ARCH 331 Note Set 13.
1 S2014abn
Common Design Loads in Building Codes
Notation:
A = name for area R = rainwater load or ice water load
AASHTO = American Association of State symbol
Highway and Transportation S = snow load symbol
Officials SEI = Structural Engineering Institute
ASCE = American Society of Civil t = name for thickness
Engineers T = effect of material & temperature
ASD = allowable stress design symbol
D = dead load symbol V = name for volume
E = earthquake load symbol w = name for distributed load
F = hydraulic loads from fluids symbol W = wind load symbol
H = hydraulic loads from soil symbol = force due to a weight
L = live load symbol = name for total force due to
Lr = live roof load symbol distributed load
LRFD = load and resistance factor design = density or unit weight
Design Codes in General
Design codes are issued by a professional organization interested in insuring safety and
standards. They are legally backed by the engineering profession. Different design methods are
used, but they typically defined the load cases or combination, stress or strength limits, and
deflection limits.
Load Types
Loads used in design load equations are given letters by type:
D = dead load
L = live load
Lr = live roof load
W = wind load
S = snow load
E = earthquake load
R = rainwater load or ice water load
T = effect of material & temperature
H = hydraulic loads from soil
F = hydraulic loads from fluids
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ARCH 331 Note Set 13.1 S2014abn
Determining Dead Load from Material Weights
Material density is a measure of how much mass in a unit volume causes a force due to gravity.
The common symbol for density is . When volume, V, is multiplied by density, a force value
results:
W V
Materials “weight” can also be presented as a weight per unit area or length. This takes into
account that the volume is a thickness times an area: V = tA; so the calculation becomes:
W = (weight/unit area)A
w = (weight/unit volume)t which is a weight per unit area
w = (weight/unit volume)A which is a weight per unit length
Minimum Concentrated Loads
adapted from SEI/ASCE 7-10: Minimum Design Loads for Buildings and Other Structures
Location Concentrated load lb (kN)
Catwalks for maintenance access 300 (1.33)
Elevator machine room grating (on area of 2 in. by 2 in. 300 (1.33)
(50 mm by 50 mm))
Finish light floor plate construction (on area of 1 in. by 1 in. 200 (0.89)
(25 mm by25 mm))
Hospital floors 1,000 (4.45)
Library floors 1,000 (4.45)
Manufacturing
Light 2,000 (8.90)
Heavy 3,000 (13.40)
Office floors 2,000 (8.90)
Awnings and canopies
Screen enclosure support frame 200 (0.89)
Roofs – primary members and subject to maintenance workers 300 (1.33)
School floors 1,000 (4.45)
Sidewalks, vehicular driveways, and yards subject to trucking (over
wheel area of 4.5 in. by 4.5 in. (114 mm x 114 mm) 8,000 (35.60)
Stairs and exit ways on area of 2 in. by 2 in. (50 mm by 50 mm) non-
concurrent with uniform load 300 (1.33)
Store floors 1,000 (4.45)
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ARCH 331 Note Set 13.1 S2014abn
Allowable Stress Design (ASD)
Combinations of service (also referred to as working) loads are evaluated for maximum stresses
and compared to allowable stresses. The allowed stresses are some fraction of limit stresses.
ASCE-7 (2010) combinations of loads:
1. D When F loads are present, they shall be
2. D + L included with the same load factor as
3. D + 0.75(Lr or S or R) dead load D in 1 through 6 and 8.
4. D + 0.75L + 0.75(Lr or S or R)
5. D + (0.6W or 0.7E) When H loads are present, they shall have
6a. D + 0.75L + 0.75(0.6W) + 0.75(Lr or S or R) a load factor of 1.0 when adding to load
6b. D + 0.75L + 0.75(0.7E) + 0.75S
7. 0.6D + 0.6W effect, or 0.6 when resisting the load when
8. 0.6D + 0.7E permanent.
Load and Resistance Factor Design – LRFD
Combinations of loads that have been factored are evaluated for maximum loads, moments or
stresses. These factors take into consideration how likely the load is to happen and how often.
This “imaginary” worse case load, moment or stress is compared to a limit value that has been
modified by a resistance factor. The resistance factor is a function of how “comfortable” the
design community is with the type of limit, ie. yielding or rupture...
ASCE-7 (2010) combinations of factored nominal loads:
1. 1.4D When F loads are present, they shall be
2. 1.2D + 1.6L + 0.5(Lr or S or R) included with the same load factor as
3. 1.2D + 1.6(Lr or S or R) + (L or 0.5W) dead load D in 1 through 5 and 7.
4. 1.2D + 1.0W + L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + L + 0.2S When H loads are present, they shall have
6. 0.9D + 1.0W a load factor of 1.6 when adding to load
7. 0.9D + 1.0E effect, or 0.9 when resisting the load when
permanent.
Minimum Uniformly Distributed Live Loads
adapted from SEI/ASCE 7-10: Minimum Design Loads for Buildings and Other Structures
Location Uniform load psf (kN/m2)
Apartments (see Residential)
Access floor systems
Office use 50 (2.4)
Computer use 100 (4.79)
Armories and drill rooms 150 (7.18)
Assembly areas
Fixed seats (fastened to floor) 60 (2.87)
Lobbies 100 (4.79)
Movable seats 100 (4.79)
Platforms (assembly) 100 (4.79)
Stage floors 150 (7.18)
Assembly areas (other) 100 (4.79)
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ARCH 331 Note Set 13.1 S2014abn
Location Uniform load psf (kN/m2)
Balconies and decks 1.5 times the live load for the
area served. Not required`to
exceed 100 psf (4.79 kN/m2)
Catwalks for maintenance access 40 (1.92)
Corridors
First floor 100 (4.79)
Other floors same as occupancy served
except as indicated
Dining rooms and restaurants 100 (4.79)
Dwellings (see Residential)
Elevator machine room grating (on area of 2 in. by 2 in. 300 (1.33)
(50 mm by 50 mm))
Finish light floor plate construction (on area of 1 in. by 1 in. 200 (0.89)
(25 mm by 25 mm))
Fire escapes 100 (4.79)
On single-family dwellings only 40 (1.92)
Garages
Passenger vehicles only 40 (1.92)
Helipads 60 (2.87)
Hospitals
Operating rooms, laboratories 60 (2.87)
Patient rooms 40 (1.92)
Corridors above first floor 80 (3.83)
Hotels (see Residential)
Libraries
Reading rooms 60 (2.87)
Stack rooms 150 (7.18)
Corridors above first floor 80 (3.83)
Manufacturing
Light 125 (6.00)
Heavy 250 (11.97)
Office buildings
File and computer rooms shall be designed for heavier loads based
on anticipated occupancy
Lobbies and first floor corridors 100 (4.79)
Offices 50 (2.40)
Corridors above first floor 80 (3.83)
Penal institutions
Cell blocks 40 (1.92)
Corridors 100 (4.79)
Recreational uses
Bowling alleys, poolrooms, and similar uses 75 (3.59)
Dance halls and ballrooms 100 (4.79)
Gymnasiums 100 (4.79)
Reviewing stands, grandstands, and bleachers 100 (4.79)
Stadiums and arenas with fixed seats (fastened to the floor) 60 (2.87)
Residential
One- and two-family dwellings
Uninhabitable attics without storage 10 (0.48)
Uninhabitable attics with storage 20 (0.96)
Habitable attics and sleeping areas 30 (1.44)
All other areas except stairs 40 (1.92)
All other residential occupancies
Private rooms and corridors serving them 40 (1.92)
Public rooms and corridors serving them 100 (4.79)
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ARCH 331 Note Set 13.1 S2014abn
Location Uniform load psf (kN/m2)
Roofs
Ordinary flat, pitched, and curved roofs 20 (0.96n
Roofs used for roof gardens 100 (4.79)
Roofs used for assembly occupancies Same as occupancy served
Roofs used for other occupancies As approved by authority
having jurisdiction
Awnings and canopies
Fabric construction supported by a skeleton structure 5 (0.24) nonreducible
Screen enclosure support frame 5 (0.24) nonreducible
and based on the tributary
area of the roof supported by
the frame
All other construction 20 (0.96)
Schools
Classrooms 40 (1.92)
Corridors above first floor 80 (3.83)
First-floor corridors 100 (4.79)
Scuttles, skylight ribs, and accessible ceilings 200 (0.89)
Sidewalks, vehicular driveways, and yards subject to trucking 250 (11.97)
Stairs and exit ways 100 (4.79)
One- and two-family dwellings only 40 (1.92)
Storage areas above ceilings 20 (0.96)
Storage warehouses (shall be designed for heavier loads if required for
anticipated storage)
Light 125 (6.00)
Heavy 250 (11.97)
Stores
Retail
First floor 100 (4.79)
Upper floors 75 (3.59)
Wholesale, all floors 125 (6.00)
Walkways and elevated platforms (other than exit ways) 60 (2.87)
Yards and terraces, pedestrian 100 (4.79)
Live load reductions are not permitted for specific types (see code).
Some occupancies must be designed for appropriate loads as approved by the authority having jurisdiction.
Library stack room floors have specified limitations (see code)
AASHTO lane loads should also be considered where appropriate.
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ARCH 331 Note Set 13.1 S2014abn
Building Material Weights-AISC Manual of Load and Resistance Factor Design, 3rd ed.
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ARCH 331 Note Set 13.1 S2014abn
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ARCH 331 Note Set 13.1 S2014abn
Example 1
Determine the controlling load combinations(s) using AISC-LRFD for a building column subject to the following
service or nominal (unfactored) axial compressive loads: D = 30 k, L = 50 k, Lr = 10 k, W = 25 k, E = 40 k
Using a spreadsheet analysis:
FACTORED
LRFD (ASCE-7)
LOAD
1.4D
1.4D = 42 kips
1.2D + 1.6L + 0.5(Lr or S or R)
1.2D + 1.6L + 0.5Lr = 121
1.2D + 1.6(Lr or S or R) + (L or 0.5W)
1.2D + 1.6Lr + L = 102
1.2D + 1.6Lr + 0.5W = 64.5
1.2D + 1.6Lr - 0.5W = 39.5
1.2D + 1.0W+ L + 0.5(Lr or S or R)
1.2D + 1.0W+ L + 0.5Lr = 116
1.2D - 1.0W+ L + 0.5Lr = 66
1.2D + 1.0E + L + 0.2S
1.2D + 1.0E + L = 126
1.2D - 1.0E + L = 46
0.9D + 1.0W
0.9D + 1.0W = 52
0.9D - 1.0W = 2
0.9D + 1.0E
0.9D + 1.0E = 67
0.9D - 1.0E = -13
Critical Factored Load 126 kips (C)
-13 kips (T)
Example 2
