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Re: NY State Building Code requirements

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----- Original Message -----
From: Mark Gilligan <MarkKGilligan(--nospam--at)compuserve.com>
Date: Wed, 25 Jun 2003 10:38:07 -0400

>The building code for NYC is unique and is not based on any of the model
>building codes (unless changed in the last few years).

A few years ago, I asked the NYC Building Department's Executive Engineer, the person who was responsible for maintaining the code, what the code was based on.  He told me BOCA.  FWIW, he took a buyout recently.

>The wind provisions in the NYC code are minimal, >and some would say inadequate.

Opinions vary.  To let others judge, I attached to this posting excerpts from the code in text form.  Please excuse the loss of formatting.

>It is my understanding that because of this state >of affairs that the engineers in NYC typically >follow ASCE 7 for  wind loads.

I suspect the real reason may be more because of familiarity with ASCE 7.
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§[C26-904.0] 27-569 Wind loads and earthquake loads. - (a) Wind loads. The structural frame and exterior
components of all buildings, tanks, and other exposed constructions shall be designed to resist the pressures due to wind as prescribed in reference standard RS 9-5. Wind shall be assumed to act from any direction. For continuous framing, the effects of partial loading conditions shall be considered.

REFERENCE STANDARD RS 9-5
MINIMUM DESIGN WIND PRESSURES
1. DESIGN WIND PRESSURES ON STRUCTURAL FRAMES.-Minimum design pressures due to wind acting
on vertical surfaces shall be in accordance with table RS 9-5.1, and minimum design pressures acting normal to horizontal or inclined surfaces shall be in accordance with table RS 9-5.2. The occurrence of the pressures on vertical, horizontal, and inclined surfaces of the building shall be considered as simultaneous.
TABLE RS 9-5.1 DESIGN WIND PRESSURES ON VERTICAL SURFACES
______________________________________________________________
Height Zone Design Wind Pressure on (ft. above curb level) Vertical Surfaces (psf of
projected solid surface)
______________________________________________________________
Structural Panels
Frame Glass
______________________________________________________________
0-50 (signs and similar constructions of shallow
depth only) .......??............ 15 ?
0-100 .................?......................... 20 30
101-300 ??...................................... 25 30
301-600 ...................?.?????? 30 35
601-1000 .................??????.? 35 40
Over 1000 ........................??............ 40 40
___________________________________________________________________________________
TABLE RS 9-5.2 DESIGN WIND PRESSURES ON HORIZONTAL AND INCLINED SURFACES
____________________________________________________________________
Roof Slope Design Wind Pressure Normal to Surface
____________________________________________________________________
30 degrees or less Either pressure or suction equal to 40 per cent
of the values in Table RS 9-5.1 over the en-
tire roof area
More than 30 degrees Windward slope-pressure equal to 60 per cent
of values in Table RS 9-5.1.
Leeward slope -suction equal to 40 per cent of
values in Table RS 9-5.1.
__________________________________________________________________________________________
2. WALL ELEMENTS.-For design of mullions, muntins, girts, panels, and other wall elements (including their
fastenings), other than glass panels, the wind pressure acting normal to wall surfaces shall be 30 psf or a 20 psf
suction, for all height zones up to 500 ft. These values shall be deemed to include allowance for gust pressures.
For height zones over 500 ft., the applicable design pressures shall be specifically investigated, but shall not be
less than the values indicated in table RS 9-5.1.
3. ROOF ELEMENTS.-The wind pressures acting on purlins, roofing, and other roof elements (including their
fastenings) supporting small contributory areas of wind presentment shall be 1 1/2 times the values given in table
RS 9-5.2.
4. OTHER BUILDING ELEMENTS.-Minimum wind pressures to be used in the design of other building
elements shall be the values in table RS 9-5.1 multiplied by the following shape factors given in table RS 9-5.3.
TABLE RS 9-5.3 SHAPE FACTORS
______________________________________________________________
Construction Shape Factor
______________________________________________________________
Signs (and their supports), or portions thereof, having
70 percent or more of solid surface .........................................???? 1.5
Signs (and their supports), or portions thereof, having less than
70 percent of solid suface ........................................................????. 2.0
Tanks, cooling towers, and similar constructions ............................???? 1.5
Upright, circular cylindrical surfaces...............................................????. 0.7
Square and rectangular chimneys ....................................................????. 1.5
___________________________________________________________________________________
For special structures such as curved and saw-toothed roofs, guys and cables, open trussed structures, parallel
solid girders, and spheres, the design wind pressure shall be determined on the basis of recognized engineering
analysis or by test.
5. EAVES AND CORNICES.-Eaves, cornices, and overhanging elements of the building shall be designed for
upward pressures of twice the values given in table RS 9-5.1.
6. WIND LOAD BY MODEL TEST.-In lieu of the design wind pressures established in sections 1 and 2 of
this reference standard, and subject to review and approval of the commissioner, design wind pressures may be
approximated from suitably conducted model tests. The tests shall be predicated on a basic wind velocity of 80
mph at the 30 ft. level, and shall simulate and include all factors involved in considerations of wind pressure,
including pressure and suction effects, shape factors, functional effects, gusts, and internal pressures and suctions.
**(4) 7. CONSTRUCTION ELEVATOR AND MATERIAL HOIST TOWER BACK STRUCTURES
DEFINITIONS:
Back Structure: A system of landing platforms and/or supports designed to transmit construction elevator or
material hoist tower loads into the building structure.
Inland: As defined by ASCE 7-98, exposure Category A
Coastal: As defined by ASCE 7-98, exposure Category D
WIND LOADS
{W} Storm Wind Load: equivalent to 25 yr. Mean recurrence wind per ASCE 7-98 standard, taking into account
the exposure terrain, height zone, shielding coefficients, etc. In lieu of detailed analysis by the design
professional, the following values may be used:
Design storm wind (25 yr. Mean Recurrence)
Wind pressure loading (in psf) on gross cross sectional area of the back structure
Zone
/Elevation
0-50 feet 50-150 feet 150-400 feet 400-700 feet >700 feet
Inland 14.4 20.7 25.6 33.8 40
Coastal 14.4 25.6 43.2 65.5 69.6
Unless the structure is fully enclosed in curtain walls, the following wind loading shall be analyzed:
1. Parallel to the building façade per the above table.
2. Normal to the building façade at one-half the value of the above table.
Wind directions shall be considered to be non-concurrent.
{w} In-Service wind: a 35 mph (wind pressure of 3.13 psf) from any direction acting on the back structure.
** DOB 9-2-01