that expands during setting and thereby applies a tension to the connected rods and maintains said tension after setting.

7. Method of erecting a pre-cast concrete structure on a concrete support, said structure having embedded therein metal reinforcing rods projecting from a surface thereof and the support having embedded therein metal reinforcing rods projecting lbeyond an opposed supporting surface thereof, comprising the steps of: positioning the pre-cast structure in relation to the support with the said surfaces thereof in opposite and spaced relation so as to leave a free intervening space; firmly securing each rod projecting from the structure to a rod projecting from the support to form for each rod a connection adapted to transmit tensile stress; thereafter maintaining the interval between said surfaces so as to hold the connected rods tautly and filling the said intervening space completely between the said surfaces with a load-sustaining material that includes a hydraulic cementitious aggregate of the type that contains expanding cement in amountat least to maintain its volume against shrinkage during setting and hardens to form a firm, essentially nonplastic mass; and allowing the said hydraulic cementitious aggregate to set, whereby the portions of said connected rods between said surfaces are secured tautly after setting.

8. Method of erecting a pre-cast concrete structure on a concrete supporting base, said structure having embedded therein metal reinforcing rods projecting downwardly beneath a downwardly directed surface thereof and the base having embedded therein metal reinforcing rods projecting upwardly beyond an upwardly directed supporting surface thereof, comprising the steps of: positioning the pre-cast structure above the base with the said surfaces thereof in opposite and vertically spaced relation so as to leave a free intervening space; lrrnly securing each rod projecting kfrom the structure to Va rod projecting from the base to form Vfor each :rod a connection adapted to transmit tensile stress; and thereafter iilling the said intervening space completely between the said surfaces with fa load-sustaining'material that includes a hydraulic cementitious aggregate of the type that expands during setting and thereby applies va tension to the connected rods and maintains said tension after setting.

9. Method of connecting a horizontal pre-cast concrete beam having a substantially vertical surface to an upright concrete support having a substantially vertical surface, said beam having embedded therein metal rods projecting horizontally beyond said surface thereof and said support having embedded therein metal reinforcing rods projecting horizontally beyond said substantially vertical surface thereof, comprising the steps of: positioning the beam in relation to the support wtih the said surfaces thereof in opposite and horizontally spaced relation so as to leave a free intervening space; firmly securing each rod projecting from the beam .to a rod projecting from the support to form for each rod a connection adapted to transmit tensile stress; and thereafter filling the said intervening space completely between the said surfaces with a load-sustaining material that includes a hydraulic cementitious aggregate of the type that expands during setting and hardens to form a firm, essentially non-plastic mass and Ythereby applies a tension to the connected rods and maintains said tension. after setting.

l0. Method of connecting in `juxtaposition separately cast concrete floor slabs that have embedded therein metal reinforcing rods projecting horizontally beyond the adjacent marginal surfaces of the slabs, comprising the steps of: positioning said iloor slabs in relation to one another to place said marginal surfaces in opposed and horizontally spaced relation so as to leave a free intervening space; rmly securing each rod projecting from one of the floor slabs to a rod projecting from the other floor slab to form for each rod a connection adapted to transmit tensile stress; thereafter maintaining the interval between said surfaces so as to hold the connected rods tautly and filling the said intervening space between the said surfaces with a load-sustaining material that includes a hydraulic cementitious aggregate of the type that contains expanding cement in amount at least to maintain its volume against shrinkage during setting and hardens to form a hard, essentially non-plastic mass; and allowing the said hydraulic cementitious aggregate to set, whereby the portions of said connected rods between said marginal surfaces are secured tautly after setting.

l-l. Method of connecting a pre-cast concrete beam to a separately cast supporting girder member extending transversely thereto at the intermediate parts of said members, at least one of said members having a notch that is materially longer than the width of the other member, said one member having reinforcing rods embedded therein and projecting longitudinally into said notch from opposite ends thereof and said other member having a transverse reinforcing rod projecting laterally from the sides thereof, comprising the steps of: positioning said beam member on and transversely to said girder member for support thereby with said other member at least partly within the said notch in the one member so as to leave an intervening space within the notch on each side of the said other member; rmly connecting each longitudinally projecting rod to a laterally projecting rod to form for each rod a connection adapted to transmit tensile stress; maintaining the intervals between the sides of said other member and the ends of the notch so as to hold the connected rods tautly and filling the said intervening spaces about the connected rods completely between the end of the notch and the side of said other member with a load-sustaining material that includes a hydraulic cementitious aggregate of the type that contains expanding cement in amount at least to maintain its volume against shrinkage during setting and hardens to form a rm, essentially non-plastic mass; and allowing the said hydraulic cementitious aggregate to set, whereby the portions of said connected rods within said loadsustaining material are secured tautly after setting.

l2. Method of connecting a pre-cast concrete beam to a separately cast supporting girder at the intermediate parts of the beam and girder, said girder having an upwardly open notch of a length at least equal to the width of the beam and the beam having a downwardly open notch of a length materially in excess of the width of the girder, said beam having a longitudinal reinforcing rod embedded therein and projecting longitudinally into the latter notch from at least one end thereof and said girder having a transverse reinforcing rod projecting beyond a side of the girder beneath the said notch therein, comprising the steps of: positioning said beam on the girder transversely thereto with the said notches in interlocking relation for support of the beam between bases of the notches with the said reinforcing rods in juxtaposition so as to leave an intervening space within said notch of the beam on each side of the girder whereat a reinforcing rod projects; welding each longitudinally projecting rod of the beam to a laterally projecting rod of the girder; and thereafter filling the said intervening space completely between the end of the notch and the side of the girder with -a load-sustaining material that includes a hydraulic cementitious aggregate of the type that expands during setting and hardens to fonn a hrm, essentially nonplastic means and thereby applies a tension to the connected rods and maintains said tension after setting.

13. IThe combination uniting separately cast, metalrcinforced concrete structures which comprises: a first and a second pre-cast concrete structure, each said structure having a bounding surface and the said bounding surfaces of the structures being situated in opposed and spaced relation, each of said structures having a plurality of metal reinforcing rods embedded therein and projecting beyond said surface thereof towards the other structure; a irm connection between each of the said reinforcing rods projecting from one structure and a reinforcing rod projecting from the other structure adapted to transmit tensile stress; and a rm, essentially non-plastic and cohesive, load-sustaining material consisting essentially of hardened hydraulic cementitious aggregate which contains hardened expanding cement extending continuously between said surfaces and surrounding the said projecting rods and the said connections thereon, said material being under compressive stress and said connected projecting reinforcing rods being under tensile stress.

14. A combination according to claim 13 wherein said precast concrete structures are concrete oor slabs, said terminal surfaces thereof are adjacent lateral marginal surfaces thereof, and said reinforcing rods project horizontally from said marginal surfaces.

15. In combination with the elements recited in claim 14, a support beam having an upwardly projecting metal reinforcing rod embedded therein, the said lateral margins of the two oor slabs being in supported engagement on the said beam on opposite sides of said upwardly projecting rod, the last-mentioned rod being rmly secured to said horizontally projecting rods of the floor slabs, and the said rods of the *door slabs and the said load-sustaining material being all situated above the said support beam.

16. In combination with the elements recited in claim 14, a pair of spaced support beams, each said oor slab being supported at the intermediate part on one of the said beams and projecting laterally beyond said beams, the said adjacent marginal surfaces of the floor slabs are situated between the said support beams.

17. A combination according to claim 13 wherein one of said concrete structures is a girder member and the other is a beam member extending transversely thereto, at least one of said members having a notch that is materially longer than the width of the other member and said other member being situated at least partially within the notch with the sides thereof in spaced relation to the ends of the notch, each end of said notch constituting a bounding surface of the member containing the notch and each side of said other member constituting a bounding surface thereof.

18. The combination uniting a pre-cast concrete girder and a separately pre-cast concrete beam which comprises: a girder having an upwardly open notch at an intermediate part thereof, said notch having a length at least equal to the width of the beam; a beam extending transversely to the girder having a downwardly open notch at an intermediate part thereof and supported from said beam through the bases of the said notches, said notch in the beam having a length which is materially in excess of the width of the girder and extends to each side of the girder; a longitudinal metal reinforcing rod embedded in the beam on each end of the notch and projecting longitudinally into said notch toward the girder; a transverse metal reinforcing rod embedded in the girder beneath the notch therein and projecting laterally beyond the sides of the girder into the notch in the beam; a iirm connection between each said longitudinally projecting rod and said transverse metal rod; and a rm, essentially non-plastic and cohesive, load-sustaining material consisting essentially of hardened hydraulic cementitious aggregate which contains hardened expanding cement lextending continuously between each side of the girder and the ends of the notch in the beam and surrounding the said projecting rods and the said connections thereon, said material being under compressive stress.

19. The combination uniting a concrete base and a structure comprising: a pre-cast concrete base having an upwardly directed supporting surface and a plurality of metal reinforcing rods embedded therein and projecting upwardly above said surface; a pre-cast concrete structure supported by said base and having a downwardly directed surface situated in vertically spaced relation above said supporting surface, said pre-cast structure having metal reinforcing rods embedded therein and projecting downwardly below said surface thereof; a rm connection between each said reinforcing rod projecting from the structure to a corresponding reinforcing rod projecting from the base adapted to transmit tensile stress between the rods; and a iirm, essentially non-plastic and cohesive, load-sustaining material consisting essentially of hardened hydraulic cementitious aggregate which contains hardened expanding cement extending continuously between said surfaces and surrounding `the said projecting rods and the said connections thereon, said material being under compressive stress and said welded rods being under tensile stress.

20. A combination according to claim 19 wherein said downwardly projecting rods are arranged in a pattern corresponding to the pattern of the upwardly projecting rods and each rod is substantially in alignment with the downwardly projecting rod connected thereto, both groups of rods extending sufliciently beyond their respective surfaces to overlap over a major part of the vertical distance between the said surfaces, and said firm connections are weldments extending substantially over the full lengths of the overlapping portions of the rods.

References Cited in the tile of this patent UNITED STATES PATENTS 2,053,562 Jorgensen Sept. 8, 1936 2.483,175 Billner Sept. 27, 1949 2,580,174 Henderson Dec. 25, 1951 FOREIGN PATENTS 376,308 Great Britain July 8, 1932 451,798 Italy Sept. 26, 1949 591,431 Great Britain Aug. 18, 1947 665,855- Great Britain Jan. 30, 1952

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