04/20/2018

Structural Deflection Limits per International Building Code 2015 (IBC 2015), Table 1604.3

In this post, I will provide a brief overview of the structural deflection limits of structural elements based on loading conditions specified in the International Building Code 2015 (IBC 2015), Table 1604.3.

 

Roof Members Deflection Limits

Members supporting plaster or stucco ceiling (Live Load) = L/360

Members supporting plaster or stucco ceiling (Snow or Wind load) = L/360

Members supporting plaster or stucco ceiling (Dead + Live Load) = L/240

 

Members supporting nonplaster ceiling (Live Load) = L/240

Members supporting nonplaster ceiling (Snow or Wind load) = L/240

Members supporting nonplaster ceiling (Dead + Live Load) = L/180

 

Members not supporting ceiling (Live Load) = L/180

Members not supporting ceiling (Snow or Wind load) = L/180

Members not supporting ceiling (Dead + Live Load) = L/120

 

Floor Members Deflection Limits

Floor members  (Live Load) = L/360

Floor members (Snow or Wind load) = N/A

Floor members (Dead + Live Load) = L/240

 

Exterior Walls Deflection Limits

Walls with plaster or stucco finishes (Live Load) = N/A

Walls with plaster or stucco finishes (Snow or Wind load) = L/360

Walls with plaster or stucco finishes (Dead + Live Load) = N/A

 

Walls with other brittle finishes (Live Load) = N/A

Walls with other brittle finishes (Snow or Wind load) = L/240

Walls with other brittle finishes (Dead + Live Load) = N/A

 

Walls with flexible finishes (Live Load) = N/A

Walls with flexible finishes  (Snow or Wind load) = L/120

Walls with flexible finishes  (Dead + Live Load) = N/A

 

Interior Partitions Deflection Limits

Partitions with plaster or stucco finishes (Live Load) = L/360

Partitions with plaster or stucco finishes (Snow or Wind load) = N/A

Partitions with plaster or stucco finishes (Dead + Live Load) = N/A

 

Partitions with other brittle finishes (Live Load) = L/240

Partitions with other brittle finishes (Snow or Wind load) = N/A

Partitions with other brittle finishes (Dead + Live Load) = N/A

 

Partitions with flexible finishes (Live Load) = L/120

Partitions with flexible finishes  (Snow or Wind load) = N/A

Partitions with flexible finishes  (Dead + Live Load) = N/A

 

Farm Buildings Deflection Limits

Farm Buildings (Live Load) = N/A

Farm Buildings (Snow or Wind load) = N/A

Farm Buildings (Dead + Live Load) = L/180

 

Greenhouses

Greenhouses (Live Load) = N/A

Greenhouses (Snow or Wind load) = N/A

Greenhouses (Dead + Live Load) = L/120

04/16/2018

Uniform Live Load Reduction Using ASCE 7-10, Section 4.7

In this post, I will provide a brief overview of how to reduce uniform live loads using ASCE 7-10, Section 4.7. This post does not cover the reduction of roof uniform live loads. .

 

Uniform Live Load Reduction Formula, ASCE Equation 4.7-1

 

 

Parameter Definitions

 

L = Reduced design live load per ft2 (m2) of area supported by the member

Lo = Unreduced design live load per ft2 (m2) of area supported by the member (ASCE 7-10, Table 4-1)

KLL = Live Load Element Factor (Table 4-2)

AT = Tributary area in ft2 (m2)

 

 

Limitations / Conditions for Reducing Live Loads

 

  1. Uniform live loads may only be reduced if the limitations listed in Sections 4.7.3 – 4.7.6 are satisfied
  2. Uniform load loads may only be reduced for members for which the product of the live load element factor and tributary area is at least 400 ft(KLL*AT ≥ 400)
  3. L  ≥ 0.5L for members supporting one floor
  4. L  ≥ 0.4L for members supporting two or more floors
04/16/2018

Live Load Element Factors Used in the Reduction of Uniform Live Loads per ASCE 7-10, Table 4-2

In this post, I will provide a brief overview of the live load element factors,KLL, used in the reduction of uniform live load specified in ASCE 7-10, Table 4-2.

 

Live Load Element Factors, KLL, by Element Type

 

Live load element factor for interior columns, KLL =  4

Live load element factor for exterior columns without cantilever slabs, KLL =  4

Live load element factor for edge columns with cantilever slabs, KLL = 3

Live load element factor for corner columns with cantilever slabs, KLL = 2

Live load element factor for edge beams without cantilever slabs, KLL = 2

Live load element factor for interior beams, KLL = 2

Live load element factor for edge beams with cantilever slabs, KLL = 1

Live load element factor for cantilever beams, KLL = 1

Live load element factor for one-way slabs , KLL = 1

Live load element factor for two-way slabs, KLL = 1

Live load element factor for members without provisions for continuous shear transfer normal to their span, KLL = 1

Live load element factor for all other members not identified, KLL = 1

 

04/14/2018

Importance Factors by Risk Category of Buildings and Other Structures for Snow, Ice, and Earthquake Load per ASCE 7-10, Section 1.5

In this post, I will provide a brief overview of the importance factors by risk category of buildings and other structures for snow, ice, and earthquake loads that are specified in ASCE 7-10, Section 1.5. 

 

Risk Category I

 

Snow Importance Factor, Is = 0.80

Ice Importance Factor – Thickness, Ii = 0.80

Ice Importance Factor – Wind, Iw = 1.00

Seismic Importance Factor, Ie = 0.80

 

Risk Category II

 

Snow Importance Factor, Is = 1.00

Ice Importance Factor – Thickness, Ii = 1.00

Ice Importance Factor – Wind, Iw = 1.00

Seismic Importance Factor, Ie = 1.00

 

Risk Category III

 

Snow Importance Factor, Is = 1.10

Ice Importance Factor – Thickness, Ii = 1.25

Ice Importance Factor – Wind, Iw = 1.00

Seismic Importance Factor, Ie = 1.25

 

Risk Category IV

 

Snow Importance Factor, Is = 1.20

Ice Importance Factor – Thickness, Ii = 1.25

Ice Importance Factor – Wind, Iw = 1.00

Seismic Importance Factor, Ie = 1.50

04/13/2018

Nominal Load Combinations for Allowable Stress Design in ASCE 7-10

In this post, I will provide a brief overview of the nominal load combinations for allowable stress design that are specified in ASCE 7-10, Section 2.4. Before identifying the load combinations, it’s a good idea to review the definitions of parameters used in these allowable stress design load combination formulas.

 

Parameter Definitions

D = Dead Load

E = Earthquake Load

L =Live Load

Lr = Roof Live Load

R = Rain Load

S = Snow Load

W = Wind Load

 

Load Combinations for Allowable Stress Design, Formulas

  1. D
  2. D + L
  3. D + (Lr or S or R)
  4. D + 0.75L + 0.75(Lr or S or R)
  5. D + (0.6W or 0.7E)
  6. D + 0.75L + 0.75(0.6W) + 0.75(Lr or S or R)
  7. D + 0.75L + 0.75(0.7E) + 0.75S
  8. 0.6D + 0.6W
  9. 0.6D + 0.7E

 

Load Combinations for Allowable Design, Text

  1. Dead load
  2. Dead load + Live load
  3. Dead load + the maximum of (roof live load or snow load or rain load)
  4. Dead load + 0.75 times live load + 0.75 times the maximum of (roof live load or snow load or rain load) 
  5. Dead load + the maximum of (0.6 times wind load or 0.7 times earthquake load)
  6. Dead load + 0.75 times live load + 0.75 times 0.6 times wind load + 0.75 times the maximum of (roof live load or snow load or rain load)
  7. Dead load + 0.75 times live load + 0.75 times 0.7 times earthquake load + 0.75 times snow load
  8. 0.6 times dead load + 0.6 times wind load
  9. 0.6 times dead load + 0.7 times earthquake load