Guide to Earthquake Vulnerable Commercial Building Types

Certain building types are particularly vulnerable to damage in earthquakes. This page provides a summary of some of these building types that are typical for commercial buildings.

Jump to: unreinforced masonry buildings | tilt-up concrete buildings | non-ductile concrete frame buildings | non-structural elements |other construction types

Unreinforced Masonry Buildings

Unreinforced masonry (URM) buildings have no steel reinforcing within a masonry wall. Anchorage of the wall to the floor and roof is generally missing and the mortar is typically of low strength. Nearly all URM structures in California were built before 1933. Many URM buildings have been retrofitted as a result of local ordinances mandated by California state law.

Expected damage: Unretrofitted buildings may incur substantial damage including severely cracked or collapsed walls. Separation may also occur between the floors and the walls, jeopardizing the vertical support of roof and floor systems, leading to collapse.

Retrofit Approach: Typical retrofit activities include tying walls to floor and ceiling elements or anchoring unsupported masonry walls, installing bracing, or applying overlays to the walls to add strength.

Local Governments: Mitigation and policy opportunities | Find out what other local governments are doing
Building Owners: Benefits of mitigating your building

Tilt-Up Concrete Buildings

Tilt-ups are relatively cheap and fast to build, and are common as warehouses, strip malls, and light industrial facilities. Many tilt-up warehouses have also been repurposed as offices, recreational facilities, and even schools or assembly buildings. Most tilt-up concrete buildings built prior to 1995 lack adequate connection between the roof and the walls.

Expected damage: Typically when the walls are rigid and the roof is flexible, the connection between the roof and walls fail and the wall panels can fall away from the building, causing the roof to collapse into the building.

Retrofit approach:The main retrofit approach is to bracket the walls to the roof, which reduces the chances of the walls separating from the roof and collapsing.

Local Governments: Mitigation and policy opportunities | Find out what other local governments are doing
Building Owners: Benefits of mitigating your building

Non-Ductile Concrete Frame Buildings

Concrete structures need embedded steel reinforcing bars to add ductility, or the ability to bend without breaking. Many pre-1980 concrete structures may not contain adequate reinforcement and may be deadly in an earthquake.

Expected damage: Lateral movement from earthquake shaking can put too much strain on non-ductile concrete buildings, pushing them past their breaking point and causing catastrophic collapse.

Retrofit approach: Retrofitting non-ductile concrete buildings includes jacketing or wrapping concrete structural columns to improve strength and ductility of the columns or adding interior walls to increase the strength and ductility of the entire structure. Non-ductile concrete structures often require sophisticated engineering for evaluation or retrofit design.

Local Governments: Find out what other local governments are doing
Building Owners: Benefits of mitigating your building

Non-Structural Elements

Non-structural external building components such as chimneys, brick veneer, concrete cladding, parapets, or decorative features can pose falling hazards during an earthquake. Internal non-structural elements within the building including HVAC equipment, shelving and other furniture, windows, and light fixtures may also be hazardous.

Expected damage: External components can become detached from the building, threatening people below. Interior elements may fall and injure occupants, impede evacuation or access to injured people, or, if the elements themselves sustain damage, can take a building out of service.

Retrofit approach: Restraints and braces can be used to attach furniture, HVAC, and other equipment to structural elements. Bolting and additional means of attachment can be used for external decorative elements. More information on bracing and bolting.

Local Governments: Mitigation and policy opportunities
Building Owners: Get additional information about securing nonstructural elements

Other Construction Types

Other vulnerable construction types include soft-story wood frame buildings, which typically have large wall openings in the form of garages or storefronts on the ground floor, making the first story vulnerable to collapse in an earthquake. More information on soft-story buildings.

Local Governments: Soft-story mitigation and policy opportunities
Building Owners: Benefits of mitigating your building

Additional Information

Guide to Earthquake Vulnerable Housing Types
Last updated: 09.17.2014