US1982343A

US1982343A - Building construction

Info

Publication number: US1982343A
Application number: US556793A
Authority: US
Inventors: Charles S Kane
Original assignee: Individual
Current assignee: Individual
Priority date: 1931-08-13
Filing date: 1931-08-13
Publication date: 1934-11-27
Anticipated expiration: 1951-11-27

Description

Nov. 27, 1934.

c. s. KANE BUILDING CONSTRUCTION Filed Aug. 15, 1931 6 Sheets-Sheet 1 cI-IARLEssKANE fiwmll ATTORNEY I Nov. 27, 1934. c. s. KANE 1,982,343

BUILDING CONSTRUCTION Filed Aug. 13, 1931 6 Sheets-Sheet 2 INVE NTOR CHARLES. S. KAN E Nov. 27, 1934. c. s. KANE 1,982,343

BUILDING CONSTRUCTION Filed Aug. 13, 1931 6 SheetsSheet 3 8 14:16 7 58 f 55 54:, y A I I.

INVEN 'IO R ATTORNEY Nov. 27, 1934. c. s KANE 1,982,343

BUILDING CONSTRUCTION Filed Aug. 13, 1931 6 Sheets-Sheet 4 CHAR LERSKAH E Nov. 27, 1934.

c. s. KANE BUILDING CONSTRUCTION Filed Aug. 13, 1951 6 Sheets-Sheet 5 INVENTOH CHARLE$.S.KANE

ATTORNEY Patented Nov. 27 1934 rarest osrlcs 1,982,343 BUILDING CONSTRUCTION Charles s. Kane, Montreal, Quebec, Canada Application August 13, 1931, Serial No. 556,793

3 Claims. (o1. 72 '15) This invention relates to the erection of fireproof building structures in which the structural columns, beams, floor joists and other steel framing elements are embedded in fireproofing concrete.

In the usual structure of this class, the steel framing must be made heavy and strong enough to carry all loads without the assistance of the concrete. This is required in the interests of safe practise since the bonding of the concrete to the usual design of steel framing is not consistently such as to permit the strength of the concrete component of the framing to be safely calculated as part of the required load and stress bearing capacity.

The object of the present invention is to provide an improved construction in which the steel framing is designed so that the fireproofing concrete is combined therewith to provide a truly composite metal and concrete framing which is of such a character that the concrete component may be safely relied upon to carry a certain proportion of the load which the composite framing is called upon to hear. The principal advantage of this composite construction is that it enables the metal structure of the framing to be made lighter than heretofore so that a considerable saving in steel is effected without decreasing the strength and load bearing capacity of the fireproof framing, since the lightness of the metal component of the framing is compensated for by the load and stress bearing capacity of the concrete component.

According to this invention, the weight of the framing is primarily reduced by substituting light welded trusses of theopen web or lattice type for the heavy solid beams heretofore employed to carry the floor joists. The open structure of these trusses permits the fireproofing concrete to combine therewith to form composite metal and concrete girders of a character permitting the concrete component to be safely relied upon to carry a definite proportion of the load which the composite girder is called upon to bear. The trusses of the composite girder are preferably made continuous at the columns and are designed to Withstand all construction loads imposed thereon prior to the setting of the concrete in which the trusses are embedded. The iioor joists supported by the composite girder are preferably of the trussed or open web type and, in some instances, are made continuous at the girder by the use of special field joints. This type of floor joist affords a further saving in steel and when encased in concrete provides a composite metal and concrete joist in which the concrete component may be safely relied upon to carry a definite part of the load which the joist is required to withstand. The

use of open web girders and floor joists also facilitates the placement of pipes and ducts since sleeves for the passage of these pipes and ducts may be arranged to extend through the web portions of the girders and joists prior to the pouring and setting of the concrete in which these elements are embedded.

Other advantages and characteristic features of the construction afforded by the present invention will be more readily understood from the following detail'description considered in connection with the accompanying drawings, in which Figure 1 is an isometric view of a portion of a building structure erected in accordance with this invention. v

Figure 2 is a View similar to Figure 1, but showing a modified assembly. 7

Figures 3 to inclusive are detail views illustrating various methods of joining and supporting the steel structure of the composite girders at the columns. 7

Figures 16 to 23 inclusive are diagrammatic views illustrating the application of the various girder supporting methods shown in detail in Figs. 3 to 15 inclusive.

Figures 24 to 27 inclusive are detail views illustrating the method of joining contiguous girder sections.

Figures 26 and 29 are detail views illustrating a method of making rolled steel girders continuous at the columns.

Figure 30 is a detail view illustrating one method of making open web beams. continuous at the girders when rolled steel girders are employed.

Figure 31 is a detail View illustrating one method of making solid rolled beams continuous at the girders when rolled steel girders are employed to carry these beams.

Figures 32 and 33 are detail views illustrating a method of mounting through and butt girder trusses at the columns.

Referring to the construction shown in Figure 1, numeral 5 designates steel floor joists of the lattice or open web type comprising top and bottom chord members 5a joined together by rods, flats, angles or other structural shapes 5b forming the web structure. These joists arecarried at each end by a welded trussed steel girder structure 6 passing through a series of supporting columns one of which is indicated at '7.

Each girder structure 6 comprises a plurality of separately formed sections or girders having their top and bottom chords joined together in the bays between adjacent columns and at points 6a corresponding as closely as possible to the points where the minimum chord stresses are developed. In other words, the contiguous sections forming the girder 6 are joined together approximately at points which, in a continuous beam, are technically known as the points of contra flexure at which the chord stress is theoretically zero.

Considering each girder 6 to be continuous at the columns '7, the top chord is composed of two angles 8 strong enough to withstand the positive compression and negative tension due to the construction load and part of the negative tension due to superimposed load. The bottom chord is composed of two angles 9 capable of withstanding the positive tension due to total load, the negative compression due to construe-- tion load and part of the negative compression due to superimposed load. The open web of the girder is composed of diagonals 10 in the form of rods, flats, angles or other structural shapes and is designed to withstand the construction shear stresses.

In the present instance, one girder section 6 is shown passing through the central portion or" the column 7 and having its top chord connected to the top chord of the contiguous girder section by a welded joint or splice 6a which is offset with respect to the joint or splice 6a connecting the bottom chords, the location of the two splices coinciding as nearly as possible with the points of minimum chord stress.

The column 7 is shown as a composite or built up split column comprising a fabricated steel core which, at a suitable stage of construction, is embedded in the concrete fireproofing 11 including the usual reinforcing bars 12 and column hooping 13. The steel core structure of the col- 'umn consists principally of four vertically extending angles arranged in pairs with the angles 14 of one pair spaced a suitable distance from the angles 15 of the remaining pair. The two pairs of column angles are tied together at intervals by tie plates 16 spanning the intervening opening 17 and welded or otherwise secured to the inwardly projecting flanges of the angles. The girder section 6 which passes'through the column opening 17 is fastened to the column by angles or other structural shapes 18 welded to the top and bottom chords of the girder section and to certain of the tie plates 16.

The floor joists 5 rest on the top chord of the girder 6 preferably at points where the top chord is intersected by the diagonals 10. As indicated in Figure 1, the two series of floor joists supported by each girder 6 are arranged with the ends of one series resting on the top chord of the girder in abutting relation with the ends of the opposing series. The abutting ends of the two series of floor joists are equipped with shop-welded angles 19 bolted or otherwise secured together to make the iioor joists substantially continuous at the girders. These angles 19 may also be welded or otherwise secured to the top chord of the girder 6.

After erection, the steel girders 6 and floor joists 5 are encased in fireproofing concrete which combines therewith to provide a composite steel and concrete frame of such a character that the forms include steel floor tiles 20 in the form of inverted channel members. These floor tiles are arranged in spaced parallel relation to provide intervening valleys for the reception of the floor joists 5. The floor of each valley is formed by a channel member 21 having its side flanges 22 directed upwardly and engaging the inner surfaces of the tile flanges 23 which form the sides of the valley. These metal forms are assembled with the floor joists and tied thereto in a suitable manner (not shown) prior to the mounting of the joists in place between the girders 6.

Pairs of negative reinforcing bars appearing at 24 in Figure l, are mounted in the floor joist forms prior to the pouring of the concrete so that the bars of each pair are embedded in the concrete enveloping the girder 6 and the adjacent ends of contiguous floor joists 5 and extend through the open web of the girder 6 so that the ends of these rods lie close to opposite sides of the bottom chords of the floor joists.

The open web structure of the floor joists 5 permits the concrete poured into the valleys between the floor tiles 20 to bond with the metal of each joist in such manner that the resulting structure is a composite concrete and metal joist in which the bond between the metal and concrete is such that the concrete component may be safely relied upon to bear a definite proportion of the load imposed on the joist. The web portions of the floor tiles 20 which bridge the spaces between adjacent floor joists serve to support the wire-mesh reinforced concrete floor slabs 25 during setting of the concrete.

Suitable metal forms (not shown) are also associated with each girder 6 so that the concrete poured around these girders takes the form of a T, the stem of which is indicated at 27 and the T-head at 28. The girder forms (not shown) may be tied to the girder 6 by stirrups 29 or in any other suitable manner. It will also be understood that the column forms, while not shown herein, are fabricated in a suitable manner to take the concrete 11 which is poured around the metal column structure after the girders 6 have been assembled therewith.

The open web design of the girder 6 permits the enveloping concrete to combine therewith to form a composite concrete and metal beam in which the stem portion 27 of the concrete serves to withstand the punching shear and part of the negative compression due to superimposed load while the T-head portion 28 of the concrete withstands positive compression due to superimposed load. Since. in a composite beam of this nature the concrete component has a definite safe load and stress bearing capacity, the metal structure of the beam may be made correspondingly lighter.

The .cost of fabricating the open web steel girders and floor joists is offset by the fact that the permissible use of this design in the comsagas "mi ts pi-p e sleeves to be placed in the forms to extend through the girders before the concrete is poured so that pipes or conduits may be subsequently passed through the composite concrete and steel girders without drilling through steel or concrete as now required in connection with the use of solid steel or reinforced concrete framing. The use of open web trussed steel girders (especially when the companion angles of the top and bottom chords are spaced apart to receive the diagonals of the web therebetween, as hereinafter described) also eliminates the honey com-bing of the concrete beneath the girder flanges which commonly occurs in connection with the concrete fireprooring of solid steel girders. Due to this honeycombing and to other defects in the bonding of the fireproofing concrete to solid steel girders and floor joists, it is not permissible to erect a structure of this character unless the solid steel framing is made heavy and strong enough to carry all of the load independently of the concrete flreproofing. In a structure -designed in accordance with the present invention, the concrete combines with the fabricated steel girders and floor joists to provide a composite concrete and steel framing structure which is of such load bearing capacity that the weight of the steel structure may be lightened to an extent dependent upon the load and stress bearing capacity or" the concrete component. The saving in weight due to the use of welded open web girders and floor joists is also augmented by the use of the herein described composite columns consisting of steel cores embedded in concrete.

Referring again to Figure 1, it will be noted that suitable bridging is associated with the floor joists 5. In the present instance I have shown a straight bridging rod 30 crossing the top chords of the floor joists and clipped or otherwise connected thereto. I have also shown a V-type bridging consisting of two lines of bridging wires or rods indicated at 31 and 32, each line being wrapped tightly around the top chord of one joist and then around the bottom chord of the next joist, the ends of the wires being anchored in a suitable manner (not shown).

Tie beams 33 are also provided for tying together adjacent columns 7. While the construction of these tie beams may be varied as hereinafter described, the tie beams shown in Fig. 1

are of welded open web or trussed construction comprising top and bottom chords 34 connected by diagonals 35, the ends of the top and bottom chords being joined to the steel structure of the columns by angles 36 welded or otherwise secured in place.

In the modified assembly shown in Fig. 2, the composite column '7 is provided with a solid steel core 37 which is herein shown as consisting of a vertically extending H-beam, although other structural shapes may be substituted. In this case the trussed steel girder sections 38and 39 (corresponding to the previously described girder sections 6) are welded to the flanges of the beam the remaining series, but it will be understood that the floor joists may also be made continuous at the supporting girders as described in connection with Fig. 1.

The assembly shown in Fig. 2 also illustrates the manner in which pipe sleeves 46 are passed through the open web of the girder structure and embedded in the reinforcing or flreproofing concrete to facilitate the subsequent passage of pipes or conduits 47 through the composite girder. It will also be understood that similar sleeves may be arranged to extend through the open webs of the floor joists 5 prior tothe pouring and setting of the concrete in which the joists are embedded.

Solid steel tie beams 48 are shown in Fig. 2 for connecting the steel cores 3'? of adjacent columns, but it will be understood that these solid tie beams may be replaced by the welded trussed tie beams appearing in Fig. 1. The trussed tie beams appearing in Fig. 1 may likewise be replaced by the solid tie beams appearing in Fig. 2. The floor slab hyrib'construction appearing at 49 in Fig. 2 and the ceiling lath construction appearing at 50 are also applicable to the floor joists of Fig. 1.

In place of the arrangement shown in Fig. 1 the girder section 6 passing through the columns 7 may be fastened to the steel core of the column as indicated in Figs. 3 and 4. In this case the bottom chord angles 9 of the girder section are welded or otherwise secured to oppositely projecting flanges 16a formed integral with the upper edge of a tie plate 16b corresponding to the previously described tie plates 16. The tie beam 33 shown at the right of Fig. 3 corresponds to that 1 previously described in connection with Fig. 1 while the tie beam 48 appearing at the left 013 Fig. 3 corresponds to that described in connection with Fig. 2 and is welded or otherwise fastened to the column angles 14 through the medium of 1 suitable angles 52 or other structural shapes.

Instead of passing through the fabricated steel columns as shown in Fig. 1, the trussed steel girders 6 may be passed along one side of each column and supported therefrom as shown in 1 Figs. 5 to 7 inclusive. In this case tie beams 54 are passed through the column openings 17 and joined in end to end relation by plates 55 and bolts 56. At the opening 17 the tie beams are fastened to the column tie plates 16 by suitable 1 angles 57 welded or bolted in place. At each column the upper chord angles 8 of the girder 6 are mounted on the cantilever support afforded by the projecting end 54a of the tie beam passing through the column. The top chord angles 8 are 1 preferably equipped with'a shop-welded saddle plate 58 adapted to be welded or otherwise secured to the tie beam end 540.. The bottom chord angles 9 of the girder are also equipped with a shop welded plate 59 adapted to be welded or 1 otherwise anchored to one of the column tie plates 16 by an angle 60 which is welded or otherwise secured in place.

A further modification is shown in Figs. 8 to 10 inclusive, wherein the diagonals 62 of the trussed 1 steel girder 63 are interposed between the companion angles 64 of the top chord and between thecompanion angles 65 of the bottom chord. The resulting spacing of the companion angles of the two chords gives a better bond with the 1 v concrete when the latter is applied to the girder and tends to prevent honeycombing of the concrete beneath the girder flanges. In some instances, however, the girder shown in these last mentioned figures may be provided with a rein- 1 forcing. plate fifiwelded or otherwise secured to the upper. surface of the top chord. angles. 6d.

Thegirder section. 63 passes alongoneside of the composite supporting column whichis pro: vided with a solid steel core in the form eta structural steel beam 68. In this instance the top andbottom chords of the girder are supported from the steel column core byangle's 69 or other.

having its ends supported bythe upper angles 69 which, as previously described, are employed 'for fastening thetop chord of thegirder to the steel column core. I

Figs. 11 and 12 illustrate one method of. passing a trussed steel girder through a column having afsolid steel core. In this instance the steel I core is composed of superimposed sections 75 and,

76 in the form of Hsbeams fastened together by" side plates '7? bolted or welded thereto. The web 7511 of the lower section 75 is provided at its upper end with a V -shaped notch '78 and the upper chord 79a. of the girder section '79 is passed through this notch, as shown, so that the top surface of. the

chord is practically .fiush with the upper end of the column section '75. The lower chord 79b of the girder section is split to provide a gap accommodating therein the web 75a of the columnsection 75v as shown to. advantage in Fig. 12, wherein.

it will be noted that the ends of the chord lying at opposite sides of the gap are joined to the web 756; by welded or. bolted angles 80 and. plates 81.

The upper. chord 79a of the girder. is shown. as secured to the upper steel column section '76 by a welded angle 82. In erecting the assembly shown in Figs. 11 and 12 it will, of course, be understood, that is assembled'as described with the lower steel column section 75 prior to erection of the upper steel column section 76.

13 illustrates, a slight. modification of. the inbly appearing in Figs. 11 and'lZ. Accorde g, to this modification the girder is arranged with the vertical flanges 84. of the top chord passing through a s1ot85 in the web 86 of. the lower,-

steel column section 87. In this instancethe. horizontal flanges 88 of the topgirder.chordrest. flatly on the upper end of the .web,.85 between suitable filler plates 89 on which thelowe'r end of the upper column sectionQO is supported.

Figs. 14 and 15 illustrate one method of freak;

contiguous girder sections continuous atthe" e column when the latter, is. provided l d steel core. In this instance-the. bot.-

ancnored to opposite sides of theweb' 95 of the core 96 by means of header platesBV... These header p t s are perierably.shopf'weldedtothe chord a and fastened. toihe web 95 byweld- 3 ing or ho- The top chord angles. 98 or the two 2r sections here referred to are shown as.

terminating short of the web 95 and connected together by'welding to opposite ends-of a tension member 99 arranged to pass through a slot 100,;

formed in the web 95. The tension memberQil. is preferably arranged to join the top chord of the two girder sections togethe at points positioned. at or near the pointsof contrai'iexure. Where. it Passes through: the e 9 he easements ofthe two. girder. sectionsare preferably anchoredto the web by one or more angles 101. arranged as shown and welded or otherwise fasten'edin place. The method of joining. the girder sections as illustrated in Figs. 14: and may also be used in connection with 001- umns having a fabricated steel core of the type In the latter instance the botsho'wn in Fig. 1. t'orn chord angles 94 would be suitably secured to one of thecolumn tie plates 16 while the tension member 99 would pass through the column opening 17 and be secured to another one of the columntieplates 16.

With respect to the various girder supporting arrangements shown in Figs. 3 to 13 inclusive, it,

willbe understood that in each instance the girder section passing through or by the steel core of the columnhas its top and bottom chords joined to corresponding chords of contiguous girder sections at points between the columns corresponding as nearly as practicable to the points of contraflexure or minimum chord stress. This will be readily understood from the following reference to Figs. 16 to2 3 inclusive.

The girder supporting arrangement illustrated in detail in Figs. 3 and 4 is shown diagrammatically in Figs. 16 and 1'7, in which A indicates the steel column core, B the girders, and C the joining of contiguous girder sections at points between the columns corresponding to the points of minimum chord stress.

The icy-passing ofthe steel column cores bythe, girders. in accordance with the arrangements shownin detail in Figs. 5 to 10 inclusive is illustrated diagrammatically in Figs. 18 and 19, in which D designates thesteel column cores, E the girder sections passing along the sides of the steel column cores, and Fthe joining of the girdersections at points between the column cores corresponding to the points of minimum chord stress.

The passing of the girder sections through columns equipped with solid steel cores as shown in detail in Figs. 11 to 13 inclusive is illustrated diagrammatically in Figs. and 21, in which G designates the steel column cores, H the girder sections, I the joining of contiguous girder sections between the columns at points corresponding'to the points of minimum chord stress, and

J the joining of the column web with the separated botto n chord members of the girder sectime passing through the column.

'Thearrangement. shown in detail in Figs. 14

and 15 is. illustrated diagrammatically in Figs. 22

and, 23 in which K indicates the steel column. cores; L the contiguous girder sections; M the. joints between the column cores and the bottom: chord angles of the girder sections, and Nthe tension members passing through the column cores andjo'ine d to the top chords of the girder, sections 'at points 0 representing the points of minimum chord stress.

Figs. to 27. inclusive illustrate a method of jecting angle 105 of the contiguous girder. sec-,

tion.. The end of the angle 105 of each girder section is thereby positioned close to the end of I:

the angle 106 of the contiguous girder section and the. opposing ends of these anglesare joined by weldingfto a joint. plate 107.

In this. instance. the top chord In like, manner. the

lower chord. angle, 108 of each girder section is' projected beyond the companion angle 109 and short of the girder and are made continuous by is joined to the angle 109 of the contiguous section by a welded plate 110. The web of the girder is formed by diagonal angles 111 welded to the vertical legs of the top and bottom chord angles and the shear introduced between the chord angles is provided for by making the vertical leg of one top and one bottom chord angle longer than the vertical leg of the companion angle to provide additional welding space for developing this shear.

Figs. 28 and 29 illustrate a method of making contiguous girder sections continuous at the solid steel cores of the columns when rolled solid steel girders are substituted for the previously described trussed or welded open web girders, such substitutions being sometimes necessary or desirable in certain positions of a structure erected in accordance with this invention. In these figures the steel column core comprises superimposed

sections

113 and 114 joined together by bolted or welded side plates 115. The solid rolled girder sections are indicated at 116 and 117. The lower opposing end portions of these girder sec tions carry shop welded header plates 113 bolted or otherwise secured to opposite sides of the web portion 119 of the lower column section 114. At their upper surfaces the opposing ends of the girder sections are welded to the extremities of a tension member 120 passing between filler plates 121 separating the adjacent ends of the

column sections

113 and 114. The tension member 120 serves to join the

girder sections

116 and 117 at points closely approximating the points of contraflexure and serves to induce continuity of the girder sections at the columns.

.When the columns are spanned by rolled solid girders these girders may be employed to carry welded open web beams as shown in Fig. 30 or rolled solid beams as shown in Fig. 31.

In the construction shown in Fig. 30, the rolled girder is indicated at 125 and serves to support the adjacent ends of contiguous

open web beams

126 and 127. The bottom chords of the beams are joined to the web of the girder by header plates 128. The top chords of the beams stop joining to the ends of a tension member 129 which passes over the top of the girder and joins the top of the beams at points corresponding approximately to the points of minimum chord stress.

In the construction shown in Fig. 31 the adjacent ends of the rolled

beams

130 and 131 have their lower portions joined to the web of the rolled girder 132 by suitable header plates 133. The upper end portions of the

beams

130 and 131 are made substantially continuous by joining to the ends ofa tension member 134 passing across the top of the girder and joining the beams at or near the points of minimum chord stress.

Figs. 32 and 33 show further modifications dealing with the anchorage of both butt and through trusses at the columns. The steel column cores illustrated in these figures is of the fabricated construction shown in Fig. 1. The through truss indicated at 136 passes through the column opening 17 and is anchored to certain of the column tie plates 16 by the angles 137 and the plate 138. The top chord angles of the truss 136 are also preferably reinforced by tension rods 139 welded thereto and also extending through the column opening 17. The butt trusses indicated at 140 and 141 have their bottom chords fastened to the column angles 14 and 15 by angle plates or other structural shapes 142. The top chord angles of the butt trusses 140 and141 are joined at points corresponding to the points of minimum chord stress by tension rods 143 welded thereto and passing through suitable openings formed in the column angles 14 and 15. The top chord angles of the butt trusses 140 and 141. are also joined directly to the

column flanges

14 and 15 by suitable angles 143a.

While Figs. 32 and 33 show the through truss 136 and the butt trusses 140, and 141 joined to a split column, it will be understood that the same construction could be used in connection with'a solid column by providing the column with suitable slots or openings for the passage of the

tension rods

139 and 143.

Having thus described my invention, what I claim is:-

1. A composite metal and concrete building structure including composite columns comprising relatively light self-sustaining lattice type steel column cores embedded in concrete, composite girders supported by said columns, each girder being arranged to span the spaces between a row of columns and consisting of contiguous open web steel trusses embedded in concrete continuous with the concrete components of the columns, the ends of the girder trusses being secured to and supported by the steel column cores and composite floor joists supported between adjacent girders each floor joist comprising a welded open web truss embedded in concrete continuous with the concrete components of the girders, the ends of the steel trusses of the floor joists being supported on and secured to the top chords of the steel trusses of the girders, and the contiguous steel trusses of each girder being joined together in end to end relation to form a continuous beam passing through openings in the steel column cores, the joints between the component girders of said beam being located at points approximating the points of contrafiexure I or minimum chord stress.

2. A composite metal and concrete building structure including composite columns comprising steel column cores embedded in concrete, composite girders supported by said columns, each girder being arranged to span the spaces between a row of columns and consisting of contiguous open web steel trusses embedded in concrete, the

bottom chords of the contiguous trusses of each 1 girder being anchored to the steel column cores by field joints and the top chords of said trusses terminating short of the steel column cores and being welded to the extremities of a tension mem ber passing through the columns, said tension M member joining the top chords of the girders at points approximating the points of contrafiexure or minimum chord stress and serving to assist in taking care of negative tension.

3. A fireproof building structure comprising a light, rigid and self-sustaining steel frame comprising self-sustaining lattice type'steel column cated at points approximating the points of coni traflexure or minimum chord stress, a series of floor joists supported between parallel girders, each floor joist comprising an open-web steel truss, the steel trusses of contiguous floor joists being joined together at the girders inehd to end relation, the aforesaid elements of the steel framing being embedded in concrete so that the concrete component or the steel ccl-ul rm cores is made continuous with the concrete component of the girders and the steel floor joists to provide a fee