The types of buildings and structures included in Risk Category III suggest that life safety is most important for health care facilities. The new criteria continue that judgment based definition by including the coastal areas that are approximately consistent with those given in prior editions of ASCE 7 for Risk Category II.
A straight translation of the and mph wind speeds from ASCE to the year return period maps in ASCE would yield triggers of mph and mph respectively. This is due to the changes in the hurricane simulation model that reduces the magnitude of wind speeds for long return periods.
However, while the applicability of the WBDR has essentially been shifted by 10 mph, the applicable region for Risk Category II and Risk Category III buildings excluding health care facilities has be substantially narrowed and eliminated in some places as compared to the regions applicable in ASCE and prior editions.
Design pressures for both roof and wall surfaces are determined directly from a set of tables. In addition to the normal limitations listed in Chapter 27 Section Enclosed simple diaphragm building as defined in Section The procedure can be applied for buildings with either rigid or flexible diaphragms as discussed in Section Net wind pressures for wall and roof surfaces are determined from Tables A procedure is also specified for determining pressures for roof parapets see Figure Loads from the tables are applied to the walls and roof simultaneously.
The step by step procedure is defined at the front of Chapter 27 Part 2 Table An excerpt from Table For roofs, the procedure covers flat, gable, hip, monoslope and mansard roofs as referenced in Table For wall pressures determined from Table The uppermost row in the table defines ph which is the roof pressure at the top of the building. The lower row shown shaded defines p0 which is the pressure at the base of the building. A linear variation of pressure between the two is to be used in design as shown at the front of Table It is to be noted that the procedure includes the calculation of the Gust Effect Factor based on conservative assumptions for building frequency and damping.
Further details on the derivation of tabulated pressure values can be found in the commentary to ASCE The method for CC covers both wall and roof surfaces. Roof and wall pressures for flat, gable, mansard, hip and monoslope roof buildings are covered Table Tabulated pressures are shown for five zones that include all wall and roof surfaces as shown in the figures in Table The step by step procedure is defined at the front of Chapter 30 Part 4 in Table However, pressures for all exposures can be determined by applying the Exposure Adjustment Factor shown in a graph within the table.
Tabulated values are shown for an effective wind area of 10 sf but reduction factors are shown in graphs part of the table for other effective wind areas.
The various factors are applied to the tabulated pressures according to Equation A procedure is also specified for determining pressures on parapets refer to Figure An excerpt to Table Minimum wind load pressure was increased from 10 psf to 16 psf to account for the change in load factors. Improved exposure and roughness examples. New figures were added to the commentary to provide examples on how to determine exposure conditions for different roughness conditions around the building. Provisions for roof-top equipment.
Provisions have been added to quantify both lateral and vertical wind loads on rooftop equipment. The reorganization and change in the return period of the wind speed maps has made the overall format of the wind load provisions similar to that of the ASCE 7 seismic provisions. Wind Eng. Peterka, J. Vickery, and T. Stafford, T. Wadhera, M. Powell and Y. Wadhera, L. Twisdale Jr. Lavelle, b. Steckley and L. Vickery, P. Skerlj and L.
Wadhera, J. Galsworthy, J. Peterka, P. Irwin, and L. Related Papers. By Arkan J. By Peter Vickery and Jon Galsworthy. By Rizki P. Chapter 16 Structural Loads. By vikash patsariya. Design Wind Speeds in the Caribbean. By Peter Vickery. Download pdf. Log in with Facebook Log in with Google. Remember me on this computer. Enter the email address you signed up with and we'll email you a reset link. Need an account? Click here to sign up.
Visit FileOpen to see the full list. In this helpful guide, authors Coulbourne and Stafford focus on the provisions that affect the planning, design, and construction of buildings for residential and commercial purposes. Whereas the revision of ASCE 7 has retained the previously reorganized wind load provisions, the important changes in the ASCE wind load provisions are. New provisions for roof top solar arrays, canopies, and bins, tanks, and silos; and. This updated guide introduces readers to the relevant sections of the standard and provides an extensive overview of the design procedures and the revised wind speed maps.
This guide includes 14 chapters with 10 worked examples of real-life design problems applying the appropriate use of analytical and simplified procedures for calculating wind loads for a variety of common structure types, as well as answers to more than 30 frequently asked questions, grouped by topic. William L. Coulbourne, P.
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