The International Code Council (ICC) uses an 18-month code-development cycle and a three-year code-publication cycle. There were more than 350 proposed code changes to the structural provisions in Chapters 16 through 23 of the 2006 IBC. Of these proposed code changes, approximately 200 were successful and will be incorporated into the 2009 edition of the IBC.

This article presents a brief overview of the more significant structural changes in the 2009 IBC. For a complete history of all the successful code changes, refer to the 2009 IBC Code Changes Resource Collection, which is expected to be available from the ICC in the spring of 2009.

This article is presented in two parts: changes to Chapter 16 and 17 were included in Part 1 and was published in the March 2009 issue of Structural Engineer; changes to Chapters 18-23 are included here.

Chapter 18—Soils and Foundations
Substantial portions of Chapter 18 were reorganized, reformatted, and updated to reflect current foundation design and construction practice. The general requirements related to design of all foundations and the specific requirements related to the design of shallow foundations (footings) were reorganized. The deep foundation (piles and piers) requirements were reorganized to eliminate redundancy, resolve conflicting definitions, and simplify the provisions wherever possible. Deep foundations are now classified into two categories: driven deep foundations and cast-in-place deep foundations. Foundation walls, retaining walls, and embedded posts and poles were consolidated into one section. Although most of the changes to Chapter 18 are editorial, some technical changes were made to update the code requirements related to foundations.

Section 1803—The term geotechnical is now consistently used throughout the chapter as it relates to geotechnical investigations and geotechnical reports.

Section 1807.2.3—Determination of the safety factor against sliding for retaining walls was clarified. A clarification in language ensures that lateral soil pressures on both sides of a keyway are considered in the sliding analysis. Where retaining walls are designed for a safety factor against sliding and overturning of 1.5, the code now states that the load combinations of Section 1605 do not apply. An exception was added that permits the factor of safety of 1.1 for overturning and sliding of retaining walls subjected to earthquake loading.

Section 1808.3.1—The code is now consistent with Section 12.13.4 of 2005 American Society of Civil Engineers/Structural Engineering Institute’s Minimum Design Loads for Buildings and Other Structures (ASCE 7-05) regarding reduction of seismic overturning for foundation design where either strength design or allowable stress design load combinations are used.

Sections 1810.3.1.5, 1810.3.5.3.3—New provisions were added to the deep foundation provisions for design and installation of helical pile foundations systems.

Section 1810.3.1.3—Requirements for foundation seismic ties in Seismic Design Category C were relaxed and coordinated the provision for consistency with ASCEI 7-05 Sections 12.13.5.2 and 12.13.6.2.

Chapter 19—Concrete
The majority of changes to the concrete provisions of Chapter 19 were done to coordinate the code requirements with the 2008 edition of the American Concrete Institute’s Building Code Requirements for Structural Concrete (ACI 318-08) standard. New section references in the code correspond to the final published version of ACI 318-08.

Section 1908.1—Many of the amendments to ACI 318-08 in Section 1908 were deleted in the 2009 IBC because these provisions were subsequently incorporated into the 2008 edition of the ACI 318 standard. Changes to the definitions related to structural walls were made to coordinate the terminology used in ACI 318-08 with ASCE 7-05.

Section 1908.1.9—Added exceptions to the anchorage ductility requirements of ACI 318-08 Appendix D apply to anchors designed to resist wall out-of-plane forces with design strengths equal to or greater than the force determined in accordance with ASCE 7-05 Equation 12.11-1 or 12.14-10.

Sections 1909.6.1, 1909.6.3—The structural plain concrete provisions in the code were updated to be consistent with the provisions of ACI 318-08.

Chapter 20—Aluminum
No changes were made to the requirements or referenced standards for design and construction of aluminum structures.

Chapter 21—Masonry
Substantial portions of Chapter 21 were deleted and replaced with references to the 2008 edition of the Building Code Requirements & Specification for Masonry Structures and Related Commentaries, known as the Masonry Standards Joint Committee (MSJC) code. In addition to deleting many code sections, modifications were made to coordinate the requirements in Chapter 21 of the IBC with the provisions in the 2008 MSJC code. In addition, the name of the 2008 MSJC code was changed to TMS 402/ACI 530/ASCE 5.

Seismic design requirements for masonry structures reference the seismic provisions in the MSJC code and Section 1613.

Sections 2106, 1613.6.4—Seismic design coefficients and limitations were added to Section 1613 for autoclaved aerated concrete (AAC) masonry (ordinary reinforced) shear wall systems that extend the use of these systems to Seismic Design Category B and C.

Sections 2111.3, 2111.4, 2113.3, 2113.4—The requirements for reinforcing and anchorage of masonry and concrete fireplaces and chimneys in Seismic Design Category D were extended to also apply to structures in Seismic Design Category C.

Chapter 22—Steel
The most significant change to Chapter 22 is the updated reference to the 2007 editions of the American Iron and Steel Institute (AISI) standards for design of cold-formed steel framing. Many changes correlated the IBC provisions with the latest editions of the various AISI standards.

Section 2206.5—Steel joist manufacturers are now required to submit a certificate of compliance in accordance with Section 1704.2.2.

Section 2209.2—New code language references two new Steel Deck Institute (SDI) standards for design and construction of cold-formed steel floor and roof decks that can be used in lieu of the more formal approach of AISI S100.

Section 2208—Chapter 22 references the latest version of the Rack Manufacturers Institute (RMI) standard that includes many clarifications that address issues related to seismic design of racks in previous editions of the RMI standard. The provisions are now coordinated with ASCE 7-05.

Section 2210.3—For cold-formed steel trusses, the code references the new North American Standard for Cold-Formed Steel Framing—Truss Design (AISI S214). Code language was added for cold-formed steel trusses similar to requirements for wood trusses in Section 2303.4. Specific requirements were added for design of temporary and permanent bracing for cold-formed steel trusses spanning 60 feet or greater. In addition, cold-formed steel trusses spanning 60 feet or greater require special inspection.

Section 2210.5—A new standard for cold-formed steel floor and roof framing has been added. Some editorial changes were made to terminology and code language to be consistent with other code provisions.

Chapter 23—Wood
Sections 2305, 2306, 2307—The most significant change to Chapter 23 is the deletion of substantial portions of Section 2305 because the code now references the 2008 edition of the American National Standards Institute/American Forest & Paper Association National Design Standard (ANSI/AF&PA NDS) Supplement "Special Design Provisions for Wind and Seismic" (SDPWS) standard for lateral design of wood structures. In addition, many general design provisions for wood structures in Section 2306 were also deleted because they are contained in the AF&PA SDPWS standard. Since the SDPWS is a dual-format standard (ASD/LRFD), a reference to the SDPWS was added to Section 2307 for load and resistance factor design (LRFD) of wood structures.

Section 2301.2—Chapter 23 now includes a reference to the new ICC-400 Standard for the Design and Construction of Log Structures, thus giving designers and building officials code provisions for design, construction, and inspection of log construction.

Section 2303.4.3—Specific requirements were added for design of temporary and permanent bracing for wood trusses spanning 60 feet or greater. In addition, wood trusses spanning 60 feet or greater require special inspection.

Section 2304.6.1, Table 2304.6.1—A new table for selecting wood structural panel wall sheathing to resist component and cladding wind loads was added to Section 2304.

Section 2304.9.5—Changes to the provisions for fasteners in preservative-treated and fire retardant-treated wood are intended to reduce confusion between the code requirements and the manufacturer’s recommendations.

Section 2304.9.5.1—Plain carbon steel nails, timber rivets, wood screws, and lag screws used in SBX/DOT and zinc borate preservative-treated wood in an interior, dry environment are not required to be hot dipped galvanized.

Section 2304.11.2.5—A minimum vertical clearance of 2 inches between wood siding and concrete steps, porch slabs, and patio slabs is now specified in the code.
Section 2306.6—Allowable shear values for fiberboard shear walls were modified to be consistent with AF&PA SDPWS for nailed fiberboard shear walls.

Section 2306.7—The allowable shear value for 3/8-inch gypsum lath and 1/2-inch plaster was increased to 180 pounds per linear foot (plf) from 100 plf as it was in previous editions of the code.

Several changes were made to the prescriptive conventional construction provisions in Section 2308 as follows:

Section 2308.2.1—The reference to the outdated ICC legacy Standard SSTD 10—99 was replaced with a reference to the new ICC—600 Standard for Residential Construction in High Wind Regions.

Section 2308.2—The exception for wind speeds up to 110 mph in Exposure Category B was modified so that buildings located in the hurricane-prone region are excluded from using the exception.

Section 2308.2—Code language regarding floor-to-floor and stud height limitations has been clarified.

Section 2308.3.2—Changes were made to the prescriptive wall bracing provisions that clarify connections applies to braced wall lines instead of the braced wall panel portions of a braced wall lines.

Sections 2308.6, 2308.12.8—Prescriptive sill plate anchorage provisions were changed to permit the use of strap anchors in lieu of anchor bolts in general and in high seismic regions where conventional construction is permitted.

Section 2308.9—Except for trimmer and cripple studs at openings in walls, wall studs are now specifically required to be continuous from a support at the sole plate to a support at the top plate to resist out-of-plane loads perpendicular to wall. The result is where scissor trusses are used to create vaulted ceilings, gable end walls must be balloon framed to the bottom chord of the gable end truss or entirely balloon framed to the roof deck.

Referenced standards
Some of the referenced structural standards in the 2009 IBC have been updated and some are the same as in the 2006 IBC. Table 1 shows a comparison of the main structural standards referenced in the 2006 and 2009 IBC.