McLellan Advises LA Retrofit Ordinance

Partner Structural Design Engineer Russell McLellan, EIT, yesterday presented design recommendations and a design example at the Strengthening our Cities Summit hosted by the Structural Engineers Association of Southern California (SEAOSC). McLellan was part of a committee that developed the example and recommendations for the new Los Angeles Seismic Retrofit Ordinance.

The objective of the design example was to demonstrate the basic steps to retrofit an existing wood frame building subject to the Los Angeles seismic ordinance, which is officially known as the “Mandatory Earthquake Hazard Reduction in Existing Wood-Frame Buildings with Soft, Weak, or Open-Font Walls”. “The intent of the ordinance is to eliminate the open-front wall line condition that exists on many wood framed multifamily residential buildings where the permit for construction was applied for before January 1, 1978,” said McLellan.

Soft, Weak, or Open-Front Walls

The open-front wall line condition is often the result of an area of the first floor of the building being used for parking with an occupied wood-framed structure above it, and commonly referred to as “tuck-under construction”.

Because at least a portion of the perimeter of a building does not have walls or valid lateral load-resisting system, this open wall line condition can create or add to the severity of a soft or weak story. During strong ground motion, drift may be excessive along the open wall line which could lead to complete or partial collapse of the building. The open wall line condition is considered critical to the seismic performance of the building and represents a clear global stability deficiency of the building during strong ground motion.

Because at least a portion of the perimeter of a building does not have walls or valid lateral load resisting system, this open wall line condition can create or add to the severity of a soft or weak story. During strong ground motion, drift may be excessive along the open wall line which could lead to complete or partial collapse of the building. The open wall line condition is considered critical to the seismic performance of the building and represents a clear global stability deficiency of the building during strong ground motion.

LA Seismic Retrofit Ordinance

1. Wood-framed multifamily buildings that contain large areas of tuck under parking with a stability weakness at the ground floor level – commonly known as a “soft-story” or “weak story” condition. Affected buildings are those with four or more units constructed under original building permit applications prior to January 1, 1978 that contain an identified “soft-wall line”.
2. Non-ductile concrete buildings constructed under original building permit applications prior to January 13th1977. The LA ordinance is they country’s first to mandate compulsory retrofits of concrete buildings.

For more information about the ordinance and how it will impact property owners, investors, brokers, and lenders, see here and here.