1、55.1CHAPTER 55SEISMIC- AND WIND-RESISTANT DESIGNSEISMIC-RESISTANT DESIGN 55.1Terminology . 55.2Calculations . 55.2Applying Static Analysis 55.3Computation of Loads at Building Connection . 55.6Ansi Steel Bolts 55.7Lag Screws into Timber 55.7Concrete Post-Installed Anchor Bolts 55.7Weld Capacities 55
2、.8Seismic Snubbers . 55.8Seismic Restraints 55.9Restraint of Pipe and Duct Risers 55.10Examples 55.11Installation Problems . 55.14WIND-RESISTANT DESIGN . 55.15Terminology 55.15Calculations . 55.16Wall-Mounted HVAC these act onthe center of gravity. The analysis assumes the equipment does notmove dur
3、ing an earthquake; thus, the sum of the forces andmoments must be zero. When calculating the overturning moment,including an uplift factor, the vertical component Fpvat the center ofgravity is typically defined (for the IBC) to beFpv = 0.2SDSD (5)If the equipment being analyzed is isolated, the fina
4、l computedforce must be doubled per section 1621.3.1 of the code.Per section 1621.1.7 of the code, forces used when computingthe loads for shallow (under 8 bolt diameter) embedment anchorsare to be increased by a factor of 1.3Rp.Per section 1621.3.12.2 of the code, the only permitted expan-sion anch
5、ors for non-vibration-isolated equipment over 7.46 kW areundercut anchors.Tables 4 and 5 contain brief listings of Ssfactors that can be usedto calculate the magnitude of the horizontal static seismic forceacting at the equipment center of gravity. Values for IBC 2006 areavailable on the USGS web si
6、te for U.S. locations or in Tables F-2and G-2 of DOD (2005) for worldwide locations.1.3 APPLYING STATIC ANALYSISThe prescriptive method in the IBC allows that an equivalentstatic force can be calculated that represents the dynamic motions ofan earthquake. The static forces acting on a piece of equip
7、ment arevertical and lateral forces resulting from the earthquake, the force ofgravity, and forces at the restraints that hold the equipment in place.The analysis assumes that the equipment does not move during theearthquake and that the relative accelerations between its center ofgravity and the gr
8、ound generate forces that must be balanced byreactions at the restraints. Guidance from the code bodies indicatesthat equipment can be analyzed as though it were a rigid component;however, a factor apis applied in the computation to address flexi-bility issues on particular equipment types or flexib
9、le mountingarrangements. (Note: for dynamic analysis, it is common to use a5% damping factor for equipment and a 1% damping factor for pip-ing.) Although the basic force computation is different, the detailsof load distribution in the examples that follow apply independentlyof the code used.The forc
10、es acting on the restraints include both shear and tensilecomponents. The application direction of the lateral seismic accel-eration can vary and is unknown. Depending on its direction, it islikely that not all of the restraints will be affected or share the loadequally. It is important to determine
11、 the worst-case combination ofTable 1 IBC Seismic Analysis RequirementsComponent Operation Required forLife SafetyBuilding Seismic Design Category*Required Analysis TypeAnchorageEquipment StructuralCapacityEquipment OperationalCapacityCertificate ofComplianceNo A Not required Not required Not requir
12、ed Not requiredNo B, C Not required Not required Not required Not requiredNo D Static Dynamic or test Not required For mounting onlyYes C, D Static Dynamic or test Dynamic or test For continued operationNo E Static Dynamic or test Dynamic or test For continued operationNo C, D Static Not required No
13、t required Not requiredYes C, D Static Dynamic or test Dynamic or test For continued operationNo F Static Dynamic or test Not required For mounting onlyYes F Static Dynamic or test Dynamic or test For continued operation*If in question, reference structural documents.Table 2 Coefficients for Mechani
14、cal ComponentsMechanical and Electrical Component or Element apRpGeneral MechanicalBoilers and furnaces 1.0 2.5PipingHigh-deformability elements and attachments 1.0 3.5Limited-deformability elements and attachments 1.0 2.5Low-deformability elements or attachments 1.0 1.25HVAC EquipmentVibration isol
15、ated 2.5 2.5Non-vibration isolated 1.0 2.5Mounted in-line with ductwork 1.0 2.5Source: IBC (2006).Table 3 Values of Site Coefficient Faas Function of Site Class and Spectral Response Acceleration at Short Period (Ss)Site ClassSoil Profile NameMapped Spectral Response Acceleration at Short PeriodsaSs
16、 0.25 Ss =0.50 Ss =0.75 Ss =1.00 Ss 1.25A Hard rock 0.8 0.8 0.8 0.8 0.8B Rock 1.0 1.0 1.0 1.0 1.0C Very dense soil and soft rock1.2 1.2 1.1 1.0 1.0DcStiff soil profile1.6 1.4 1.2 1.1 1.0E Soft soil profile2.5 1.7 1.2 0.9 bF See IBC for more informationaUse straight-line interpolation for intermediat
17、e values of mapped spectral accelera-tion at short period Ss.bSite-specific geotechnical investigation and dynamic site response analyses must beperformed to determine appropriate values.cD is the default Site Class unless otherwise stated in the approved geotechnical report.55.4 2015 ASHRAE Handboo
18、kHVAC Applications (SI)forces at all restraint points for any possible direction that the lateralwave front can follow to ensure that the attachment is adequate.Once the overall seismic forces Fpand Fpvhave been determined(as indicated in the previous section or per the local code requirement),the l
19、oads at the restraint points can be determined. There are manydifferent valid methods that can be used to determine these loads, butthis section suggests a couple of simple approaches.Under some instances (particularly those relating to life-supportissues in hospital settings), newer code requiremen
20、ts indicate thatcritical equipment must be seismically qualified to ensure itsTable 4 SsNumbers* for Selected U.S. Locations (U.S. COE 1998)State, City ZIP SsState, City ZIP SsState, City ZIP SsState, City ZIP SsAlabama Ft. Wayne 46835 0.162 Butte 59701 0.599 Rhode IslandBirmingham 35217 0.328 Gary
21、46402 0.173 Great Falls 59404 0.248 Providence 02907 0.267Mobile 36610 0.124 Indianapolis 46260 0.182 Nebraska South CarolinaMontgomery 36104 0.170 South Bend 46637 0.121 Lincoln 68502 0.177 Charleston 29406 1.56Arkansas Kansas Omaha 68144 0.127 Columbia 29203 0.578Little Rock 72205 0.461 Kansas Cit
22、y 66103 0.122 Nevada South DakotaArizona Topeka 66614 0.184 Las Vegas 89106 0.637 Rapid City 57703 0.153Phoenix 85034 0.226 Wichita 67217 0.142 Reno 89509 1.29 Sioux Falls 57104 0.113Tuscon 85739 0.325 Kentucky New York TennesseeCalifornia Ashland 41101 0.221 Albany 12205 0.275 Chattanooga 37415 0.5
23、00Fresno 93706 0.592 Covington 41011 0.186 Binghampton 13903 0.185 Knoxville 37920 0.589Los Angeles 90026 1.50 Louisville 40202 0.247 Buffalo 14222 0.319 Memphis 38109 1.25Oakland 94621 1.55 Louisiana Elmira 14905 0.173 Nashville 37211 0.305Sacramento 95823 0.568 Baton Rouge 70807 0.144 New York 100
24、14 0.425 TexasSan Diego 92101 1.54 New Orleans 70116 0.130 Niagara Falls 14303 0.311 Amarillo 79111 0.166San Francisco 94114 1.50 Shreveport 71106 0.165 Rochester 14619 0.248 Austin 78703 0.088San Jose 95139 2.05 Massachusetts Schenectady 12304 0.278 Beaumont 77705 0.116Colorado Boston 02127 0.325 S
25、yracuse 13219 0.192 Corpus Christi 78418 0.093Colorado Springs 80913 0.178 Lawrence 01843 0.376 Utica 13501 0.250 Dallas 75233 0.117Denver 80239 0.187 Lowell 01851 0.355 North Carolina El Paso 79932 0.358Connecticut New Bedford 02740 0.261 Charlotte 28216 0.345 Ft. Worth 76119 0.110Bridgeport 06606
26、0.332 Springfield 01107 0.260 Greensboro 27410 0.255 Houston 77044 0.107Hartford 06120 0.274 Worchester 01602 0.271 Raleigh 27610 0.211 Lubbock 79424 0.099New Haven 06511 0.285 Maryland Winston-Salem 27106 0.281 San Antonio 78235 0.133Waterbury 06702 0.287 Baltimore 21218 0.199 North Dakota Waco 767
27、04 0.095Florida Maine Fargo 58103 0.073 UtahFt. Lauderdale 33328 0.070 Augusta 04330 0.318 Grand Forks 58201 0.054 Salt Lake City 84111 1.79Jacksonville 32222 0.142 Portland 04101 0.369 Ohio VirginiaMiami 33133 0.061 Michigan Akron 44312 0.179 Norfolk 23504 0.132St. Petersburg 33709 0.078 Detroit 48
28、207 0.123 Canton 44702 0.316 Richmond 23233 0.300Tampa 33635 0.083 Flint 48506 0.091 Cincinnati 45245 0.191 Roanoke 24017 0.290Georgia Grand Rapids 49503 0.087 Cleveland 44130 0.197 VermontAtlanta 30314 0.258 Kalamazoo 49001 0.116 Columbus 43217 0.164 Burlington 05401 0.446Augusta 30904 0.419 Lansin
29、g 48910 0.109 Dayton 45440 0.206 WashingtonColumbia 31907 0.169 Minnesota Springfield 45502 0.216 Seattle 98108 1.51Savannah 31404 0.402 Duluth 55803 0.056 Toledo 43608 0.171 Spokane 99201 0.315Iowa Minneapolis 55422 0.057 Youngstown 44515 0.163 Tacoma 98402 1.23Council Bluffs 41011 0.186 Rochester
30、55901 0.055 Oklahoma Washington, D.C.Davenport 52803 0.130 St. Paul 55111 0.056 Oklahoma City 73145 0.339 Washington 20002 0.178Des Moines 50310 0.073 Missouri Tulsa 74120 0.160 WisconsinIdaho Carthage 64836 0.149 Oregon Green Bay 54302 0.066Boise 83705 0.344 Columbia 65202 0.178 Portland 97222 1.04
31、 Kenosha 53140 0.133Pocatello 83201 0.553 Jefferson City 65109 0.207 Salem 97301 0.929 Madison 53714 0.114Illinois Joplin 64801 0.138 Pennsylvania Milwaukee 53221 0.120Chicago 60620 0.190 Kansas City 64108 0.122 Allentown 18104 0.289 Racine 53402 0.124Moline 61265 0.135 Springfield 65801 0.120 Bethl
32、ehem 18015 0.304 Superior 54880 0.055Peoria 61605 0.174 St. Joseph 64501 0.120 Erie 16511 0.164 West VirginiaRock Island 61201 0.131 St. Louis 63166 0.586 Harrisburg 17111 0.224 Charleston 25303 0.206Rockford 61108 0.170 Mississippi Philadelphia 19125 0.326 Huntington 25704 0.221Springfield 62703 0.
33、263 Jackson 39211 0.191 Pittsburgh 15235 0.129 WyomingIndiana Montana Reading 19610 0.293 Casper 82601 0.341Evansville 47712 0.754 Billings 59101 0.134 Scranton 18504 0.232 Cheyenne 82001 0.183*Nominal values based on ZIP codes. See www.usgs.gov for calculator to check actual Ssusing latitude and lo
34、ngitude for best results.Seismic- and Wind-Resistant Design 55.5Table 5 SsNumbers for Selected International Locations (U.S. COE 1998)Country City SsCountry City SsCountry City SsCountry City SsAfrica Tsingtao1.24 Haiti . Port au Prince 1.24 Serbia . Belgrade. 0.62Algeria .Alger 1.24 Wuhan 0.62 Jama
35、ica Kingston 1.24 Spain. Barcelona. 0.62Oran . 1.24 Cyprus . Nicosia .1.24 Leeward Islands . All 1.24 Bilbao 0.62AngolaLuanda . 0.06 India. Bombay1.24 Puerto Rico All 0.83 Madrid . 0.06BeninColonou . 0.06 Calcutta 0.62 Trinidad this technique deemphasizes stresses in the equip-ment frame and is more
36、 suitable for nonrigid equipment types.Eccentric loads can be addressed with either the polar method or thelump mass method.Note: Although only two methods of computing forces for moregeneral equipment cases are illustrated here, there are many othervalid methods that can be used to distribute the r
37、estraint forces. It isimportant that any method used include the ability to account forequipment mass, seismic uplift forces, overturning forces, and anoffset center of gravity within the equipment.Polar MethodLateral forces are equally distributed among the restraints. If theequipments center of gr
38、avity does not coincide with its geometriccenter, a rotational factor is added to account for the imbalance. Thisfactor is determined in three steps. First, compute the true chordlength in the horizontal plane between the equipments center ofgravity and the restraints geometric center. Second, multi
39、ply theequipment total seismic lateral force by this length (to obtain a rota-tional moment). Third, divide this figure by the number of moment-resisting restraints times their distance from the geometric center.(The moment-resisting restraints are those farthest and equallyspaced from the geometric
40、 center.) The resulting load can then beadded to the original (balanced) figure. This method transfers allimbalance loads to the corner restraints and provides a valid methodof restraint as long as the equipment acts as a rigid body. The assump-tion that a piece of equipment can transfer these loads
41、 out to the cor-ners becomes less accurate as the equipment becomes less rigid.Calculation of the tensile/compressive forces at the restraints ismore complex than that for determining the shear loads, and mustinclude mass, vertical seismic force, overturning forces, and (if iso-lated) the type of is
42、olator/restraint system used. The total tensile andcompressive forces are the worst-case summation of each of thesecomponents. For clarity, each component is addressed here as a sep-arate entity.The nominal mass component at each restraint is simply the totaloperating mass divided by the number of r
43、estraints. The vertical seis-mic force is simply the mass component at each location multipliedby the vertical seismic force factor in terms of the total Fpvload ex-pressed in gs, the gravitational constant (Fpv/Wp, where Fpvis thevertical seismic load component as defined by the code and Wpis theto
44、tal operating mass of the equipment). This can be directed eitherupward or downward when summing forces.Lump Mass MethodIn the lump mass method, the total equipment mass is distributedamong the restraints in a manner that reflects the equipments actualmass distribution. There are many methods of det
45、ermining the dis-tribution analytically or by testing, although they are not addressedin this section. Frequently, a mass distribution can be obtained fromthe equipment manufacturer.Once the static point loads are obtained or computed for eachrestraint location, they can be multiplied by the lateral
46、 seismicTable 6 Load Combinations(Equation Numbers as Referenced in IBC)ASD LRFD5. (1.0 + 0.14SDS)D + H + F + 0.7QE5. (1.2 + 0.2SDS)D + QE+ L + 0.2S8. (0.6 + 0.14SDS)D + 0.7QE + H 7. (0.9 0.2SDS)D + QE + 1.6HFig. 1 Equipment with Rigidly Mounted Structural BasesSeismic- and Wind-Resistant Design 55.
47、7acceleration factor (Fp/Wp) to determine lateral forces at each re-straint point. Thus, if the mass at each restraint point is Wn, thenVeff = (Fp/Wp)Wn(7)This method considers the loads at all the restraints individuallyand computes the overturning forces for each in 1 increments for afull 360 of p
48、ossible seismic wave front angle; it is only practical toperform using a spreadsheet. The total lateral seismic force Fpisdivided into x- and y-axis components for each possible wave frontapproach angle. These forces are multiplied by the height of theequipment center of gravity above the point of r
49、estraint hcg. Theresulting moments are then resolved into forces at each restraintbased on the x- and y-axis moment arms associated with the partic-ular restraint location and the proportion of the load that it will bear. Resilient Support FactorsIf the equipment being restrained is isolated, the following threefactors must be considered:For all forces that are not directed along the principal axes, onlythe corner restraints can be considered to be effective. Thus, foreither distribution method, only the corner restraints can be con-sidered capable of absorbing vertical
