Example Floor Systems

The floor systems described here are only a few of the many tested between 1890 and 1910. They include the most common floors and a few oddities that often confuse modern engineers.

The floors are grouped by type (arches, catenaries, and beams) and in the order that the types became popular. The earliest floor systems used with iron beams in the Untied States were arches. During the 1880s and 90s, various tile arch forms were the most popular floors in use, and were still used into the 1920s. The draped-mesh (catenary) floors developed in the 1890s became the most popular form in the late 1910s and 1920s, and were only permanently replaced by a beam-type floor when composite metal deck was developed inthe 1950s.

2.1 Arch floors

Neither brick vault floors nor plain segmental terracotta tile arches were tested in New York, as both were allowed without limitation. They were typically not tested elsewhere, as they were considered ordinary and familiar floors.

Both generic and proprietary flat terra-cotta tile arches were tested in New York because neither met the geometric requirements for exemption. These systems consisted of precast terra-cotta blocks with thin webs, arranged as flat-arch voissoirs. There were two major types: side construction, with terra-cotta voids perpendicular to the vault span, and the newer end construction, with voids parallel to the span. (Figs 1, 2) The tiles were typically set low, to cover the bottom of the steel beams, and fill was placed over the top to protect the tops of the beams and provide a base for wood flooring. (no author 1897)

The Guastavino Timbrel Vault was an interesting variant on the standard terra-cotta tile-arch floor, using Catalan hard-burned tiles and thin-shell construction to meet the American testing standards. (Fig. 3) It was not popular for ordinary floors, although the

Figure 2. End-construction Flat Tile Arch (Birkmire 1898).

Figure 2. End-construction Flat Tile Arch (Birkmire 1898).

Figure 3. Uastavino section, elevation, and plan (Guas-tavino 1892).

Guastavino company achieved fame in the construction of domes and long-span floors, roofs, and ceilings. Two or three layers of thin tiles were arranged with staggered joints. (no author 1889, no author 1897, Freitag 1921, Collins 1982)

The Roebling Arch Floor is one of a class of early concrete floors produced by several manufacturers. (Fig. 4) Wire-mesh arches spanned between the beam bottom flanges and served as forms for stone concrete vaults. More wire mesh was hung from the beams to create a plaster ceiling for fireproofing. (no author 1897, Birkmire 1898, Hool 1913).

2.2 Catenary floors

The Metropolitan System was an early draped-wire floor, approved in 1899. (Fig. 5) The reinforcing consisted of twisted pairs of wires individually strung across the building, anchored at slab edges, and draping over the floor beams and under a hold-down bar at mid-span. Since the wires carried all loads, the slabs

Figure 7. Rapp Floor: wood sleepers to attach finish flooring, fill ("concrete"), brick, and inverted Ts. (Birkmire 1898).

Figure 4. Roebling Arch: wood sleepers for finish flooring, concrete fill, wire-mesh arch, hung ceiling. (Birkmire 1898).

Figure 7. Rapp Floor: wood sleepers to attach finish flooring, fill ("concrete"), brick, and inverted Ts. (Birkmire 1898).

Fic. 71.—Metropolian Floor— Pjnelied Construction,

Figure 5. Metropolitan Floor (Freitag 1899).

Fic. 71.—Metropolian Floor— Pjnelied Construction,

Figure 5. Metropolitan Floor (Freitag 1899).

Figure 6. Cinder-concrete, draped-mesh slab, (Buel & Hill 1906).

Figure 6. Cinder-concrete, draped-mesh slab, (Buel & Hill 1906).

Figure 8. Expanded Metal Floor (Freitag 1899).

Figure 8. Expanded Metal Floor (Freitag 1899).

Figure 9. Columbian Floor, with wood flooring on sleepers, and rebar supported by light-gage straps over the beam tops. The bottom transverse section shows the double-cross bars. (Freitag 1899).

were structurally unstressed and were composed of gypsum plaster mixed with wood chips. (no author 1897, Freitag 1898, Birkmire 1899, no author 1895)

Draped-mesh floors were first developed under proprietary names, but the presence of the existing catenary patents meant that the basically similar mesh floors quickly became generic commodities. (Fig. 6) Various proprietary forms of mesh were used early on, but since the floor only required a specified standard size of wire at a specified spacing, the generic floors were ultimately more common than the named ones. As with the Metropolitan floor, the mesh passed over the top of the floor beams, near the top of the slab, and at midspan draped down to the bottom of the slab. Because the mesh wires take all of load in tension, the slab serves only to provide a walking surface and fire-proofing. Because the concrete is not stressed, material of poor quality and low strength, such as cinder concrete, was frequently used. (Perrine & Strehan 1915, Waite 1914)

2.3 Beam floors

The Rapp Floor consisted of common brick, supporting a layer of fill and supported by light-gage steel inverted Ts, which span between the bottom flanges of the floor beams. (Fig .7)(Birkmire 1899)

The Expanded Metal Company Floor is a thin concrete slab reinforced with a sheet of "expanded metal," created by slitting a light-gage steel sheet and pulling the sheet to open the slits. (Fig. 8) The reinforcing sheet sat directly on the tops of the floor beams. The system had an overall slab thickness of only 5 inches, in part because the beams were at a close spacing. (no author 1897, Freitag 1899)

The Columbian Floor system was an early bar-reinforced concrete slab. Bars with a cross or double-cross section were hung from the beam tops using light-gage steel straps to serve as flexural reinforcing in a cinder-concrete slab. (Fig. 9) The typical beam encasement provided the only shear transfer. (no author 1897, Birkmire 1898, Hool 1913)

Figure 10. Roebling Flat Slab Floor, showing strap reinforcing twisted at the beam top. (Freitag 1899).

The Roebling Flat Slab Floor was basically similar to the Columbian floor, except that the reinforcing was rectangular bars set vertically and twisted horizontally to rest on the floor beams. (Fig. 10) (Freitag 1899, Hool 1913)

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