Seismic Evaluation and Retrofit of Existing Buildings

Prepared by the Seismic Evaluation and Retrofit of Existing Buildings Committee of the Codes and Standards Activities Division of the Structural Engineering Institute of ASCE

Seismic Evaluation and Retrofit of Existing Buildings, Standard ASCE/SEI 41-23, describes deficiency-based and systematic procedures that use performance-based principles to evaluate and retrofit existing buildings to withstand the effects of earthquakes. The standard presents a three-tiered process for seismic evaluation according to a range of building performance levels by connecting targeted structural performance and the performance of nonstructural components with seismic hazard levels. The deficiency-based procedures allow evaluation and retrofit efforts to focus on specific potential deficiencies deemed to be of concern for a specified set of building types and heights. The systematic procedure, applicable to any building, sets forth a methodology to evaluate the entire building in a rigorous manner.

This standard establishes analysis procedures and acceptance criteria and specifies requirements for foundations and geologic site hazards; components made of steel, concrete, masonry, wood, and cold-formed steel; architectural, mechanical, and electrical components and systems; and seismic isolation and energy dissipation systems. Checklists are provided for a variety of building types and seismicity levels in support of the Tier 1 screening process. This new edition, which updates and replaces previous versions of ASCE 41, introduces provisions to align with the multipoint response spectra in the new USGS seismic hazard model. The standard now points to AISC 342 and ACI 369 for provisions related to structural steel and reinforced concrete existing buildings, respectively, both of which significantly revised the provisions found in the 2017 edition of the standard. There are a number of other changes, including significant revisions to the nonlinear analysis provisions, how to develop structural component modeling parameters and acceptance criteria, and provisions for unreinforced and reinforced masonry.

ASCE 41-23 is a primary reference for structural engineers addressing the seismic resilience of existing buildings and for building code officials reviewing such work. It also will be of interest to architects, construction managers, academic researchers, and building owners.