Tilt-up concrete commercial and industrial buildings in California may be extremely vulnerable to collapse in earthquakes if built prior to the late 1990s under less stringent building codes existing at the time.
While economical to construct and requiring minimal maintenance, the flawed design standard used for these older buildings leaves them likely to fail in earthquakes. These oider tilt-up buildings can be made more safe by seismic retrofits, which typically include providing wall supports and securing connections of wooden roofs to walls to prevent collapses.
Tilt-up buildings are favored for large commercial and industrial uses, where they are occupied by workers, machines and business inventory. However, building and business owners face serious consequences caused by full or partial collapse during earthquakes that can be very costly in terms of death, injuries and loss of products, supplies and highly technical equipment. The cost of losses inside these buildings can often be far greater than the actual value of the building itself.
Structural engineering experts at Optimum Seismic, Inc. indicate there are multiple benefits to retrofitting an aging tilt-up building. These benefits include:
- Limiting property damage by ensuring your building’s structural safety
- Preventing loss of equity and income due to earthquakes
- Avoiding building replacement costs
- Avoiding costly litigation and judgements for earthquake liability
- Limiting business interruption costs
- Limiting loss of market share for your business
- Extending the building’s life
- Improving the value and marketability of the building
- Limiting the risk of deaths and injuries to tenants and employees
- Reducing insurance costs
- Meeting financial institution requirements for financing
Tilt-ups get their name from the construction method used to cast concrete walls on a slab before they are pulled – or tilted – into place. The roof is then lifted and set into place, tying the structure together.
Tilt-up buildings grew in popularity in California following World War II. Tragically, the 1971 San Fernando earthquake revealed shortcomings of tilt-up construction in relation to earthquakes. In many cases, the connection between the roof and walls was simply inadequate to provide proper support at the top of the walls. As a result, heavy concrete walls would separate from the roof, leading to partial or total collapse.
Despite updated building codes following the San Fernando quake, the Northridge earthquake in 1994 again illustrated deficiencies with tilt-up construction, as some 400 tilt-up structures sustained significant damage. According to Structure magazine, tilt-up buildings erected prior to the Northridge quake are subject to partial collapse during a moderate earthquake.
The primary concern with tilt-up structures related to seismic movement is a deficiency in the roof-to-wall anchorage systems, such as poorly constructed, flexible or eccentric anchors. Other factors that can create seismic deficiencies include:
- Irregular shapes or configurations of the building
- Wall panels with large, unreinforced openings
- Irregular corners or buttress walls
- Mezzanines, canopies or multiple roof levels
- Roofs weakened by leaks or previous damage
- Proximity to a fault line
Developing engineering plans and constructing a retrofit for a tilt-up structure is a practical and generally inexpensive process. A full-service tilt-up building retrofit may commonly include:
- Addition of roof-to-wall anchors
- Installation of continuity ties
- Roof nailing (if needed or scheduled as part of a re-roof)
- Steel braced frames and concrete footings (if needed based on the building’s geometry)
It is simply good business and good economics for building owners to protect themselves from the numerous threats earthquakes bring in terms of loss of life, injury, legal liability and repair costs.
Contact Optimum Seismic today to have our professional engineers assess your building’s structural integrity. If necessary, our experienced construction team is also available to perform your earthquake retrofit and help your building pass seismic inspection and code standards.
Optimum Seismic is a recognized expert in seismic engineering, steel fabrication and retrofit construction in California. The Optimum Seismic team has decades of experience working with clients to customize solutions that match their goals and needs. Contact Optimum Seismic today to arrange for a complimentary assessment of your concrete tilt-up building’s structural safety.