Asce 7 Wind Load Example

[Suyay Escarsega]

Week2: Determine Wind Loads on a 1-story Warehouse

Introduction

Finding design wind speed

Directional procedure for MWFRS

Determine the MWFRS external and internal pressure coefficients

Learning Exercise - Using wind speed map utilities

Determine internal pressure coefficient

Calculate external MWFRS wind pressures on roof and walls

Determine C&C external pressure coefficients

Calculate C&C pressures for wall panels, wall girts, and roof trusses that span

Learning Exercise - Impact of openings on internal pressure coefficients

Conclusion

Week 3: Determine Wind Loads on a 50 ft. High Rectangular Building

Introduction

Finding design wind speed

Envelope procedure for MWFRS

Describe how to determine the MWFRS pressures on the parapet

Learning Exercise - Impact of terrain on exposure classification

Determine internal pressure coefficient

Calculate external MWFRS wind pressures on roof, walls and parapets

Determine C&C external pressure coefficients on roof, walls and parapets

Calculate C&C pressures for wall panels, wall girts, and roof trusses that span

Learning Exercise - Determine the effect parapets have on roof pressures

Conclusion

Week 4: Determine Wind Loads on Octagonal Building with Cupula 80 ft. tall

Introduction

Finding the wind speed

Describe how to determine the MWFRS pressures on the cupula

Determine the internal pressure coefficient

Learning Exercise - Theoretical exercises

Calculate external MWFRS wind pressures on roof and walls

Determine the loads at the cupula to roof connection

Determine C&C external pressure coefficients on roof and walls

Calculate C&C pressures for wall panels, wall girts, and roof framing

Learning Exercise - Practical exercises

Summary

Conclusion

Exam: Weeks 1-4

Week 5: Influence of Local Terrain on Wind Loads

Introduction

Description of Building and Local Wind Environment

Determination of Wind Speeds for Mapped Windspeed Locations

Determination of Wind Speeds for Special Wind Region

Learning Exercise - Theoretical exercises

Determination of Exposure Category for all Three Sites

Determination of Windward Wind pressure distribution for all Three Sites, and Comparison Among Sites

Modification of Wind Pressures for a Site on an Escarpment

Learning Exercise - Practical exercises

Conclusion

Week 6: Factors that Affect Wind Loads on a 10-story Building

Introduction

Description of Building

Surface Pressures and Overall Forces

Gust Factor Basics

Learning Exercise - Theoretical Exercises

Influence of Gust Factor on MWFRS Forces

Overview of Wind Load Determination

Learning Exercise - Practical Exercises Conclusion

Week 7: Comparison of Directional and Envelope Procedures for determining wind loads on two buildings

Introduction

Description of building systems and locations. Determination of basic parameters for the buildings

Determination of Wind Loads for the Hotel using the Directional Procedure

Determination of Wind Loads for the Hotel using the Envelope Procedure

Learning Exercise - Theoretical exercise

Determination of Wind Loads for the Metal Building using the Directional Procedure

Determination of the Wind Loads for the Metal Building using the Envelope Procedure

Comparison and Discussion of Results for the Two buildings

Learning Exercise - Practical Exercises

Conclusion

Week 8: Determine Base Shear and Overturning Moments for a 20-Story office Building in Austin, Texas (Using the Directional Procedure)

Introduction

Description of Building, Intended Structural Systems, and Wind Environment

Determination of Wind Pressures and Pressure Coefficients

Determination of Lateral Loads and Torsional Loads

Learning Exercise - Theoretical exercise

Analytical Model and Wind Forces on MEFRS

Discussion on Possible Advantages for Using a Wind Tunnel Test

Learning Exercise - Practical exercise

Conclusion

Exam: Weeks 4-8

Week 9: Determine Wind Loads on Roof Mounted Equipment

Introduction

Description of the roof top equipment in conjunction with roof plan and height

Determining velocity pressures for various heights required by the problem

Determining wind force on air handling equipment

Learning Exercise - Theoretical exercise

Determining wind force on chimney

Determining wind force on trussed tower

Determine wind force on solid sign

Learning Exercise - Practical exercise

Conclusion

Week 10: Determine Wind Loads on Tanks and Chemical Processing Equipment

Introduction

Resources and how they are different (ASCE 7 and Wind Loads for Petrochemical and Other Industrial Facilities)

Determine velocity pressures for the various equipment types

Determine wind forces on both large and small tanks

Learning Exercise - Theoretical exercise

Determine wind forces on pressure vessel and cooling tower

Determine wind forces on pipe rack and partially clad open frames

Finding components and cladding wind pressures for industrial equipment

Learning Exercise - Practical exercise

Conclusion

Week 11: Determine Wind Loads on Roof Mounted Solar Collectors

Introduction

Limitations on use of ASCE 7 provisions for roof mounted solar collectors

Solar panel collector layout

Differences in solar panel provisions between sloped panels and parallel to roof panels

Learning Exercise - Theoretical exercise

Describe how differences in building plan affect solar panel layout

Determine wind pressures for the various solar panel configurations

Using C&C pressure coefficients

Practical exercise

Learning Exercise - Practical exercise

Conclusion

In this article, an example wind load pressure calculation for an L-shaped building in Cordova, Tennessee will be shown. This calculation will be in accordance with ASCE 7-16 wind load calculations (directional procedure).

A similar calculation for a gable roof construction using ASCE 7-10 (imperial units) is referenced in this example and can be accessed using this link. The formula in determining the design wind pressure are:

The first thing in determining the design wind pressures is to classify the risk category of the structure, which is based on the use or occupancy of the structure. Since this example is a plant structure, the structure is classified as Risk Category IV. See Table 1.5-1 of ASCE 7-16 for more information about risk categories classification.

Depending on the wind direction selected, the exposure of the structure shall be determined from the upwind 45 sector. The exposure to be adopted should be the one that will yield the highest wind load from the said direction. The description of each exposure classification is detailed in Section 26.7.2 and 26.7.3 of ASCE 7-16.

For our example, since the location of the structure is in a farmland in Cordova, Memphis, Tennessee, without any buildings taller than 30 ft, therefore the area is classified as Exposure C. A helpful tool in determining the exposure category is to view your potential site through a satellite image (Google Maps for example).

Given: The enclosed office building shown in Figure 7.4.1.1. The building is located in a region with a wind speed (3-sec gust) of 120 mph. The exposure is Exposure C. The building is on flat terrain.

For this part of the problem we need to determine pressure coefficients for the locations shown in Figure 7.4.1.2 as well as for the side walls. These coefficients are then combined with the gust factor and velocity pressures to obtain the external pressures in each region.

For the roof, the slope angle is 14.0 degrees. This is close to 15 degrees and probably not worth interpolating between the values given in ASCE 7-05 Figure 6-6. We also need to know that h/L = 25.1'/50' = 0.50. From the Figure we get that the values of Cp for the Windward side of the roof is -0.70 and -0.18. These values represent two different load cases. For the Leeward side, Cp is -0.50.

The net forces are found by multiplying the appropriate pressures by the areas over which they act. In this building all but the gable ends are rectangles, making the area calculation easier. Note that we are computing actual surface areas (as opposed to projected areas) in each of the cases below. Also, the sign is important. Negative signs indicate a force that is outward from the surface and a positive sign is inward. All forces are normal to their respective surfaces.

Figure 7.4.1.4 defines the pressures (with the exception of the lateral/side wall pressures) that need to be computed for wind loading from the E/W direction. In this case we combined all the leeward wall segments into one because they all have the same pressures.

Note that some of the pressures are applied to differently oriented surfaces. When the same pressure is applied to a different surface, we have chosen to label on as "a" and the other as "b". See Figure 7.4.1.5 for force applications. Four cases are computed, based on combinations of maximum/minimum roof pressures and + internal pressures.

Wind load analysis, which involves the computation of forces exerted by the wind on structures like building or fixtures, is a crucial aspect of structural engineering. Wind can exert significant lateral forces on a structure, which can cause it to sway or even collapse if it is not properly designed to withstand these loads.

To ensure the integrity of the structure is maintained, structural engineers must take steps to accurately analyze and transfer these lateral loads using various structural elements. By doing so, they can help to ensure that the building remains stable and safe for its occupants, particularly in regions prone to severe weather conditions such as hurricanes or typhoons.

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