N.Y.C. Admin. Code § BC 3102: Section BC 3102: Membrane Structures

3102.1 General.

The provisions of Sections 3102.1 through 3102.8 shall apply to air-supported structures, air-inflated structures, membrane-covered cable structures, membrane-covered frame structures and tents, and tensile membrane structures, collectively known as membrane structures.

3102.1.1 Certificates of Occupancy.

The duration of Certificates of Occupancy for air-inflated structures, air-supported structures, and tents shall be limited in accordance with the requirements of Chapter 1 of Title 28 of the Administrative Code.

3102.1.2 Temporary installations.

In addition to the requirements of Section 3102 of this code, temporary installations of air-supported structures, air-inflated structures, membrane-covered cable structures, tensile membrane structures, membrane-covered frame structures and tents, collectively known as membrane structures shall comply with the requirements of Article 111 of Chapter 1 of Title 28 of the Administrative Code.

3102.2 Definitions.

The following terms are defined in Chapter 2:

AIR-INFLATED STRUCTURE.

AIR-SUPPORTED STRUCTURE.

Double skin.

Single skin.

CABLE-RESTRAINED, AIR-SUPPORTED STRUCTURE.

MEMBRANE-COVERED CABLE STRUCTURE.

MEMBRANE-COVERED FRAME STRUCTURE.

NONCOMBUSTIBLE MEMBRANE STRUCTURE.

TENSILE MEMBRANE STRUCTURE.

TENT.

3102.3 Type of construction.

Noncombustible membrane structures shall be classified as Type IIB construction. Noncombustible frame or cable-supported structures covered by an approved membrane in accordance with Section 3102.3.1 shall be classified as Type IIB construction. Heavy timber frame-supported structures covered by an approved membrane in accordance with Section 3102.3.1 shall be classified as Type IV construction. Other membrane structures shall be classified as Type V construction.

3102.3.1 Membrane and interior liner material.

Membranes and interior liners shall be either noncombustible as set forth in Section 703.5, or meet the fire propagation performance criteria of Test Method 1 or Test Method 2, as appropriate, of NFPA 701 and the manufacturer's test protocol.

3102.4 Allowable floor areas.

The area of a membrane structure shall not exceed the limitations specified in Section 506.

3102.5 Maximum height.

Membrane structures shall not exceed one story nor shall such structures exceed the height limitations in feet specified in Section 504.3. Membrane structures may be erected above the roof of a building provided that such roof is of noncombustible construction required to have a fire-resistance rating.

Exception: Noncombustible membrane structures serving as roofs only.

3102.6 Mixed construction.

Membrane structures shall be permitted to be utilized as specified in this section as a portion of buildings of other types of construction. Height and area limits shall be as specified for the type of construction and occupancy of the building.

3102.6.1 Noncombustible membrane.

A noncombustible membrane shall be permitted for use as the roof or as a skylight of any building or atrium of a building of any type of construction provided such membrane is not less than 20 feet (6096 mm) above any floor, balcony or gallery, and meets the fire classification requirements of Section 1505 for roof assemblies.

3102.6.1.1 Membrane.

A membrane meeting the fire propagation performance criteria of Test Method 1 or Test Method 2, as appropriate, of NFPA 701 shall be permitted to be used as the roof or as a skylight on buildings of Type IIB, III, IV and V construction, provided such membrane is not less than 20 feet (6096 mm) above any floor, balcony or gallery, and meets the fire classification requirements of Section 1505 for roof assemblies.

3102.7 Engineering design.

Membrane structures, except tensile membrane structures, shall be designed and constructed to sustain dead loads; loads due to tension or inflation; live loads including wind, snow or flood and seismic loads and in accordance with Chapter 16 and Appendix G.

3102.7.1 Lateral restraint.

For membrane-covered frame structures, the membrane shall not be considered to provide lateral restraint in the calculation of the capacities of the frame members.

3102.7.2 Design.

Tents, air-inflated structures, and air-supported structures shall be designed by either an alternate engineering design approved by the commissioner or as follows:

1. Tents. Tents shall be guyed, supported, and braced to withstand a wind pressure of 10 psf (478.8 Pa) of projected area of the tent. The poles and their supporting guys, stays, stakes, fastenings, etc., shall be of sufficient strength and attached so as to resist wind pressure of 20 psf (957.6 Pa) of projected area of the tent.

2. Air-inflated structures and air-supported structures.

2.1. Air-inflated structures and air-supported structures shall be anchored to the ground or supporting structure by either ballast or positive anchorage, sufficiently and evenly distributed, and adequate to resist the inflation lift load, the aerodynamic lift load, and the drag (shear) load due to wind impact. The latter factors shall be based on a fastest mile wind speed of 70 mph (112.65 km/hr), and an estimated stagnation of not less than 0.5 q for structures on grade whose height is equal to, or less than, the width of the structure. For greater heights, or for elevated structures, increased anchorage shall be provided, justified by analytical and/or experimental data subject to approval by the commissioner.

2.2. The skin of the structure shall be of such strength, and the joints so constructed, as to provide a minimum dead load strip tensile strength at 70°F (21°C) of four times the 70 mph (121.65 km/hr) design load (inflation and aerodynamic loading). The joints shall provide a dead load strip tensile strength of 160°F (71°C) of twice the 70 mph (121.65 km/hr) design load (i.e., a factor of safety of 4 and 2, respectively). In addition, the material shall provide a trapezoidal tear strength of not less than 15 percent of the maximum design tensile load. Material and joint strengths shall be so certified by the manufacturer, justified by analytical and/or experimental data.

3102.7.3 Tensile membrane structures.

The design and construction shall be in accordance with ASCE 55. The provisions of Sections 3102.1 through 3102.6 shall also apply.

3102.8 Inflation systems.

Air-supported structures and air-inflated structures shall be provided with primary and auxiliary inflation systems to meet the minimum requirements of Sections 3102.8.1 through 3102.8.3.

3102.8.1 Equipment requirements.

The primary inflation system shall consist of one or more blowers and shall include provisions for automatic control to maintain the required inflation pressures. Such system shall be so designed as to prevent overpressurization of the system.

3102.8.1.1 Auxiliary inflation system.

In addition to the primary inflation system, in structures exceeding 1,500 square feet (140 m

2

) in area, an auxiliary inflation system shall be provided with sufficient capacity to maintain the inflation of the structure in case of primary system failure. The auxiliary inflation system shall operate automatically when there is a loss of internal pressure and when the primary blower system becomes inoperative. Initiation of auxiliary inflation system shall be indicated by an audible and visual alert at the entrance or a regularly attended location.

3102.8.1.2 Blower equipment.

Blower equipment shall meet all of the following requirements:

1. Blowers shall be powered by continuous-rated motors at the maximum power required for any flow condition as required by the structural design.

2. Blowers shall be provided with inlet screens, belt guards and other protective devices as required by the commissioner to provide protection from injury.

3. Blowers shall be housed within a weather-protecting structure.

4. Blowers shall be equipped with backdraft check dampers to minimize air loss when inoperative.

5. Blower inlets shall be located to provide protection from air contamination. The location of inlets shall be approved.

3102.8.2 Standby power.

Wherever an auxiliary inflation system is required, an approved standby power-generating system shall be provided. However, notwithstanding Section 2702.1, the standby power-generating system shall be equipped with a suitable means for automatically starting the generator set upon failure of the normal electrical service and for automatic transfer and operation of all of the required electrical functions at full power within 60 seconds of such service failure. Standby power shall be capable of operating independently for not less than 4 hours. Initiation of standby power shall be indicated by an audible and visual alert at the entrance or a regularly attended location.

3102.8.3 Support provisions.

A system capable of supporting the membrane in the event of deflation shall be provided for in air-supported structures and air-inflated structures having an occupant load of 50 or more or where covering a swimming pool regardless of occupant load. Such support system shall be capable of maintaining the membranes not less than 7 feet (2134 mm) above the floor, seating area or surface of the water. When air-supported structures or air-inflated structures are used as a roof on Type I or II construction buildings, such support system shall be capable of maintaining the membranes not less than 20 feet (6096 mm) above the floor or seating area.

3102.9 Separation.

No air-inflated structure, air-supported structure, or tent shall be erected closer than 20 feet (6096 mm) to any interior lot line nor closer than 30 feet (9144 mm) in any direction to an unprotected opening, required exterior stairway or corridor, or required exit door, on the same level or above the level of such structure. Such structure may abut another building on the same tax lot if the following conditions exist:

1. No unprotected openings or exits are located above or within 30 feet (9144 mm) of such structure.

2. No doors serving as a required exit are located between such structure and the abutted building.

3. The exterior wall of the abutted building meets the requirements of Section 705 for fire walls.

3102.10 Exits.

In addition to the requirements of Chapter 10, travel distance to an exit from any point within a tent, air-supported structure, or air-inflated structure shall not exceed 75 feet (22 860 mm).

3102.10.1 Exit openings from tents.

Exit openings from tents shall remain open unless covered by a flame-resistant curtain of a contrasting color to the tent. Such curtain shall be supported not less than 80 inches (2032 mm) above the floor level at the exit and, when open, no part of the curtain shall obstruct the exit.

3102.10.2 Exit openings from air-supported structures and air-inflated structures.

Exit doors in air-supported structures and air-inflated structures shall close automatically against normal operational pressures. Opening force at the edge of such doors shall not exceed 15 pounds (6.80 kg), with the structure at operational pressure. Exit doors shall be located in frames constructed such that they will remain operative and support the weight of the pressurized membrane structure in a state of total collapse.