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# 1609.6.2 Symbols and Notations

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Coefficients and variables used in the alternative all-heights method equations are as follows:

C_{net} | = | Net-pressure coefficient based on K[(_{d }G) (C) - (_{p}GC)], in accordance with Table 1609.6.2._{pi} |

G | = | Gust effect factor for rigid structures in accordance with ASCE 7 Section 26.9.1. |

K_{d} | = | Wind directionality factor in accordance with ASCE 7 Table 26-6. |

P_{net} | = | Design wind pressure to be used in determination of wind loads on buildings or other structures or their components and cladding, in psf (kN/m^{2}). |

NET PRESSURE COEFFICIENTS, *C*_{net}^{a, b}

STRUCTURE OR PART THEREOF | DESCRIPTION | C FACTOR_{net} | ||||

1. Main windforce- resisting frames and systems | Walls: | Enclosed | Partially enclosed | |||

+ Internal pressure | - Internal pressure | + Internal pressure | - Internal pressure | |||

Windward wall | 0.43 | 0.73 | 0.11 | 1.05 | ||

Leeward wall | -0.51 | -0.21 | -0.83 | 0.11 | ||

Sidewall | -0.66 | -0.35 | -0.97 | -0.04 | ||

Parapet wall | Windward | 1.28 | 1.28 | |||

Leeward | -0.85 | -0.85 | ||||

Roofs: | Enclosed | Partially enclosed | ||||

Wind perpendicular to ridge | + Internal pressure | - Internal pressure | + Internal pressure | - Internal pressure | ||

Leeward roof or flat roof | -0.66 | -0.35 | -0.97 | -0.04 | ||

Windward roof slopes: | ||||||

Slope < 2:12 (10°) | Condition 1 | -1.09 | -0.79 | -1.41 | -0.47 | |

Condition 2 | -0.28 | 0.02 | -0.60 | 0.34 | ||

Slope = 4:12 (18°) | Condition 1 | -0.73 | -0.42 | -1.04 | -0.11 | |

Condition 2 | -0.05 | 0.25 | -0.37 | 0.57 | ||

Slope = 5:12 (23°) | Condition 1 | -0.58 | -0.28 | -0.90 | 0.04 | |

Condition 2 | 0.03 | 0.34 | -0.29 | 0.65 | ||

Slope = 6:12 (27°) | Condition 1 | -0.47 | -0.16 | -0.78 | 0.15 | |

Condition 2 | 0.06 | 0.37 | -0.25 | 0.68 | ||

Slope = 7:12 (30°) | Condition 1 | -0.37 | -0.06 | -0.68 | 0.25 | |

Condition 2 | 0.07 | 0.37 | -0.25 | 0.69 | ||

Slope = 9:12 (37°) | Condition 1 | -0.27 | 0.04 | -0.58 | 0.35 | |

Condition 2 | 0.14 | 0.44 | -0.18 | 0.76 | ||

Slope = 12:12 (45°) | 0.14 | 0.44 | -0.18 | 0.76 | ||

Wind parallel to ridge and flat roofs | -1.09 | -0.79 | -1.41 | -0.47 | ||

Nonbuilding Structures: Chimneys, Tanks and Similar Structures: | ||||||

h/D | ||||||

1 | 7 | 25 | ||||

Square (Wind normal to face) | 0.99 | 1.07 | 1.53 | |||

Square (Wind on diagonal) | 0.77 | 0.84 | 1.15 | |||

Hexagonal or octagonal | 0.81 | 0.97 | 1.13 | |||

Round | 0.65 | 0.81 | 0.97 | |||

Open signs and lattice frameworks | Ratio of solid to gross area | |||||

< 0.1 | 0.1 to 0.29 | 0.3 to 0.7 | ||||

Flat | 1.45 | 1.30 | 1.16 | |||

Round | 0.87 | 0.94 | 1.08 | |||

2. Components and cladding not in areas of discontinuity—roofs and overhangs | Roof elements and slopes | Enclosed | Partially enclosed | |||

Gable of hipped configurations (Zone 1) | ||||||

Flat < Slope < 6:12 (27°) See ASCE 7 Figure 30.4-2B Zone 1 | ||||||

Positive | 10 square feet or less | 0.58 | 0.89 | |||

100 square feet or more | 0.41 | 0.72 | ||||

Negative | 10 square feet or less | -1.00 | -1.32 | |||

100 square feet or more | -0.92 | -1.23 | ||||

Overhang: Flat < Slope < 6:12 (27°) See ASCE 7 Figure 30.4-2A Zone 1 | ||||||

Negative | 10 square feet or less | -1.45 | ||||

100 square feet or more | -1.36 | |||||

500 square feet or more | -0.94 | |||||

6:12 (27°) < Slope < 12:12 (45°) See ASCE 7 Figure 30.4-2C Zone 1 | ||||||

Positive | 10 square feet or less | 0.92 | 1.23 | |||

100 square feet or more | 0.83 | 1.15 | ||||

Negative | 10 square feet or less | -1.00 | -1.32 | |||

100 square feet or more | -0.83 | -1.15 | ||||

Monosloped configurations (Zone 1) | Enclosed | Partially enclosed | ||||

Flat < Slope < 7:12 (30°) See ASCE 7 Figure 30.4-5B Zone 1 | ||||||

Positive | 10 square feet or less | 0.49 | 0.81 | |||

100 square feet or more | 0.41 | 0.72 | ||||

Negative | 10 square feet or less | -1.26 | -1.57 | |||

100 square feet or more | -1.09 | -1.40 | ||||

Tall flat-topped roofs h > 60 feet | Enclosed | Partially enclosed | ||||

Flat < Slope < 2:12 (10°) (Zone 1) See ASCE 7 Figure 30.8-1 Zone 1 | ||||||

Negative | 10 square feet or less | -1.34 | -1.66 | |||

500 square feet or more | -0.92 | -1.23 | ||||

3. Components and cladding in areas of discontinuity—roofs and overhangs | ||||||

Gable or hipped configurations at ridges, eaves and rakes (Zone 2) | ||||||

Flat < Slope < 6:12 (27°) See ASCE 7 Figure 30.4-2B Zone 2 | ||||||

Positive | 10 square feet or less | 0.58 | 0.89 | |||

100 square feet or more | 0.41 | 0.72 | ||||

Negative | 10 square feet or less | -1.68 | -2.00 | |||

100 square feet or more | -1.17 | -1.49 | ||||

Overhang for Slope Flat < Slope < 6:12 (27°) See ASCE 7 Figure 30.4-2B Zone 2 | ||||||

Negative | 10 square feet or less | -1.87 | ||||

100 square feet or more | -1.87 | |||||

6:12 (27°) < Slope < 12:12 (45°) Figure 30.4-2C | Enclosed | Partially enclosed | ||||

Positive | 10 square feet or less | 0.92 | 1.23 | |||

100 square feet or more | 0.83 | 1.15 | ||||

Negative | 10 square feet or less | -1.17 | -1.49 | |||

100 square feet or more | -1.00 | -1.32 | ||||

Overhang for 6:12 (27°) < Slope < 12:12 (45°) See ASCE 7 Figure 30.4-2C Zone 2 | ||||||

Negative | 10 square feet or less | -1.70 | ||||

500 square feet or more | -1.53 | |||||

Monosloped configurations at ridges, eaves and rakes (Zone 2) | ||||||

Flat < Slope < 7:12 (30°) See ASCE 7 Figure 30.4-5B Zone 2 | ||||||

Positive | 10 square feet or less | 0.49 | 0.81 | |||

100 square feet or more | 0.41 | 0.72 | ||||

Negative | 10 square feet or less | -1.51 | -1.83 | |||

100 square feet or more | -1.43 | -1.74 | ||||

Tall flat topped roofs h > 60 feet | Enclosed | Partially enclosed | ||||

Flat < Slope < 2:12 (10°) (Zone 2) See ASCE 7 Figure 30.8-1 Zone 2 | ||||||

Negative | 10 square feet or less | -2.11 | -2.42 | |||

500 square feet or more | -1.51 | -1.83 | ||||

Gable or hipped configurations at corners (Zone 3) See ASCE 7 Figure 30.4-2B Zone 3 | ||||||

Flat < Slope < 6:12 (27°) | Enclosed | Partially enclosed | ||||

Positive | 10 square feet or less | 0.58 | 0.89 | |||

100 square feet or more | 0.41 | 0.72 | ||||

Negative | 10 square feet or less | -2.53 | -2.85 | |||

100 square feet or more | -1.85 | -2.17 | ||||

Overhang for Slope Flat < Slope < 6:12 (27°) See ASCE 7 Figure 30.4-2B Zone 3 | ||||||

Negative | 10 square feet or less | -3.15 | ||||

100 square feet or more | -2.13 | |||||

6:12 (27°) < 12:12 (45°) See ASCE 7 Figure 30.4-2C Zone 3 | ||||||

Positive | 10 square feet or less | 0.92 | 1.23 | |||

100 square feet or more | 0.83 | 1.15 | ||||

Negative | 10 square feet or less | -1.17 | -1.49 | |||

100 square feet or more | -1.00 | -1.32 | ||||

Overhang for 6:12 (27°) < Slope < 12:12 (45°) | Enclosed | Partially enclosed | ||||

Negative | 10 square feet or less | -1.70 | ||||

100 square feet or more | -1.53 | |||||

Monosloped Configurations at corners (Zone 3) See ASCE 7 Figure 30.4-5B Zone 3 | ||||||

Flat < Slope < 7:12 (30°) | ||||||

Positive | 10 square feet or less | 0.49 | 0.81 | |||

100 square feet or more | 0.41 | 0.72 | ||||

Negative | 10 square feet or less | -2.62 | -2.93 | |||

100 square feet or more | -1.85 | -2.17 | ||||

Tall flat topped roofs h > 60 feet | Enclosed | Partially enclosed | ||||

Flat < Slope < 2:12 (10°) (Zone 3) See ASCE 7 Figure 30.8-1 Zone 3 | ||||||

Negative | 10 square feet or less | -2.87 | -3.19 | |||

500 square feet or more | -2.11 | -2.42 | ||||

4. Components and cladding not in areas of discontinuity —walls and parapets | Wall Elements: h ≤ 60 feet (Zone 4) ASCE 7 Figure 30.4-1 | Enclosed | Partially enclosed | |||

Positive | 10 square feet or less | 1.00 | 1.32 | |||

500 square feet or more | 0.75 | 1.06 | ||||

Negative | 10 square feet or less | -1.09 | -1.40 | |||

500 square feet or more | -0.83 | -1.15 | ||||

Wall Elements: h > 60 feet (Zone 4) See ASCE 7 Figure 30.6-1 Zone 4 | ||||||

Positive | 20 square feet or less | 0.92 | 1.23 | |||

500 square feet or more | 0.66 | 0.98 | ||||

Negative | 20 square feet or less | -0.92 | -1.23 | |||

500 square feet or more | -0.75 | -1.06 | ||||

Parapet Walls | ||||||

Positive | 2.87 | 3.19 | ||||

Negative | -1.68 | -2.00 | ||||

5. Components and cladding in areas of discontinuity—walls and parapets | Wall elements: h ≤ 60 feet (Zone 5) ASCE 7 Figure 30.4-1 | Enclosed | Partially enclosed | |||

Positive | 10 square feet or less | 1.00 | 1.32 | |||

500 square feet or more | 0.75 | 1.06 | ||||

Negative | 10 square feet or less | -1.34 | -1.66 | |||

500 square feet or more | -0.83 | -1.15 | ||||

Wall elements: h > 60 feet (Zone 5) See ASCE 7 Figure 30.6-1 Zone 4 | ||||||

Positive | 20 square feet or less | 0.92 | 1.23 | |||

500 square feet or more | 0.66 | 0.98 | ||||

Negative | 20 square feet or less | -1.68 | -2.00 | |||

500 square feet or more | -1.00 | -1.32 | ||||

Parapet walls | ||||||

Positive | 3.64 | 3.95 | ||||

Negative | -2.45 | -2.76 |

For SI: 1 foot = 304.8 mm, 1 square foot = 0.0929m^{2}, 1 degree = 0.0175 rad.

- Linear interpolation between values in the table is permitted.
- Some
*C*values have been grouped together. Less conservative results may be obtained by applying ASCE 7 provisions._{net}

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