The present invention is directed to a method and apparatus for constructing buildings in a modular fashion, and in particular to building construction which uses monolithic concrete modules having an inverted channel shape.

BACKGROUND INFORMATION A number of attempts have been made to facilitate the construction of buildings by providing some or all building components in modular form, i.e., a plurality of substantially similarly shaped units which are preferably prefabricated (fabricated at a location different from the construction site and transported thereto). In some cases, a given horizontal or vertical surface was constructed by joining together a plurality of prefabricated, substantially, planar, slabs. In some cases, monolithic modular units have included both horizontal and vertical components (such as floors and columns).

Previous devices and methods, however, are believed to have certain deficiencies. In many previous devices it has been difficult or impossible to achieve modular devices having long spans, such as more than about 30 feet (about 9 meters) between vertical walls or other vertical supports. Previous devices have been relatively difficult to cast or form, and have also been relatively difficult to transport and erect.

Accordingly, it would be useful to provide prefabricated building modules incorporating both vertical and horizontal surfaces in a monolithic fashion, having increased spans and with increased ease of casting, forming, and/or erection.

SUMMARY OF THE INVENTION The present invention provides a building module having vertical and horizontal components that are monolithically cast to provide a long span, such as a span greater than about 30 feet (about 9 meters). The module generally has an inverted channel or inverted square-U shape. The vertical walls are preferably substantially planar and substantially perpendicular to the planar ceiling section, although preferably windows or other openings can occupy up to about 50% of the vertical walls. In one embodiment, pre-stressed construction is used such as providing a slanted or draped strand which

is tensioned during pouring of the concrete, and preferably tension-released after substantial hardening but preferably before full curing of the concrete.

In one embodiment, the channel is initially cast in a form configured with the channel lying on its side, and the channel is subsequently rotated upward to assume the attitude it will have in the final building project.

In one embodiment, the span which will become a roof or ceiling span is cast in a mold configured to impart a bow or camber to the span. When the channel is rotated to an upright attitude, the deadweight of the roof/ceiling span partially counters the as-cast camber, such as leaving an upward camber to the roof/ceiling span of about 0.25 inches.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing an inner mold form and an outer mold form in phantom; Fig. 2 is a top plan view of a module form and tensioned strand in accordance with an embodiment of the present invention; Fig. 2A is a partial top plan view of a module with tensioned strand; Fig. 3 is a partial perspective view of reinforcement and insulation components for a module placed around an inner form according to an embodiment of the present invention; Fig. 4 is a top plan view of a module according to an embodiment of the present invention; Fig. 5 is a cross-section view taken along line 5-5 of Fig. 4; Fig. 6 is a partial view of region 6 of Fig. 5; Fig. 7 is a cross-sectional view taken along the line 7-7 of Fig. 4; Fig. 8 is a partial cross-sectional view of region 8 of Fig. 7; Fig. 9 is a partial end elevational view of the device of Fig. 4; Fig. 10 is a cross-sectional view taken along line 10-10 of Fig. 4, showing an adjacent module in phantom; Fig. 10A is a cross-sectional view taken along line 10A-IOA of Fig. 4, showing an adjacent module in phantom; Fig. ii is a partial perspective view of a plurality of adjacent modules, coupled together to form a portion of a building according to an embodiment of the present invention;

Fig. 12 is a partial end elevational view showing use of plates for connecting a module to a floor; Fig. 13 is a cross-sectional view taken along line 13-13 of Fig. 12; Fig. 14 depicts an inverted channel portion with a sidewall; Fig. 14A is a top plan view of a compression beam and tensioned strands; Fig. 15 is a perspective view of a stantion; Fig. 16 is a perspective view of a standoff; Fig. 17 is a perspective view of a mold and compression beams; Fig. 18 is a perspective view of a channel bracing; and Figs. 19A and 19B are schematic perspective views of a channel according to an embodiment of the present invention, in as-cast and upright attitudes, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As depicted in Fig. 1, preferably the module according to the present invention is initially monolithically cast of concrete on its side. Thus, after casting, the device will be rotated 90" 112 to provide a device having a ceiling portion with a first span 114, and at least one, and preferably two, end walls, formed monolithically with the ceiling plate, each having a height 116 and a depth 118. A number of different sizes of modules can be formed according to the present invention and, preferably, the molds for forming the module (described more fully below) can be easily modified to produce a module with different span 114, height 116, or depth 118, e.g., by adding or removing form sections, inserting form dams, and the like. The present invention is capable of producing a module which can be transported and erected at a remote site, having a relatively long span 114, such as a span of 30 feet or more (about 9 meters or more). In one embodiment, the form 122, 128 is adjustable in span for 20 to 40 foot applications (about 6 meters to about 12 meters). In one embodiment, the height 116 is about 10 feet (about 3 meters), and the depth 118 is about 8 feet (about 2.4 meters).

In the configuration shown on Fig. 1, a substantially C-shaped inner form 122 is provided with regions which protrude outwardly from the plane of the inner mold, such as lightening pans 124a through h. These produce waffle-like indentations in the finished module, to produce a product which is lighter than would otherwise be the case. Although only 8 lightening pans are depicted in Fig. la, larger or smaller number of lightening pans, or pans having a different size or shape can be provided.

Preferably, lightening pans are also provided in the portion of the mold 126 used for forming the underside of the ceiling. An outer mold positioned adjacent the inner mold is depicted in Fig. 1 in phantom lines 128. The mold form is preferably a self-stressing steel form that can withstand approximately 200 kips of force, plus an additional draped center force (described below) of about 25 kips. In one embodiment, this is accomplished by creating a truss (Fig. 14) between the exterior form jacket and the compression beams 1412a, 1412b, 1412c (Fig. 17) (whalers), also used as a catwalk.

The inner mold 122 and outer mold 128 are spaced apart to define a mold volume 132.

Before filling the mold volume 132 with a matrix such as concrete, reinforcement and, preferably, insulating materials are positioned in the volume 132. Fig. 1 depicts an insulation sheet 134 positioned in the portion of the volume that will define one of the vertical walls of the module. A number of materials can be used as an insulation device, including Styrofoam. In one embodiment, insulation sold under the trade name Thermomass can be used. In one embodiment, the insulation may have a thickness of about 2 inches. Preferably, the insulation device 134 is maintained in a position interior to the volume 132, without contacting either the adjacent inner or outer mold 132, 138, so that the insulating material 134 will be completely surrounded by and sandwiched between layers of concrete. If desired, dams or other blocking structures can be provided to define openings 136 in the vertical walls, e.g., for windows, doors, and the like. Preferably, the openings 136 in any given vertical wall occupy less than 50% of the vertical wall.

The volume 132 may define a number of different thickness. The wall thicknesses may be, e.g., between about 8 inches and about 12 inches. The ceiling thickness may be, e.g. between about 10 inches and about 15 inches.

As seen in Fig. 2, before the mold is filled with concrete, preferably a tensioned reinforcing strand is inserted. The strand is draped or positioned such that near the middle of this strand it is closer to the inner form and near the ends (i.e., near the vertical walls) is closer to the outer form.

The strand 212 is preferably one-half inch or five-eighth inch diameter steel strand, preferably monostrand, preferably hardened rather than mild steel. In one embodiment, the first end is locked into a stantion 214 beyond the outer form 128, so that it is stationary. The opposite end is passed through a second stantion 216 positioned beyond the outer form and locked with an outer chuck 222.

In one embodiment, depicted in Figs. 14-17, the stantions 214, 216 are bolted 1502a, 1502b, 1502c, 1502d or otherwise coupled to I-beams 1412a, 1412b, 1412c positioned exterior to the outside molds 128, and substantially parallel to the longitudinal axis of the ceiling portion. The pre-stressed strands

can pass through the top slab of the channel just short of the sidewalls (Fig. 2A), thereby leaving the preferably insulated sidewalls free of penetrations. An inner chuck or swedge is positioned inside the form at each end 218a, 218b, and will form a pocket in the final module. The strand 212 is tensioned, e.g., to a tension of about 20 to 35 kips, preferably about 25 to 30 kips and more preferably about 28,000 pounds per square inch (or 28 kips). The middle region of the strand can be maintained near the inner form surface, despite this tensioning, by a number of devices, such as using a standoff 1602 (Fig. 16) between the strand and the outer form surface, tying to a reinforced inner form and the like. Recessed I-beam type pocket assemblies can also be provided for camber alignment. The amount of drape of the strand and the tension vary according to the span 114 and the anticipated dead load/live load. At this point, both swedges 218a, 218b, are adjacent the outside form.

In typical pre-stressing situations, upon release of tension on the strands, the strand portions near the end of the span will slip, such as slipping for approximately 24 to 28 inches near the anchor points. According to one embodiment of the invention such slippage is reduced or eliminated. In the depicted embodiment, by pre-stressing a swedge or chuck onto the strand that gets buried in the concrete near the ends (sidewalls) the strand tails 213 (that are not embedded in concrete) are free of tension, but the pre-stressing valve is utilized substantially all the way to the ends of the span section, and strand slippage is reduced or eliminated.

In one embodiment, multiple tensioned strands are provided. As depicted in Fig. 3 six strands 212a through f, are provided, spaced apart to allow regions 312a, 312b, where lightening pans can be used. In the depicted embodiment, the strands 212a, b, c, d, e, f are arranged in pairs through swedges 218b, c, d. As seen in Fig. 3, in addition to strands 212, other reinforcement can be provided, such as steel mesh 314a, 314b, and reinforcement bars (rebar) such as mild steel rebar 316.

Mesh such as 4-inch by 4-inch mesh, are rebar may be tied together or otherwise connected in a manner well-known in the art.

After the desired strands, other reinforcement and insulation, as well as any desired conduits, e.g., for electrical or plumbing purposes, are in place, the concrete is poured into the form.

Standard concrete fabrication techniques, such as vibration, can be used. Preferably the concrete is allowed to harden, (but preferably not to fully cure) before the tension on the strands 212 is released.

In one embodiment, after the concrete is cured to about 4,000 PSI (pounds per square inch) or more, the tension is released such as by cutting a temporary chuck 222, thereby releasing the pre-stress

force into the concrete. This release of force will cause the ceiling or span portion to slightly camber up 224. It is believed that release of cables tensioned to at least about 14 KPSI is sufficient to achieve the desired camber-up for long-span modules, in at least some configurations.

As seen in Fig. 4, in one embodiment transverse bars 412a, b, c, d, e, f, are positioned in the mold before filling with concrete. As seen in Figs. 5 and 6, the transverse bars 412 are position in the regions between the lightening pan 414a, 414b, 414c, in the thickened or beam regions 512a, 512b, or end regions 514a, 514b. As best seen in Fig. 6, the bars 412 can be used in positioning the monostrand 212 to have the desired slope or drape.

In the embodiment of Fig. 5, the channel span portion 522 has an overall length of 45 feet 4 inches (about 13.8 meters) and leg portions 524a, 524b define a depth of 8 feet (about 2.4 meters), and a height of 11 feet (about 3.3 meters). In the embodiments depicted in Fig. 4 a total of 10 tension strands are provided.

As depicted in Fig. 7, bars 712a, 712b, can also be provided in the wall portions. In the depicted embodiment the lightening pans 401 4b in the span or ceiling section have a depth 812 of about 9 inches, and the lightning pans in the walls 714 have a depth of about 5 inches.

As seen in Fig. 9, after the module is removed from the mold and the external swedges 218 are removed, pockets 912 remain where the swedges formerly were positioned.

After the module has been formed, it is transported to the building site and positioned, e.g., on a concrete pad 1112. The modules may be transported either in the attitude as cast (on edge) or uprighted. It is important, such as during transport, rotation and erection, to maintain the segment or module in balance. To achieve this, the pick points (e.g., for attachment of cables for lifting or rotating by a crane) are positioned substantially at or near the centroid of the piece or a longitudinal axis passing through the centroid to locate centroid-defined points 526a, 526b (Fig. 5).

Once the position is rotated into final use attitude (with the upper span or slab 522 lying in a substantially horizontal plane) the dead weight of the span slab and the stress force of the draped strands substantially counteract one another. However, before rotation, this is not the case.

Accordingly, in one embodiment, temporary bracing is applied from a point near the inside bottom of each sidewall to the underside of the roof slab 528a, 528b. This allows the sidewalls (which as noted

are reinforced, e.g., with mild steel) to work against the uplift of the span slab. In one embodiment, the bracing 528a, 528b is provided with turn buckles 532a, 532b for adjusting the effective length of the braces 528a, 528b. It is believed that the braces 528a, 528b assist, e.g., during transit, with keeping frequency of the span slab movement low thus reducing or minimizing cracking.

According to one embodiment, bracing can be provided in the configuration depicted in Fig.

18. In this figure, bracing, which may be, e.g., angle iron 1802a, 1802b, 1802c, extends between lower edges of opposed walls 1804a, 1804b and is attached thereto, e.g., using plates 1806a, 1806b, 1806c. Diagonal braces 1808a, 1808b extend from the ends of the mid-brace 1806b to the middle of the lower brace 1802c. A cross brace 1812 couples the mid points of the longitudinal braces 1802a, 1802b, 1802c and extension braces 1814a, 1814b extend to the mid span of the ceiling 1816 and are attached thereto, e.g., via plates 1806d. Openings which extend to an edge such as door opening 1818 preferably have a threshold or edge brace 1822 across the opening edge.

To complete the building, a plurality of inverted channel modules 1114a, 1114b, 11 14c are positioned side-by-side (Fig. 11). Adjacent modules can be joined, e.g., by plates 1012 (Fig. 10) coupled to embedded angle irons 1014a, 1014b. The channel-to-channel connection 1012, 1014, can be used to increase load-bearing capacity of specific areas, if desired. Preferably, the modules of 1114 are configured to fit tightly edge-to-edge so that the joints 1132 can readily be concealed by hand-troweling. A similar coupling can be used for joining an end cap wall to cover the open end of the structure 1116. Although the modules 114a, b, c are substantially similar, there may be differences among the modules to accommodate the desired building designs such as by providing windows 118, 120a, b, c, or other openings 122, doorways, and the like.

After the module is positioned on the pad 112, it is preferably coupled to the pad by coupling an angled plate 1212a, 1212b partially cast in and/or otherwise coupled to the floor, to corner plates 1214a, 1214b, partially cast in the lower corners of each module 1114. As depicted in Fig. 13, the resulting structure can be covered, such as by welding a cover plate 1312 over the structure. After storage and transportation of a module, it is possible that the wall-to-wall distance at the bottom of the structure 534 may vary slightly from the dimension as cast. Typically the foundation or slab 1112, and the plates 1214a, 1214b coupled thereto are positioned at locations based on the nominal dimension or the dimension as cast. Consequently, a slight spreading or contracting of the legs 524a, 524b may be required. Preferably this adjustment may be made, e.g., using turn buckles 532a, 532b while some of the segment weight is still being held by the erection crane. In one embodiment, first

one leg 524a is fastened, e.g., using the plate connections 1212, 1214, then the adjustment is made by rotating turnbuckles 532a, 532b as needed, the second leg 524b is secured using the plates 1212, 1214 and the crane cables are relaxed to no longer support a portion of the segment weight. In some cases it may be found that edges of span portions of adjacent modules are not precisely aligned and in one embodiment differential variances, segment-to-segment, at mid-span are reduced or eliminated with a recessed bolt 242 which acts to squeeze the span slabs together at mid-span (Fig. 10A).

Sidewalls can be added to the inverted channels with steel studs on one side to facilitate wiring, plumbing, etc. (Fig. 14A) by placing two low tensioned strands 1412a, 1412b the thin wall section can be supported until it is in final position.

Figs 19A and 19B illustrate another embodiment of the invention. The depicted embodiment can be used without the need for employing prestressed strands for creating a camber. Instead, a mold with a curved shape for the span which will eventually become the roof/ceiling span, is used.

Although it would be possible to use pre-stressed strands (alone, or combined with a curved mold) to create the roof camber, the pre-stressed strand procedure is relatively labor-intensive, and is believed to increase costs, compared to using a curved mold.

The illustration of Figs 19A and 19B is schematic, and does not depict the wall or ceiling recesses produced by mold "pans." The illustration is also exaggerated to more clearly show the roof/ceiling camber. In the illustrated embodiment, the channel is poured on its side as shown in Fig l9A. In this on-side attitude, the roof/ceiling span 1901 has a first camber 1903. When the channel is rotated 1905 to its final upright attitude (Fig 19B) the deadweight partially counters the camber 1903 to result in a somewhat smaller upward camber 1907 of the roof/ceiling span 1903. The depth of the mold pans may be adjusted to adjust of deadweight of the roof/ceiling span 1903. In one embodiment, the amount of the as-molded camber 1903 is selected such that the deadweight of the roof/ceiling span 1903 results in an upright-attitude camber 1907 of about 0.25 inches (about 6 mm).

In light of the above description, a number of advantages of the present invention can be seen. The module is preferably monolithically cast in the shape of an inverted channel, preferably using a combination of mild steel, mesh, and pre-stressed strand. Pre-stressed strand is held in tension during casting, e.g. by adjustable cantilevered angles fashioned to a form brace. The top slab pre-stressing strand is draped about six inches from the outer wall to center span. In one embodiment the strand is held in place by a jacket-supported stand-off. A number of different spans and product

widths can be cast in a single adjustable form. Outer walls can be sandwich-insulated if desired, and the composite action of the inner and outer wall widths can be encompassed into the overall design, lightening the total reinforcement requirements. In the final position the top slab pre-stressing force, coupled with the pinned leg connections, work in tandem to reduce or minimize steel reinforcing requirements. Excess concrete is removed from the underside of the roof slab via coffers or lightening pans, to minimize or reduce unnecessary dead weight. The coffered areas can be fitted with sound absorptive panels for both aesthetic and acoustical purposes. As much as half the leg width can be eliminated without compromising the structural integrity of the segment. Head room and inside height is infinitely adjustable, e.g., between one inch and 11 feet or more. Several different exposed or concealed connections can be used to fasten the segment or module into position.

A number of variations and modifications of the invention can also be used. If desired, the sidewalls or legs can extend upward beyond the level of the span or ceiling to create monolithic parapets. Units can be cast with only one leg, and the legless side supported from drappling the adjacent segments. A monolithically cast corbel on the exterior of either sidewall can support hollow core planks, slabs or steel framing members as desired. Stairwell openings can be cast parallel with the spans, and can be accommodated without compromising the structural integrity of the segment.

The segments can be stacked vertically as well as joined horizontally, for multi-story applications.

Channels can be monolithically cast with a party wall. The party wall can handle shear action, e.g., as needed for seismic requirements. Burkes can be embedded, e.g., for strapping and handling.

Although the invention has been described by way of a preferred embodiment and certain variations and modifications, other variations and modifications can also be used, the invention being defined by the following claims: