The present invention relates to composite structure construction, and more particularly to a composite slab and joist assembly.
The prior art is replete with examples of composite structure constructions employing composite slab and joist assemblies. In many of these examples, the slabs of concrete are positioned on the joists, and, during construction, to support the newly-poured unset concrete that will become parts of the slabs, forms for the concrete are mounted between adjacent joists of the assemblies.
Butts et al. (U.S. Pat. No. 3,845,594) discloses an example of a composite slab and joist assembly in which the forms for the unset concrete are made of plywood. After the concrete hardens, the plywood is removed and reused.
Other methods of forming composite slab and joist assemblies employ metal deck panels for concrete forms in place of wood, and the deck panels remain as parts of the assemblies. When metal deck panels are used, labor for removing wooden forms is unnecessary, and, by not using wood to construct the composite slab and joist assemblies, the number of trades required for the construction is fewer. Thus, constructing the assemblies using metal deck panels eliminates some of the labor costs.
Person et al. (U.S. Pat. No. 4,700,519) discloses an example of a composite slab and joist assembly employing metal deck panels. With reference to the perspective view of
In the example of
As shown also in the
To form assembly 100, a plurality of joists 108 are spaced apart on supporting members, such as building girders, beams, or walls, and deck panels 200, typically formed of rolled corrugated steel, are positioned therebetween. As shown in
Reinforcing mesh 112 is placed on deck panels 200. As shown also with reference to
As is apparent in
Referring in particular to
Dutil (U.S. Pat. No. 5,544,464) discloses a configuration that overcomes this problem. As shown in
For joist 208 to support an edge 232 of a deck panel 236 on the opposite side from structural element 216, a structural angle 240 is added so that structural element 216 aid structural angle 240 enclose the top of web 224 therebetween. However, for welding structural angle 240 to web 224, access is limited due to the positioning of structural element 216. Consequently, it is difficult to weld structural angle 240 sufficiently to develop its working capacity beyond supporting a deck panel 236. Also, additional reinforcement of top chord 212 may be necessary to reinforce joist 208 during the non-composite stage (before the concrete sets), thus requiring more material and additional formation steps. For example, the top chord may be reinforced by welding steel to the “S”-shaped section.
Accordingly, to the best knowledge of the present inventors, there is an unmet need for an economical composite slab and joist assembly in which the joist top chords have segments which extend vertically into the concrete slab and simultaneously have segments that extend vertically, whether upwardly or downwardly, offering expanded surface area for joining to joist webs in such a configuration with sufficient access for attachment of the webs to the corresponding top chords to thereby develop greater working capacity, that is, greater ability to support loads over the life of the structure.
A general objective of the present invention is to provide a composite slab and joist assembly that overcomes the aforementioned problems of the prior art. The composite slab and joist assembly of the present invention is suitable, not only for floors, but also for roofs and ceiling structures.
The present invention may be embodied as a joist formed as combination of a bottom chord, a top chord, and a web affixed therebetween. The top chord is formed from a first elongated structural angle and a second elongated structural angle. The first structural angle is oriented so that, in cross-section, it has a horizontally-extending leg ad an upwardly-extending leg meeting at a corner. The second structural angle is oriented so that, in cross section, it has a horizontally-extending leg and a downwardly-extending leg meeting at a corner. The joist elements are assembled such that an upper portion of the web is joined to the top chord second structural angle against the downwardly-extending leg, and the first structural angle is joined to the second structural angle. The structural angles of the top chord may be joined together in any of top-to-bottom, back-to-back, and corner-to-corner relationships.
The present invention has additional aspects. For example, the joist first structural angle may have, at a top portion of the upwardly-extending leg, a bend in cross-section.
Also, at a longitudinal end of the top chord, the joist may have a shoe. The shoe may have a T-shaped cross-section, wherein the top chord second structural angle, at the longitudinal end, is coped to allow the shoe to be attached to the first and second structural angles to be flush with a longitudinal end of the first structural angle.
Additionally, the joist may have, in its upwardly-extending leg of the top chord first structural angle, a series of transverse protrusions and indentations such that a protrusion on one side of the upwardly-extending leg has a corresponding indentation located transversely on the opposite side of the upwardly-extending leg, with the protrusion and corresponding indentation each located at the same longitudinal position along the length of the top chord. On each side of the upwardly-extending leg of the first structural angle, the protrusions may be positioned longitudinally adjacent the indentations, and the indentations may be positioned longitudinally adjacent the protrusions.
As another aspect of the present invention, the joist may have a top chord that has at least one splice in one of its structural angles. Additionally, both structural angles of the top chord may have splices that are longitudinally offset from each other along the length of the top chord.
The joist of the present invention may be formed with a web that has a series of adjacent compression and tension members. The web may further be formed with two series of adjacent compression and tension members having a gap therebetween.
The present invention may also be embodied as a composite slab and joist assembly that is formed as combination of a joist, at least one deck panel, slab reinforcement, and a slab of concrete. The joist may be formed as described above. The deck panel is positioned on one of the horizontally-extending legs of the top chord of the joist. The slab reinforcement, which may be a mesh, is positioned above the joist and the deck panel. The slab of concrete is formed on the deck panel and the top of the joist such that the slab encloses the slab reinforcement and a top portion of the joist.
The present invention may further be embodied as a method of manufacturing a joist. The method would include: orienting first and second elongated structural angles so that, in cross-section, the first structural angle has a horizontally-extending leg and an upwardly-extending leg meeting at a corner, and the second structural angle has a horizontally-extending leg and a downwardly-extending leg meeting at a corner; joining the first structural angle to the second structural angle to form a top chord; joining an upper portion of a web to the second structural angle against the downwardly-extending leg; and joining a bottom chord to a bottom portion of the web.
The method of the present invention has additional aspects. For example, the method may include: adding a series of transverse protrusions and indentations to the upwardly-extending leg of the first structural angle. A protrusion on one side of the upwardly-extending leg may have a correspondingly indentation located transversely on the opposite side of the upwardly-extending leg, and the protrusion and corresponding indentation may each be located at the same longitudinal position along the length of the top chord. Further, on each side of the upwardly-extending leg of the first structural angle, the protrusions may be added longitudinally adjacent the indentations, and the indentations may be added longitudinally adjacent the protrusions. The transverse protrusions and indentations may be added by stamping the first structural angle.
Alternatively, the protrusions and indentations may be added by inserting the first structural angle between a pair of counter: rotating dies, each having at least one protrusion and at least one indentation. The dies would be set so that a protrusion from one die and an indentation from the other die simultaneously deform the first structural angle there between to add a protrusion and a corresponding indentation.
The present invention may also be embodied as a method of manufacturing a composite slab and joist assembly. The method would include: manufacturing a joist; positioning at least one deck panel on a horizontally-extending leg of a top chord of the joist; positioning slab reinforcement above the joist and the deck panel; and forming a slab of concrete on the deck panel and on the top of the joist to enclose the slab reinforcement and the joist. The joist may be formed as described above.
The present invention is an improvement over prior art steel and concrete structures that have at least one pair of spaced-apart parallel joists, each of which includes at least a top chord, and where a wooden form is mounted between the respective top chords of the pair of joists for subsequently pouring a concrete slab therebetween, the wooden form subsequently being removed once the concrete has cured. In this improvement, the top chord of each joist has two complementary structural angles including first and second structural angles secured to each other. The first structural angle has an upwardly-extending leg and a horizontally-extending leg forming a first corner therebetween. The second structural angle has a downwardly-extending leg and a horizontally-extending leg forming a second corner therebetween. The horizontally-extending leg of the second structural angle extends in a direction oppositely of the horizontally-extending leg of the first structural angle. The first and second angle members are disposed such that their respective corners substantially engage or confront one another, thereby forming in cross-section a substantially “plus” symbol. A panel is permanently mounted horizontally between the pair of joists, thereby providing a concrete form, and concrete poured over the panel to form a slab. Thus, the present invention eliminates the necessity of constructing, and subsequently removing, a wooden form between the pair of joists.
The above-described improvement has additional aspects. For example, the panel may be a metal corrugated panel. Also, the upwardly-extending legs of the first structural angles may have alternately-disposed protrusions and indentations, which improve the bonding of the joists to the concrete slab. Additionally, each joist may include a bottom chord connected to the top chord by a web. Further, the web may include compression and tension members, each of which has an upper end and a lower end, the respective upper ends being connected to the downwardly-extending leg of the second structural angle, which provides improved structural integrity. The structure may include girders, beams, or walls on which the joists are supported, and wherein a reinforcing shoe is disposed at the respective ends of the joists and contact the girders, beams, or walls of the structure. Also, the bottom chord may include a pair of complementary structural angles having respective upwardly-extending spaced-apart legs for securing therebetween the lower ends of the respective compression and tension members of the web.
As an additional aspect, the present invention is an improvement over prior art building structures that have at least a first joist which includes a top chord, a bottom chord, and a web therebetween that includes compression and tension members, each of which has respective upper and lower ends. In this improvement, the top chord includes at least one structural angle having a horizontally-extending leg and a downwardly-extending leg, and the respective upper ends of the tension and compression members of the are secured to the downwardly-extending leg of the structural angle.
This improvement has additional aspects. For example, the building structure may include an additional structural angle having an upwardly-extending leg and a horizontally-extending leg disposed oppositely to the horizontally-extending leg of the other structural angle. In this configuration, both structural angles members are connected thereto to form, in cross-section, a substantially “plus” configuration. Also, a second joist may be included that is parallel to and spaced apart from the first joist with a corrugated metal panel secured between the respective top chords and with a concrete slab is poured over the corrugated metal panel and between the respective top chords of the first and second joists. Further, the respective upwardly-extending legs of the additional structural angles of the top chords may have respective alternating protrusions and indentations, which improve the bonding of the joists to the concrete slab.
The present invention is described in detail below with reference to the accompanying drawings, which are summarized as follows:
The invention summarized above and defined by the claims below may be better understood by referring to the present detailed description, which should be read with reference to the accompanying drawings. This detailed description presents preferred embodiments of the present invention. This description is not intended to limit the scope of the claims but instead to provide examples of the invention.
Described first are preferred embodiments of joists configured in accordance with the present invention. Also described are implementations for manufacturing the joists. Then described is a preferred embodiment of a composite slab and joist assembly in accordance with the invention.
As illustrated in
With additional reference to the cross-section of
Top chord structural angles 272,276 are oriented so that each has in cross-section a horizontally-extending leg 304,308. First structural angle 272 has also has an upwardly-extending leg 312, which meets horizontally-extending leg 304 at a corner 316. Second structural angle 276 has a downwardly-extending leg 320, which meets horizontally-extending leg 308 at a corner 324. An upper portion of web 256 is joined to second structural angle 276 against downwardly-extending leg 320, and first structural angle 272 is joined to second structural angle 276.
As shown perhaps most clearly in the cross-sectional view of
Structural angles 272 and 276 need not be joined in a top-to-bottom relationship to remain within the scope of the present invention. Other embodiments of the present invention implement “back-to-back” and “corner-to-corner” relationships, which are described as follows with reference to
In the alternate embodiment represented in
In the alternate embodiment represented in
As shown above with reference to
An alternate embodiment joist top chord is illustrated in
The joist of the present invention may also include a shoe attached to a longitudinal end of its top chord to provide a bearing seat for the joist.
In a preferred embodiment, shoe 348 may be formed from a “bisected” hot-rolled I-beam, having a T-shaped cross-section. As shown in
By attaching shoe 348 to the end or top chord 252 as described, joist 244 can better accommodate high end reactions and shear at positions near the supporting members (for example, girders, beams, or walls) on which joist 244 rests. By connecting shoe 348 to both web 256 and top chord 252, shear loads are more easily transferred to the supporting members.
Another aspect of the present invention relates to the configuration of first structural angle 272 of top chord 252. With reference to
A protrusion 252 on one side of upwardly-extending leg 312 has a corresponding indentation 256 located transversely on the opposite side. As shown in the drawings, each protrusion 252 and corresponding indentation 356 are located at the same longitudinal position along the length of top chord 252. In one preferred embodiment, protrusions 352 and indentations 356 alternate along the length of top chord 252 such that, on a particular side of upwardly-extending leg 312, protrusions 352 are longitudinally adjacent indentations 356, and indentations 356 are longitudinally adjacent protrusions 352. Protrusions 352 and indentations 356 may be added to first structural angle 272 by stamping upwardly-extending leg 312 accordingly.
Alternatively, protrusions 252 and indentations 256 may be added by inserting first structural angle 272 between a pair of counter-rotating dies 360 as illustrated in the top view of
Another aspect of the present invention relates to the suitability of the structural angles of the top chord for splicing. To increase top chord length, structural angles may bc connected end-to-end, for example, by welding, and the process may be automated.
Reference is made to the top view of
An exemplary implementation for spliced top chords may occur if 40-foot structural angles were commercially available to form 25-foot joists. To form the joists, 40-foot structural angles would be cut into 25-foot structural angles and 15-foot structural angles. The 25-foot structural angles would be ready for forming chords. The 15-foot structural angles would be spliced to form 30-foot structural angles and then cut into 25-foot structural angles and 5-foot structural angles. The spliced 25-foot structural angles would be arranged so that the splices would be longitudinally, offset and then joined to form a top chord. Of course, spliced 25 foot structural angles can be joined to unspliced 25 foot structural angles to form the top chord.
An alternative embodiment of the joist of the present invention may comprise a web that has gap separating two series of adjacent compression and tension members. The gap provides a larger area for which to insert items such as ventilation ducts or piping. As shown in the side view of
Another preferred embodiment of the present invention is a composite slab and joist assembly 432, as illustrated in perspective in
Deck panels 440 are positioned between adjacent joists 436 to rest on the horizontally-extending legs of the structural angles of the top chords. Deck panel 440 may be corrugated composite metal form deck panels and may have dimples for engaging concrete. Deck panels 440 are secured to the top chords, for example, by screws, powder actuated fasteners, or welds. By structurally fastening deck panels 440 to the horizontally-extending legs of the structural angles, deck panels 440 add to the interface shear connection between the joists 436 and a concrete slab (discussed below).
Slab reinforcement 444 is positioned above joists 436 and deck panels 440. Slab reinforcement 444 may be a mesh, which is sometimes referred to as “welded wire fabric” or “WWF.” Sometime, a set of bars is used as reinforcement. In this embodiment, slab reinforcement 444 initially contacts both joists 436 and deck panels 440. A slab of concrete 448 is formed on deck panels 440 and on top of joists 436. Before the concrete sets, deck panels 440 may be vibrated in a fashion known to those skilled in the art so that wet concrete will penetrates below slab reinforcement 444. Slab 448 encloses slab reinforcement 444 and a top portion of joists 436.
In this embodiment, joists 436 have protrusions and indentations in the upwardly-extending legs of one of the structural angles of the top chord. These protrusions and indentations engage the concrete of slab 448 and act as sheer connectors to transfer compression forces from the top chord to concrete slab 448. Also, the upwardly-extending legs act as high-chairs to raise slab reinforcement 444 to a position higher than that at a location between adjacent joists 436. Thus, the upwardly-extending legs effect negative slab reinforcement.
Additionally, in this embodiment, deck panels 440 compliment the strength of slab 448. Therefore, slab 448 need not made as thick to provide adequate strength for the given building need.
Having thus described example embodiments of the invention, it will be apparent that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements, though not expressly described above, are nonetheless intended and implied to be within the spirit and scope of the invention. Accordingly, the foregoing discussion is intended to be illustrative only; the invention is limited and defined only by the following claims and equivalents thereto.
This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 60/400,205, filed Jul. 31, 2002, which is hereby incorporated by reference in its entirety.
Number | Name | Date | Kind |
---|---|---|---|
1863817 | Wells | Jun 1932 | A |
2061103 | Roberts | Nov 1936 | A |
2860743 | Cliff | Nov 1958 | A |
3527007 | McManus | Sep 1970 | A |
3686819 | Atkinson | Aug 1972 | A |
3845594 | Butts et al. | Nov 1974 | A |
4106256 | Cody | Aug 1978 | A |
4700519 | Person et al. | Oct 1987 | A |
4937998 | Goldberg | Jul 1990 | A |
5544464 | Dutil | Aug 1996 | A |
Number | Date | Country | |
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60400205 | Jul 2002 | US |