ASCE Tsunami Design Zone Maps for Selected Locations. American . Minimum Design Loads for Buildings and Other Structures (ANSI/ASCE ). ANSI/ASCE Book set: ASCE 7ISBN (print): ISBN (PDF): Committee of Management Group F, Codes and Standards, of ASCE. The objective of the Guide to the Use of the Wind Load Provisions of ASCE is to provide guidance in the use of the wind load provisions set forth in ASCE.
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Documents Flashcards Grammar checker. For the purposes of this document, all figures and tables for this section are located at the end of the section. Temporary bracing should be provided to resist wind assce on structural components and structural assemblages during erection and construction phases.
This section specifies a minimum wind load to be applied horizontally on the entire vertical projection of the building as shown in Fig. This load case is to be applied as a separate load case in addition to the normal load cases specified in other portions of Chapter 6.
These terms are used throughout the standard and are provided to clarify application of the standard provisions. Can consist of a structural frame or an assemblage of structural elements that work together to transfer wind loads acting on the entire structure to the ground.
These definitions relate to the proper selection of internal pressure coefficients, GC pi. Building, open and building, partially enclosed are specifically defined. All other buildings are considered to be enclosed by definition, although there may be large openings in two or more walls.
An example of this is a parking garage through which the wind can pass. Cladding receives wind loads directly. Examples of components include fasteners, purlins, girts, studs, roof decking, and roof trusses. Components can be part of the MWFRS when they act as shear walls or roof diaphragms, but they may also be loaded as individual components. The engineer needs to use appropriate loadings for design of components, which may require certain components to be designed for more than one type of loading, for example, long-span roof trusses should be designed for loads associated with MWFRSs, and individual members of Minimum Design Loads for Buildings and Other Structures trusses should also be designed for component and cladding loads [Ref.
Examples of cladding include wall coverings, curtain walls, roof coverings, exterior windows fixed and operable and doors, and overhead doors. Effective wind area is the area of the building surface used to determine GC p.
This area does not necessarily correspond to the area of the building surface contributing to the force being considered. In the usual case, the effective wind area does correspond to the area tributary to the force component being considered. For example, for a cladding panel, the effective wind area may be equal to the total area of the panel. For a cladding fastener, the effective wind area is the area of cladding secured by a single fastener.
A mullion may receive wind from several cladding panels. In this case, the effective wind area is the area associated with the wind load that is transferred to the mullion.
The second case arises where components such as roofing panels, wall studs, or roof trusses are spaced closely together. The area served by the component may become long and narrow. To better approximate the actual load distribution in such cases, the width of the effective wind area used to evaluate GC p need not be taken as less than one third the length of the area.
This increase in effective wind area has the effect of reducing the average wind pressure acting on the component.
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Note, however, that this effective wind area should only be used in determining the GC p in Figs. The induced wind load should be applied over the actual area tributary to the component being considered.
For membrane roof systems, the effective wind area is the area of an insulation board or deck panel if insulation is not used if the boards are fully adhered or the membrane is adhered directly to the deck. If the insulation boards or membrane are mechanically attached or partially adhered, the effective wind area is the area of the board or membrane secured by a single fastener or individual spot or row of adhesive.
For typical door and window systems supported on three or more sides, the effective wind area is the area of the door or window under consideration.
For simple spanning doors i. A building or other structure is considered flexible if it contains a significant dynamic resonant 77-95.
Resonant response depends on the gust structure contained in the approaching wind, on wind loading pressures generated by the wind flow about the building, and on the dynamic properties of the building or structure.
Gust energy in the wind is smaller at frequencies above about 1 Hz. Therefore, the resonant response of most buildings and structures with lowest natural frequency above 1 Hz will be sufficiently small that resonant response can often be ignored.
A useful calculation procedure for natural frequency or period for various building types is contained in commentary Section C6. Defining the limits of applicability of the analytical procedures within the standard is a difficult process, requiring a balance between the practical need to use the provisions past the range for which data has been obtained and restricting use of the provisions past the range of realistic application.
Wind load provisions are based primarily on wind-tunnel tests on shapes shown in Figs. Extensive windtunnel tests on actual structures under assce show that relatively large xsce from these shapes can, in many cases, have minor changes in wind load, while in other cases seemingly small changes can have relatively large effects, particularly on cladding pressures. Wind loads on complicated shapes are frequently smaller than those on the simpler shapes of Figs.
Buildings that are clearly unusual should use the provisions ascd 6. The defining criteria for rigid, in comparison to flexible, is that the natural frequency is greater than or equal to 1 Hz. A general guidance is that most rigid buildings and structures have height to minimum width less 7-59 4. Where there is concern about whether or not a building or structure meets this adce, the provisions ascd commentary section C6.
Some buildings located in a wind-borne debris region may not be vulnerable to wind-borne debris. For example, an isolated building located a substantial distance 7-9 natural and man-made debris sources would unlikely be impacted by debris, provided that building acse from the building ascee not blown off, and provided that awce containers, lawn furniture, and other similar items where not in the vicinity of the building. However, ASCE 7 does not allow an exception for such buildings to be excluded from the ascs applicable to buildings in a xsce debris region.
While wind-borne debris can occur in just about any condition, the level of risk in comparison to the postulated debris regions and impact criteria may be also be lower than that determined for the purpose of standardization.
For example, asfe buildings may be sited away from likely debris sources that would generate significant risk of impacts similar in magnitude to pea gravel i.
This situation describes a condition of low vulnerability only as a result of limited debris sources within the vicinity of the building. In other cases, potential sources of debris may be present, but extenuating conditions can lower the 7–95.
These extenuating conditions include the type of materials and surrounding construction, the level of protection offered by surrounding exposure conditions, and the design wind speed.
Therefore, the risk of impact may differ from those postulated as a result of the conditions specifically enumerated in the standard and the referenced impact standards. The committee recognizes that there are vastly differing opinions, even within the standards committee, regarding the significance of these parameters that are not fully considered in developing standardized debris regions or referenced impact criteria.
Two figures are provided. Note that for the MWFRS in a diaphragm building, the internal pressure cancels for loads on the walls, but must be considered for the roof.
This is true because when wind forces are transferred by horizontal diaphragms e. Once transferred into the horizontal diaphragms by the wall systems, the wind forces become a net horizontal wind force that is delivered to the vertical elements. The equal and opposite internal pressures on the walls cancel each other in the horizontal diaphragm.
Method 1 combines the windward and leeward pressures into a net horizontal wind pressure, with the internal pressures canceled. The user is cautioned to consider the precise application of windward and leeward wall loads to members of the roof diaphragm where openings may exist and where particular members, such as drag struts, are designed.
For the designer to use Method 1 for the design of the MWFRS, the building must conform to all of the requirements listed in Section 6. Method 1 is based on the low-rise procedure from Method 2, as shown in Fig.
Guide to the Use of the Wind Load Provisions of ASCE
However, the torsional loading from Fig. As a result, the last requirement in Section 6. In the case of simple diaphragm buildings, here are several other concepts that will aid the user in determining if item 10 of Section 6. Generally buildings with a MWFRS in each principal direction consisting of one of the following would not be torsionally sensitive: Buildings with flexible diaphragms are not sensitive to torsion because the diaphragms are incapable of transferring the torsional moments.
Rigid roof and floor diaphragms distributing lateral force to two shear walls, braced frames, or moment frames of approximately equal stiffness that are spaced apart a distance not less than 50 percent of the width of the building normal to the principal axis. Rigid roof and floor diaphragms distributing lateral force to any number of vertical MWFRS elements of various stiffness, 7-59 of which meets ssce following at each level of the building: The torsional sensitivity of lateral ssce with more distributed stiffness is difficult to determine, however Eq.
C was developed as -795 check to ssce if the distribution of lateral forces is such that torsion will not control the design. This equation was derived based on the polar moment of inertia and relative ascw of ascs lateral elements for a building. Although it appears complex, this solution is actually very simple for most buildings covered by Method 1.
The equation is derived from the traditional analysis of the distribution of lateral loads to walls in a masonry bearing wall building. C illustrates the geometry involved in Eq. Multiplying factors are provided for other Minimum Design Loads for Buildings and Other Structures November 8, exposures and heights.
The following values have been used in preparation of the figures: Wall elements resisting two or more simultaneous windinduced structural actions e. The horizontal loads in Fig. These wall elements must also be checked for the various separately acting not simultaneous component and cladding load cases. Main wind-force resisting roof members spanning at least from the eave to the ridge or supporting members spanning at least from eave sace ridge are not required to be designed for the higher end zone loads.
The interior zone loads should be applied. This is due to the enveloped nature of the loads for roof members. The component and cladding tables in Fig. The pressures can be modified to a different exposure and 7-59 with the same adjustment factors as the MWFRS pressures.
For the acse to use Method 1 for the design of the components and cladding, 7-59 building must conform to all five requirements in Section 6.
A building may qualify for use of Method 1 for its components and cladding only, in which case, its MWFRS should be designed using Method 2 or 3. The analytical procedure provides wind pressures and forces for the design of MWFRSs and for the design of components and cladding of buildings and other structures. The procedure involves the determination of wind directionality and a velocity pressure, the selection or determination of an appropriate gust effect factor, and the selection of appropriate pressure or force coefficients.
The procedure allows for the level of structural reliability required, the effects of differing wind exposures, the speed-up effects of certain topographic features such as hills and escarpments, and the size and geometry of the building or other structure under consideration.
The procedure differentiates between rigid and flexible buildings and other structures, and the results generally envelope the most critical load conditions for the design of MWFRSs as well as components and cladding. The standard in Section 6. A rational procedure to determine directional ace loads is as follows.
Wind load for buildings using Section 6. The sector with the exposure giving highest loads will be used to define wind 7: For example, for winds from the north, the exposure from sector one or eight, whichever gives the highest load, is used.