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Wind Forces on Building Elements

id Forces on Building Elements

DK3 350预应力混凝土梁中桥工程施工组织设计Net pressures on solid surface areas of enclosed building without dominant openings (defined inAppendixB1.1)aregiven by:

Wind loads on temporary buildings and associated constructions that are not used for residency,and which will remain inposition fora oeriodof not morethanoneyear,maybedesigned for a minimumof 70%of thedesignloadsforpermanentbuildings. For designing hoarding and covered walkway associated with construction site, contractor shed,bamboo shed, tent or marquee that arenotforresidentialuse,Qzistakenas37%ofQozdefined in clause3.2and no otheradjustmentfactorshouldbeapplied.

Design Wind Pressures

3.2 Wind Reference Pressure at Effective Height

Sheltering Effects

The effects of direct shelter from other buildings surrounding a site may be taken into account by using a reduced height, i.e. the effective height, Ze, for calculation of wind pressure, turbulence intensity and force coefficient.The method of calculating effective height is given in Appendix A2.

Zemay conservativelybe taken as the actual height, Z, aboveground level.可保守取地面以上高度

Topography Effects

The effects of topography should be estimated as defined in Appendix A3.

Force and Pressure Coefficients

This section gives force and pressure coefficients for assessing total wind force on buildings and building elements respectively.They are foruse in the equations of Section 2.

Forbuildings.forcecoefficientsforrectangularplanaregivenin clause4.2.1.Considerationsofmodificationsonrectangularplanare giveninclauses4.2.2and4.2.3.Conditionswherebuildingplanscan oe treated as rectangles are given in clause 4.2.4. Forcecoefficients for buildings of circular plan with height to diameterrationotlargerthan6canbetakenas0.75.

ffect of Variation of Plan with Heigh

The force coefficient for rectangular buildings with rounded corners can bereducedbased on smooth rounding of the corners with a radius, r, by the factor:

For unsymmetrical corners,the corner that produces leastreduction shallbetaken

For a building with wings, the force coefficients should be calculated as for a rectangular building based on the dimensions of the equivalent rectangle.

Net Pressure Coefficients for an Enclosed Building Envelope without Dominant Openings

Net Pressure Coefficients for an Enclosed Building

Net pressure coefficients for an enclosed building envelopewithout dominant openings, Cp

Wind reference height and zone scaling dii towersetback fromedgeofpodium

Pressure Coefficients for Building Envelopewith Dominant Openings

(a)The solidity ratio is equal to the effective projected area of the openframework divided bythe area enclosed bythe boundary of the frame normalto the direction of the wind. (b)Linear interpolation is allowed to obtain intermediate values. (c)Pressures are applied to the solid area of the framework only.

(a)The solidity ratio is equal to the effective projected area of the openframework divided bythe area enclosed bythe boundary of the frame normalto the direction of the wind. (b)Linear interpolation is allowed to obtain intermediate values. (c) Pressures are applied to the solid area of the framework only.

Additional pressure coefficients for building attachments are given in Appendix B2.1 to B2.3.

Additional pressure coefficients for building attachments are given in Appendix B2.1 to B2.3.

Size Factor

Size Factor and Size and Dynamic Factor

Size and Dynamic Factor for Buildings

ize and Dynamic Factor for Buil

This factor can be reduced over the height of the building using formulabelow:

某百丈水库枢纽工程施工组织设计TheseformulasaredimensionalwithunitsofmetresandHertz Forbuildingsoflessthan5Omheight,the followingsimplified formula can beused tocalculate S.at all heights:

1WindModelingandInstrumentation

Requirements for Wind Tunnel Testing

Whereresonantdynamicresponsemaybesignificant,thestructure should beaccurately represented (physically or analytically)in mass distribution and stiffness in accordance with established laws of dimensional scaling and theeffect of dampingshouldbe appropriately reflected. Forbuildingsclosetoprismaticform and withH/Band H/Dless than15,itmaybeassumedforthecalculationofresonant (dynamic) amplification of thewind responsesthat only the lowest frequency modes in eachlateral directionand in torsion(3modes intotal)neec tobeconsidered

HJ 996.2-2018 污染源源强核算技术指南 农副食品加工工业一淀粉工业The topography model should include the majority of the topographic features likely to have a significantinfluence on the wind conditions atthesite. A minimum of 18 wind directions at 20° intervals is necessary. The topographic multiplier obtained from the measured wind profiles of a topographic wind tunnel test can be calculated using the formula below:

approachis from the wind profile approaching the test model and at the sameheightaboveground

If the loading on a building is likely to be significantly influenced by the presence of surrounding buildings or topographic features, it is necessary to includethe models of theseproximity features in the windtunneltesting. The proximity model should include all buildings which may significantly affect windiness around the development.A general guide is that the extent of theproximity model should normally be not less than 400m radius from the site. Wherethe local topographyis too largetobe sensiblyaccounted forin the proximity model, its effects should be accounted for as described in clause 6.1.3. A minimum of 36 wind directions at 1oointervalsisnormally necessaryforpressures andloads