A Brief History of Los Angeles Seismic Building Codes (20 Pics)

Codes will always be updated and changed in the future as we learn new preventative methods and design for seismic activity. Until we can truly perfect these measures, disasters will ensue and the best thing we can do is change beyond the aftermath. Codes enforced today are sure to protect the millions of people living around Los Angeles and most of Southern California. Though most of this data may seem like gibberish to some, it was all imperative to creating the standards and codes of today’s seismic designs and provisions. This data was taken from the Design Guide Vol. 1: City of Los Angeles Mandatory Earthquake Hazard Reduction in Existing Non-Ductile Concrete Buildings.

The evaluation of existing buildings is significantly enhanced by a thorough understanding of the historical design and construction practices of the time and region. In the early years (pre-1920s), City Council Ordinances regulating building construction were printed in local newspapers as the primary method of public notification of adoption and official compilations were published on an irregular basis.

From 1923-1957 the Los Angeles Building Ordinances were published annually in an industry collection titled the “Los Angeles Annual Builders Guide” as well as other formats.

(1850-1904: pre Code) The first building ordinance of structural relevance was Ordinance No. 100 O.S. adopted by the City Council in 1883 titled “An Ordinance of the Mayor and Council of the City of Los Angeles, for the protection of life and property from fire and explosion, and regulating the erection of buildings”, which provided basic requirements for masonry, iron, wood construction and foundations.

(1905-1932: Pre-code, Concrete Era) In 1905, the Homer Laughlin Annex was constructed in Downtown Los Angeles and was the first reinforced concrete building in the City. In 1906, 16 additional building permits were reportedly issued for reinforced concrete buildings, including the Temple Auditorium and the eight-story Hayward Hotel.

On April 18th, 1906 a 7.8 magnitude earthquake struck San Francisco, destroying much of the city and killing thousands. A majority of the destruction came in the form of fires, which spread through the city at an incredible speed, destroying most city buildings, residential structures and agricultural land.

These fires were the main reason concrete was thereafter highly promoted in construction. Aside from basically being fireproof (non-combustible), it was proven to have superior seismic performance relative to masonry and wooden structures.

Apart from material having much to do with structural failures early on, general labor and most engineered work was constructed by incompetent and non-unionized workers. An example of this is the collapse of the Bixby hotel In 1906. A partial collapse of the hotel in Long Beach killed 10 workers during construction when the shoring was removed prematurely.

Things changed in 1914 when the reinforced concrete ordinance No. 29,974 was passed, providing material testing and inspection requirements for cement and reinforced steel. After the end of WWI in 1918, concrete construction and city development increased significantly. (Picture from 1925 of the City of Los Angeles City Hall)

(1933-1942: Early Low-Code) Another major event that caused significant damage and sparked many structural provisions, was the Long Beach Earthquake on March 10th, 1933. This was a 6.4 magnitude earthquake that killed more than 100 people and destroyed dozens of masonry structures and schools.

As a result, the Los Angeles Building Code (LABC) was the first U.S. building code and earthquake design provision to enforce mandatory seismic lateral force requirements. This was done under City ordinance No. 72,968 published September 6, 1933.

(1943-1959: Low-Code) In the 1943 LABC, significant changes are found in the concrete requirements. The height restriction of 150 feet and 13 stories was removed in 1957, and design provisions were added to the building code to accommodate the demand for tall buildings. Industrial development increased significantly in Los Angeles at the start of WW II in 1941. A residential and commercial development boom followed after the war ended and continued through the 1950s.

(1960-1076: Moderate-Code) Through 1958, LABC requirements for seismic design were local ordinances that generally set the precedent for regional practice. In 1959 the first Structural Engineers Association of California (SEAOC) “Recommended Lateral Force Requirements” (commonly referred to as the “Blue Book”) was published, which served as the basis of the 1960 LABC seismic design requirements. The 1960 LABC version was the first to distinguish shear walls from regular walls.

The 1966 LABC seismic provisions were taken from the Blue Book 2nd Edition, including the requirements for concrete ductile moment-resisting space frames, shear walls and braced frames. The LABC added unique provisions to double the factored load demands in the calculations.

On February 9, 1971 a 6.7 magnitude earthquake struck near Sylmar in the San Fernando Valley, killing 64 people and causing extensive building damage, including the newly constructed reinforced concrete Olive View Hospital.

(1977- Present: High-Code) During the period of 1906 to 1977, the city of Los Angeles was recognized for its early development and adoption of state-of-the-art seismic and concrete design practices, being praised for various industry journals and often setting standards for the region and nation in these areas. From the very first edition in 1959, the SEAOC Blue Book seismic provisions were adopted in-step by the LABC.

Early on, many tall reinforced concrete buildings were height-limited by the building code. Building designers were sometimes directed to provide allowance for additional stories to be constructed when restrictions changes or it became economically viable to expand upward. Early state law would not allow material standards to be adopted wholly by reference. For this reason, prior to 1943 the LABC included detailed material specifications, tests, and inspection requirements, even when they were identical to existing specifications.

(1978-2019 – Modern) Around 1978 the LABC changed the requirements for most multi-family dwellings from wood-frame to steal and concrete construction. In January of 1994 a 6.7 magnitude earthquake struck Northridge, CA just above the San Fernando Valley, killing 57 and injuring over 9,000.

This, in turn, resulted in the most ambitious earthquake prevention ordinance in the United States, calling for mandatory retrofitting on over 15,000 wood-framed soft-story and non-ductile concrete buildings in Los Angeles alone.

Now, in 2019, a good chunk of these have been handled. Many surrounding cities (Santa Monica, Beverly Hills, West Hollywood, Pasadena) have joined in on the efforts of earthquake prevention and have released their own mandatory retrofit ordinances, very similar to the one in Los Angeles.