It shall be permitted to design a structural system comprising structural members not in accordance with 4.4.1 and 4.4.2, provided the structural system is approved in accordance with 1.10.1.

The structural system shall be designed to resist the factored loads in load combinations given in 4.3 without exceeding the appropriate member design strengths, considering one or more continuous load paths from the point of load application or origination to the final point of resistance.

4.4.5

Structural systems shall be designed to accommodate anticipated volume change and differential settlement.

4.4.6 Seismic-Force-Resisting System

4.4.6.1

Every structure shall be assigned to a Seismic Design Category in accordance with the general building code or as determined by the authority having jurisdiction in areas without a legally adopted building code.

4.4.6.2

Structural systems designated as part of the seismic-force-resisting system shall be restricted to those systems designated by the general building code or as determined by the authority having jurisdiction in areas without a legally adopted building code.

4.4.6.3

Structural systems assigned to Seismic Design Category A shall satisfy the applicable requirements of this Code. Structures assigned to Seismic Design Category A are not required to be designed in accordance with Chapter 18.

4.4.6.4

Structural systems assigned to Seismic Design Category B, C, D, E, or F shall satisfy the requirements of Chapter 18 in addition to applicable requirements of other chapters of this Code.

4.4.6.5

Structural members assumed not to be part of the seismic-force-resisting system shall be permitted, subject to the requirements of 4.4.6.5.1 and 4.4.6.5.2.

4.4.6.5.1

In structures assigned to Seismic Design Category B, C, D, E, or F, the effects of those structural members on the response of the system shall be considered and accommodated in the structural design.

4.4.6.5.2

In structures assigned to Seismic Design Category B, C, D, E, or F, the consequences of damage to those structural members shall be considered.

4.4.6.5.3

In structures assigned to Seismic Design Category D, E, or F, structural members not considered part of the seismic-force-resisting system shall meet the applicable requirements in Chapter 18.

4.4.6.6

Effects of nonstructural members shall be accounted for as described in 18.2.2.1 and consequences of damage to nonstructural members shall be considered.

4.4.7 Diaphragms

4.4.7.1

Diaphragms, such as floor or roof slabs, shall be designed to resist simultaneously both out-of-plane gravity loads and in-plane lateral forces in load combinations given in 4.3.

4.4.7.2

Diaphragms and their connections to framing members shall be designed to transfer forces between the diaphragm and framing members.

4.4.7.3

Diaphragms and their connections shall be designed to provide lateral support to vertical, horizontal, and inclined elements.

4.4.7.4

Diaphragms shall be designed to resist applicable lateral loads from soil and hydrostatic pressure and other loads assigned to the diaphragm by structural analysis.

4.4.7.5

Collectors shall be provided where required to transmit forces between diaphragms and vertical elements.

4.4.7.6

Diaphragms that are part of the seismic-force-resisting system shall be designed for the applied forces. In structures assigned to Seismic Design Category D, E, and F, the diaphragm design shall be in accordance with Chapter 18.

4.5 Structural Analysis

4.5.1

Analytical procedures shall satisfy compatibility of deformations and equilibrium of forces.

4.5.2

The methods of analysis given in Chapter 6 shall be permitted.

4.6 Strength

4.6.1

Design strength of a member and its joints and connections, in terms of moment, axial force, shear, torsion, and bearing, shall be taken as the nominal strength S_n multiplied by the applicable strength reduction factor ϕ.

4.6.2

Structures and structural members shall have design strength at all sections, ϕS_n, greater than or equal to the required strength U calculated for the factored loads and forces in such combinations as required by this Code or the general building code.

4.7 Serviceability

4.7.1

Evaluation of performance at service load conditions shall consider reactions, moments, torsions, shears, and axial forces induced by prestressing, creep, shrinkage, temperature change, axial deformation, restraint of attached structural members, and foundation settlement.

4.7.2

For structures, structural members, and their connections, the requirements of 4.7.1 shall be deemed to be satisfied if designed in accordance with the provisions of the applicable member chapters.

4.8 Durability

4.8.1

Concrete mixtures shall be designed in accordance with the requirements of 19.3.2 and 26.4, considering applicable environmental exposure to provide required durability.

4.8.2

Reinforcement shall be protected from corrosion in accordance with 20.6.

4.9 Sustainability

4.9.1

The licensed design professional shall be permitted to specify in the construction documents sustainability requirements in addition to strength, serviceability, and durability requirements of this Code.

4.9.2

The strength, serviceability, and durability requirements of this Code shall take precedence over sustainability considerations.

4.10 Structural Integrity

4.10.1 General

4.10.1.1

Reinforcement and connections shall be detailed to tie the structure together effectively and to improve overall structural integrity.

4.10.2 Minimum Requirements for Structural Integrity

4.10.2.1

Structural members and their connections shall be in accordance with structural integrity requirements in Table 4.10.2.1.

Table 4.10.2.1—Minimum requirements for structural integrity

Member type	Section
Nonprestressed two-way slabs	8.7.4.2
Prestressed two-way slabs	8.7.5.6
Nonprestressed two-way joist systems	8.8.1.6
Cast-in-place beam	9.7.7
Nonprestressed one-way joist system	9.8.1.6
Precast joints and connections	16.2.1.8

4.11 Fire Resistance

Upcodes Diagrams

4.11.1

Structural concrete members shall satisfy the fire protection requirements of the general building code.

4.11.2

Where the general building code requires a thickness of concrete cover for fire protection greater than the concrete cover specified in 20.6.1, such greater thickness shall govern.

4.12 Requirements for Specific Types of Construction

4.12.1 Precast Concrete Systems

4.12.1.1

Design of precast concrete members and connections shall include loading and restraint conditions from initial fabrication to end use in the structure, including form removal, storage, transportation, and erection.

4.12.1.2

Design, fabrication, and construction of precast members and their connections shall include the effects of tolerances.

4.12.1.3

When precast members are incorporated into a structural system, the forces and deformations occurring in and adjacent to connections shall be included in the design.

4.12.1.4

Where system behavior requires in-plane loads to be transferred between the members of a precast floor or wall system, (a) and (b) shall be satisfied:

(a) In-plane load paths shall be continuous through both connections and members.

(b) Where tension loads occur, a load path of steel or steel reinforcement, with or without splices, shall be provided.

4.12.1.5

Distribution of forces that act perpendicular to the plane of precast members shall be established by analysis or test.

4.12.2 Prestressed Concrete Systems

4.12.2.1

Design of prestressed members and systems shall be based on strength and on behavior at service conditions at all critical stages during the life of the structure from the time prestress is first applied.

4.12.2.2

Provisions shall be made for effects on adjoining construction of elastic and plastic deformations, deflections, changes in length, and rotations due to prestressing. Effects of temperature change, restraint of attached structural members, foundation settlement, creep, and shrinkage shall also be considered.