N.Y.C. Admin. Code § EBC H102: Section EBC H102: In-Place Archaic and Legacy Structural Systems or Assemblies

H102.1 Archaic and legacy structural systems.

Existing structural systems and structural elements found in buildings are described in Sections H102.2 through H102.3, as applicable. Archaic and legacy systems and assemblies include components installed based on empirical methods or vernacular methods predating engineering standardizations that were not confirmed by numerical methods or engineering theory. Methods of evaluating archaic and legacy systems and assemblies are permitted to be based on manufacturer’s technical literature, articles published by nationally recognized engineering journals and standards organizations, and general engineering principles.

H102.2 Fireproof floor systems.

Fireproof floor systems that were load tested or approved according to methods specified within the New York City Building Code may be allowed to support gravity loads permitted by this code and the New York City Building Code without testing or listing individual component material properties in accordance with Sections H102.2.1 through H102.2.5.

H102.2.1 Stone, brick, or terra cotta segmental arch floors.

Stone, brick, or terra cotta segmental arch floors that met the geometric requirements specified in prior versions of the New York City Building Code may be allowed to support code-listed gravity loads without testing or listing individual material properties. Arch thrust in spans where work is performed and in adjacent spans shall be taken into consideration when alterations are made, and the structural integrity of individual terra cotta units shall be maintained.

H102.2.2 Unreinforced masonry and concrete arch floors.

Unreinforced masonry and concrete arch floors that were approved by the department or other city or New York state agencies based on load testing may be allowed to support code-listed gravity loads without testing or listing individual material properties. Arch thrust in spans where work is performed and in adjacent spans shall be taken into consideration when alterations are made, and the structural integrity of individual terra cotta units shall be maintained. Corrugated iron-arch floors with cinder or stone concrete fill shall be analyzed as concrete arches using the material and geometry observed. Deterioration of the iron-arch material shall be assessed for removal of loose overhead sections.

H102.2.3 Draped mesh concrete floors.

Draped-mesh concrete slabs are one-way concrete slabs spanning between encased metal beams reinforced with wires or wire mesh designed to carry floor gravity loads through catenary action. Commonly made with cinder concrete (concrete with coal cinders as coarse aggregate) but sometimes with stone concrete. Load is transferred from the slabs to the beams through both the encasement and the wires. Draped mesh concrete floors that were designed using the formulas specified in prior versions of the New York City Building Code

may be allowed to support code-listed gravity loads without testing or listing individual material properties in accordance with the following:

w = (3CA

s

) / L

2

(Equation H-1)

where:

w is the allowable gross uniform load on the floor (psf).

A

s

is the cross-sectional area of the main reinforcement (in

2

/ ft of slab width).

L is the clear span between steel-beam flanges (ft).

C is a coefficient as set forth below in note b.

Note b: C is 20,000 psi for lightweight concrete (including cinder concrete) with continuous reinforcing; 14,000 psi for lightweight concrete (including cinder concrete) with reinforcing hooked or attached at 1 or both supports; 23,000 psi for stone concrete with continuous reinforcing; 15,000 psi for stone concrete (with reinforcing hooked or attached at 1 or both supports).

L may not exceed 10 feet (3048 mm) for gross floor load of 200 psf or less; L may not exceed 8 feet (2438 mm) for gross floor load that exceeds 200 psf.

Reinforcing wire must have an ultimate stress of at least 55,000 psi.

C may be increased by the ratio of the actual ultimate stress to 55,000 psi, up to a maximum 30 percent increase.

Where the slabs have been exposed to water (at the roof or at areas with plumbing) or have been previously altered, the reinforcing shall be examined for deterioration or cuts that reduce continuity or anchorage. Steel beams in cinder concrete areas exposed to water shall be examined for loss of section. Drawings for new alterations shall include details to preserve continuity and anchorage.

H102.2.4 Proprietary reinforced concrete systems.

Proprietary reinforced concrete systems with capacity listed in the drawings that were approved by the department based on load testing may be allowed to support code-listed gravity loads without testing or listing individual material properties.

H102.2.5 Proprietary floor and roof deck systems.

Proprietary floor and roof deck systems identified with prior approval by a city agency for use are not required to be strengthened provided alterations do not cause the sum of the live and dead loads to exceed the previously approved capacity limits.

H102.3 Other systems.

Other systems that have been used in New York shall be evaluated based on general engineering principles and investigations. Design references obtained from various sources, including but not limited to manufacturer’s literature, published manuals, and previous codes are permitted to be used for reference for systems and construction techniques described in Sections H102.3.1 through H102.3.15.

H102.3.1 Open web joists.

Open web joists that predate Steel Joist Institute standards issued in 1928 shall be analyzed as steel trusses.

H102.3.2 Buildings with relieving walls.

In masonry bearing wall buildings where wood-joist floors are carried above and connected by wood-stud walls parallel to the masonry bearing walls, the contribution of such relieving walls to floor and roof support shall be considered when designing alterations. The relieving walls shall be analyzed as wood bearing walls per this code and shall not be removed without providing other adequate supports to the floors.

H102.3.3 Bowstring trusses.

Wood trusses made from lightweight members, typically nominal or true two-inch members, with straight lower chords, arched upper chords and lattice or diagonal web members, were typically constructed between 1900 and the 1960. Where repairs or alterations involve bowstring trusses, the wood species and grade shall be identified, and the capacity of the truss shall be re-evaluated using material tensile capacity from current standards. The presence of lateral bracing, end conditions, splices within chords, and end connections between chords at supports shall be determined when performing any condition assessment.

Exception: Where bowstring trusses have been previously evaluated and reports accepted by the department, the tension demand-capacity ratio of bottom chord and web members need not be re-evaluated as long as no new loads are added to the truss.

H102.3.4 Cast iron columns.

Alterations involving cast iron columns shall comply with the following items:

1. Cast iron columns and supported framing shall not be altered so as to create eccentricity that causes net tension or increases existing net tension in the shaft of the column. Cast iron columns shall not be used to resist shear or bending due to wind and seismic loads.

2. Data from coupon testing of cast iron shall not be used as the basis for general design strength. See Section H103.3.

3. Structural cast iron shall not be welded.

H102.3.5 Early reinforced concrete.

Reinforced-concrete structure constructed before 1941 may have designs that are not recognized by current code, including beams without stirrups or columns without lateral or vertical reinforcing. Analysis of such structures shall include the effects of reduced anchorage, shear capacity, and confinement.

H102.3.6 Guastavino arch systems.

Arch and vault construction used for floors (see Item 2 of Section H102.2), roofs, domes, and ceilings, composed of multiple layers of solid, flat, thin tiles set in thick mortar beds. Analysis of Guastavino structures shall use thin-shell arch and vault methods.

H102.3.7 Gypsum decks.

Poured in place gypsum floor and roof decks utilize draped reinforcing mesh spanning over steel bulb tees supported by steel joist or wood framing members. Analysis shall use original manufacturer's design data or catenary formulas based on field-measured reinforcing.

H102.3.8 Nogging walls.

Wood-framed bearing walls with brick placed between wood studs or timbers as insulation or fireproofing shall be analyzed as wood-frame buildings under this code. Brick between studs shall not be considered structural but, unless replaced with material of sufficient fire resistance, shall be preserved as fire separation, including repairs to the mortar if needed.

H102.3.9 Gypsum block partitions.

Lightweight gypsum unit masonry used for partitions, usually in fire-rated buildings. These partitions shall be laterally braced and shall not be used to support any gravity load other than self-weight. Alterations shall maintain existing fire separation requirements of these partitions.

H102.3.10 Structural clay tile and terra cotta partitions.

Lightweight unit masonry used for partitions, usually in fire-rated buildings. These partitions shall be laterally braced and may be loadbearing or nonload-bearing. Alterations shall maintain existing fire separation requirements of these partitions.

H102.3.11 Reverse arch masonry foundations.

Strip footings consisting of inverted masonry arches supporting individual columns or piers. Where alterations to the structure above change the differential loading between adjacent columns or piers, the effect on the arches shall be analyzed. The arches shall not be altered in a manner that reduces their continuity unless an alternate load path is provided.

H102.3.12 Stone structural elements.

Where members of natural stone used as arches, beams, slabs, walls, or foundation elements are subject to an alteration, their carrying capacity shall be evaluated using ASTM standards for stone. The type of stone and flaws (inclusions, veining, and non-isotropic properties) shall be considered in the analysis.

H102.3.13 Tongue and groove wood diaphragms.

Tongue and groove wood diaphragms shall be analyzed for lateral load as lumber diaphragms in accordance with the “Special Design Provisions for Wind & Seismic” set forth in the National Design Specification for Wood Construction.

H102.3.14 Rubble masonry.

Allowable compressive stress on masonry and foundation wall construction using irregularly shaped and random-sized stones shall be according to Table H103.5, provided the presence and condition of the mortar is satisfactory, that the mortar fills the voids between the stones and there is sufficient unweathered binder to maintain cohesion. The condition assessment of rubble walls shall include the condition of the mortar at the interior of the wall. Such assessment shall take into account that the mortar joints are wide and can be as much as 30 percent of the wall volume.

H102.3.15 Post-installed anchors.

Anchors installed in the horizontal or upwardly inclined position when the anchors are supporting a sustained tension load shall not be used in floors composed of terra cotta, gypsum, or cinder concrete unless they pass the test procedure in Section 1709.3 of the New York City Building Code.