US1684387A - Building construction - Google Patents

Description

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@l /n w y" w W Vuil/IIJ l. m 4 fm 4\/\J m 4 MH -ril lll X d, r m anllllli llllllvll ATTORN EY A. L. BOBBS BUILDING CONSTRUCTION Sept. 18, 1928.

Fied Marchs, 1927 2 sheets-sheet 2 INVENTOR Y. -fo Mm ATTORNM Patented Sept. 18, 1928.4

UNITED STATES PATENT OFFICE.

ARTHUR L. BOBBS, OF CHAIPPAQUA, NEW YOBKpASSIGNOBTO N. WOOD- WARD, TRUSTEE, 0F CHAPPAQUA, NEW CASTLE, NEW YORK.

BUILDING CoNsrnUc'rIoN.

Application tiled Iarch 25, 1927. Serial No. 178,173.

This invention relates to building construction and especially to inclined overhanging structures such, for example, as theatre balconies and aims to ei'ect an economy of material without loss in strength by converting overturning moments into stresses tending to neutralize the stresses caused by downward forces.

The object of the invention is attained by a cantilever construction in which the overturning moments on a main supporting truss or girder, caused by the overhanging load, are

received by trusses so associated with the main girder that these overturning moments are converted into forces which tend to relieve the downward load on the main girder, and to neutralize the compression of the upper cord of the main girder and the tension of the lower cord thereof caused by such load.

In order that the invention may clearly be understood, I will describe in detail a specific embodiment of it in a theatre balcony, which is shown in the accompanying drawings, 1n which:

Fig. 1 isaplan view of a theatre balcony indicating in dotted lines the parts of the framework of the balcony which lie 'above the level of the lower cord of the main supporting girder; Fig. 2 is a plan view of the mezzanine door located under the rear portion of the balcony, showing in dotted lines the supporting framework of the balcony which lies on the level with the lower cord of the main girder;

Fig. 3 is a transverse section of the balcon taken on its center line; and

Fig.` 4 is a diagrammatic isometric perspective view of the supporting framework of the balcony, the outline of the balcony being indicated in dotted lines. A

The theatre balcony illustrated is of conventional form having an inclined stepped,

upper surface or door for the seats, and a horizontal mezzanine floor under the rear part of the balcony floor. The'balcony is supported on posts A, A, B, B located near the ends of the balcony so that the entire space below the balcony is left open and unobstructed.

The balcony has a structural steel framework which is carried by the posts A, A, B, B. The principal object of the invention is to make this framework as light as possible,

while giving it suilcient strength to support the balcony.

0 The steel framework includes as its'principal members, a longitudinal main truss girder 10, tapering balancing trusses 15 extending transversely from the ends of the mam truss girder, transverse tapered cantilever trusses 20, a longitudinal upper truss 30, and a longitudinal lower truss 40.

The main truss girder 10 extends len hwise of the balcony between the posts A with its ends resting thereon. This girder is of substantial height andis positioned in a vertlcal plane, that isto say, its upper cord 11 lies directly over its lower cord 12. It is provided with the usual struts 14 and diagonals 13.

The three cantilever trusses 20 project transversely from the mainlgirder between the posts, and are carried by the main girder. The height of the tapered cantilever ltrusses at their rear ends is the same as that of the main girder, so that their upper cords 21 and lower cords 22 may be secured directly to the l upper cord 11 and the lower lcord 12 of the main girder. The upper cord 21 of each cantllever truss is inclined downwardly toward the front end of the balcony, While its lower cord 22l is substantially horizontal, although it may be somewhat downwardly inclined as shown in Fi 3, or may be truly horizontal as shown in trusses have struts 23 and diagonals 24.

The overhanging weight of the cantilever j trusses and the load carried thereby causes an overturning on the main girder, which tends to cause the upper cord '11 of this girder to move forward and the lower 'cord 12 thereof to move backward. To resist the overturning atthe ends o f the main girder 10, the ends of the girder are held against forward or rearward bending by triangularstilening or balancing trusses 15, which project from the end struts 14 of the main girder iny a direction approximately perpendicular to the girder. While the stiifening trusses 15 might be extended either forwardly or rear wardly from the main girder, I find it desirable to extend them forwardly and incline them outwardly a little. This brings them in the front corner portions of the balcony,

ig. 4. The .cantilever and places their outer ends 16 so that they y downward movement and against horizontal movement. The overturning moments on the lntermediate portion of the main girder are carried at these four fixed supporting points, a, a, b, b, being transferred to these points by means of longitudinal trusses next to be described.

The forward component of the overturning on the intermediate portion of the upper cord 11 of the main girder between the supporting points a, a, is received and trans*- ferred to the points a, a, by the longitudinal truss 30, which extends between the supporting points a, a, and lies behind the girder in the plane of the upper cords 21 of the cantilever trusses 20. The truss has a rearcompress cordl. The upper cord 11 of the main girder serves as the front cord of the truss 30, while rearward extensions of the upper cords 21 of the cantilever trusses provide the mediate I girder between the supporting points b, b is struts 33 of the truss 30. The truss 30 is also provided with diagonals 34. The rear edge of the truss 30 may be supported against downward movement in a wall C (see Fig. 3), or in any other convenient manneras by appropriately positioned posts or girders.

The truss 30 is supported at its front corners at the supporting points a, a, and serves t0 resist the forward overturning on the upper cord 11 of the main girder, which is also the front cord ofthe truss 30. As, however, the forward overturning force on the `cord l1 acts horizontally while the resisting pull of the truss 30 acts at an angle to the horizontal, there are unbalanced components of the forward overturning force, one of which acts vertically upward on the main girder, thus tending to balance the downward load on this girder, and making it ossible to make the girder lighter than wou d otherwise be possible. Furthermore, the compression strain of the upper cord 11 of the main girder, causedb the'downward load on this girder, is partia ly neutralized by the tension strain placed on this same cord 11 by the loading of the truss 30 of which the cord 11 is also a part. This pa'rtial neutralizing of the compression strain on the cord 11 makes it possible to make this cord lighter than would otherwise be the case. It may be noted that the upward inclination of the truss 30 is not essential in obtaining this neutralizing of the compression strain in the cord 11.

The rearward overturning on the interpart of the lower cord 12 of the main received and transferred to the oints b, b, by the longitudinal truss 40, Whic extends between the supporting points b, b. The trussI 40 lies approximately in the plane of the lower cords 22 of the cantilever trusses 20.

ners at the supporting points b, b, and carries vthe rearward component of the overturning on the intermediate part of the lower cord 12 of the main girder. The compression strain, which the cord 12 receives as the front cord of the truss 40, partially neutralizes the tension str ain on this cord 12 caused by the downward load of the main girder of which it is the lower cord. This makes it possible to make the lower cord 12 of the main girder lighter than would otherwise be possible.

From the above description, it will be seen that the overturning moment on the intermediate portion of the main girder 10 are resisted by the trusses 30, 4() in such manner as to convert them into forces which (1) partially counterbalance the downward load on the main girder, (2) partially neutralize the compression strain in the upper cord of the main girder, and (3) partially neutralize the tension strain in the lower cord of the main girder. Any one of these three effects would make possible a reduction in the weight of the main girder; while, when, as in the embodiment of the invention which has been described, all three of these effects are combined, the weight of the main girder may be made approximately 80% .of that which would be necessary to carry the load upon it without such counterbalancing.

To the main elements of ,the framework which has been described may be added such light structural steel work as is found most convenient to support the flooring of the balcony andV mezzanine flooring under the rear portion of the balcony. As such subsidiary frameworkmay be arranged in various ways with which structural engineers are familiar. a detailed description thereof is considered unnecessary.

It should be noted that the main framework is so arranged that it does not obstruct the space below the balcony, and, in particular, that the struts and diagonals of the trusses 30, 40 are positioned so as to leave space for conveniently located stairs D from t 1e balcony to the mezzanine floor, and stairs E from the mezzanine floor to the main fioor.

Wha-t I claim is:

1. In building construction, the combination of a girder positioned with one of its cords directly above the other, supports for the ends ofv the girder, tapering balance tween the rea-r ends of the upper cords of the balance trusses and has its frontcord coincident with the upper cord of the girder, and the other of which extends between the rear ends of the lower cords of the balance trusses and has its front cord coincident with the lower-cord of the maingirder.

2. In building construction, 4the combination of a girder-having one of its cords directly above the other, means for holding each endpoint of each cord of the girder against downward and against horizontal movement tov provide four fixed supporting points, a forwardly. overhanging load carried by the girder causing overturningmoments on the girder between said supporting points, and means for resisting sai-d overturning moments comprising a longitudinal truss extending between the lupper supporting points having its front cord coincident with the upper cord of the girder and its rear cord behind the girder, and a second longitudinal truss extending between the lower supporting points having its front cord coincident with the lower cord of the girder and its rear cord behind the girder.

3. In building construction, the combination of a girder having one of its cords directly above the other, means for holding each end point of each cord of the girder against downward and against horizontal movement to provide four fixed supporting points, a forwardly overhanging load carried y the girder causing overturning moments on the girder between said supporting points,

and means for resisting said overturning moments comprising a longitudinal truss extending between the upper supporting points, having its front cord coincidentwith the upper cord of the girder and its rear cord to the rear of and. above the upper cord ofthe girder, and a second longitudinal truss'extending between the lower supporting-points,

having itsfront cord coincident with the lower cord of the girder and its rear cord to the `rear of and on a level with the lower cord of p the girder.

upper and lower cords in a common vertical plane, tapering trusses extending transversely from the ends of the main girder and held at their outer ends, a. plurality of tapering cantilever trusses projecting forwardly from the main girder between the supports and having the rear ends of their upper and lower cords secured to the upper and lower cords ol the mainl girder, an upper longitudinal truss extending between the ends of the upper cord of the girder with its front cord coincident with the upper cord of the main girder and lying in the plane of the upper cords of the cantilever trusses, and a lower longitudinal truss extending between the ends of the lower cord of the girder with its front cord coincident withv the lower cord of. the main girder and lying substantially in the plane of the lower cords of the cantilever trusses.

a main girder extending A 5. A framework for a theatre balcony, comprising two posts,

between `the posts with its ends supported thereon and having its upper and lower cords in a common vertical plane, tapering balance trusses extending forward from the ends of the m-ain girder and having the rear ends of their upper and lower cords secured to the ends of the upper and lower cords of the main girder, supports for the louter ends of said balance trusses, a plurality of ta ering cantilever trusses projecting forward y from the main girder and having their upper yand .lower cords secured to the upper and lower cords of the main girder, a longitudinal truss extending between the rear ends of the upper cords of the balance trusses, lying in the plan@v of the upper cords of the cantilever trusses with its struts formed by rearward extensions of said upper cords, its 'rear cord connectingthe rear end of such strutsvandits front cord coincident with the -upper cord of the main girder, and a longitudinal truss extending between the rear ends of the lower cords of the balance trusses, lying substantially/ in the plane-of the lower cords of the cantilever trusses with its struts formed by 4rearward extensions of said lower cords, its

rear cord connecting the rear end of such struts and its front cord coincident with the lower cord of the main girder.

6. In a theatre balcony having an inclined balcony i'loor and ,a horizontal mezzanine floor below the rea-r portion of the balcony floor, a supporting framework comprising two posts, a main longitudinal girder extending between said posts with its ends supported thereon, a plurality of tapering cantilever trusses projecting forwardly from the main 'rder with their upper cords substantially 125 Y 1n the plane of the balcony'ioor and their lower cords substantially in the plane of the mezzanine door, a longitudinal truss lying substantially in the plane of the balcony'oor with its front oo rd coincident with'theupper i lcord of the mam girder and its struts and diagonals ositioned to leave free spaces for stairways rom the baloony floor to the mezzanine floor, a longitudinal truss lying substantially in the plane of the l-rnezzaninefloor 5 and havin@r its front cord coincident with the lower vcor of the main girder and its struts and diagonals positioned to provide free spaces for sta-irways extending downward from the mezzanine oor,tapering trusses extendi forwardly from the ends of the 10 main girv er so that their outer ends are near the front corners of the balcony, and means for supporting the outer ends of said trusses.

In testimony whereof I have hereunto set my hand.

ARTHUR L. BOBBS.

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