5/4/2018
What is a canopy and which wind forces should I use to design? - Engineering Express®
What is a canopy and which wind forces should I use to design?
Note: Updated March 2018 in response to 3 negative negative user feedback comments for for more information. Please thumb this up! A canopy is a structure which provides overhead protection from the the elements such as rain, snow, snow, or sunlight. Canopies can be attached to a structure or they can be free standing with their own supports. They can be constructed of a variety of materials including steel, concrete, aluminum, wood, or even fabric. According to ASCE 7-10, canopies are to be designed to resist wind loads, roof live loads, dead loads, snow loads, rain loads, seismic loads, wind-on-ice loads, and weight of ice loads. ASCE 7-10 permits canopies to be designed for wind loading using equations for Open Buildings or Other Structures and Building Appurtenances depending on a variety of factors to be discussed further below. In order to determine the applied wind pressures, ASCE 7-10 has a variety of factors that affect wind loading such as wind speed, risk category, exposure category, category, flow type, etc. The code requires us to apply all of the aforementioned loads simultaneously, however we are allowed to reduce these loads based upon the load combinations specified in ASCE 7 and design our system based on the least favorable loading scenario applied in all directions. Along with ASCE 7-10, canopies are designed designed in conjunction with the governing building code in the municipality in which the project is located [i.e. Florida Building Code Sixth Edition (2017) or the 2018 International Building Code] which can contain other design limitations such as allowable member deflections and the newer use of ASCE 7-16 which is forthcoming and has many additions to the below. Free Standing Free standing canopies are self-supporting roof systems without walls such as pavilions or walkway covers. These structures are designed using the Open Buildings portion of ASCE 7-10. The wind flow for these structures can either be clear or obstructed depending on obstructions below the roof. Obstructed wind flow is considered when 50% or more of the area below the surface of the roof is composed of objects inhibiting wind flow such as a canopy atop a concrete basin at a wastewater treatment plant. Canopies with less than 50% obstructions below the roof surface would be considered clear. Components & cladding and MWFRS (main wind force resisting system) wind loading are used to design
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What is a canopy and which wind forces should I use to design? - Engineering Express®
the different elements of these structures. See ASCE 7 Main Wind Force vs. Components & Cladding Explained (MWFRS vs. C&C) for a description on when to apply C&C vs. MWFRS wind loading. Host Attached Host attached canopies rely on the superstructure for stability such as suspended canopies, louvered roofs, or fabric awnings. Wind loading on host attached canopies depends on the size of the canopy in relation to the superstructure and its location on the building. There is a new section in ASCE 7-16 called Attached Canopies on Buildings which address wind loading on these structures. However due to the lack of provisions in ASCE 7-10, host attached canopies are designed using the Roof Overhangs sections of the code. When the canopy is small in respect to the building which is common in commercial applications (see image below), the canopy is to be designed as a Roof Overhang Component. Wind tunnel tests (see images below) have confirmed that the entire canopy should be designed using C+C wind loading. Roof Overhang Components
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What is a canopy and which wind forces should I use to design? - Engineering Express®
MWFRS Roof Overhangs When the canopy is similar in size to the building which is common in residential applications (see image below), the canopy is to be designed for MWFRS Roof Overhang wind loading.
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What is a canopy and which wind forces should I use to design? - Engineering Express®
Trellises and Sunshades Trellises and sunshades are porous which allow wind/rain/snow to pass through them and are utilized to reduce sunlight. The porous nature of these roofs doesn’t allow a pressure differential to occur between the opposing faces of the roof surface and therefore are designed using the Other Structures and Building Appurtenances portions of ASCE 7-10. These wind pressures are applied vertically and laterally to the structure to develop the least favorable loading conditions. In addition, trellises and sunshades are required to resist a 300-pound concentrated load placed anywhere on the structure to simulate a maintenance worker standing on the roof surface.
Article provided and updated by Zachary A. Rubin, E.I.
Mar 28, 2016 2069 Codes & Standards, Engineering Principles ASCE 7-10 , ASCE 7-16 , Attached Canopies On Buildings , Building Appurtenances , C+C , Canopy , Carports & Canopies , Clear Wind Flow , Components , Loading , Main Wind Force Resisting System , MWFRS , Obstructed Wind Flow , Open Buildings , Other Structures & Mounts , Pavilion , Porosity , Sunshade , Trellis , Walkway Cover , Wind Tunnel Test Total 10 Votes:
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KNOWLEDEBASE Should A Professional Utilize The ASD (“Allowable Stress Design”) Method Or The LRFD (“Load Resistance Factored Design”) Method When Calculating The Required Wind Pressure For Use With Tested / Approved Systems?
1864 4 0 Did The Loading Requirements Change For Rooftop Structures For ASCE 7-10 And The 2014 Florida Building Code?
1017 1 0 What Wind Speed Should I Use For My Project?
4010 1 0 ASCE 7 Exposure Categories And How Exposure ‘D’ Works
12996 6 0 Why Are Spacing, Edge Distance, And Embedment Important For Concrete Anchors?
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POPULAR WIKI ARTICLES Should A Professional Utilize The ASD (“Allowable Stress Design”) Method Or The LRFD (“Load Resistance Factored Design”) Method When Calculating The Required Wind Pressure For Use With Tested / Approved Systems?
1864 4 0 Did The Loading Requirements Change For Rooftop Structures For ASCE 7-10 And The 2014 Florida Building Code?
1017 1 0 What Wind Speed Should I Use For My Project?
4010 1 0 ASCE 7 Exposure Categories And How Exposure ‘D’ Works
12996 6 0 Why Are Spacing, Edge Distance, And Embedment Important For Concrete Anchors?
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