Steel Frame Building Issues

Larger imageTwo types of cracks found in steel frame buildings after earthquakes.

Source: Adapted from a photo provided by the Los Angeles Times

The Problem

In past earthquakes, fractures (cracks) occurred in steel frame buildings built before 1995 in two locations:

  1. In welds and steel elements in or near steel beam-to-column connections (see drawing and photo A below); and
  2. In column base plates (see photo B).

Such fractures are often small and hard to detect because they may be covered by fireproofing, interior walls and ceilings, and exterior facades. Slender or thin-walled steel braces can buckle prematurely in buildings built before 1982 (see photo C).

Larger imagePhoto A - This steel frame connection unexpectedly cracked in the 1994 Northridge earthquake.

Source: Earthquake Engineering Research Institute

Larger imagePhoto B - A 4-inch-thick steel plate supporting the base of a column at the Oviatt Library at CSU Northridge fractured in the 1994 earthquake.

Source: Earthquake Engineering Research Institute

Larger imagePhoto C - A six-story steel braced frame building was damaged after the 1995 Kobe Earthquake in Japan. 4,000 to 8,000 small commercial buildings and 1,000 to 2,000 large commercial buildings were destroyed or severely damaged in that event.

Source: Earthquake Engineering Research Institute


The reasons for damage to steel members are not fully known but may include workmanship, design, welding procedures, and material characteristics.

Some buildings with subtle structural damage also will suffer movement-related damage such as cracked finishes around columns and beams, cracked or out-of-plumb partitions or door frames, damaged ceilings, and broken glass. In cases of extreme damage, partial collapse may be possible

How to Identify

If your steel frame buildings have been exposed to strong ground shaking in the past and you have observed the damage described above, contact an appropriately experienced structural or civil engineer or architect to assess the need to investigate critical areas in the buildings. Owners of other steel buildings who are concerned about the potential for such damage are also encouraged to obtain qualified opinions.

Building investigations typically involve removing finishes and fireproofing at the beam column connections, visual observations, and testing, where appropriate. This work may disrupt occupants for a short time.

The Solution

Repair and retrofit techniques and recommended guidelines are currently available from the Federal Emergency Management Agency (FEMA 350 to 353), the American Institute of Steel Construction (AISC 2005 Seismic Provisions and AISC 358) and the International Code Council (ICC) (see "Resource Organizations" below). Local government ordinances may also apply. Engineers should obtain and consider these latest guidelines, codes and standards when designing retrofits or repairs.


RESOURCE ORGANIZATIONS

Structural Safety Information:

American Institute of Architects
Local chapters have referral lists of licensed architects; consult telephone directory listing for "American Institute of Architects."
http://www.aia.org/

Structural Engineers Association of California
1730 I Street, Suite 240,
Sacramento, CA 95814-3017
Telephone: (916) 447-1198
http://www.seaoc.org/

Local chapter organizations have referral list for licensed structural engineers as follows:
San Diego - http://www.seaosd.org/
Southern California - http://www.seaosc.org/
Northern California - http://www.seaonc.org/
Central California - http://www.seaocc.org/

Consulting Engineers and Land Surveyors of California
1303 J Street, Suite 450
Sacramento, CA 95814
Telephone: (916) 441-7991
http://www.celsoc.org/
A referral list for licensed engineers is available.

International Code Council
5360 Workman Mill Road
Whittier, CA 90601-2298
Telephone: (800) 284-4406
http://www.iccsafe.org/

©2017 SCEC Southern California Earthquake Center @ USC