Engineer Details Earthquake Experience and Aftermath
David T. Biggs, P.E., S.E., Dist.M.ASCE, HTMS, is a consultant and former principal of Ryan-Biggs Associates, a structural engineering firm in Troy, N.Y. He specializes in the design, evaluation, and restoration of masonry structures, forensic engineering, and the development of new masonry products. Biggs was in Christchurch, New Zealand, coincidentally delivering a seminar lecture on structural engineering and seismic forensics when the earthquake struck the city on Tuesday, Feb. 22. In an exclusive to ASCE, the Distinguished Member and member of the Mohawk-Hudson Section provides a diary detailing his experiences as the quake struck, and how he joined fellow engineers in applying his expertise to assessing the safety of buildings in Christchurch. Biggs ultimately spent four days following the quake as an expert inspector. He filed daily diary entries for ASCE, starting with the one below.
Days One and Two
I am in Christchurch, New Zealand, on their south island. I am here at the invitation of Associate Professor Jason Ingham of the University of Auckland’s Department of Civil Engineering. My visit is being sponsored by Fulbright New Zealand, a joint U.S.-New Zealand program. I was requested to provide a series of seminars throughout New Zealand on structural engineering forensics. My presentation was being given along with a seminar by Jason and other University of Auckland professors on seismic assessment and improvement of buildings and foundations.
The earthquake hit Christchurch on Tuesday, Feb. 22, just before 1 p.m. local time. It was a 6.3-magnitude earthquake centered just six miles south of the city. As it struck, I had just completed my portion of the seminar. It was the third city of our tour and only by the luck of scheduling that we were in Christchurch.
The panic was immediate and very scary. People rushed to the streets. Some were crushed by falling parapets; some were trapped in collapsed buildings; a bus had been crushed.
At the time, I was in a 16-story concrete framed building (a Holiday Inn). From my perspective on the 3rd floor, I could see a building that was damaged by their September 2010 earthquake. The unreinforced masonry building had been closed and had temporary bracing. However, the roof of the building swayed about a meter side to side. Amazing that the bracing broke but the roof did not collapse.
I was separated from my colleagues once we reached the streets. A local engineer from the seminar guided me through the streets of Christchurch to his uncle’s home and ultimately to his.
The streets were a mess with sand volcanoes (liquefied sand) that percolated from fissures in roads, in sidewalks, and in grassy areas. Some buildings settled from the shaking and liquefaction.
Unreinforced masonry parapets toppled from buildings throughout the central business district. The famed Christchurch Cathedral tower totally collapsed. Some buildings had been braced following the previous earthquake but could not sustain this shaking.
That first day ended with an attempt to find shelter and food. Power was out in much of the center of the city. Water and sewer were not functioning. Several major fires broke out downtown.
The people were shaken but remained kind, helpful, and pleasant. We found a small motel and there we now stay. The first night seemed like aftershocks struck every 30 minutes or less. Two big ones at 3 a.m. and later at 6 a.m. were on the order of 5 magnitude. Not a very sleepful night!
The next day, Feb. 23, we ventured to the emergency command center. Jason used his contacts from last fall's earthquake investigation, and we were deployed to assess essential facilities for Christchurch to determine if they could reopen. We inspected six government buildings and the headquarters of Housing New Zealand. These were tilt-up concrete, steel-framed, concrete masonry, and concrete-framed buildings. We did Level 2 assessments using ATC 20 type assessments. Our last assignment was to render an open on the Grand Chancellor Hotel, the tallest building in Christchurch. The 20-story concrete frame suffered major damage and appeared as though it was going to topple onto adjacent buildings. Access was not possible but it appeared there was failure of a corner transfer girder that caused the corner to drop over a foot.
I had spent the night before the quake in that building, in a room on the 20th floor. When I had arrived in that room, there was a letter from management stating the building was under some minor cosmetic repair from the September earthquake. The letter stated a structural engineer declared the building safe and that it performed as expected for a major earthquake. Records indicate the 7.1 magnitude earthquake last fall produced accelerations 20 percent of design whereas the Feb 22 quake reached 150 percent of design. The quake was of short duration (about 9 seconds) with 1g horizontal acceleration and as much as 1.8 vertical.
Read on for Day Three of David Biggs' diary.