Building Structure For Floors And Roofs

Abstract

A building structure made of light weight plate material for easy prefabrication and on-site assembly to form floors and roofs. In one embodiment the structure forms a truss-like beam comprised of primary and secondary truss assemblies. Optimum load transfer results from nesting of these assemblies. The primary truss assembly includes diagonal web elements which are secured to a bottom chord. The secondary truss assembly includes elements nested within and engaged upon the primary web elements and secured together by bottom chords. In addition a top chord is secured to both web primary and secondary elements. In another embodiment the building structure forms a floor structure. The secondary truss assembly essentially becomes the floor and a plurality of the primary truss assemblies are spaced apart to provide the beams. The web of the floor is defined by a folded floor plate covered by a top chord in the form of a continuous deck plate and overlying concrete slab. The nested primary and secondary truss assemblies interact to share the load and thereby reduce the structural material needed.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The present invention relates to a building structure for floors and roofs, and more particularly to a building structure formed of internested truss assemblies.

2. Description of the Prior Art:

In conventional high rise or multi-story building construction, steel is the basic structural material and many steps are involved in the design and assembly of the steel components. The structural engineer must make his calculations and drawings, and the steel fabricator thereafter must make fabrication or shop drawings showing the location and dimensions of each column, main girder, and secondary beam, including bolt holes, sizes and locations; cutting, trimming, and welding indications for beam end connections, and other details too numerous to mention. These procedures must be followed for each separate job and are time consuming and expensive. There is considerable duplication of effort by the structural engineer and fabricator as they check and re-check each others work. Moreover, the larger the job the greater the confusion and possibility of human error.

Once the steel fabricator has finished his drawings and fabricated the various components, these are delivered to the job site. The columns are first erected, the main girders welded or bolted to the columns, the secondary beams or purlins next welded to the girders, and finally a steel deck is welded to both the girders and the beams and a concrete slab poured onto the deck. As the height of the building increases, all of these operations become even more timing consuming and costly.

Once the main structural components are in place there is still the problem of installing air conditioning ducts and electric waste conduits and the like.

These various operations usually involve several different trade unions and each must set up for its type of work, do the work, and then clean up the accumulation of debris. This involves considerable duplication and waste of effort. Most of these problems could be completely avoided if the building structure were such that it could be largely prefabricated in the shop and transported to the job site for easy assembly by relatively unskilled workmen.

In addition to the difficulties arising because almost all of the conventional construction is done at the job site, the building structure itself is too heavy, ponderous and expensive for the loads it must carry. In conventional building structures the load is transmitted by the deck or floor to the beams. From the beams the loads pass to the girders and then to the columns. The average weight of steel required ranges between 15 and 20 pounds per square foot, which is quite high and an important reason for high building costs.

SUMMARY OF THE INVENTION

According to the present invention, a building structure is provided which comprises primary and secondary truss assemblies having certain components which are internested to reinforce one another and thereby achieve more efficient load bearing characteristics.

The primary truss assembly includes a bottom chord, and a primary web having a succession of web elements which are alternately and oppositely diagonally oriented to define a plurality of upper apexes, and a plurality of lower apexes which are secured to the bottom chord.

The secondary truss assembly includes a secondary web having a plurality of web elements nested within and engaged upon the legs of the primary web. A top chord of the secondary truss assembly is secured to the secondary web elements and to the upper apexes of the primary web. A plurality of bottom chords are each secured to and extend between the lower extremities of a pair of the secondary web elements which are engaged to the primary web elements.

The foregoing building structure can be utilized not only as a truss, but is particularly adapted for use as a floor or roof construction in which the primary truss assembly serves as the equivalent of a truss, and the secondary assembly serves as the equivalent of the floor. Thus the web of the secondary truss assembly is made of a folded plate floor, and an overlying steel deck and concrete slab constitute the top chord for this plate. A plurality of bottom chords are also provided for this plate and they nest within the web elements of a corresponding plurality of primary truss assemblies which serve as spaced apart trusses for supporting the folded plate floor, steel deck and concrete slab. These trusses are used rather than the usual girders of conventional construction.

The important characteristic of this embodiment of the invention is the nested relation of the folded floor with the open upper portion of the truss-like beams comprising the secondary truss assemblies. This nested relation provides optimum load transfer, the concrete slab and steel deck providing compression strength in one direction for the floor and in a transverse direction for the beams. Thus, the slab strength is common to or shared by both the floor and the beams. When this latter embodiment of the building structure is described herein, the term "floor" is often used interchangably with the expression "secondary truss assembly", while "beam" is often used interchangably with the phrase "primary truss assembly".

The use of the present building structure as a continuous floor or roof enables the average weight of the steel structure to be reduced from the conventional 15 to 20 pounds per square foot to approximately 7 pounds per square foot, which includes the weight of the columns.

The size and configuration of the components of the primary and secondary truss assemblies can be precalculated and predesigned to suit all possible spans for shop fabrication. This eliminates any need for special, lengthy calculations and detailings, and special shop drawings for each job. The properties of the truss assemblies are standardizable for presentation in tables setting forth, in the case of the beam assemblies, the allowable span, allowable load per lineal foot, allowable end shear, and deflection characteristics. Comparable specifications would be set forth in similar tables for the floor assembly parts.

The web configuration of the secondary truss assembly or floor provides elongated generally triangular sections which are adapted for use as air conditioning ducts or as conduits for mechanical or electrical lines. This eliminates any need for the separate air conditioning ducts of conventional construction.

The components of the present building structure are prefabricated, transported to the job site, and assembled. Preferably the structure is assembled at ground level so that the pouring of the concrete floor slab and fireproofing of the bottom face of the floor can be done most efficiently. The completed assembly is then lifted to the proper floor level for connection to the already erected columns.

Other objects and features of the invention will become apparent from consideration of the following description taken in connection with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a building structure according to the present invention, the building structure in this case being a continuous floor structure supported by four columns;

FIG. 2 is an exploded, perspective view of the components comprising the floor structure of FIG. 1, the concrete slab being omitted for clarity;

FIG. 3 is an enlarged elevational view of the corner portion of the structure of FIG. 1, showing the attachment to the column;

FIG. 4 is an enlarged elevational view of the web and bottom chord of the floor or secondary truss assembly of FIG 3;

FIG. 5 is an enlarged view taken along line 5--5 of FIG. 1;

FIG. 6 is a view taken along line 6--6 of FIG. 5;

FIG. 7 is an enlarged detail view of the saddle connection between the beam web and bottom chord; and

FIG. 8 is a simplified view showing of a different form of folded plate floor.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, and particularly to FIGS. 1 through 7, there is illustrated a building structure 10 comprising, generally, a plurality of longitudinally spaced apart primary truss assemblies or beams 12 located beneath and extending transversely of a secondary truss assembly or floor 14.

As will be seen, portions of the beams 12 and floor 14 internest to provide important advantages, including mutual improvement of their load bearing functions. These same advantages also apply where a single beam 12 is used in combination with a section of floor 14 of approximately the same width. Such a structure is useful in many situations as a truss of light weight and capable of being prefabricated. However, the description herein is primarily concerned with a plurality of beams 12, two such beams being shown by way of example, with the floor 14 spanning the space between the beams.

Almost all of the components of the beams 12 and floor 14 are preferably made of relatively light gage sheet steel so that they can be prefabricated in a shop and transported to the job site for assembly and hoisting into position.

In constructing a typical building, a plurality of columns 16 are first located in position to provide a structure to which the floor structures can be attached. Four such columns 16 of I-beam configuration are illustrated in FIG. 1. The primary truss assemblies or beams 12, which are each to be attached to the columns 16 each includes a bottom chord 18 made of a relatively narrow band or strip of 16 gage sheet steel. The opposite extemities of each bottom chord 18 are diagonally oriented and terminate in mounting tabs or flanges 20. These are secured at the job site to the adjacent columns 16 by shear connectors such as nut and bolt assemblies 22, as best seen in FIG. 3. This type of connection greatly facilitates calculation and location of the loading upon the columns 16.

Each beam 12 also includes a web connected to the bottom chord 18 and of the same width. The web, comprising a succession of connected V-shaped sections, is formed of successive diagonal legs or web elements 24 whose alternate opposite orientation provides a plurality of upper apexes 26 which are flattened. The lower apexes 28 between the upper apexes 26 are made generally arcuate in configuration, as best seen in FIGS. 3 and 7.

The web is preferably made of a continuous length of 16 gage sheet metal suitably stiffened against bending, as by the provision of edge margins or flanges 30. Other suitable stiffening means may be used if desired, such as integral ribs (not shown).

The bottom chord 18 and the acruate lower apexes 28 are of approximately the same width, typically 12 inches, and are arranged in adjacent relation for connection by a plurality of nut and bolt connectors 32. To eliminate bending stresses in the web elements 24 and more evenly distribute the load between the web elements 24 and the bottom chord 18, a plurality of anchorages or saddles 34 are shop welded to the upper surface of the bottom chord 18 at regular intervals such that they will complementally mate with the arcuate lower apexes 28 of the web elements 24.

Each saddle 34 is of the same width as the bottom chord 18 and includes a pair of legs whose lower extremities are welded to the bottom chord 18, the span between the legs being of generally arcuate, and preferably parabolic configuration. The connectors 32 pass through the lower apexes 28, the saddles 34, and the bottom chord 18 to provide a plurality of pinned connections.

The assembly of the prefabricated beams 12 is preferably accomplished in the shop rather than at the job site. However, the prefabricated secondary truss assembly or floor 14 is preferably assembled at the job site because of its size, as will be seen.

More particularly, the floor 14 comprises a folded plate made of sections of 16 gage continuous sheet steel extending longitudinally and spanning the space between adjacent beams 12, as best seen in FIG. 2. The folded plate constitutes a web having a succession of web elements 36 alternately, oppositely, diagonally oriented to define a plurality of flattened upper apexes 38 and a plurality of rounded or arcuate lower apexes 40, each pair of apexes 40 being joined together by a bottom chord 42 made of 16 gage sheet steel of a width approximately the same as that of the components of each beam 12.

The end extremity of each section of the folded plate is arranged to overlap the end extremity of the next section for interconnection, as will be seen. These end extremities would be apexes if the folded plate were continuous, rather than made in sections. Consequently, these end extremities are identified by the numerals 38, as seen particularly in FIG. 4. The opposite extremities of the bottom chord 42 are upwardly turned and welded to the web elements 36, as best illustrated in FIG. 4.

Each section of folded plate forming the web 36 is nested within the open upper portion of the space between a pair of the web elements 24 of the beams 12. The end extremities 38 o the adjacent folded plate sections are overlapped on top of the apexes 26 of the beams 12, as best illustrated in FIG. 5.

A continuous deck 44, preferably made of 22 gage sheet steel in three sections, FIG. 2, overlies and is secured, as by spot welding or the like, to the plurality of sections of folded plates forming the web elements 36. The deck 44 includes a plurality of transversely extending corrugations 46, as seen in FIG. 1, which improve its bending strength. The deck is secured on the job site to the overlapped apexes 38 of the folded plate, and to the apexes 38 of the adjacent beams 12 by a plurality of headed shear connectors 47.

The shank of each connector 47 includes an integral circular flange 48 which bears against the upper surface of the deck 44 so that a nut 49 forming a part of the connector 47 can be tightened to urge together the overlapped apexes 38 of the adjacent folded plate sections, and the apex 26 of the associated beam 12. The central apexes 38 of the web elements 36 are also bolted to the deck 44 by connectors 50, as seen in FIG. 3.

After the sheet metal components of the floor 14 are secured to the complemental components of the beams 12, a light weight concrete is poured onto the deck 44 to form a slab 52 about 3 inches in thickness. The underside of the structure is also appropriately fire-proofed with suitable coatings (not shown), as is well known to those skilled in the art.

The concrete slab 52 is utilized as the top chord of the composite floor structure, the bottom chords 42 placing the slab 52 in compression under usual floor loads. The slab 52 provides composite strength, in one direction for the web elements 36 of the floor 14, and in directions normal to that direction for the various beams 12.

The web elements 36 rest against the web elements and 24, a W-shaped section of the element 36 being located between each pair of elements 24, the outer portions of said W-shaped section engaging element 24, strengthening one another against bending under loads transferred from the slab 52. The slab itself is strengthened against bending between the beams 12 by the continuous span provided by the web elements 36 of the folded floor sections.

If a multi-story building is being constructed, the uppermost floor 14 is connected to the beams 12 at ground level, hoisted into position, and secured to the columns 16. The next floor is then assembled and hoisted, and the process continued until all floors are in position.

The use of specific material sizes and thicknesses, particular types of connectors, and particular forms of web elements are not critical to the present invention and may be altered to suit the particular application. Moreover, a compression structure other than the slab 52 could be used if desired. Welds may be used instead of connectors. The web elements could be made in structural sandwich form for improved moment of inertia characteristics. Also, the particular form of folded plate described is not critical. In this regard, reference is made to FIG. 8 wherein a plurality of folded plate sections of different configuration are illustrated. In this embodiment the plate sections are reversely formed to define a pair of deep channels joined together at their upper extremities by a flat intermediate portion 56. Each section terminates in a pair of flattened extremities or flanges 58 which are overlapped with the adjacent plate section and secured to the beam web elements 24 by a plurality of shear connectors 46a in a manner substantially identical to that described in connection with the connectors 46 of the first embodiment.

The flat bottom portions of the adjacent pair of channels 54 are secured together by a bottom chord 42a. This bottom chord is welded in position just as was the bottom chord 42 in the first embodiment described.

The outer legs or web elements of the channels 54 and the outer extremities of the associated bottom chord 42a rest against the adjacent web elements 24, strengthening them against bending and, in turn, being strengthened against bending.

From the foregoing it will be seen that the present building structures essentially comprises a folded plate floor having an overlying steel deck and concrete slab, with truss-like beams being substituted for the usual girders to support the floor, deck, and slab. The nested relation of the folded floor with the open upper portion of the beams provides improved efficiency of load transfer which in turn allows reduction of the weight of material needed to bear the design loads.

The configuration and assembly of the various components of the present structure enables loads and stress calculations to be made easily and quickly, greatly simplifying the task of the structural engineer.

Use of sheet material for most of the structural components permits shop prefabrication, with only relatively simple assembly operations being necessary at the job site to complete the structure.

The present structure enables use of a relatively low floor-to-ceiling depth because the spaces defined by the deck 44 and web elements 36 can be utilized as conduits for air conditioning, waste, electrical equipment and the like. No extra depth is thus needed to support and conceal such equipment. In this regard, FIG. 3 illustrates how a deep web section can be formed by making the web elements of the floor longer. More specifically, web elements 36a are shown extending down in coextensive relation with the end web element 24 of each beam 12. The relatively large space 56 formed can be utilized as an air conditioning duct, ane other similar web sections can be used for return ducts, as will be apparent.

Various modifications and changes may be made with regard to the foregoing detailed description without departing from the spirit of the present invention.

Claims

I claim:

1. In a building having a plurality of pairs of columns, in which the columns of each pair are arranged in opposed relation, a building structure defining a floor and comprising:

a plurality of elongated truss assemblies arranged in parallel, spaced apart relation, each truss assembly being attached at its opposite extremities to a pair of said opposed columns, each of said truss assemblies including a longitudinally extending bottom chord and web means formed as a succession of connected V-shaped sections, the apices of the V-shaped sections being attached to said bottom chord; and

a floor assembly arranged in overlying spanning relation to said plurality of truss assemblies and including a deck plate coextensive with said floor assembly, and further including a folded plate floor attached to said deck plate, said folded plate floor being characterized by corrugations extending transversely of said truss assemblies, the lower extremities of a plurality of said corrugations depending into each of the upwardly opening V-shaped sections, the outer portions of the outer ones of said corrugations being in engaged relation with the legs of said V-shaped sections, the upper extremities of said legs being attached to said folded plate floor and to said deck plate whereby loads upon said interconnected floor assembly and truss assemblies are transferred directly to said columns.

2. A building structure according to claim 1 and including a slab of concrete connected to said deck plate in overlying, coextensive relation.

3. A building structure according to claim 1 and including a bottom chord connecting those of said corrugations within each of said V-shaped sections.

4. A building structure according to claim 1 wherein said corrugations located within each of said V-shaped sections are defined by a W-shaped section the outer legs of which rest against and have the same slope as the adjacent legs of said V-shaped sections.