Section 319 Seismic Criteria Selection for Existing Buildings
This section determines what technical approach is to be used for the seismic evaluation and design for existing buildings. For those buildings or portions of buildings for which Section 317 requires action, the procedures and limitations for the evaluation of existing buildings and design of retrofit systems and/or repair thereof shall be implemented in accordance with this section.
One of the following approaches must be used:
- Method A of Section 320;
- Method B of Section 321, with independent review of a peer reviewer as required in Section 322; or
- For state-owned buildings only, the use of one of the specific procedures listed in Section 319.1.1.
When Method B is chosen it must be approved by the building official, and, where applicable, by the peer reviewer. All referenced standards in ASCE 41 shall be replaced by referenced standards listed in Chapter 35 of the California Building Code.
- [BSC] For buildings constructed to the requirements of California Building Code, 2013 or later edition, as adopted by the governing jurisdiction, that code is permitted to be used in place of those specified in Section 319.1.
- [DSA-SS & DSA-SS/CC] For public schools and community colleges constructed to the requirements of California Building Code, 2013 or later edition, that code is permitted to be used in place of those specified in Section 319.1 provided the building complies with Seismic Design Category D or higher.
[BSC] For state-owned buildings, the following specific procedures located in Appendix A may be used, without peer review, for their respective types of construction to comply with the seismic performance requirements for Risk Category I, II or III buildings:
The existing condition and properties of the entire structure must be determined and documented by thorough inspection of the structure and site, review of all available related construction documents, review of geotechnical and engineering geologic reports, and performance of necessary testing and investigation. Where samples from the existing structure are taken or in situ tests are performed, they shall be selected and interpreted in a statistically appropriate manner to ensure that the properties determined and used in the evaluation or design are representative of the conditions and structural circumstances likely to be encountered in the structure as a whole. Adjacent structures or site features that may affect the retrofit design shall be identified.
The entire load path of the seismic-force-resisting system shall be determined, documented and evaluated. The load path includes all the horizontal and vertical elements participating in the structural response: such as diaphragms, diaphragm chords, diaphragm collectors, vertical elements such as walls frames, braces; foundations and the connections between the components and elements of the load path. Repaired or retrofitted elements and the standards under which the work was constructed shall be identified.
Data collection in accordance with ASCE 41 Section 6.2 shall meet the following minimum levels:
- [BSC] For state-owned buildings, the requirements shall be met following the data collection requirements of ASCE 41, Section 6.2.
- [DSA-SS, DSA-SS/CC] For public schools and community college buildings constructed in conformance with the Field Act, the "Usual" level as defined in ASCE 41, Section 6.2.2.
- [DSA-SS, DSA-SS/CC] For public schools and community college buildings not constructed in conformance with the Field Act, the "Comprehensive" level as defined in ASCE 41, Section 6.2.3.
Qualified test data from the original construction may be accepted, in part or in whole, by the enforcement agency to fulfill the data collection requirements.
- The number of samples for data collection may be adjusted with approval of the enforcement agency when it has been determined that adequate information has been obtained or additional information is required.
- Welded steel moment frame connections of buildings that may have experienced potentially damaging ground motions shall be inspected in accordance with Chapters 3 and 4, FEMA 352, Recommended Post Earthquake Evaluation and Repair Criteria for Welded Moment-Frame Construction for Seismic Applications (July 2000).
Where original building plans and specifications are not available, "as-built" plans shall be prepared that depict the existing vertical and lateral structural systems, exterior elements, foundations and nonstructural systems in sufficient detail to complete the design.
Data collection shall be directed and observed by the project structural engineer or design professional in charge of the design.
When the building is classified as irregular in vertical or horizontal plan by application of ASCE 7, Section 12.3 and/or ASCE 41, Sections 126.96.36.199.1 to 188.8.131.52.4, unless the irregularity is demonstrated not to affect the seismic performance of the building.
Exception: If the retrofit design removes the configurational attributes that caused the building to be classified as irregular, then Section 319.7.2 does not apply and Method A may be used.
All components of the lateral-force-resisting system must have the strength to meet the acceptance criteria prescribed in ASCE 41, Chapter 7 or as prescribed in the applicable Appendix A chapter of this code if a specific procedure in Section 319.1.1 is used. Any component not having this strength shall have its capacity increased by modifying or supplementing its strength so that it exceeds the demand, or the demand is reduced to less than the existing strength by making other modifications to the structural system.
Exception: A component's strength is permitted to be less than that required by the specified seismic load combinations if it can be demonstrated that the associated reduction in seismic performance of the component or its removal due to the failure does not result in a structural system that does not comply with the required performance objectives of Section 317. If this exception is taken for a component, then it cannot be considered part of the primary lateral-load-resisting system.
Where the nonstructural performance levels required by Section 317, Table 317.5 are N-D or higher, mechanical, electrical and plumbing components shall comply with the provisions of ASCE 41, Chapter 13, Section 13.2.
Exception: Modifications to the procedures and criteria may be made subject to approval by the building official, and concurrence of the peer reviewer if applicable. All reports and correspondence shall also be forwarded to the building official.
Structural, geotechnical and construction observation, testing and inspection as used in this section shall mean meeting the requirements of Chapter 17 of the California Building Code, with a minimum allowable level of investigation corresponding to seismic design category (SDC) D. At a minimum the project site will be visited by the responsible design professional to observe existing conditions and to review the construction work for general compliance with approved plans, specifications and applicable structural regulations. Such visits shall occur at significant construction stages and at the completion of the structural retrofit. Structural observation shall be provided for all structures. The plan for testing and inspection shall be submitted to the building official for review and approval with the application for permit.
Additional requirements: For public schools and community colleges, construction material testing, inspection and observation during construction shall also comply with Section 4-333 of the California Administrative Code.
Where modifications of existing structural components and additions of new structural components are initiated for the purpose of improving the lateral-force resisting strength or stiffness of an existing structure and they are not required by other sections of this code, then they are permitted to be designed to meet an approved seismic performance criteria provided that an engineering analysis is submitted that follows:
- The capacity of existing structural components required to resist forces is not reduced, unless it can be demonstrated that reduced capacity meets the requirements of Section 319.8.
- The lateral loading to or strength requirement of existing structural components is not increased beyond their capacity.
- New structural components are detailed and connected to the existing structural components as required by the California Building Code.
- New or relocated nonstructural components are detailed and connected to existing or new structural components as required by the California Building Code.
- A dangerous condition is not created.
Use of ASCE 41 Tier 1 and Tier 2 deficiency only retrofit procedures are pre-approved for use where Section 317.3 does not require an assessment.