The following was approved by the SEAOC Board September 24, 2016.
Seismic retrofit work, both voluntary and mandatory, has been occurring for many years. The recent adoption of mandatory seismic retrofit ordinances by several California jurisdictions, however, has led to an increase in the frequency of requests for engineers to provide seismic evaluations and retrofit designs. While some seismic evaluations or retrofits have a broad focus encompassing the entire structure, in other cases the evaluation and retrofit is partial or targeted, meaning that it addresses one or more specific seismic vulnerabilities rather than the entire seismic force resisting system. In the latter case, the engineer provides a limited scope of services. This article provides a discussion of considerations for such a limited scope of services for seismic evaluation and retrofit work.
A limited scope of services is common when providing architectural or engineering services for existing buildings. An architect or engineer is often asked to look at a particular system or portion of a building in order to provide recommendations for improved performance, or to alter the building to accommodate a particular use. When performing any type of limited services, the design professional communicates to the owner/client the services that will and will not be provided, and if applicable, the performance target associated with the design being provided.
A professional engineer performing limited scope of service projects is guided and governed by the same criteria as when designing new construction, including the California Professional Engineers Act, applicable building codes and ordinances, and the standard of care.
California Professional Engineers Act
The California Professional Engineers Act states that engineering shall be performed by licensed engineers to “safeguard life, health, property and public welfare.” A partial or targeted retrofit improving building performance would be in conformance with the Act. For example, Article 1, Division 93 of the City of Los Angeles Municipal Code (Mandatory Earthquake Hazard Reduction in Existing Wood-Frame Buildings with Soft, Weak or Open-Front Walls) begins with the following statement: “The purpose of this division is to promote public welfare and safety by reducing the risk of death or injury that may result from the effects of earthquakes on existing wood-frame multi-story building.” This wording, as well as similar phrasing found in other ordinances adopted in California, coordinates well with the Professional Engineers Act.
Building Codes and Ordinances
For many years, building codes and guidelines have provided guidance for partial retrofit of potential seismic vulnerabilities. A notable example is Section 3404.5 (through the 2013 Edition of the California Building Code and similar language in the 2016 California Existing Building Code), which broadly permits voluntary seismic improvements of any scope, provided that the improvements do not make a building more earthquake vulnerable. Another notable example is California Existing Building Code (CEBC) Appendix Chapter A3, which includes provisions for retrofit of cripple walls and anchorage to foundations in dwellings. These examples, as well as other similar provisions, are adopted by the State of California and implemented regularly throughout the state. Inherent in these provisions is the recognition that mitigating a single seismic vulnerability, while not addressing all potential seismic vulnerabilities, can encourage building owners and communities to engage in risk reducing seismic retrofit projects. As a result, individual occupants, building owners, and the larger community benefit from such reduced seismic risk.
Standard of Care
The professional service agreements that engineers enter into with their clients often include the stipulation that the standard of care for professional services performed will be the skill level and care ordinarily used by members of the profession performing similar services and practicing under similar circumstances at the same time and in the same locality. With many engineers involved in the design of partial seismic retrofits across the state of California on a daily basis, there is ample practice from which the standard of care for this type of work can be defined.
One fundamental guiding principle within the standard of care is that partial seismic retrofit work should not increase the seismic life-safety hazard posed by the building. This concept is incorporated into the previously discussed Section 3404.5 of the California Building Code, and is fundamental to the concept of providing the benefit of reduced seismic risk.
Partial or targeted seismic retrofits are an acceptable and established approach to reducing seismic risk. This type of limited scope of services project can be performed in accordance with the California Professional Engineers Act, applicable building codes and ordinances, and the standard of care for professional engineers. Furthermore, partial seismic retrofits can encourage building owners and communities to perform seismic retrofit projects that may not otherwise be undertaken. Partial seismic retrofits, or any other work of limited scope, requires clear communication between the engineer and owner.