CBC · California Building Code

How is composite structural steel and concrete regulated?

For homeowners: the California Building Code requires steel beams and composite steel‑and‑concrete parts to be designed to national steel standards (AISC 360), but in seismic situations stricter AISC 341 detailing and extra inspections apply. The code also sets minimum connection strengths and special rules when a concrete slab acts compositely with steel (for example, connection reductions if studs and slab reinforcement meet specified criteria).

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Last reviewed: July 5, 2026

What the code requires — 2–4 sentences

The California Building Code requires that the design, fabrication and erection of structural steel and composite structural steel-and-concrete elements follow the American Institute of Steel Construction (AISC) standards — specifically AISC 360 as the base standard (§2202.1) . Where seismic design is required, the CBC prescribes AISC 341 detailing and quality‑assurance requirements for seismic force‑resisting systems (with specific rules that depend on Seismic Design Category and the chosen response modification coefficient) (§2202.2 and §2202.2.1) . Additional performance and connection minimums for composite frames (for example column splice and beam end‑connection tensile capacity, and stud/diaphragm conditions that permit reduced connection requirements) are found elsewhere in CBC structural provisions (see §1616.2.2.1 and §1616.2.2.2) .

Requirements in detail

Governing standards and scope

  • Base requirement: Design, fabrication and erection of structural steel and composite steel‑concrete elements must be in accordance with AISC 360 (§2202.1) .
  • Seismic force‑resisting systems: When seismic design applies, the CBC requires AISC 341 detailing, fabrication and erection for systems assigned to certain Seismic Design Categories or when chosen R (response modification) values dictate it (§2202.2, §2202.2.1, §2202.2.1.2) .
  • Administrative/special‑jurisdiction modifications: Chapter 22A (DSA/OSHPD amendments) contain agency‑specific modifications and limitations for composite systems; the CBC text identifies those alternate requirements where applicable (§2202A, noted in Chapter 22A) .

Connection and minimum strength rules (decision‑relevant numeric limits)

Decision item Value / limit Code Reference
Governing standard for general composite steel & concrete design AISC 360 (base) §2202.1
Slenderness limit for members in tension (exception) L/r ≤ 300 (for tension‑designed members per exception) §2202.1 (exceptions)
Slenderness limit for members in compression (exception) KL/r ≤ 200 (for compression‑designed members per exception) §2202.1 (exceptions)
Beam/girder end‑connection minimum nominal axial tensile strength ≥ required vertical shear (ASD) or ≥ 2/3 required shear (LRFD); not less than 10 kips (45 kN) §1616.2.2.2
Reduced end‑connection axial requirement when composite slab with studs and distributed reinforcement present ASD: permitted to take connection strength = 1/2 required vertical shear; LRFD: = 1/3 required shear; not less than 10 kips (45 kN) — requires studs ≤ 12 in. o.c. and slab reinforcement area ≥ 0.0015 × concrete area §1616.2.2.2 (exception)
Minimum unit shear strength for contact surface in composite concrete cores (testing) ≥ 100 psi (689 kPa) (sampling & testing requirements apply) §1910.2.4

Notes on the table:

  • The AISC references in the CBC are normative: AISC 360 for general composite design; AISC 341 is required for seismic detailing where the CBC specifies it (§2202.2 series) .
  • The beam‑connection numeric values (10 kips / 45 kN minimum) and the studs/reinforcement criteria that permit reduced connection sizing are stated in the structural integrity section for frame structures (§1616.2.2.2) .

Seismic design branching (how to decide which AISC standard)

  • If seismic design is required, follow §2202.2. The CBC splits the seismic requirements by Seismic Design Category:
    • SD Category B or C: structures may use any construction permitted in §2202, but if an R from ASCE 7 Table 12.2‑1 is used then AISC 341 detailing is required (with an exception for some steel systems allowed to use AISC 360 wording) (§2202.2.1.1) .
    • SD Category D, E or F: AISC 341 detailing and design is required for composite and structural steel seismic systems (with limited exceptions listed in ASCE 7) (§2202.2.1.2) .
  • Practical outcome: For high‑seismic buildings (D/E/F) you must use the seismic provisions of AISC 341 for the seismic force‑resisting components; for lower categories check the R value and specific exceptions in §2202.2.1.1 before assuming AISC 360 alone is sufficient .

Inspection and testing expectations

  • Special inspections and quality assurance: Where AISC 341 is required, the CBC invokes associated special inspection and quality assurance provisions (see CBC Chapter 17 special inspections referencing AISC 341 items) — these include continuous/periodic special inspection requirements for structural steel in seismic force‑resisting systems (§1705.A.13.1 and following) .
  • Composite concrete shear tests: For composite concrete construction there are sampling/testing rules (cores taken and tested at ~28 days) to verify shear capacity of interface — minimum unit shear = 100 psi; sampling frequency specified (§1910.2.4) .

Exceptions & special cases

  • Slenderness exceptions: The CBC includes explicit exceptions to AISC 360 for slenderness ratios (L/r ≤ 300 for tension; KL/r ≤ 200 for compression) for certain non‑typical hanger/bracing conditions (§2202.1 exceptions) .
  • Reduced connection requirements with composite slab: If a concrete slab (monolithic or equivalently bonded) has continuous distributed reinforcement (≥ 0.0015 × concrete area in each orthogonal direction) AND the slab is attached to supporting beams/girders with headed shear studs (3/8‑in. studs or equivalent) at ≤ 12 in. o.c., the code allows reduced axial connection capacity values for beams (§1616.2.2.2 exception) .
  • Agency amendments: DSA (Division of the State Architect) and OSHPD (hospital authority) adopt Chapter 22A modifications that may change allowable systems or require extra provisions for composite systems — always check Chapter 22A when the project is under those jurisdictions (§2202A and related notes) .
  • Alternative system note: The CBC text treats composite steel‑concrete seismic systems as an “alternative system” in some OSHPD jurisdictions unless specifically permitted otherwise (§2202.2.1 preface) .

Common mistakes

  • Assuming AISC 360 is always sufficient in seismic regions. For many seismic force‑resisting systems (especially in SD D/E/F or when certain R values are used) the CBC requires AISC 341 detailing and QA; design in AISC 360 alone can be noncompliant (§2202.2 and §2202.2.1) .
  • Forgetting the minimum connection floor/roof rules in frame integrity provisions. Beam end‑connection axial tensile minima and column splice tensile requirements are mandatory in the structural integrity chapter; these are independent checks beyond AISC code compliance (§1616.2.2.1–.2) .
  • Ignoring special inspection and testing requirements tied to AISC 341 and composite structures (e.g., composite cores testing). If AISC 341 is invoked, the applicable special inspection tasks in Chapter 17 apply and J10 items for composite structures are explicitly identified in the CBC special inspection guidance (§1705 and §1910.2.4) file.
  • Misapplying the composite‑slab “reduction” exception: it only applies when the slab attachment and distributed reinforcement meet the stated criteria (stud size/spacing and reinforcement ratio) — do not reduce connection design without verifying those conditions (§1616.2.2.2 exception) .

Worked example — applied numbers

Scenario: A beam end connection must be checked for axial tensile capacity for a frame member that is part of a non‑special moment frame. Required vertical shear at the end of the beam (from strength calculations) is 30 kips. The project is designed using ASD.

Step 1 — CBC baseline requirement:

  • Per §1616.2.2.2, the end connection must have a minimum nominal axial tensile strength equal to the required vertical shear for ASD (i.e., 30 kips), but not less than 10 kips (45 kN) .

Step 2 — Check if the composite slab exception applies:

  • If the supported slab is attached to the beam with headed shear studs of at least 3/8‑in. dia at an average spacing ≤ 12 in. o.c., and the slab has continuous distributed reinforcement with an area ≥ 0.0015 × concrete area in each orthogonal direction, then the CBC permits taking the nominal axial tensile strength as one‑half the required vertical shear for ASD (i.e., 0.5 × 30 kips = 15 kips), but again not less than 10 kips .

Conclusion for this scenario:

  • If the slab + stud + reinforcement criteria are NOT met → design/verify the end connection for 30 kips (ASD requirement) (§1616.2.2.2) .
  • If the slab + stud + reinforcement criteria ARE met → the connection may be designed/verified for 15 kips (subject to the ≥10 kip floor) (§1616.2.2.2 exception) .

Also check seismic applicability:

  • If the structure is in a high seismic category or the chosen R requires AISC 341, ensure that the connection detailing and fabrication meet AISC 341 and that special inspections per Chapter 17 are performed (§2202.2, §1705) file.

Related provisions

  • §2202.1 — General requirement: design/fabrication/erection per AISC 360 (and slenderness exceptions) .
  • §2202.2 — Seismic design rules for structural steel and composite systems (governs when AISC 341 is required) .
  • §2202.2.1 / §2202.2.1.1 / §2202.2.1.2 — Seismic design categories and when AISC 341 applies; exception allowing certain AISC 360 use for low‑severity steel systems (§2202.2.1.1) .
  • §1616.2.2.1 — Column splice tensile strength requirement (frame integrity rules) .
  • §1616.2.2.2 — Beam end‑connection axial tensile minimums and the composite slab exception (studs + reinforcement criteria) .
  • §1705 (Chapter 17 special inspections) — Quality assurance/special inspection required where AISC 341 is invoked for seismic force‑resisting systems .
  • §1910.2.4 — Composite construction core testing and minimum unit shear strength (100 psi) for cast‑to‑precast interfaces .
  • Chapter 22A (e.g., §2202A and related) — Agency‑specific modifications (DSA/OSHPD) that affect composite systems in those jurisdictions .

Code references

Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:

  • CBC § 0.0015 High relevance — show source text

    Exception: Where concrete slabs with continuous reinforcement having an area not less than 0.0015 times the concrete area in each of two orthogonal directions are present and are either monolithic with or equivalently bonded to beams, girders or columns, the longitudinal reinforcing or prestressing steel passing through the column reinforcement shall have a nominal tensile strength of one-third of the required one-way vertical strength of the connection of the floor or roof system to the column in each direction of beam or slab reinforcement passing through the column.

    1616.2.2 Structural steel, open web steel joist or joist girder, or composite steel and concrete frame structures. Frame structures constructed with a structural steel frame or a frame composed of open web steel joists, joist girders with or without other structural steel elements or a frame composed of composite steel or composite steel joists and reinforced concrete elements shall conform to the requirements of this section.

    1616.2.2.1 Columns. Each column splice shall have the minimum design strength in tension to transfer the design dead and live load tributary to the column between the splice and the splice or base immediately below.

    1616.2.2.2 Beams. End connections of all beams and girders shall have a minimum nominal axial tensile strength equal to the required vertical shear strength for allowable stress design (ASD) or two-thirds of the required shear strength for load and resistance factor design (LRFD) but not less than 10 kips (45 kN). For the purpose of this section, the shear force and the axial tensile force need not be considered to act simultaneously.

    Exception: Where beams, girders, open web joist and joist girders support a concrete slab or concrete slab on metal deck that is attached to the beam or girder with not less than [3] / 8 -inch-diameter (9.5 mm) headed shear studs, at a spacing of not more than 12 inches (305 mm) on center, averaged over the length of the member, or other attachment having equivalent shear strength, and the slab contains continuous distributed reinforcement in each of two orthogonal directions with an area not less than 0.0015 times the concrete area, the nominal axial tension strength of the end connection shall be permitted to be taken as half the required vertical shear strength for ASD or one-third of the required shear strength for LRFD, but not less than 10 kips (45 kN).

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    STRUCTURAL DESIGN

    1616.3 Bearing wall structures. Bearing wall structures shall have vertical ties in all load-bearing walls and longitudinal ties, transverse ties and perimeter ties at each floor level in accordance with this section and as shown in Figure 1616.3.

    FIGURE 1616.3—LONGITUDINAL, PERIMETER, TRANSVERSE AND VERTICAL TIES

    1616.3.1 Concrete wall structures. Precast bearing wall structures constructed solely of reinforced or prestressed concrete, or combinations of these shall conform to the requirements of Sections 16.2.4 and 16.2.5 of ACI 318.

    1616.3.2 Other bearing wall structures. Ties in bearing wall structures other than those covered in Section 1616.3.1 shall conform to this section.

  • CBC § 2201.5 High relevance — show source text

    2201.5 Anchor rods. Anchor rods shall be set in accordance with the approved construction documents. The protrusion of the threaded ends through the connected material shall fully engage the threads of the nuts, but shall not be greater than the length of the threaded portion of the bolts.

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    2201.5.1 Shear transfer at column base plate. [OSHPD 1R, 2 & 5] Where the holes in column base plates are more than [1] / 8 inch (3 mm) larger than the anchor rods, as permitted by AISC 360, the anchor rods shall be designed for the induced bending stresses in combination with axial and shear stresses. Alternatively, shear lugs designed in accordance with ACI 318 Section 17.11 shall be permitted to transfer shear forces between column base plates and the supporting structure.

    SECTION 2202—STRUCTURAL STEEL AND COMPOSITE STRUCTURAL STEEL AND CONCRETE

    2202.1 General. The design, fabrication and erection of structural steel elements and composite structural steel and concrete elements in buildings, structures and portions thereof shall be in accordance with AISC 360.

    Exceptions : [OSHPD 1R, 2 & 5] 1. For members designed based on tension, the slenderness ratio (L/r) shall not exceed 300, except for the design of hangers and bracing in accordance with NFPA 13 and for rod hangers in tension. 2. For members designed based on compression, the slenderness ratio (KL/r) shall not exceed 200, except for the design of hangers and bracing in accordance with NFPA 13.

    2202.2 Seismic design. Where required, the seismic design, fabrication and erection of buildings, structures and portions thereof shall be in accordance with Section 2202.2.1 or 2202.2.2, as applicable.

    2202.2.1 Structural steel seismic force-resisting systems and composite structural steel and concrete seismic force-resist- ing systems. The design, detailing, fabrication and erection of structural steel seismic force-resisting systems and composite structural steel and concrete seismic force-resisting systems shall be in accordance with the provisions of Section 2202.2.1.1 or 2202.2.1.2, as applicable.

    [ OSHPD 1R, 2 & 5 ] Seismic requirements for composite structural steel and concrete construction shall be considered as an alter- native system, except as permitted by Section 2202.4.1.

    2202.2.1.1 Seismic Design Category B or C. Structures assigned to Seismic Design Category B or C shall be of any construction permitted in Section 2202. Where a response modification coefficient, R, in accordance with ASCE 7, Table 12.2-1, is used for the design of structures assigned to Seismic Design Category B or C, the structures shall be designed and detailed in accordance with the requirements of AISC 341. Beam-to-column moment connections in structural steel special moment frames and intermediate moment frames shall be prequalified in accordance with AISC 341, Section K1, qualified by testing in accordance with AISC 341, Section K2, or shall be prequalified in accordance with AISC 358.

  • CBC § 2201A.5.1 High relevance — show source text

    2201 A .5 Anchor rods. Anchor rods shall be set in accordance with the approved construction documents. The protrusion of the threaded ends through the connected material shall fully engage the threads of the nuts, but shall not be greater than the length of the threaded portion of the bolts. 2201A.5.1 Shear transfer at column base plate. Where the holes in column base plates are more than [1] / 8 inch (3 mm) larger than the anchor rods, as permitted by AISC 360, the anchor rods shall be designed for the induced bending stresses in combination with axial and shear stresses. Alternatively, shear lugs designed in accordance with ACI 318 Section 17.11 shall be permitted to transfer shear forces between column base plates and the supporting structure.

    SECTION 2202 A —STRUCTURAL STEEL AND COMPOSITE STRUCTURAL STEEL AND CONCRETE

    2202 A .1 General. The design, fabrication and erection of structural steel elements and composite structural steel and concrete elements in buildings, structures and portions thereof shall be in accordance with AISC 360.

    Exceptions : [OSHPD 1 & 4]

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    STEEL

    1. For members designed based on tension, the slenderness ratio (L/r) shall not exceed 300, except for the design of hangers and bracing in accordance with NFPA 13 and for rod hangers in tension. 2. For members designed based on compression, the slenderness ratio (KL/r) shall not exceed 200, except for the design of hangers and bracing in accordance with NFPA 13.

    2202 A .2 Seismic design. Where required, the seismic design, fabrication and erection of buildings, structures and portions thereof shall be in accordance with Section 2202 A .2.1 or 2202 A .2.2, as applicable.

    2202 A .2.1 Structural steel seismic force-resisting systems and composite structural steel and concrete seismic force- resisting systems. The design, detailing, fabrication and erection of structural steel seismic force-resisting systems and composite structural steel and concrete seismic force-resisting systems shall be in accordance with the provisions of Section 2202 A .2.1.1 or 2202 A .2.1.2, as applicable. Seismic force-resisting systems of structural steel acting compositely with reinforced concrete shall be considered as an alternative system, except as permitted by:

    [DSA-SS] Section 2202A.6.1.

    [OSHPD 1 & 4] Section 2202A.4.1.

    2202 A .2.1.1 Seismic Design Category B or C. Not permitted by DSA-SS and OSHPD.

  • CBC § 1901A.1.1 High relevance — show source text

    1901A.1.1 Application. The scope of application of Chapter 19A is as follows: 1. Structures regulated by the Division of the State Architect-Structural Safety (DSA-SS), which include those applications listed in Section 1.9.2.1. These applications include public elementary and secondary schools, community colleges and state- owned or state-leased essential services buildings. 2. Applications listed in Sections 1.10.1 and 1.10.4, regulated by the Department of Health Care Access and Information/Office of Statewide Hospital Planning and Development (OSHPD). These applications include hospitals and correctional treatment centers.

    1901A.1.2 Amendments in this chapter. DSA-SS and OSHPD adopt this chapter and all amendments.

    Exception: Amendments adopted by only one agency appear in this chapter preceded with the appropriate acronym of the adopt- ing agency, as follows: 1. Division of the State Architect-Structural Safety:

    [DSA-SS] For applications listed in Section 1.9.2.1. 2. Office of Statewide Hospital Planning and Development.

    [OSHPD 1] – For applications listed in Section 1.10.1.

    [OSHPD 4] – For applications listed in Section 1.10.4.

    1901 A .2 R einforced concrete. Structural concrete shall be designed and constructed in accordance with the requirements of this chapter and ACI 318 as supplemented in Section 1905 A of this code, except that plain concrete is not permitted.

    1901 A .3 Anchoring to concrete. Anchoring to concrete shall be in accordance with ACI 318 as supplemented in Section 1905 A, and applies to cast-in (headed bolts, headed studs and hooked J- or L-bolts), post-installed expansion (torque-controlled and displacement-controlled), undercut, screw, and adhesive anchors.

    1901 A .4 Composite structural steel and concrete structures. Systems of structural steel acting compositely with reinforced concrete shall be designed in accordance with Section 2206 A of this code.

    1901 A .5 Construction documents. The construction documents for structural concrete construction shall include:

    1. The specified compressive strength of concrete at the stated ages or stages of construction for which each concrete element is designed.
    2. The specified strength or grade of reinforcement.
    3. The size and location of structural elements, reinforcement and anchors.
    4. Provision for dimensional changes resulting from creep, shrinkage and temperature.
    5. The magnitude and location of prestressing forces.
    6. Anchorage length of reinforcement and location and length of lap splices.
    7. Type and location of mechanical and welded splices of reinforcement.
    8. Details and location of contraction or isolation joints.
    9. Minimum concrete compressive strength at time of posttensioning.
    10. Stressing sequence for posttensioning tendons.
    11. For structures assigned to Seismic Design Category D, E or F, a statement if slab on grade is designed as a structural diaphragm. 12. Openings larger than 12 inches (305 mm) in any dimension shall be detailed on the structural drawings.
  • CBC § 2.1 High relevance — show source text

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    1. For members designed based on tension, the slenderness ratio (L/r) shall not exceed 300, except for the design of hangers and bracing in accordance with NFPA 13 and for rod hangers in tension. 2. For members designed based on compression, the slenderness ratio (KL/r) shall not exceed 200, except for the design of hangers and bracing in accordance with NFPA 13.

    2202 A .2 Seismic design. Where required, the seismic design, fabrication and erection of buildings, structures and portions thereof shall be in accordance with Section 2202 A .2.1 or 2202 A .2.2, as applicable.

    2202 A .2.1 Structural steel seismic force-resisting systems and composite structural steel and concrete seismic force- resisting systems. The design, detailing, fabrication and erection of structural steel seismic force-resisting systems and composite structural steel and concrete seismic force-resisting systems shall be in accordance with the provisions of Section 2202 A .2.1.1 or 2202 A .2.1.2, as applicable. Seismic force-resisting systems of structural steel acting compositely with reinforced concrete shall be considered as an alternative system, except as permitted by:

    [DSA-SS] Section 2202A.6.1.

    [OSHPD 1 & 4] Section 2202A.4.1.

    2202 A .2.1.1 Seismic Design Category B or C. Not permitted by DSA-SS and OSHPD.

    2202 A .2.1.2 Seismic Design Category D, E or F. Structures assigned to Seismic Design Category D, E or F shall be designed and detailed in accordance with AISC 341. Beam-to-column moment connections in structural steel special moment frames and intermediate moment frames shall be prequalified in accordance with AISC 341, Section K1, qualified by testing in accordance with AISC 341, Section K2, or shall be prequalified in accordance with AISC 358.

    2202 A .2.2 Structural steel elements. The design, detailing, fabrication and erection of structural steel elements in seismic forceresisting systems, including struts, collectors, chords and foundation elements, shall be in accordance with AISC 341.

    2202A.3 Modifications to AISC 341. [OSHPD 1 and 4]

    2202A.3.1 Section A4. Modify Section A4.1 Item (c) by adding the following:

    (c) Locations and dimensions of protected zones. The fabricator shall permanently mark protected zones of structural elements in the seismic force-resisting system in the building that are designated on the construction documents. If these markings are obscured during construction, such as after the application of fire protection, the owner’s designated representative shall re-mark the protected zones as they are designated on the construction documents. [OSHPD 1 & 4] Primers or paints used to mark protected zones on steel surfaces, which are to receive sprayed fire-resistance material, shall comply with California Building Code Section 704.13.3.2.

  • CBC § 1910A.4 High relevance — show source text

    All couplings shall develop at least 95 percent of the minimum specified strength of the prestress-_ ing steel and shall not reduce the elongation at rupture below the requirements of the tendon itself. 3. If the prestressing tendon is a bar, one 7-foot (2134 mm) length complete with one end anchorage shall be furnished and, in addition, if couplers are to be used with the bar, two 4-foot (1219 mm) lengths of bar fabricated to fit and equipped with one coupler shall be furnished. 4. Mill tests of materials used for end anchorages shall be furnished. In addition, at least one Brinnell hardness test shall be made of each thickness of bearing plate.

    1910A.4 Composite construction cores. Cores of the completed composite concrete construction shall be taken to demonstrate the shear strength along the contact surfaces. The cores shall be tested when the cast-in-place concrete is approximately 28 days old and shall be tested by a shear loading parallel to the joint between the precast concrete and the cast-in-place concrete. The minimum unit shear strength of the contact surface area of the core shall not be less than 100 psi (689 kPa). At least one core shall be taken from each building for each 5,000 square feet (465 m [2] ) of area of composite concrete construction and not less than three cores shall be taken from each project. The architect or structural engineer in responsible charge of the project or his or her representative shall designate the location for sampling.

    1910A.5 Proof tests for post-installed anchors in concrete. When post-installed anchors are used in lieu of cast-in place bolts, the proof test loads, frequency and acceptance criteria shall be in accordance with this section.

    Exceptions. Proof tests are not required for the following:

    1. Undercut anchors that allow visual confirmation of full set.

    2. Repetitively installed anchors (with 3 or more identical anchors) of diameter one-quarter ( [ 1] / 4 ) in. or less used for distributed systems or architectural components. 3. Power actuated fasteners used to attach tracks of interior nonstructural partition walls resisting only shear loads and with at least three fasteners per segment of track. 4. Shear dowels across cold joints in slabs on grade where the slab is not structural in accordance with Section 1907A.1.

    1910A.5.1 General. Test loads or torques, test frequencies, and acceptance criteria shall be shown on the construction documents.

    If any anchor fails testing, all untested anchors of the same type and installed by the same trade shall be tested until twenty (20) consecutive anchors pass, then resume the initial test frequency.

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    CONCRETE

    Anchors to be tested shall be selected at random by the special inspector or inspector of record (IOR), when 100 percent of the anchors are not tested.

    The testing of the post-installed anchors shall be done in the presence of the special inspector and a report of the test results shall be submitted to the enforcement agency.

  • CBC § 2202.2 High relevance — show source text

    2202.2 Seismic design. Where required, the seismic design, fabrication and erection of buildings, structures and portions thereof shall be in accordance with Section 2202.2.1 or 2202.2.2, as applicable.

    2202.2.1 Structural steel seismic force-resisting systems and composite structural steel and concrete seismic force-resist- ing systems. The design, detailing, fabrication and erection of structural steel seismic force-resisting systems and composite structural steel and concrete seismic force-resisting systems shall be in accordance with the provisions of Section 2202.2.1.1 or 2202.2.1.2, as applicable.

    [ OSHPD 1R, 2 & 5 ] Seismic requirements for composite structural steel and concrete construction shall be considered as an alter- native system, except as permitted by Section 2202.4.1.

    2202.2.1.1 Seismic Design Category B or C. Structures assigned to Seismic Design Category B or C shall be of any construction permitted in Section 2202. Where a response modification coefficient, R, in accordance with ASCE 7, Table 12.2-1, is used for the design of structures assigned to Seismic Design Category B or C, the structures shall be designed and detailed in accordance with the requirements of AISC 341. Beam-to-column moment connections in structural steel special moment frames and intermediate moment frames shall be prequalified in accordance with AISC 341, Section K1, qualified by testing in accordance with AISC 341, Section K2, or shall be prequalified in accordance with AISC 358.

    Exception: The response modification coefficient, R, designated for “Steel systems not specifically detailed for seismic resistance, excluding cantilever column systems” in ASCE 7, Table 12.2-1, shall be permitted for structural steel systems designed and detailed in accordance with AISC 360, and need not be designed and detailed in accordance with AISC 341.

    2202.2.1.2 Seismic Design Category D, E or F. Structures assigned to Seismic Design Category D, E or F shall be designed and detailed in accordance with AISC 341, except as permitted in ASCE 7, Table 15.4-1. Beam-to-column moment connections in structural steel special moment frames and intermediate moment frames shall be prequalified in accordance with AISC 341, Section K1, qualified by testing in accordance with AISC 341, Section K2, or shall be prequalified in accordance with AISC 358.

    [OSHPD 1R, 2 & 5] All structural steel seismic force-resisting systems in ASCE 7 Table 15.4-1 shall be designed in accordance with AISC 341.

    2202.2.2 Structural steel elements. The design, detailing, fabrication and erection of structural steel elements in seismic forceresisting systems other than those covered in Section 2202.2.1, including struts, collectors, chords and foundation elements, shall be in accordance with AISC 341 where either of the following applies:

    1. The structure is assigned to Seismic Design Category D, E or F, except as permitted in ASCE 7, Table 15.4-1.
    2. A response modification coefficient, R, greater than 3 in accordance with ASCE 7, Table 12.2-1, is used for the design of the structure assigned to Seismic Design Category B or C.
  • CBC § 22-1 Medium relevance — show source text

    CHAPTER 22 STEEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-1

    2201 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-3

    2202 Structural Steel and Composite Structural Steel and Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . 22-4

    2203 Structural Stainless Steel . . . . . . . . . . . . . . . . . . . . . . 22-6

    2204 Cold-Formed Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-6

    2205 Cold-Formed Stainless Steel. . . . . . . . . . . . . . . . . . . . 22-6

    2206 Cold-Formed Steel Light-Frame Construction . . . . 22-6

    2207 Steel Joists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-7

    2208 Steel Deck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-8

    2209 Steel Storage Racks . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-8

    2210 Metal Building Systems . . . . . . . . . . . . . . . . . . . . . . . . 22-9

    2211 Industrial Boltless Steel Shelving . . . . . . . . . . . . . . . 22-9

    2212 Industrial Steel Work Platforms. . . . . . . . . . . . . . . . . 22-9

    2213 Stairs, Ladders and Guarding for Steel Storage Racks and Industrial Steel Work Platforms . . . . . 22-9

    2214 Steel Cable Structures . . . . . . . . . . . . . . . . . . . . . . . . . 22-9

    2215 Additional Requirements for Community Colleges [DSA-SS/CC] . . . . . . . . . . . . . . .22-9

    2216 Testing and Field Verification

    [OSHPD 1R, 2 & 5]. . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-10

    CHAPTER 22A STEEL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22A-1

    2201A General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22A-3

    2202A Structural Steel and Composite Structural Steel and

  • CBC § 2.1 Medium relevance — show source text

    1616 A .2.1 Concrete frame structures. Frame structures constructed primarily of reinforced or prestressed concrete, either castin-place or precast, or a combination of these, shall conform to the requirements of Section 4.10 of ACI 318. Where ACI 318 requires that nonprestressed reinforcing or prestressing steel pass through the region bounded by the longitudinal column reinforcement, that reinforcing or prestressing steel shall have a minimum nominal tensile strength equal to two-thirds of the

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    STRUCTURAL DESIGN

    required one-way vertical strength of the connection of the floor or roof system to the column in each direction of beam or slab reinforcement passing through the column.

    Exception: Where concrete slabs with continuous reinforcement having an area not less than 0.0015 times the concrete area in each of two orthogonal directions are present and are either monolithic with or equivalently bonded to beams, girders or columns, the longitudinal reinforcing or prestressing steel passing through the column reinforcement shall have a nominal tensile strength of one-third of the required one-way vertical strength of the connection of the floor or roof system to the column in each direction of beam or slab reinforcement passing through the column.

    1616 A .2.2 Structural steel, open web steel joist or joist girder, or composite steel and concrete frame structures. Frame structures constructed with a structural steel frame or a frame composed of open web steel joists, joist girders with or without other structural steel elements or a frame composed of composite steel or composite steel joists and reinforced concrete elements shall conform to the requirements of this section.

    1616 A .2.2.1 Columns. Each column splice shall have the minimum design strength in tension to transfer the design dead and live load tributary to the column between the splice and the splice or base immediately below.

    1616 A .2.2.2 Beams. End connections of all beams and girders shall have a minimum nominal axial tensile strength equal to the required vertical shear strength for allowable stress design (ASD) or two-thirds of the required shear strength for load and resistance factor design (LRFD) but not less than 10 kips (45 kN). For the purpose of this section, the shear force and the axial tensile force need not be considered to act simultaneously.

    Exception: Where beams, girders, open web joist and joist girders support a concrete slab or concrete slab on metal deck that is attached to the beam or girder with not less than [3] / 8 -inch-diameter (9.5 mm) headed shear studs, at a spacing of not more than 12 inches (305 mm) on center, averaged over the length of the member, or other attachment having equivalent shear strength, and the slab contains continuous distributed reinforcement in each of two orthogonal directions with an area not less than 0.0015 times the concrete area, the nominal axial tension strength of the end connection shall be permitted to be taken as half the required vertical shear strength for ASD or one-third of the required shear strength for LRFD, but not less than 10 kips (45 kN).

  • CBC § 2.1.2 Medium relevance — show source text

    2202 A .2.1.2 Seismic Design Category D, E or F. Structures assigned to Seismic Design Category D, E or F shall be designed and detailed in accordance with AISC 341. Beam-to-column moment connections in structural steel special moment frames and intermediate moment frames shall be prequalified in accordance with AISC 341, Section K1, qualified by testing in accordance with AISC 341, Section K2, or shall be prequalified in accordance with AISC 358.

    2202 A .2.2 Structural steel elements. The design, detailing, fabrication and erection of structural steel elements in seismic forceresisting systems, including struts, collectors, chords and foundation elements, shall be in accordance with AISC 341.

    2202A.3 Modifications to AISC 341. [OSHPD 1 and 4]

    2202A.3.1 Section A4. Modify Section A4.1 Item (c) by adding the following:

    (c) Locations and dimensions of protected zones. The fabricator shall permanently mark protected zones of structural elements in the seismic force-resisting system in the building that are designated on the construction documents. If these markings are obscured during construction, such as after the application of fire protection, the owner’s designated representative shall re-mark the protected zones as they are designated on the construction documents. [OSHPD 1 & 4] Primers or paints used to mark protected zones on steel surfaces, which are to receive sprayed fire-resistance material, shall comply with California Building Code Section 704.13.3.2.

    2202A.3.2 Section I2. [OSHPD 1 & 4] Replace Section I2.1 Item (d) as follows:

    (d) Decking attachments that penetrate the beam flange shall not be placed on beam flanges within the protected zone, except power-actuated fasteners up to 0.18 inch in diameter are permitted, provided that the penetration is less than 85 percent of beam flange thickness.

    2202A.4 Modifications to AISC 358. [OSHPD 1 and 4]

    2202A.4.1 Modifications to AISC 358 Chapter 10. [OSHPD 1 and 4] Steel and concrete ConXtech ConXL composite special moment frame connections shall be permitted, provided: 1. Beams are provided with reduced beam sections (RBS); 2. Web extension to beam web two-sided fillet welds are sized to develop expected strength of the beam web and shall not be less than a [1] / 4 inch fillet weld; and 3. The built-up box column wall thickness shall not be less than 1.25 inches and the HSS column wall thickness shall not be less than [1] / 2 inch.

    2202A.4.2 Modifications to AISC 358 Chapter 11 Welded Moment Connection. The welded side plate steel moment connection shall be permitted, provided: 1. The beams shall consist of either rolled or built-up wide flange sections. 2. The biaxial dual-strong axis and column minor axis configurations of the moment connection shall be considered as an alternative system. 3. For SMF and IMF systems, U-shaped cover plates shall be used and the hinge-to-hinge span to beam depth, L h _/d,

  • CBC § 2201A.4.1 Medium relevance — show source text

    2201 A .2 Identification. Identification of steel members shall be in accordance with the applicable referenced standards within this chapter. Other steel furnished for structural load-carrying purposes shall be identified for conformity to the ordered grade in accordance with the specified ASTM standard or other specification and the provisions of this chapter. Where the steel grade is not readily identifiable from marking and test records, the steel shall be tested to verify conformity to such standards. [DSA-SS] All material iden- tification and testing shall be in accordance with Chapter 17A.

    2201 A .3 Protection. The protection of steel members shall be in accordance with the applicable referenced standards within this chapter.

    2201 A .4 Connections. The design and installation of steel connections shall be in accordance with the applicable referenced standards within this chapter. For special inspection of welding or installation of high-strength bolts, see Section 1705 A .2.

    2201A.4.1 Restrained welded connections. [OSHPD 1 & 4] Welded structural steel connections having a medium or high level of restraint, as defined by AWS D1.1 Annex H, shall have a minimum pre-heat temperature of not less than 150 [o] F (66 [o] C). Welded struc- tural steel connections with welds to flange, web, wall or plate having a high level of restraint shall maintain a post-heat temperature of 300 [o] F (149 [o] C) for a minimum of 1 hour after completion of welding.

    2201 A .5 Anchor rods. Anchor rods shall be set in accordance with the approved construction documents. The protrusion of the threaded ends through the connected material shall fully engage the threads of the nuts, but shall not be greater than the length of the threaded portion of the bolts. 2201A.5.1 Shear transfer at column base plate. Where the holes in column base plates are more than [1] / 8 inch (3 mm) larger than the anchor rods, as permitted by AISC 360, the anchor rods shall be designed for the induced bending stresses in combination with axial and shear stresses. Alternatively, shear lugs designed in accordance with ACI 318 Section 17.11 shall be permitted to transfer shear forces between column base plates and the supporting structure.

    SECTION 2202 A —STRUCTURAL STEEL AND COMPOSITE STRUCTURAL STEEL AND CONCRETE

    2202 A .1 General. The design, fabrication and erection of structural steel elements and composite structural steel and concrete elements in buildings, structures and portions thereof shall be in accordance with AISC 360.

    Exceptions : [OSHPD 1 & 4]

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    STEEL

  • CBC § 21A-8 Medium relevance — show source text

    2106A Seismic Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-8

    2107A Allowable Stress Design . . . . . . . . . . . . . . . . . . . . . . . . . 21A-9

    2108A Strength Design of Masonry. . . . . . . . . . . . . . . . . . . . . 21A-10

    2109A Empirical Design of Adobe Masonry . . . . . . . . . . . . . 21A-10

    2110A Glass Unit Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-10

    2111A Masonry Fireplaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-10

    2112A Masonry Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-13

    2113A Masonry Chimneys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-13

    2114A Dry-Stack Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-18

    CHAPTER 22 STEEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-1

    2201 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-3

    2202 Structural Steel and Composite Structural Steel and Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . 22-4

    2203 Structural Stainless Steel . . . . . . . . . . . . . . . . . . . . . . 22-6

    2204 Cold-Formed Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-6

    2205 Cold-Formed Stainless Steel. . . . . . . . . . . . . . . . . . . . 22-6

    2206 Cold-Formed Steel Light-Frame Construction . . . . 22-6

    2207 Steel Joists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-7

    2208 Steel Deck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-8

    2209 Steel Storage Racks . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-8

Frequently asked questions

Does the CBC mandate AISC 341 for all composite steel‑concrete buildings?

Not for all — the CBC mandates AISC 341 for seismic force‑resisting systems when required by Seismic Design Category or by the R value/ASCE 7 criteria; otherwise AISC 360 governs general composite design (§2202.1 and §2202.2) file.

When can connection strength be reduced for composite slabs?

When the slab is monolithic or equivalently bonded, has continuous distributed reinforcement ≥ 0.0015 of the concrete area in each orthogonal direction, and is attached to beams with 3/8‑in. headed shear studs (or equivalent) at ≤ 12 in. o.c.; then the allowable reduction in required end‑connection axial strength permitted by §1616.2.2.2 may be used .

Are special inspections required for composite structural elements?

Yes — where AISC 341 is required (seismic force‑resisting systems) the CBC requires the related special inspection/quality assurance tasks per Chapter 17; composite structure inspection items are explicitly addressed in the special inspection listings (§1705) .

What is the minimum tensile capacity for beam end connections?

Per §1616.2.2.2 the nominal axial tensile strength must be at least the required vertical shear for ASD (or two‑thirds the required shear for LRFD) and not less than 10 kips (45 kN); exceptions can reduce that value when composite slab criteria are met .

How does the CBC verify bond/shear at concrete‑to‑concrete interfaces in composite construction?

The CBC requires composite construction cores be taken and shear‑tested (~28 days) with a minimum unit shear strength of 100 psi (689 kPa) and specified sampling frequencies (§1910.2.4) .

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Structural steel and composite steel‑concrete design (AISC & seismic)

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