1602.

1 Definitions
The following terms are defined in Chapter 2:

ALLOWABLE STRESS DESIGN.

DEAD LOADS.

DESIGN STRENGTH.

DIAPHRAGM.

Diaphragm, blocked.

Diaphragm boundary.

Diaphragm chord.

ESSENTIAL FACILITIES.

FABRIC PARTITION.

FACTORED LOAD.

HELIPAD.

ICE-SENSITIVE STRUCTURE.

IMPACT LOAD.

LIMIT STATE.

LIVE LOAD.

LIVE LOAD (ROOF).

LOAD AND RESISTANCE FACTOR DESIGN (LRFD).

LOAD EFFECTS.

LOAD FACTOR.

LOADS.

NOMINAL LOADS.

OTHER STRUCTURES.

PANEL (PART OF A STRUCTURE).

RESISTANCE FACTOR.

RISK CATEGORY.

STRENGTH, NOMINAL.

STRENGTH, REQUIRED.

STRENGTH DESIGN.

SUSCEPTIBLE BAY.

VEHICLE BARRIER.

NOTATIONS.

1 of 12 Exported from
 D = Dead load.

Di = Weight of ice in accordance with Chapter 10 of ASCE 7.

E = Combined effect of horizontal and vertical earthquake induced forces as defined in Section 12.4.2 of ASCE 7.

F = Load due to fluids with well-defined pressures and maximum heights.

Fa = Flood load in accordance with Chapter 5 of ASCE 7.

H = Load due to lateral earth pressures, ground water pressure or pressure of bulk materials.

L = Roof live load greater than 20 psf (0.96 kN/m2) and floor live load.

Lr = Roof live load of 20 psf (0.96 kN/m2) or less.

R = Rain load.

S = Snow load.

T = Self-straining load.

Vasd = Nominal design wind speed (3-second gust), miles per hour (mph) (km/hr) where applicable.

Ultimate design wind speeds (3-second gust), miles per hour (mph) (km/hr) determined fromFigure 1609.3(1), 1609.3(2), 1609.3(3) or ASCE
Vult =
7.

W = Load due to wind pressure.

Wi = Wind-on-ice in accordance with Chapter 10 of ASCE 7.

1604.11 Snow, Wind and Earthquake Design Factors

Ground snow load, pg, ultimate design wind speed (three second gust), Vult, and earthquake response accelerations for the maximum considered earthquake,
S S and S1, for each city and town in the Commonwealth shall be as given inTable 1604.11.

TABLE 1604.11 SNOW LOADS, WIND SPEEDS, AND SEISMIC PARAMETERS

SEISMIC PARAMETERS
SNOW LOADS BASIC WIND SPEED, Vult (mph)
(g)

Ground Minimum
Snow Load, Flat Roof Snow Load, Risk Category Risk Category Risk Category III or
City/Town Ss S1
Pg Pf1 I II IV
(psf) (psf)

Abington 35 30 122 132 143 0.196 0.065

Acton 50 35 114 124 134 0.213 0.070

Acushnet 30 30 129 138 149 0.172 0.059

Adams2 60 40 105 115 120 0.172 0.069

Agawam 35 35 109 120 128 0.174 0.065

2 40 40 105 115 120 0.169 0.066

Alford

Amesbury 50 30 113 123 134 0.267 0.078

Amherst 40 35 106 118 125 0.172 0.066

Andover 50 30 114 124 135 0.247 0.075

Aquinnah (Gay Head) 25 25 133 140 154 0.141 0.052

Arlington 40 30 117 127 138 0.219 0.070

Ashburnham 60 35 108 118 128 0.200 0.071

Ashby 60 35 108 119 128 0.210 0.072

Ashfield 50 40 105 115 120 0.170 0.067

Ashland 40 35 116 127 137 0.190 0.066

Athol 60 35 106 117 125 0.183 0.069

Attleboro 35 30 122 132 143 0.181 0.063

Auburn 50 35 114 125 135 0.177 0.065

Avon 35 35 121 131 142 0.196 0.065

Ayer 50 35 111 122 132 0.212 0.071

2 of 12 Exported from
 Barnstable 30 25 132 140 152 0.152 0.055

Barre 50 35 109 120 130 0.180 0.067

Becket2 60 40 105 115 120 0.168 0.066

Bedford 50 30 115 125 136 0.221 0.071

Belchertown 40 35 109 119 129 0.173 0.066

Bellingham 40 35 118 129 139 0.181 0.064

Belmont 40 30 117 127 138 0.215 0.070

Berkley 30 30 125 135 146 0.181 0.061

Berlin 50 35 113 124 134 0.193 0.068

Bernardston 60 35 105 115 120 0.176 0.069

Beverly 50 30 117 127 138 0.245 0.073

Billerica 50 30 114 124 135 0.229 0.073

Blackstone 40 35 119 129 140 0.177 0.063

Blandford 50 40 105 116 122 0.171 0.065

Bolton 50 35 113 123 134 0.199 0.069

Boston 40 30 118 128 139 0.217 0.069

Bourne 30 25 130 139 150 0.168 0.058

Boxborough 50 35 113 123 134 0.208 0.070

Boxford 50 30 115 125 136 0.252 0.075

Boylston 50 35 113 123 134 0.191 0.068

Braintree 35 30 120 131 142 0.203 0.066

Brewster 25 25 132 140 152 0.147 0.054

Bridgewater 30 30 124 134 145 0.188 0.063

Brimfield 40 35 112 123 133 0.173 0.065

Brockton 35 30 122 132 143 0.193 0.064

Brookfield 50 35 112 122 132 0.174 0.065

Brookline 40 30 118 128 139 0.211 0.068

Buckland 2 60 40 105 115 120 0.171 0.068

Burlington 50 30 115 125 136 0.227 0.072

Cambridge 40 30 117 128 139 0.216 0.069

Canton 40 35 120 130 141 0.195 0.065

Carlisle 50 30 114 124 135 0.222 0.072

Carver 30 30 127 136 147 0.182 0.061

Charlemont 2 60 40 105 115 120 0.172 0.068

Charlton 50 35 114 124 135 0.174 0.064

Chatham 25 25 134 140 154 0.135 0.051

Chelmsford 50 30 113 123 134 0.229 0.073

Chelsea 40 30 118 128 139 0.221 0.070

2 60 40 105 115 120 0.171 0.068

Cheshire

Chester 60 40 105 115 120 0.169 0.066

Chesterfield 50 40 105 115 120 0.169 0.067

Chicopee 35 35 108 119 127 0.172 0.065

Chilmark 25 25 134 140 154 0.140 0.052

Clarksburg2 60 40 105 115 120 0.175 0.069

3 of 12 Exported from
 Clinton 50 35 113 123 133 0.194 0.068

Cohasset 35 30 122 131 142 0.211 0.067

Colrain2 60 40 105 115 120 0.174 0.069

Concord 50 35 114 125 136 0.214 0.070

Conway 50 40 105 115 120 0.171 0.067

Cummington 2 60 40 105 115 120 0.169 0.067

Dalton2 60 40 105 115 120 0.169 0.067

Danvers 50 30 116 126 137 0.245 0.074

Dartmouth 30 30 129 139 150 0.169 0.058

Dedham 40 35 119 129 140 0.201 0.067

Deerfield 50 35 105 115 120 0.172 0.068

Dennis 30 25 132 140 152 0.150 0.054

Dighton 30 30 125 135 146 0.180 0.061

Douglas 40 35 117 127 138 0.175 0.064

Dover 40 35 118 128 139 0.196 0.067

Dracut 50 30 112 122 133 0.240 0.075

Dudley 50 35 116 126 136 0.173 0.064

Dunstable 50 35 111 121 132 0.231 0.074

Duxbury 30 30 125 135 146 0.192 0.063

E. Bridgewater 35 30 123 133 144 0.191 0.064

E. Brookfield 50 35 112 122 133 0.175 0.065

E. Longmeadow 35 35 110 121 130 0.174 0.065

Eastham 25 25 132 140 152 0.146 0.054

Easthampton 40 35 106 117 124 0.171 0.066

Easton 35 30 122 132 143 0.187 0.064

Edgartown 25 25 135 140 155 0.136 0.051

Egremont2 40 40 105 115 120 0.169 0.065

Erving 50 35 105 116 122 0.178 0.069

Essex 50 30 117 127 138 0.253 0.075

Everett 40 30 117 128 139 0.222 0.070

Fairhaven 30 30 129 139 150 0.169 0.058

Fall River 30 30 126 137 148 0.176 0.060

Falmouth 30 25 132 140 152 0.154 0.055

Fitchburg 60 35 110 120 130 0.202 0.071

Florida2 60 40 105 115 120 0.173 0.069

Foxborough 35 35 120 131 142 0.186 0.064

Framingham 40 35 116 127 137 0.194 0.067

Franklin 40 35 119 129 140 0.183 0.064

Freetown 30 30 126 137 147 0.178 0.060

Gardner 60 35 108 119 128 0.191 0.070

Georgetown 50 30 114 124 135 0.258 0.076

Gill 50 35 105 115 120 0.177 0.069

Gloucester 50 30 118 128 139 0.252 0.074

Goshen 50 40 105 115 120 0.169 0.067

4 of 12 Exported from
 Gosnold 30 25 132 140 152 0.153 0.055

Grafton 50 35 115 126 136 0.180 0.065

Granby 35 35 108 119 127 0.172 0.066

Granville 50 40 106 117 125 0.173 0.065

Great Barrington2 50 40 105 115 120 0.169 0.066

Greenfield 50 35 105 115 120 0.173 0.068

Groton 60 35 111 121 132 0.218 0.072

Groveland 50 30 113 123 134 0.259 0.077

Hadley 40 35 106 117 124 0.171 0.066

Halifax 30 30 124 134 145 0.189 0.063

Hamilton 50 30 116 126 137 0.253 0.075

Hampden 35 35 111 122 131 0.173 0.065

2 50 40 105 115 120 0.172 0.068

Hancock

Hanover 35 30 123 133 144 0.198 0.065

Hanson 35 30 123 133 144 0.195 0.064

Hardwick 50 35 110 120 130 0.176 0.066

Harvard 50 35 112 123 133 0.206 0.070

Harwich 25 25 133 140 153 0.141 0.053

Hatfield 40 35 106 117 124 0.171 0.066

Haverhill 50 30 112 123 134 0.260 0.077

Hawley2 60 40 105 115 120 0.171 0.068

Heath2 60 40 105 115 120 0.173 0.069

Hingham 35 30 121 131 142 0.210 0.067

Hinsdale 2 60 40 105 115 120 0.169 0.067

Holbrook 35 30 121 131 142 0.198 0.065

Holden 50 35 112 122 133 0.183 0.067

Holland 40 35 114 124 134 0.173 0.064

Holliston 40 35 117 128 138 0.188 0.066

Holyoke 35 35 107 118 126 0.172 0.065

Hopedale 40 35 117 128 138 0.181 0.065

Hopkinton 40 35 116 127 137 0.186 0.066

Hubbardston 50 35 109 120 130 0.185 0.068

Hudson 50 35 114 124 135 0.197 0.068

Hull 35 30 120 130 141 0.215 0.068

Huntington 50 40 105 116 122 0.170 0.066

Ipswich 50 30 116 126 137 0.257 0.076

Kingston 30 30 125 135 146 0.188 0.062

Lakeville 30 30 126 136 147 0.181 0.061

Lancaster 50 35 112 122 133 0.197 0.069

Lanesborough2 50 40 105 115 120 0.171 0.068

Lawrence 50 30 113 123 134 0.250 0.076

Lee 2 50 40 105 115 120 0.169 0.066

Leicester 50 35 113 123 134 0.178 0.066

Lenox2 50 40 105 115 120 0.169 0.066

5 of 12 Exported from
 Leominster 60 35 111 121 131 0.199 0.070

Leverett 40 35 105 117 124 0.173 0.067

Lexington 40 30 116 126 137 0.218 0.070

2 60 40 105 115 120 0.176 0.069

Leyden

Lincoln 40 35 115 126 136 0.213 0.070

Littleton 50 35 112 123 133 0.214 0.071

Longmeadow 35 35 109 120 129 0.174 0.065

Lowell 50 30 112 123 134 0.235 0.074

Ludlow 35 35 109 120 129 0.173 0.065

Lunenburg 60 35 110 120 131 0.207 0.071

Lynn 40 30 117 128 139 0.233 0.071

Lynnfield 50 30 116 126 137 0.237 0.073

Malden 40 30 117 127 138 0.224 0.070

Manchester 50 30 117 128 139 0.249 0.074

Mansfield 35 30 121 131 142 0.186 0.064

Marblehead 40 30 118 128 139 0.239 0.072

Marion 30 30 129 139 150 0.170 0.058

Marlborough 50 35 114 125 135 0.194 0.068

Marshfield 35 30 124 134 145 0.196 0.064

Mashpee 30 25 131 140 152 0.156 0.055

Mattapoisett 30 30 129 139 150 0.169 0.058

Maynard 50 35 114 124 135 0.206 0.069

Medfield 40 35 118 129 139 0.191 0.066

Medford 40 30 117 127 138 0.221 0.070

Medway 40 35 118 129 139 0.185 0.065

Melrose 40 30 117 127 138 0.227 0.071

Mendon 40 35 118 128 138 0.179 0.064

Merrimac 50 30 112 123 133 0.265 0.078

Methuen 50 30 112 122 133 0.251 0.076

Middleborough 30 30 125 135 146 0.183 0.062

Middlefield 60 40 105 115 120 0.169 0.066

Middleton 50 30 115 125 136 0.245 0.074

Milford 40 35 117 128 138 0.182 0.065

Millbury 50 35 115 125 136 0.178 0.065

Millis 40 35 118 129 139 0.188 0.065

Millville 40 35 118 129 139 0.177 0.063

Milton 40 30 119 130 141 0.205 0.067

Monroe2 60 40 105 115 120 0.174 0.069

Monson 40 35 111 122 132 0.173 0.065

Montague 50 35 105 116 122 0.173 0.068

Monterey 50 40 105 116 122 0.170 0.065

Montgomery 40 40 105 117 123 0.171 0.066

Mount Washington2 40 40 105 115 120 0.171 0.065

Nahant 40 30 118 128 139 0.229 0.071

6 of 12 Exported from
 Nantucket 25 25 139 140 158 0.113 0.047

Natick 40 35 117 127 138 0.197 0.067

Needham 40 35 118 128 139 0.201 0.067

2 50 40 105 115 120 0.173 0.068

New Ashford

New Bedford 30 30 129 139 150 0.170 0.058

New Braintree 50 35 111 121 131 0.176 0.066

New Marlborough 50 40 105 115 120 0.171 0.065

New Salem 50 35 106 117 125 0.177 0.068

Newbury 50 30 114 125 136 0.263 0.077

Newburyport 50 30 114 124 135 0.265 0.078

Newton 40 30 117 127 138 0.208 0.068

Norfolk 40 35 119 129 140 0.186 0.065

2 60 40 105 115 120 0.175 0.069

North Adams

North Andover 50 30 113 123 134 0.251 0.076

North Attleborough 35 30 121 131 142 0.180 0.063

North Brookfield 50 35 112 122 132 0.176 0.066

North Reading 50 30 115 125 136 0.240 0.073

Northampton 40 35 106 117 124 0.171 0.066

Northborough 50 35 114 124 135 0.188 0.067

Northbridge 40 35 116 127 137 0.179 0.065

Northfield 60 35 105 115 120 0.179 0.069

Norton 35 30 122 133 144 0.184 0.063

Norwell 35 30 123 133 144 0.203 0.065

Norwood 40 35 119 129 140 0.195 0.066

Oak Bluffs 25 25 133 140 154 0.144 0.053

Oakham 50 35 111 121 131 0.179 0.067

Orange 60 35 106 117 124 0.180 0.069

Orleans 25 25 132 140 152 0.144 0.053

Otis 50 40 105 115 120 0.170 0.066

Oxford 50 35 115 125 136 0.174 0.064

Palmer 40 35 111 121 131 0.173 0.065

Paxton 50 35 112 122 133 0.180 0.066

Peabody 50 30 117 127 138 0.240 0.073

Pelham 40 35 107 118 126 0.173 0.067

Pembroke 30 30 124 134 145 0.195 0.064

Pepperell 60 35 110 120 131 0.223 0.073

Peru 2 60 40 105 115 120 0.169 0.067

Petersham 50 35 108 118 127 0.180 0.068

Phillipston 60 35 108 118 127 0.185 0.069

Pittsfield2 50 40 105 115 120 0.170 0.067

Plainfield 2 60 40 105 115 120 0.170 0.067

Plainville 40 35 121 131 142 0.182 0.063

Plymouth 30 30 126 136 147 0.185 0.061

Plympton 30 30 125 135 146 0.187 0.062

7 of 12 Exported from
 Princeton 50 35 111 121 131 0.188 0.068

Provincetown 25 25 128 138 148 0.177 0.060

Quincy 40 30 120 130 141 0.208 0.067

Randolph 35 30 121 131 142 0.198 0.066

Raynham 35 30 123 134 145 0.185 0.063

Reading 50 30 116 126 137 0.234 0.072

Rehoboth 35 30 124 134 145 0.179 0.062

Revere 40 30 118 128 139 0.224 0.070

Richmond2 50 40 105 115 120 0.169 0.067

Rochester 30 30 128 138 149 0.176 0.059

Rockland 35 30 122 132 143 0.198 0.065

Rockport 50 30 118 128 139 0.255 0.074

2 60 40 105 115 120 0.173 0.069

Rowe

Rowley 50 30 115 125 136 0.259 0.076

Royalston 60 35 106 116 123 0.188 0.070

Russell 40 40 105 116 123 0.171 0.065

Rutland 50 35 111 121 132 0.182 0.067

Salem 50 30 117 127 138 0.240 0.073

Salisbury 50 30 113 124 134 0.266 0.078

Sandisfield 50 40 105 115 120 0.171 0.065

Sandwich 30 25 130 139 150 0.165 0.057

Saugus 40 30 117 127 138 0.230 0.071

Savoy2 60 40 105 115 120 0.170 0.068

Scituate 35 30 123 133 144 0.207 0.066

Seekonk 35 30 123 134 145 0.177 0.061

Sharon 35 35 120 130 141 0.191 0.065

Sheffield 2 40 40 105 115 120 0.171 0.065

Shelburne 50 40 105 115 120 0.172 0.068

Sherborn 40 35 117 127 138 0.192 0.066

Shirley 60 35 111 121 132 0.207 0.071

Shrewsbury 50 35 114 124 135 0.184 0.066

Shutesbury 40 35 106 117 125 0.174 0.067

Somerset 30 30 126 136 147 0.178 0.061

Somerville 40 30 117 127 139 0.218 0.070

South Hadley 35 35 107 118 126 0.171 0.066

Southampton 40 35 106 117 124 0.171 0.066

Southborough 40 35 115 125 136 0.191 0.067

Southbridge 40 35 114 125 135 0.173 0.064

Southwick 40 35 107 118 126 0.174 0.065

Spencer 50 35 113 123 133 0.176 0.066

Springfield 35 35 109 120 128 0.173 0.065

Sterling 50 35 112 122 132 0.192 0.068

Stockbridge2 50 40 105 115 120 0.169 0.066

Stoneham 40 30 116 126 137 0.229 0.071

8 of 12 Exported from
 Stoughton 35 35 121 131 142 0.194 0.065

Stow 50 35 114 124 135 0.204 0.069

Sturbridge 40 35 114 124 134 0.173 0.064

Sudbury 40 35 115 125 136 0.203 0.069

Sunderland 40 35 105 116 122 0.172 0.067

Sutton 50 35 115 126 136 0.177 0.065

Swampscott 40 30 118 128 139 0.234 0.072

Swansea 30 30 126 136 147 0.177 0.061

Taunton 35 30 124 134 145 0.183 0.062

Templeton 60 35 108 118 127 0.187 0.069

Tewksbury 50 30 113 124 135 0.237 0.074

Tisbury 25 25 133 140 153 0.146 0.053

Tolland 50 40 105 115 122 0.172 0.065

Topsfield 50 30 115 125 136 0.251 0.075

Townsend 60 35 109 119 130 0.216 0.073

Truro 25 25 129 139 149 0.164 0.057

Tyngsborough 50 30 111 121 132 0.234 0.074

Tyringham 2 50 40 105 115 120 0.169 0.066

Upton 40 35 116 127 137 0.181 0.065

Uxbridge 40 35 117 128 138 0.177 0.064

Wakefield 50 30 116 126 137 0.232 0.072

Wales 40 35 113 123 133 0.173 0.064

Walpole 40 35 119 130 141 0.190 0.065

Waltham 40 30 116 127 138 0.211 0.069

Ware 40 35 110 120 131 0.174 0.066

Wareham 30 30 129 138 149 0.173 0.059

Warren 40 35 111 121 132 0.173 0.065

Warwick 60 35 105 115 121 0.183 0.070

Washington2 60 40 105 115 120 0.168 0.066

Watertown 40 30 117 127 138 0.213 0.069

Wayland 40 35 116 126 137 0.203 0.068

Webster 50 35 116 126 136 0.173 0.064

Wellesley 40 35 117 127 138 0.200 0.067

Wellfleet 25 25 130 140 150 0.157 0.056

Wendell 50 35 105 117 123 0.177 0.068

Wenham 50 30 116 126 137 0.249 0.074

W. Boylston 50 35 112 123 133 0.186 0.067

W. Bridgewater 35 30 123 133 144 0.189 0.063

W. Brookfield 40 35 112 122 132 0.174 0.065

W. Newbury 50 30 113 123 134 0.263 0.078

W. Springfield 35 35 108 119 128 0.173 0.065

2 40 40 105 115 120 0.169 0.066

W. Stockbridge

W. Tisbury 25 25 134 140 154 0.141 0.052

Westborough 50 35 115 125 136 0.186 0.066

9 of 12 Exported from
 Westfield 40 35 107 118 125 0.172 0.065

Westford 50 35 112 123 133 0.223 0.072

Westhampton 50 40 105 116 122 0.170 0.066

Westminster 60 35 109 120 130 0.194 0.069

Weston 40 35 116 126 137 0.207 0.069

Westport 30 30 128 139 149 0.172 0.059

Westwood 40 35 119 129 140 0.196 0.066

Weymouth 35 30 121 131 142 0.206 0.067

Whately 50 35 105 116 122 0.171 0.067

Whitman 35 30 123 133 144 0.194 0.064

Wilbraham 35 35 110 121 130 0.173 0.065

Williamsburg 50 40 105 116 121 0.170 0.067

2 50 40 105 115 120 0.176 0.070

Williamstown

Wilmington 50 30 115 125 136 0.233 0.073

Winchendon 60 35 107 117 125 0.197 0.071

Winchester 40 30 116 126 137 0.224 0.071

2 60 40 105 115 120 0.169 0.067

Windsor

Winthrop 40 30 118 129 140 0.222 0.070

Woburn 50 30 116 126 137 0.226 0.071

Worcester 50 35 114 124 134 0.180 0.066

Worthington 60 40 105 115 120 0.169 0.067

Wrentham 40 35 120 130 141 0.184 0.064

Yarmouth 30 25 132 140 152 0.149 0.054

NOTES:

1. The design flat roof snow load shall be the larger of the calculated flat roof snow load using Pg or the value of Pf listed in this table.

2. Special Wind Region. Local conditions may cause higher wind speeds than the tabulated values. See ASCE/SEI 7.

1604.12 Revisions to AISC 341-10

F1.1 Scope
Add last sentence as follows:

Eccentricities less than the beam depth are permitted if they are accounted for in the member design by determination of eccentric moments using the
amplified seismic load.

1608.4 Concave Curved Roofs

Section 7.4.3 of ASCE 7 applies to convex curved roofs only.The effective loaded area of a concave curved roof shall be that area of the surface of the roof
where the tangents to the surface have a slope of 50° or less. The total uniform snow load for concave curved roofs shall be Pƒ multiplied by the total
horizontal projected area of the roof.This total load shall be applied uniformly over the effective loaded area of the roof.

1608.5 Drifts on Multiple Level Roofs

For multiple stepped roofs similar to that shown in Figure 1608.5.1, the sum of all the roof lengths upwind above the drift under consideration, ul *, in Figure
1608.5.1, shall replace lu in Figure 7-8 of ASCE 7. For multiple level roofs similar to that shown in Figure 1608.5.2, if the total calculated height of a drift and the
underlying uniform snow layer on the upwind side of a higher roof (hd + hb) is equal to or greater than 0.7(hb + hc), then the length, lu*, as shown in Figure
1608.5.2, shall be used in place of lu in Figure 7-8 of ASCE 7.

FIGURE 1608.5.1

10 of 12 Exported from
 FIGURE 1608.5.2

1608.6 Very High Roof Separations

When the ratio hr/L T is greater than 1.0, where LT is the dimension in feet of the upper roof perpendicular to the wind flow (perpendicular to ul in Figure7-8 of
ASCE 7) and hr = hb + hc, the drift surcharge load on the lower roof due to drifting of snow from the upper roof may be reduced. The reduced height of the drift
surcharge, hdr, shall be not less than: hdr = hr (2 - hr/L T ), except that when hr/L T is greater than 2.0, hdr be equal to zero.

1608.7 Snow Pockets or Wells

Account shall be taken of the load effects of potentially excessive snow accumulation in pockets or wells of roofs or decks.

1608.8 Roof Projections

The term roof projections used herein and in section 7.8 of ASCE 7 shall be interpreted to include screenwalls, parapets, fire wall projections, and mechanical
equipment. Drift loads at roof projections shall be in accordance with section 7.8 of ASCE 7.

1608.9 Sliding Snow

In addition to the sliding snow load on a lower roof as required in section 7.9 of ASCE 7, the lower roof shall be designed for a windward drift surcharge at the
wall separating the upper and lower roofs in accordance with Figure 1608.5.1 and section 7.8 of ASCE 7. The sliding snow load and the windward drift
surcharge need not be considered to act concurrently.

1608.10 Snow Guards

Sliding snow from an adjacent sloping high roof need not be considered on the low roof if snow guards, as specified herein, are provided on the high roof. In
this case, the sloping roof with snow guards shall be designed for the unit snow loads required for a flat roof. The roof area(s) requiring snow guards shall be
indicated on the construction documents.

Snow guards shall be designed by a registered design professional. The registered design professional shall insure that there are adequate load paths from the
snow guards into the supporting members and from the supporting members into the primary structure. The structural design of snow guards shall account
for the impact of the sliding snow. The effectiveness in preventing the sliding of snow of proprietary snow guard systems shall be demonstrated by tests.

1608.11 Snow Storage and Collection Areas

Consideration of potentially excessive snow accumulation shall be given to portions of structures designated or used as snow collection or storage areas
during and after snow removal operations (e.g., temporary snow collection areas when mechanically removing snow from a roof; snow storage areas for
parking structures).

1610.2 Seismic Loads on Foundation Walls and Retaining Walls

Exterior foundation walls and retaining walls shall be designed to resist an earthquake force, Fw, for horizontal backfill surface, equal to:

Fw = 0.100(SS)(F a )(γ t )(H) 2

where SS is the maximum considered earthquake spectral response acceleration from Table 1604.11, Fa is the site coefficient from Table
1613.3.3(1), γt is the total unit weight of the soil, and H is the height of thewall measured as the difference in elevation of finished ground surface
or floor in front of and behind the wall. The earthquake force from the backfill shall be distributed as an inverted triangle over the height of thewall

11 of 12 Exported from
 Surcharges that are applied over extended periods of time shall be included in the total static lateral soil pressure and their earthquake lateral force shall be
computed and added to the force determined above. The point of application of the earthquake force from extended duration surcharge shall be determined
on an individual case basis.

If the backfill or the existing soil behind the backfill consists of loose saturated granular soil, the potential for liquefaction of the backfill or existing soil adjacent
to the wall during seismic loading shall be evaluated in accordance with the requirements of section 1806.4.

If the backfill or existing soil beyond the backfill is potentially subject to liquefaction, the increase in design lateral load on the foundation wall or retaining wall
shall be determined by a registered design professional.

For wall strength design, a load factor of 1.43 shall be applied to the earthquake force calculated above.

12 of 12 Exported from