2006 IBC REQUIREMENTS FOR NONBUILDING STRUCTURES

1
2006 IBC REQUIREMENTS FOR NONBUILDING STRUCTURES

• J. G. (Greg) Soules, P.E., S.E., SECB
• Principal Engineer
• CBI
• The Woodlands, Texas

2007 Structures Congress
2
Nonbuilding Structures

• Self supporting structures other than buildings
  that support gravity loads and resist overturning
  moments at their base.
• In 1997 UBC Requirements located in
• Section 1634 Nonbuilding Structures
• Section 1629 Criteria Selection
• Section 1630 Minimum Design Lateral
  Forces
• In 2006 IBC Refers to ASCE 7-05 including
  Supplement 1
• Chapter 15 - Seismic Design
  Requirements for
• Nonbuilding Structures
• Chapter 12 - Seismic Design
  Requirements for Building
• Structures
• Chapter 13 - Seismic Design
  Requirements for
• Nonstructural
  Components

3
Types of Nonbuilding Structures

• In both 1997 UBC and 2006 IBC there are two types
  of nonbuilding structures
• Those that have seismic force resisting systems
  that are similar to buildings (e.g. pipe racks)
• Those that do not have seismic force resisting
  systems that are similar to a building (e.g. flat
  bottom tanks)

4
Similar vs. Not Similar System
Pipe Rack - Similar
Flat Bottom Tank Not Similar
5
Nonbuilding Structures Limits of Applicability

• 1997 UBC Wherever UBC Adopted (Western States)
• Not required in Seismic Zone 0 but everywhere
  else
• For structures similar to building same
  restrictions as for building structures with
  similar systems.
• For structures not similar to buildings no
  restrictions.
• 2006 IBC applies throughout the US with
  following exceptions
• Not required for Seismic Design Category A except
  Sec11.7
• For structures similar to building same
  restrictions as for building structures with
  similar systems but with additional options.
• For structures not similar to buildings some
  restrictions

6
Nonbuilding Structure Demands

• In both codes same base shear equations used
  for building structures.
• Basically the same equation in the 1997 UBC and
  2006 IBC except for site ground motion
  terminology.
• However, the R values, I values and minimum
  values are significantly different in the two
  codes.
• Also the 2006 IBC specifies Oo and Cd values,
  detailing requirements along with height limits
  and restrictions for all systems while the 1997
  UBC only specifies R and Oo values.

7
ELF Equations for Structures w/ Systems Similar
to Buildings

• 1997 UBC
  2006 IBC
• ( Ts Cv / 2.5 Ca
  ) ( Ts SD1 / SDS )
• T lt Ts V Ca I W
  V SDS W
• R
  (R / I)
• T gt Ts V Cv I W
  V SD1 W
• R T
  (R / I ) T
• 
  T gt TL V SD1TL W
• 
  (R / I ) T2
• Min V V 0.11 CaI W
  V 0.01 W
• Min Zone 4 V 0.8 Z NV I W
  V 0.5 S1 W
• (S1 gt 0.6) R
  (R / I )

8
ELF Equations for Structures w/ Systems Not
Similar to Buildings

• 1997 UBC
  2006 IBC
• ( Ts Cv / 2.5 Ca )
  ( Ts SD1 / SDS )
• T lt Ts V Ca I W
  V SDS W
• R
  (R / I)
• T gt Ts V Cv I W
  V SD1 W
• R T
  (R / I ) T
• 
  T gt TL V SD1TL W
• 
  (R / I ) T2
• Min V V 0.56 CaI W V
  0.03 W (or 0.01 W)
• Min Zone 4 V 1.6 Z NV I W V
  0.8 S1 W (or 0.5 S1 W )
• (S1 gt 0.6) R
  (R / I ) (R / I )

9
Comparison of Minimum Values for Structures Not
Similar to Buildings

• To Compare assume a rock site with I 1.0
• 1997 UBC Z 0.4, Ca 0.40, Nv 1.0,
  Cv 0.4 and
• 2006 IBC SDS 1.0, S1 0.60, SD1
  0.40
• 1997 UBC
  2006 IBC
• R2.2 R3.6
  R 2.2 R3.6
• V min 0.22 W 0.22 W
  0.03 W 0.03 W
• 
  (or 0.01W) (or 0.01W)
• Zone 4 V min 0.29 W 0.17 W
  0.22 W 0.13 W
• 
  (or 0.14W) (or
  0.08W)
• 
  For Comparison Only

10
Emergency Change to Minimum Base Shear Value

• Preliminary results from ATC 63 for tall, RC
  special moment frames seem to indicate that the
  elimination of the 0.044SDSIW minimum base shear
  from ASCE 7-02 was probably an error.
• ASCE 7 Main Committee is currently balloting a
  proposal to reinstate this minimum value as a
  Supplement 2 to ASCE 7-05.

11
Nonbuilding Structure Importance Factor I

• Both the 1997 UBC and 2006 IBC have assigned
  Seismic Importance Factors, I.
• In the 1997 UBC, the value of I is either 1.0
  or 1.25 and is based on the Occupancy Category.
• In the 2006 IBC, the value of I is either 1.0,
  1.25 or 1.5 and is based on largest value from
• Referenced standards for the structure type
• Occupancy Category (Table 11.5-1)
• Specified values in Chapter 15

12
Nonbuilding Structures Similar to BuildingsR
Factors and Height Limits

• In the 1997 UBC, R, Oo and height limits are the
  same as for building structures with 2
  exceptions
• Concrete IMRFs permitted to height of 50 feet
  rather than NP in Zones 3 and 4 if R is taken as
  2.8 rather than 5.5
• Height limits may be increased by 50 if regular
  structures that are not occupied or accessible to
  general public
• In the 2006 IBC, the R, Oo, Cd and height limits
  are same as for building structures with
  additional options
• Height limits of certain systems are permitted to
  higher levels if lower R values are used (see
  next slide)
• SCBF and special shear wall height limits can be
  increased by 50 if regular structures with
  multiple lines of resistance same as permitted
  for buildings

13
Similar Nonbuilding Structure OptionsOrdinary
Steel Concentrically Braced Frames

• System Detailing R
  Height Limit (ft.)
• 
  B C D E F
• Steel OCBFs AISC 341 3.25 NL
  NL 35 35 NP
• With Permitted AISC 341 2.5
  NL NL 160 160 100
• Height Increase
• With Unlimited AISC 360 1.5
  NL NL NL NL NL
• Height

14
Similar Nonbuilding Structure
OptionsIntermediate Moment Frames of Steel

• System Detailing R
  Height Limit (ft.)
• 
  B C D E F
• Steel IMFs AISC 341 4.5
  NL NL 35 NP NP
• With Permitted AISC 341 2.5
  NL NL 160 160 100
• Height Increase
• With Unlimited AISC 341 1.5
  NL NL NL NL NL
• Height

15
Similar Nonbuilding Structure OptionsOrdinary
Moment Frames of Steel

• System Detailing R
  Height Limit (ft.)
• 
  B C D E F
• Steel OMFs AISC 341 3.5
  NL NL NP NP NP
• With Permitted AISC 341 2.5
  NL NL 100 100 NP
• Height Increase
• With Unlimited AISC 360 1.0
  NL NL NL NL NL
• Height

16
Similar Nonbuilding Structure
OptionsIntermediate Reinforced Concrete Moment
Frames

• System Detailing R
  Height Limit (ft.)
• 
  B C D E F
• Concrete IMFs ACI 318 5.0 NL
  NL NP NP NP with Ch. 21
• With Permitted ACI 318 3.0
  NL NL 50 50 50
• Height Increase with Ch. 21
• With Unlimited ACI 318 0.8
  NL NL NL NL NL
• Height with Ch. 21

17
Similar Nonbuilding Structure OptionsOrdinary
Reinforced Concrete Moment Frames

• System Detailing R
  Height Limit (ft.)
• 
  B C D E F
• Concrete OMFs ACI 318 NOT 3.0 NL
  NL NP NP NP
  with Ch. 21
• With Permitted ACI 318 NOT 0.8
  NL NL 50 50 50
• Height Increase with Ch. 21

18
Comparison of Selected Not Similar Nonbuilding
Structure R values

• Structure Type
  R value
• 
  1997 UBC 2006 IBC
• Skirt Supported Vessels 2.9 2 or 3
• Cast in Place Silos 3.6 3.0
• Elevated Tanks/Pressurized Spheres 2.2 2 or 3
• Cooling Towers 3.6 3.5
• Bins and Hoppers 2.9 2 or 3
• Signs and Billboards 3.6 3.5
• Amusement Structures/Monuments 2.2 2.0
• Trussed Towers 2.9 3.0

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Load Combinations

• In both codes, strength, ASD and alternate ASD
  load combinations are provided.
• In both codes, there are Eh and Ev loads.
• In the 1997 UBC Ev may be taken as zero for the
  alternate ASD load combinations. In the 2006 IBC,
  Ev is used and not taken as zero for except for
  foundation sizing.
• In both codes, redundancy factor, ?, is specified
  as 1.0 for not similar nonbuilding structures.
  Same as buildings for similar.
• In both codes, Oo is specified. However in the
  1997 UBC not really explained how to use but its
  explained to a certain extent in the 2006 for
  some nonbuilding structures.

20
Fundamental Period DeterminationFor Nonbuilding
Structures

• In 1997 UBC Requires that period be determined
  by rational methods such as Method B (Rayleigh's
  approach).
• In 1999 SEAOC Bluebook states Method A should not
  apply to both similar and not similar
  nonbuilding structures. Suggests Rayleigh's
  approach or dynamic analysis. BB Section C
  109.1.4
• In 2006 IBC Fundamental Period to be determined
  by rational building type procedures or by the
  Rayleigh's formula Specifically excludes Method
  A type procedures to be used in determining the
  period of nonbuilding structures.
  

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Nonstructural Components vs. Nonbuilding
Structures (NBS)

• In 1997 UBC, no clearly defined boundary between
  nonstructural components (Section 1632) and
  nonbuilding structures (Section 1634)
• Overlap between nonstructural components (Table
  16-O) and nonbuilding structures (Table 16-P).
• Interaction effects must be considered in
  structures supporting flexible nonstructural
  components whose combined weight exceeds 25 of
  structure.

22
Nonstructural Components vs. Nonbuilding
Structures (NBS)

• In 2006 IBC, better defined boundary between
  nonstructural components (ASCE 7-05 Chapter 13)
  and nonbuilding structures (ASCE 7-05 Chapter
  15).
• Most overlap between Table 13.6-1 and Table
  15.4-2 eliminated with possible exception of
  Other.
• If NBS weight less than 25 of combined weight of
  NBS and supporting structure, component designed
  using rules of Chapter 13.
• If NBS weight greater than or equal to 25 of
  combined weight of NBS and supporting structure,
  component designed using rules of Chapter 15.
  Specific rules depend on whether component is
  rigid or flexible. If flexible, interaction
  effects must be considered.

23
Design and Detailing Requirement forStructures
Similar to Buildings

• In 1997 UBC No specific additional requirements
  provided
• In 2006 IBC
• Same requirements as for buildings except where
  noted
• Steel Storage Racks RMI plus additional
  requirements
• Towers supporting tanks and vessels added
  requirements
• Piers and wharves only for those accessible to
  the public

24
Design and Detailing Requirement forStructures
Not Similar to Buildings

• 1997 UBC makes use of approved national
  standards in Section 1634.4 (Tanks with
  Supported Bottoms) and Section 1634.5 (Other
  Nonbuilding Structures) as long as
• Standards conform to same seismic zones and
  occupancy categories.
• Total lateral force and overturning moment not
  less than 80 of values determined using 1997
  UBC.
• Standards must be approved by building official.
• 2006 IBC (ASCE 7-05 Chapter 15) makes use of
  reference standards as follows
• Chapter 15 modifies the seismic provisions of
  these standards.
• Detailing requirements in Table 15.4-1 and 15.4-2
  must be followed.
• For NBS not similar to buildings, only API 650
  10th Ed. Add. 4 and AWWA D100-05 are adopted by
  reference.

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Design and Detailing Requirement forStructures
Not Similar to Buildings

• In 2006 IBC Some requirements provided for the
  following
• Earth Retaining Structures
• Secondary Containment Structures
• Flat Bottom Tanks - AWWA 100, API 650, ACI 313
• Elevated Tanks for Liquids and Granular Material
• Boilers and Pressure Vessels ASME BPVC
• Liquid and Gas Spheres/ Refrigerated ASME BPVC
  API
• Horizontal Vessels

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Final Comments AboutNonbuilding Structures

• Approaches between 1997 UBC and 2006 IBC similar.
• Force levels, height limits and detailing
  requirements for structures similar to
  buildings very different between codes.
• Forces levels for structures not similar to
  buildings very similar except for I factors.
• More detailing requirements provided in the 2006
  IBC.