ARCH 331 Note Set 13.1 S2014abn 1 Common Design Loads in Building Codes Notation: A = name for area AASHTO = American Association of State Highway and Transportation Officials ASCE = American Society of Civil Engineers ASD = allowable stress design D = dead load symbol E = earthquake load symbol F = hydraulic loads from fluids symbol H = hydraulic loads from soil symbol L = live load symbol Lr = live roof load symbol LRFD = load and resistance factor design R = rainwater load or ice water load symbol S = snow load symbol SEI = Structural Engineering Institute t = name for thickness T = effect of material & temperature symbol V = name for volume w = name for distributed load W = wind load symbol = force due to a weight = name for total force due to distributed load  = 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 fluidsARCH 331 Note Set 13.1 S2014abn 2 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: VW  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 = tA; 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 Elevator machine room grating (on area of 2 in. by 2 in. (50 mm by 50 mm)) Finish light floor plate construction (on area of 1 in. by 1 in. (25 mm by25 mm)) Hospital floors Library floors Manufacturing Light Heavy Office floors Awnings and canopies Screen enclosure support frame Roofs – primary members and subject to maintenance workers School floors Sidewalks, vehicular driveways, and yards subject to trucking (over wheel area of 4.5 in. by 4.5 in. (114 mm x 114 mm) Stairs and exit ways on area of 2 in. by 2 in. (50 mm by 50 mm) non-concurrent with uniform load Store floors 300 (1.33) 300 (1.33) 200 (0.89) 1,000 (4.45) 1,000 (4.45) 2,000 (8.90) 3,000 (13.40) 2,000 (8.90) 200 (0.89) 300 (1.33) 1,000 (4.45) 8,000 (35.60) 300 (1.33) 1,000 (4.45)ARCH 331 Note Set 13.1 S2014abn 3 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 Computer use Armories and drill rooms Assembly areas Fixed seats (fastened to floor) Lobbies Movable seats Platforms (assembly) Stage floors Assembly areas (other) 50 (2.4) 100 (4.79) 150 (7.18) 60 (2.87) 100 (4.79) 100 (4.79) 100 (4.79) 150 (7.18) 100 (4.79)ARCH 331 Note Set 13.1 S2014abn 4 Location Uniform load psf (kN/m2) Balconies and decks Catwalks for maintenance access Corridors First floor Other floors Dining rooms and restaurants Dwellings (see Residential) Elevator machine room grating (on area of 2 in. by 2 in. (50 mm by 50 mm)) Finish light floor plate construction (on area of 1 in. by 1 in. (25 mm by 25 mm)) Fire escapes On single-family dwellings only Garages Passenger vehicles only Helipads Hospitals Operating rooms, laboratories Patient rooms Corridors above first floor Hotels (see Residential) Libraries Reading rooms Stack rooms Corridors above first floor Manufacturing Light Heavy Office buildings File and computer rooms shall be designed for heavier loads based on anticipated occupancy Lobbies and first floor corridors Offices Corridors above first floor Penal institutions Cell blocks Corridors Recreational uses Bowling alleys, poolrooms, and similar uses Dance halls and ballrooms Gymnasiums Reviewing stands, grandstands, and bleachers Stadiums and arenas with fixed seats