US1774827A - Trussed structure - Google Patents

Description

Sept. 2, 1930. sz 1,774,827

TRUS SED STRUCTURE Filed Dec. 12, 1925 3 Sheets-Sheet 1 I gwom'toz H. F FREASE TRUS SED S 'IRUC TURE Sept. 2, 1-930.

Se t. 2, 1930.

H. F. FREASE TRUSSED STRUCTURE Filed Dec. 12, 1925 s SheetS- -Sheet a flit/"mm Gamm I Patented Septr'Z; 1930 I by the distance between the truss chord and Webfmembers, and by H mish. FIELD raEAsE; or ciuvroiv, orno I TRUSSEI) sriwc'runn I "Application. f iledbeeember 12, 1925. series No..-74,988.

a .The invention relates to trussed'structures,

.having spaced chord-members and connectmg Web members oined together 5. and: more particularly to trussed structures for use as r pendulously supported floor joists.

Trussed floor joists are usually supported at their end, and it -is; desirable that these ends have centers of gravity adapted for stable equilibrium and beof such construe tion as to resist not onlyv shear loads, but

also any bending loads Which any accidental or purposeful fixing" of the joistends may that Which Would cause failure bythe primary direct stresses set up-by frame structure or truss actlon 1n, the oist.

Such a secondaryfailure may "beindi cated by buckling of the upper compression chord members of a trussed floor joistf under usual conditions of loading.

Buckling may, of course, be the result of the primary direct, compression stresses set up in the upperchord members bythetruss actionof the joist When loa ded. v

Such buckling mayalso be indu'cedbythe 11 secondary bending stresses P set upin the upper chord members of a trussed oist, since the upper chord members i under A ordinary loading conditions are themselvescontinuo'us beams, ora series of short b'eamssupported at the junctions of'thechord' and bers ofthe joist.

secondary stresses is, of course, determined j unctions of the nature of the loading; 1

' Ordinary floor JO1StS are sually designed for loads uniformly distributed over the span, in which case the maximum bending stresses are set up in the'central portions of the truss chord members. 7 1

Other types of' loading may setup maximum stresses elsewhere in the chord mem- 50 bers Whose :location and magnitude lmay-Lbe" "adapted for stable equilibrium.

determined-by themethods'of the'science of l I structures. c r Y .flnxcases Where it, is possible to predicttvhere the maximum bending'stresses Will be set u itis desirableto reinforce thetr uss mem ers subject to these maximumstresses. On the other hand," where it is desired to attain a trussed structure having -:a minimum Weight for a glven type of loadmg,

maximum stress reinforcing shouldbe eliminated from; truss members not subject to maximum stresses. j

v The objects of the presentinvention are to provide a trussed structure more particularly for use as a pendulously supported, floor joist and'wh'ich shall have ends adapted ra sr frEs once:

to resist shearv and bendingcloads as afo'resaid, andqwhich may be provided with "re-' inforcing to resist primary and/or secondary stresses, and reinforcing for the truss members subj 'ect, to maximum stresses.

7 A further object of the'inventionis toprovide such a :trussed structure provided with suitable ends which have centers of gravity AFfurther object of' the invention at) provide/a trussed structurewhiclrmay have a minimum Weight for a desiredloading,

.and which may for production economy be made of bar parts all having the same cross section.

.rThese objects are attained by the use of spaced shear and bending reinforcing plates,

a" plurality off spaced chord bars, and a web secured between the spaced plates and to the chord bars,'the Webbeing preferably made e relative efiecb of f from a continuous bar or strip'of material,

- bars and forming boxbeam ends.

so I

Severalembodiments of the iinvention'are illustrated "in the accompanying drawings forming'part hereof, 1n Wh1ch- Figure 1 is-a side elevation of one form of 9 the lmproved trussed structurefor use as a pend ulously supported floor joist, and which includes a Web preferably made from a continuo'us barorstrip of materiahthe web inclu ding a truss element having spaced chord and web members connected to each other at preferably abutting apexes for a portion of the joist span, a zig-zag element having con nected web members for other portions of the span, and terminals for the joist ends includ ng upper and lower chord" members connected. to each other by members angular thereto, and to the other members of the web, the web being secured bet-ween spaced shear and bending reinforcing plates, and to a plurality of spaced chord bars.

Fig. 2, side elevations of disassembled-bar v and plate members for the joist of Fig. 1;

Fig. 3, a vertical cross section of the same as on line 3,3,Fig. l;

' Fig. 4, another verticalcross section of the 1 same as on line 4-4, Fig. 1;

v end'as on line 55, Fig. 1;

Fig. 5, a Vertical cross section of the joist I Fig. 6, a sideelevation of a modified form of the invention for use as a pendulously supported floor joist, similarto that illustrated in Fig. 1, but differing therefrom in that the span portion of the web consists of zig-zag connected web members;

Fig.' 7, side elevations of disassembled plate and bar members for the joist of Fig. 6

Fig. 8, a vertical cross section of the same as on line 8-8, Fig. 6;

Fig. 9, a vertical cross section of the end of the same ason line 99, Fig. 6; V

Fig. 10, a side elevation of another modification of the invention for use. as a pendulollsly supported floor joist, in which the spaced shear and bending reinforcing plates do not extend across the entire joist span and in which thespan portion of the web'consists of a truss element including spaced chord and tion angles; I j

Fig. 11, side elevations of the bar members for the joist of Fig. 10 i Fig. 12, an enlarged, fragmentary'side elevation of the end of the joist of Fig. 10, a portion of one shear and bending reinforcing plate being broken away to illustrate the verweb members connectedto each other at j un-c tical connection between the upper and lower chord portions of the webterminal, and

as on line 13113, Fig. 12.

throughout the drawings.

Fig-13, a vertical cross section of the same Similar numerals refer to similar parts 7 of material, and including a truss element indicated-generally at 7, zig-zag elements indicated generally'at 8, and terminals indicated generally at 9.

The truss element 7 of the web 5 includes spaced chord members 10 and connecting web members 11, there being preferably abutting apexes 12 between the chord and web members.

V The zig-zag elements 8 of the web 5 include connected web members 11, there being alternate apeXes 12 between the web members.

The terminals 9 of the web 5 include upper chord members 13, and lower chord members 14: connected to each other by members angular thereto including vertical end members 15 and diagonal members 16 and 17, the chord ' members 13, and 14 being preferably spaced parallel with each other as shown, and diagonals 17 preferably terminating in chord extensions 18 parallel with members 13 and 14.

The lower chord bars 4 include central portions 4 provided near their ends with upwardly extending diagonal portions 19 connecting with terminals 20, said terminals being preferably parallel with the central portions 4;. 1

The spaced plates 2 may be provided with bent up angle legs 2 at their ends.

The structure 1 may. thus be assembled from theparts illustrated in 2 by interposing a web 5 between a pair of spaced plates 2 arranged along the upper longitudinal edge of the web and securing the plates to the web and to the spaced upper and lower chord bars '3 and 4 as by arc welding 6 to form the completed structure 1.

Spacedterminal chordbars 13 and 14 and their connecting end'bar 15 are secured to the outer boundaries of the plates 2, thus forming box beam ends for the joist which are further strengthened by the terminals of the chord bars 3 and 4 secured thereto as best illustrated by the cross-section view of Fig. 5. The box ends thus formed have centers of gravity more adapted for stable equilibrium against lateral tipping than are other types of ends for :bar joists and which may have end plates not spaced nor secured to'an interposed web bar terminal, or which may consist merely of a T-bar welded to the terminals of the chord bars.

The spaced plates may extend the entire length of the joist as illustrated in Figure 1, in which case a reinforcing is provided for resisting either primary or direct stresses in the upper chord members of the structure. In fact if the plates 2 extending the entire length of the joist be of sufliciently heavy gauge material upper chord bars 3 might be entirely eliminated or utilized only toprovide lateral stiffness for the joists.

By providing the centrally located truss element 7 in the web, that portion of the truss'ed structure between the terminals of the truss element 7 has a greater moment of inertia than those portions of the trussed structure between the terminals of the zigzag elements 8, thus providing an eificient strucof'the span, under which c on ditionst-he maxi mum imposed bending momentoccursnear the center of the span, decreasing to'zero at v the supportsif'the joist be freely supported at its'ends."

ConsequentlyQforresisting suchfia type of loading thei'reqmre'd moment ofinertia in the central portions of the 'joist is greater thanj V stantially constant momentofinertia is provided' a'crossthe entirespan by the elimination of the truss element Tjlhavingch'ord portions 7 thefrequiredmoment of inertia-between the central portions andthe ends; sothat a construction which enables the fabrication of joist having a varying moment of inertia pro; vides a joist having a the required strength.

The constructlon of the present invention enables the construc'tion of-a bar oist having a varyingmoment of inertia and ends adapted to'resist'shear and bending loads as heretofore v described and whlch' ma 'be made of bar a parts all hav ng the same cross sectional'area,

which is very desirable from the standpoint of stores and production economy. 1

The cross section of Fig. '4 as compared 7 with the cross section'of Fig. 3 illustrates that a reater moment of inertia is attained in the joist at tionsiare between web and chord apeXes or panel po nts, since the chordarea ofthe cross section at H is made up of three bar sections here illustrated asall being: equal inarea, while the cross sections at 3-3 is made up of only two bar sections here illustrated as being equal in area, it being assumed thatfor the purposes of this particular comparison the gauge of the plates 2 is sufficiently light not to materially affect the resisting "moment of thejoi st.

The modified embodiment of the invention indicated generally at 2"1 illustrated in Figs.

1 6, 8 and 9, and whose disassembled partsare includes'connectcd 1 illustrated in Fig. 7,

eluding a zig-zag element indicated generally .at 28,. and terminals indicated generally at 'The zig-zag elementf 'l of the web 2 5 web members 2-11, there being alternate apexes2-12 between the web members. p i

The terminals 2-9 of the web 2-5'includv upper chord members 2 13 and: lower chord members-2-14:"connected to each other, by members angular thereto including vertical end members 2-'1 5 and diagonal members 2 16 and 2-17, the chord members 2-13 and 2-14 being preferably spaced parallel with each other as shown, and diagonals 217 7 preferably terminating a chord extension minimum weight for includes spaced {plates 2..3, spaced tralpOrtiOnsfB- Q.

2'1 8parallelwithmembers2-43 and 2-44. 2-4; include centralj The lower 'chord bars portions. 2 4: providednear their ends with upwardly extendingjdiagonal portions 2-19 connecting withterminals 2--20, saidterminals being preferably parallel withthe central portions 2:j4".;.

The spaced plates with bent}.up angle'jlegs 2+2 JOist-Z- ldiifers from joist 1; in thatasub' struction illustrat'ed in Fig; 6, and just described; 21- further modification of the invention may be employed which is illustrated in may proyided "at their ends.

. i stantiall'yfconstant'moment of inertia a Figs. 10, 12 and 13.'and whose disassembled p, is are illustrated in Fig.1l.

I, This modified trussed structure indicated generally at 8 1 includes spaced plates 3-2,

spacednpper chordbars 3-8, spaced-lower g chord bars (S- l, and a web ind cated general- ,7

lyat 35 securedgbetween thespacedplates and to the chord bars as by arc welding 3+6, theweb being preferablymade from a con- 3 7 and terminalsindicated generally at spaced chord members 3-1O and connecting web members '311, there being preferably abutting apexes 3-12between the chordand web members. I Theterminals of the} web include upper chord members 3+1?) and lower chord members8b14 connected to each other by mem- '95 tinuous bar orstripof material, andin'clud fiing "a truss element indicated generally at here angulartheretoiincluding vertical end" i i members 3'15 and diagonal members .f I l i 3-"14l'being preferably spaced parallel with, 1 each other as 'shown',aandth'e chord members 3+1?) preferably abutting the terminal chord and} 3;'17, the-"chord members 3-13 and members 3-1O ofthetruss'element 37. I The lower chord bars 34:'includecentra'l upwardlyfextending diagonal portions 3-19 connecting with terminals 3,20,' said .te'r? minals being preferably parallelfwith'the cenbodimentsof the invention in thatjthe plates 's-2 sta -be provided 3 -2 jdovnot extend,.,across the entire length i of the joist, and-ingthat the web is provided 'withatruss element havingpchiord portions across a greater'portion of the span for prop 1:15 portions 3%i' provided near their-ends with i.

the jo vid-ing ajoist having a substantially constant moment of inertia'somewhat greater than the substantially constant moment of inertiaof ist heretofore described and illustrated in Fig. 6.

,Iclaimi 1" J J ,I 1. An end for a pendulously; supported her j'oistand the like including spaced plates, and, the terminal of a continuous web bar interposed between the plates and; secured thereto and the terminalincluding spaced 1 and the terminal ofa continuous web bar interposed between the plates and secured thereto,the terminal including spaced chord mem' bers connected with each other endwise by a member angular to the chord members.

4. An end for a pendulou'sly supported bar oist and the like including spaced plates, and thete'rminalof a continuous web bar interposed between the plat'es and secured thereto, the terminal including spacedchord members connected to the. outer boundaries of the, plates. Y l I -5.- A structure for-a pendulously supported bar joist and the like including spaced plates, a continuous web bar interposed between the plates and secured thereto, and chord bars secured to the web bar, the web bar including a bar terminal interposed between the plates'and connected to the upper, end, and lower outer boundariesof the plates. j

6. A structure for apendulously supported bar joist andthe like including spaced plates,

I 1 a continuous web bar interposed between the g plates and secured thereto, andchord bars secured to the webbar, the Web bar includinga bar terminal interposed between the plates and connectedthereto,a zig-Zag element including connected web members and alternate apexes between the web members, and a truss element including spaced chord members and connecting web members and apeXes between the chord and web'members.

7. A structure for a pendulously supported bar joist andthe like includinga plurality of spaced chord bars and a web secured thereto, the web including a zig-zag element including connected, web membersand alter nate apexesbetween the web members, and a truss element including spaced chord members and connecting web members and apexes between the chord and web 'members.

8. A structure for apendulously supported bar joist and the like including a plurality of spaced chord bars and-a web secured there- 9. A web for a structure for a pendulously supported bar joist and the like including a zig-zag element including connected web members and alternate apeses between the web members, and a truss element-including spaced chord members and connecting web members and apexes between the chord and web members, all the elements 1.- mg formed ina single continuous bar.

10. A web for astructure for a pendulously supported bar joist and the like including a terminal including spaced chord members connected to each other by member angular to the chord members, a zig-Zag element in cluding connected web members and alternate apexes between the web members, and a truss element including spaced chord members and connecting web members and apexes between the chord and web members, the terminal and the elements being formed in a single continuous bar. 7

11. A bar joist and the like having a central spanning of varying moment of inertia, and including upper and lower parallel chord bars each, having a substantially uniform cross section and a continuous web bar of substantially uniform cross section.

In testimony that I claim the above, I have hereunto subscribed my name.

HURXTI-IAL FIELD FREASE.

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