Wind Speed to Pressure Conversion Tables For Sunrooms – Pergolas – Overhead Canopies (MPS 20-25696)

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Description

This master plan provides ASCE 7-16 wind pressure values for a variety of open & host enclosed patio, pergola, conopy & sunroom conditions, wind speeds, and exposures. It is designed to be used in conjunction with certified roof and wall patio component performance tables to provide a complete package for permit.
Note: To purchase more detailed answers that may save you money, visit our online wind speed to pressure calculator click here.
This certification is generic and installations beyond this scope or site specific applications shall require custom engineering that can be performed by Engineering Express. For states not listed here, please contact us.
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Click Here for our online tool that provides better answers than this generic chart.

 

Click Here to learn more about why this was created and the problem it solves.


For variations of this plan, click here - select 'Revision To One Of Our Projects' when asked, & reference the MPS SKU number listed herein.

Additional information

Weight .32 oz
Dimensions .01 × 11 × 17 in
Plan Designer

Engineering Express

Plan Type

Manufacturer-Based Plan, Master Plan Sheet – MPS, Wind Pressure Chart

Plan Format

Digitally Sealed File, Sealed Hardcopy

Material

Glass, Window

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When is a Fence or Railing 75% Open?

The Scenario
The question comes up from time to time regarding requirements for a fence or railing to be 75% open (such as in the Lighthouse Point FL Building Code Amendments).  This is the case for example in Florida when overlooking the Intracoastal in Broward County.  This porosity also affects the design calculations for the components and foundation as affected by wind. The porosity of a barrier system varies with the components used.  For the condition of the requirement of a barrier to be designed such that it resists a 4" sphere, two scenarios below are offered for consideration.  
The Calculation
The first uses a 1" picket and standard components to develop the porosity calculation.  You'll see by the formula presented that the porosity is 71%, below the 75% requirement which is typically used in our calculation for member and foundation integrity, and thus labeled on our design plans as the critical design factor.    Engineering Express 1 inch picket porosity calculation   Switching the pickets to 3/4" which is also permitted on our plans yield the desired 75% porosity calculation with other standard dimensions and extrusions:   Engineering Express three quarter inch picket porosity calculation   Engineering Express® can help you with all your fence, railing, and gate needs using a variety of our state of the art resources.  Browse our Online Store for pre-engineered Safeguard Master Plan sheets, browse our expanding array of online calculators, or request a quote for a site specific project in any of the 21+ states to which we are licensed.
 

ASCE 7 Basic Wind Speed

Per definition by ASCE 7-10, Section 26.2 is defined as:   BASIC WIND SPEED (V): Three-second gust speed at 33ft (10m) above the ground in Exposure C (see Exposure Categories) as determined in accordance with ASCE 7-10 Section 26.5.1.   The wind shall be assumed to come from any horizontal direction. The basic wind speed shall be increased where records or experience indicate that the wind speeds are higher than those reflected in ASCE 7-10 Section 26.5.1.   Most local jurisdictions have set their own Basic Wind Speeds. Check out Engineering Express’s Database of Local Windspeeds: EXD4-10 ASCE 7-10 Vult Windspeeds.
 

ASCE 7 EXPOSURE CATEGORIES AND HOW EXPOSURE ‘D’ WORKS

About Exposure D

Exposure 'D' is a multiplier when converting wind velocity to wind pressure that represents coastal areas.  It's used in many formulas in ASCE 7 for wind, a larger topic than covered here.  Non coastal areas have Exposure categories B and C.  Exposure D is a moving target from the coastline based on several factors, the height of the building in question being a major one. Below is a how to checklist.  Be sure to see our graphic attached for an easier visual representation.
1. CONFIRM SURFACE ROUGHNESS DISTANCE AND THE INITIATION POINT OF EXPOSURE D: The Initiation pPoint (Ip) of Exposure D occurs at the point on land where "Surface Roughness D" prevails in the upwind direction for a distance of 5000 feet minimum (Think: the runway for wind approaching the structure shall be at least a mile - 5,280ft to create an exposure D area or start / insertion point). INITIATION POINT (Ip) = SURFACE ROUGHNESS > 5000FT 2. DETERMINE DISTANCE OF STRUCTURE FROM THE INITIATION POINT (Sdist). 3. CONFIRM PRIMARY EXPOSURE D REGION: The primary Exposure D condition occurs (for all structures) from the Exposure D Initiation Point at the directly exposed coastline area (that mark that was at the end of the runway above), running inland for a distance of 600 feet (Dprimary = 600 FT) (Think: Any structure 600 ft from what we have determined creates exposure D).  AND IF (Sdist) < (Dprimary) THEN EXPOSURE D APPLIES 4. CONFIRM BUILDING-SPECIFIC EXPOSURE D REGION: A secondary Exposure D condition may occur based on the structure itself. To determine the building-specific Exposure D region, multiply the Mean Roof Height (MRH) of the structure by 20 (Dsecondary=MRH*20). Compare Dsecondary to the Sdist. (Think:  D can be greater than 600ft from this insertion point if the distance of the structure is less than or equal to the height of the structure * 20). IF (Sdist) < (Dsecondary) THEN EXPOSURE D APPLIES Click for larger image of visual explanation of Exposure D

Other Exposure Categories:

(With excerpts from the ASCE 7-05 Commentary to help explain):
 

Exposure Category A

Exposure A was deleted. Previously, Exposure A was intended for heavily built-up city centers with tall buildings. However, the committee has concluded that in areas in close proximity to tall buildings the variability of the wind is too great, because of local channeling and wake buffeting effects, to allow a special category A to be defined. For projects where schedule and cost permit, in heavily built-up city centers, Method 3 is recommended because this will enable local channeling and wake-buffeting effects to be properly accounted for. For all other projects, Exposure B can be used.
 

Exposure Category B

  Exposure B Example 3     Exposure B Example 2     Exposure B Example 1  

Exposure Category C

  Exposure C Example 2     Exposure C Example 1    

How to use the ASCE 7-10 Components & Cladding Wind Pressure Calculator

If you'd prefer to hear this in Spanish, use the video below.
Si prefiere escuchar esto en español, utilice el siguiente vídeo.


 

ASCE 7 Main Wind Force vs. Components & Cladding Explained (MWFRS vs. C&C)

ASCE 7 separates wind loading into three types: Main Wind Force Resisting System (MWFRS), Components and Cladding (C&C), and Other Structures and Building Appurtenances. MWFRS is defined as “(a)n assemblage of structural elements to provide support and stability for the overall structure.” Typically, members which receive loading from two surfaces are designed to resist MWFRS loading. Let’s say you had a steel moment resisting frame building with metal roof and wall panels as pictured above, you would design the moment frames and the spread footings at the base of the frames to resist MWFRS loading from the lateral wind pressure on the wall panels and positive/negative wind pressure on the roof panels. C&C is defined as “(e)lements of the building envelope that do not qualify as part of the MWFRS”. Let’s take the metal building again shown above as an example. The metal roof and wall panels would be considering cladding. The overhead door, walk door, and window would be considered components. Also, the roof purlins and wall girts are receiving loading from the cladding and are therefore considered components as well. The wind pressure then varies on these components and cladding based upon their respective effective wind area. Other Structures and Building Appurtenances are defined as “rooftop structures, rooftop equipment, solid freestanding walls, freestanding solid signs, chimneys, tanks, open signs, lattice framework, and trussed towers”. Let’s say we were to add a rooftop mounted mechanical air conditioning unit to the roof purlins of our metal building, we would use this section of the code to determine the appropriate wind loading on the mechanical unit itself. Article provided and updated by Zach Rubin, EI

How to Find Wind Speed Using the Applied Technology Council Hazards by Location Website

The Applied Technology Council (ATC) offers site-specific information that is used in our calculators to determine the wind velocity. For the best results, the address of the site may be used. To find your wind speed, follow the step-by-step guide below. 
    1. Navigate to https://hazards.atcouncil.org/#/ 
    2. Enter your address, zip code, or city and state in the search bar and press the search button. Image 1
    3. On the left side of the screen, check that the “wind” tab is selected.Image 2
    4. Determine your wind speed based on your Risk Category. Wind speeds may differ depending on if ASCE 7-05, ASCE 7-10, or ASCE 7-16 is being used. If you are unsure, please check with an Engineering Express Technician.
    5. Using the ASCE 7-10 definitions for Risk Categories I-IV:
        1. Use Risk Category I for “buildings and other structures that represent a low risk to human life in the event of failure.” Such as fences or gates.
        2. Use Risk Category II for “all buildings and other structures except those listed in Risk Categories I, III, and IV.” Such as canopies or pergolas. Most Engineering Express calculators will ask for Risk Category II wind speeds.  
        3. To use Risk Category III, contact Engineering Express for a site-specific design. Use Risk Category III for “buildings and other structures, not included in Risk Category IV, with potential to cause a substantial economic impact and/or mass disruption of day-to-day civilian life in the event of failure; buildings and other structures not included in Risk Category IV (including, but not limited to, facilities that manufacture, process, handle, store, use, or dispose of such substances as hazardous fuels, hazardous chemicals, hazardous waste, or explosives) containing toxic or explosive substances where their quantity exceeds a threshold quantity established by the authority having jurisdiction and is sufficient to pose a threat to the public if released.” 
        4. To use Risk Category IV, contact Engineering Express for a site-specific design. Use Risk Category IV for “buildings and other structures designated as essential facilities; buildings and other structures, the failure of which could pose a substantial hazard to the community; buildings and other structures (including, but not limited to, facilities that manufacture process, handle, store, use, or dispose of such substances as hazardous fuels, hazardous chemicals, or hazardous waste) containing sufficient quantities of highly toxic substances where the quantity exceeds a threshold quantity established by the authority having jurisdiction to be dangerous to the public if released and is sufficient to pose a threat the public if released; or buildings and other structures required to maintain the functionality of other Risk Category IV structures.”
      Image 3
Works Cited
Engineers, American Society of Civil. Minimum Design Loads for Buildings and Other Structures (ASCE Standard). American Society of Civil Engineers, 2010.
“Hazards by Location.” ATC Hazards by Location, Applied Technology Council, hazards.atcouncil.org/.

ASCE 7 Least Horizontal Dimension

The Least Horizontal Dimension can be taken as the shortest possible distance that can be taken between two parallel lines that fully encompass the building The Least Horizontal Dimension is further demonstrated as follows: Where B is the Least Horizontal Dimension.    

ASCE 7 Wall and Roof Zones Explained

Per ASCE 7-10, buildings are composed of 5 different zones, depending on the wind loading they are subjected to. These zones are defined as follows:
Zone 1: Has the lowest load; this zone accounts for approximately 80% of the roof surface, represented in the interior zones of the roof. Zone 2: Higher loading than Zone 1; this zone accounts for approximately 15% of the roof surface, represented in the perimeter of the roof. Zone 2H: Used for roof overhang area along the perimeter of Zone 2. Zone 3: Has the highest load; this zone accounts for about 5% of the roof surface, represented the corners of the roof. Zone 3H: Used for roof overhang area along the perimeter of Zone 3. Zone 4: Any areas between the wall corners that are not included within Zone 5. Zone 5: 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but not less than either 4 percent of least horizontal dimension or 3 ft (0.9 m). Key Terms and Definitions: Mean Roof Height (h) Least Horizontal Dimension. The interpretation of zones should be left to a licensed professional engineer when in doubt.  Otherwise, the most critical zone is suggested. An illustration of where zones are applied comes from ASCE 7 table 30.7-2 for enclosed buildings less than or equal to h = 160'; whereas, each zone is equal to 'a' unless noted otherwise: ASCE 7 Wind Zone Figure Below is a video that helps illustrate how the zone 5 vortexes form and how to better understand the theory of the zone 5 effect.  Keep in mind when watching that the wind has to come from an opposing direction (all structures are analyzed with wind approaching from all angles), and create the turbulent effects in the video.  Areas protected from the turbulent effect are generally not wind zone 5.  

Additionally per AAMA TIR A-15-14, zones 4 & 5 can be further explained as:

170 Degrees: Unobstructed exterior corner is considered Zone 5 if angle < 170 degrees open as shown

 

ASCE Risk Categories Explained

Background

Building codes require that buildings be classified by their level of importance in determining the risk taken with safety factors against their failure under critical design loads. Calculations for the structure's overall stability, flexure, and fatigue are all based on the assumption of a given risk category design level.  ASCE 7 references risk category factors typically referenced in building codes (table 1.5.1 ASCE 7-10). ASCE 7 officially defines risk category as A categorization of buildings and other structures for determination of flood, wind, snow, ice, and earthquake loads based on the risk associated with unacceptable performance. The loose theory regarding risk categories is that a structure with a risk category I should theoretically fail before a II, III, or IV. Morally, a risk category I structure should not cause undue damage to its neighboring structures, but barring that moral issue they should fail before the neighboring habitable host structures.  Examples of structures design-able as category I structures would be freestanding signs which could list or break over and technically fail before a building but cause no damage to the building, screen and patio-sunroom enclosures, tool sheds, greehouses, etc.  A more complete list and description is below from IBC/FBC building codes: Risk Categories are used to find an appropriate design wind velocity for determining corresponding design pressures to design structures and building components. The process is RISK CATEGORY > WIND VELOCITY > WIND PRESSURES > FORCES > DESIGN. to see wind speeds for your area based on respective risk categories, click here To determine corresponding design wind pressures for openings, click here for our interactive design pressure calculator and more on the topic and see this article  

TABLE 1604.5

RISK CATEGORY OF BUILDINGS AND OTHER STRUCTURES

RISK CATEGORY NATURE OF OCCUPANCY
I Buildings and other structures that represent a low hazard to human life in the event of failure, including but not limited to:
• Agricultural facilities.
• Certain temporary facilities.
• Minor storage facilities.
II Buildings and other structures except those listed in Risk Categories I, III and IV.
III Buildings and other structures that represent a substantial hazard to human life in the event of failure, including but not limited to:
• Buildings and other structures whose primary occupancy is public assembly with an occupant load greater than 300.
• Buildings and other structures containing Group E occupancies with an occupant load greater than 250.
• Buildings and other structures containing educational occupancies for students above the 12th grade with an occupant load greater than 500.
• Group I-2 occupancies with an occupant load of 50 or more resident care recipients but not having surgery or emergency treatment facilities.
• Group I-3 occupancies.
• Any other occupancy with an occupant load greater than 5,000.a
• Power-generating stations, water treatment facilities for potable water, wastewater treatment facilities and other
public utility facilities not included in Risk Category IV.
• Buildings and other structures not included in Risk Category IV containing quantities of toxic or explosive materials that:
Exceed maximum allowable quantities per control area as given in Table 307.1(1) or 307.1(2) or per
outdoor control area in accordance with the California Fire Code; and
Are sufficient to pose a threat to the public if released.b
IV Buildings and other structures designated as essential facilities, including but not limited to:
• Group I-2 occupancies having surgery or emergency treatment facilities.
• Fire, rescue, ambulance and police stations and emergency vehicle garages.
• Designated earthquake, hurricane or other emergency shelters.
• Designated emergency preparedness, communications and operations centers and other facilities required for emergency response.
• Power-generating stations and other public utility facilities required as emergency backup facilities for Risk Category IV structures.
• Buildings and other structures containing quantities of highly toxic materials that:
Exceed maximum allowable quantities per control area as given in Table 307.1(2) or per outdoor control
area in accordance with the California Fire Code; and
Are sufficient to pose a threat to the public if released.b
• Aviation control towers, air traffic control centers and emergency aircraft hangars.
• Buildings and other structures having critical national defense functions.
• Water storage facilities and pump structures required to maintain water pressure for fire suppression.
  1. For purposes of occupant load calculation, occupancies required by Table 1004.1.2 to use gross floor area calculations shall be permitted to use net floor areas to determine the total occupant load.
  2. Where approved by the building official, the classification of buildings and other structures as Risk Category III or IV based on their quantities of toxic, highly toxic or explosive materials is permitted to be reduced to Risk Category II, provided it can be demonstrated by a hazard assessment in accordance with Section 1.5.3 of ASCE 7 that a release of the toxic, highly toxic or explosive materials is not sufficient to pose a threat to the public.

About ASCE 7’s Directionality Factor Kd

The directionality factor (Kd) used in the ASCE 7 wind load provisions for components and cladding is a load reduction factor intended to take into account the less than 100% probability that the design event wind direction aligns with the worst case building aerodynamics.   Per ASCE 7-10,Section 26.6, the Directionality Factor Kd is defined as a parameter that makes the design more rational by considering the dependencies of the wind speed, the frequency of occurrence of extreme wind and the aerodynamic property on wind direction. The wind Directionality Factor Kd is affected by the frequency of occurrence and the routes of typhoons, climatological factors, large-scale topographic effects and so on.   See Table 26.6-1 below for the Wind Directionality Factors required per structure type. kd values   The question then comes as to whether load combinations exist for windows & doors.  According to a declaratory statement published by the state of Florida, they do exist and the above can be used.   Additionally, Broward County publishes a 'deemed to comply' document inside the HVHZ allowing Kd=0.85 to be used for windows and doors.   Last, ASCE 7-16 has addressed this issue and clarified the use of Kd=0.85 for component and cladding design in a revised table.
 

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