Lending a Hand With Damage Assessment
Roberto T. Leon, P.E., Ph.D., president of the Structural Engineering Institute, was in Christchurch, New Zealand, when the 6.3 magnitude earthquake struck on Tuesday, Feb. 22. The professor of structural engineering, engineering mechanics and materials at Georgia Institute of Technology’s School of Civil and Environmental Engineering was a week into the start of a teaching fellowship at the University of Canterbury in Christchurch. Below, he relates his experience in aiding building inspections on and off campus in the days that followed the quake; click to read part one of his account.
Wednesday, Feb. 23
Early on Wednesday a number of the civil engineering faculty at Canterbury gathered at the university’s emergency center to begin an assessment of the building conditions at the university. This survey was a great opportunity for me to get an overview of New Zealand construction, as the university owns everything from large multi-story buildings (the 11-story library being the tallest) to numerous single-family homes in the Fedalton area that area used to house visiting faculty. In between is everything from dormitories to laboratory facilities housing hazardous materials. The university moved from downtown in the mid-1960s, and many buildings date from that era. It is important to remember that the New Zealand seismic code went through a big revision in the mid-1980s and that the latest version with significant changes dates from 1992. Having had the experience of the September earthquake, the university’s emergency plan was in full force and I was impressed with the dedication and professionalism of the entire staff. I believe American universities should send people down here in a few months to learn from them, just as they learned from us (much of their emergency planning came from unfortunate episodes in U.S. campuses).
The priority on day one was the student dormitories, so Dr. Andy Buchanan and I went to visit a number of them that dated from the early days of the university. The staff there had done a great job of keeping the students safe and reassured as much as possible (a number of the students were 17-year olds that had just arrived to the university). The vast majority of these buildings are some combination of reinforced concrete frames with infill masonry and concrete shear walls. Without any data except purely my visual observations, it appears that these buildings will have more than twice as many walls as similar buildings in the U.S., and that the sharp distinction that we tend to make between gravity and lateral load systems is not as common here – most of their structures seem to be well tied together so that they have great redundancy and overstrength. The dormitories were basically undamaged, with a couple of areas where spalling or separations led us to recommend very restricted access.
Another important thing that I have learned since arriving in New Zealand is that basically they operate, from an insurance standpoint, on a “no fault” basis for everything. Thus their perception of risk is entirely different from ours – while I would be thinking of the smallest thing that could go wrong with a structure, my New Zealand colleagues have been much more focused on the bigger picture and whether a) the structure performed as intended and b) it presents any obvious immediate hazard to occupants or adjacent structures.
The day continued with surveys to other buildings including the Civil Engineering one, where aside from a few cracks on the shear walls and transfer beams that had already opened up in the previous earthquake and extended somewhat on this, the major damage was a few fallen ceiling tiles and light fixtures. The visit was important to me as my computer (my lifeline) and my bag (with most documents, as I had still had to complete administrative tasks at the university) had been locked in the building since the earthquake and I had had to rely on my very expensive Verizon service from the U.S. for my communications.
Book cases and file cabinets down or emptied by the earthquake were the most common sights in most buildings. Most ceiling tiles that I have seen on the floor in New Zealand are significantly heavier than what we tend to have in the U.S. Thus they are a bigger hazard to human safety. This is also the case for exterior wall panels that architects seem to love here, and which lead to very heavy masses being cantilevered from small projections in the buildings. They are generally well tied together but lead to local damage nevertheless. The vast majority of the buildings that we looked at ended with a “green tag” for the equivalent of a fast Level 2 inspection. In all buildings that I entered mechanical and HVAC systems, including sprinklers and such, performed extremely well; I only saw a couple of situations where there were minor water leaks. Surprisingly, however, not all critical equipment seemed to be well-tied.
There were a number of teams conducting these surveys and addressing the buildings that seemed to have some damage. Probably 35-40 percent of the main buildings were done on that first day. Crews were ready to do rapid intervention as needed for hazmat or similar issues. Overall, again, I think the university did an outstanding job.
Thursday, Feb. 24
We continued very similar work to the one on Tuesday throughout Wednesday; I was paired with a very knowledgeable and bright graduate student from the university and inspected a large number of buildings. For me, some of the more interesting ones were a set of three buildings that contained, as far as I can tell, very clean “Park-Paulay-type” RC moment frames – they looked to be 1960s or 1970s vintage, and behaved very well, although there was some flexural and shear cracking near the corners of the buildings, where the presence of stairways meant there was no floor slab.
A number of buildings at Canterbury were in the process of upgrading following damage from the September earthquake, and the main library was probably the most significant of those buildings. We inspected levels 6 through 11 which contained mostly stacks of books. The newly installed racks seemed to have worked well, as we did not see any collapses (there had been massive collapses of book racks in the previous earthquake, which occurred at night and thus no one was injured), but most books were on the floor on the 11th floor, with progressively less mess as one went down in the building. Much of the retrofit had made it to the 5th floor and there was no significant observable damage in those areas. The only damage was mostly cosmetic (broken windows and damaged partitions) to several cantilevered sections near the top of the building.
There was also damage due to pounding where pedestrian bridges connected buildings; most of this was quite predictable but the amount of visible damage (mostly cosmetic) could be minimized with better detailing. I will try to get permission to post some pictures from what I saw inside buildings at the University; I am not doing it now because the damage is minor (so the pictures show very little), and I would like permission from my hosts before I do so.
We had a meeting of the Erskine fellows in the afternoon, at which the vice-provost updated us on the conditions in the University and the city. The university thinks that staff could be back in during the middle of next week and classes could potentially restart as early as March 7; however, they need permission from the city, and given the conditions there, a date of March 14 or so appears much more likely to me. The university told Erskine fellows to do as they thought best, and basically released us from any commitments.
In the early evening I walked to the southern edge of Hagley Park to attend a briefing at OPUS Engineering on the city’s plan to begin conducting a Level 1 assessment of the entire cordoned-off area in the central business district (CBD). A large number of engineers were there, many who had already been involved in the first round of evaluations to allow rescuers to enter buildings. We got clear, concise instructions as to what was going to happen and were told to show up with a document handed out at the meeting to an entry point near the Art Gallery, where daily introductions and training where to happen at 7:30 a.m. beginning the next day.
Friday, Feb. 25
We finished with the inspections at the university; we were down to looking at the less damaged or intact buildings and to taking a second look at whatever had been flagged as “yellow tags” during the inspection. Most of the latter, along with a smatter of “red tags,” related to situations where broken glass and fallen ceiling tiles required that maintenance come in and do some heavy duty cleanup before any staff could be allowed into the buildings.
I had the opportunity to go shopping – the largest nearby supermarket had reopened on Thursday and was fully stocked (apart from Coca-Cola products, as their distribution center had been badly damaged). A short, small aftershock that occurred while I was there gave me a good idea of how loud and disconcerting an earthquake can be; it was so small that nothing remotely moved much in the shelves, but the noise of containers rattling against each other was certainly impressive. The nearby gas stations (some of which had also reopened on Thursday and most of them in our area by early Friday) were open and there were small queues at all of them, but that is because people are coming from all over the city to find gas here, as the supply is plentiful. The media and government, through social networks, have done a great job of keeping people informed about what is available and where.
Saturday, Feb. 26
I woke up early and met with university colleagues and grad students to go to the Art Gallery and offer our services downtown. It was not difficult to get in as we travelled in only two fully loaded vehicles and many of us had the proper documentation. There were three checkpoints on the way and a heavy police and military presence everywhere. We went through a detailed briefing of what was expected of us, a short safety lecture, and a Q&A sessions before we formed into teams of two (I went with Greg MacRae) that had at least one chartered structural engineer as a member. We had to wait in line for some more paperwork. I got steel-toed Wellington boots that came in very handy alter as I had to walk through a lot of liquefaction muck, and then we were assigned a large block just north of the Avon River to check out. We also were assigned a dedicated search and rescue person to be with us at all times; his name was Darryl and he was from a lake town near Auckland. His job was to stand in the middle of the street and blow a whistle to alert us to any impending danger as Greg and I walked outside the perimeter of the buildings.
As we walked towards our assigned block, I was able to see the damage to some of the landmarks that I had admired only a week before, such as the law courts. Evidence of liquefaction was everywhere, but damage to modern structures ranged from limited to major. All these observations are from a quick, external look at buildings.
The damage to older structures, however, was considerable. Entire sets of adjacent URM two-story buildings along primarily Colombo Street are a total loss. A number of these structures had been damaged in the previous earthquake, as obvious by the number of scaffolding within the rubble. It was not clear whether the scaffold meant that there were active attempts at retrofit or they were only meant to be temporary supports until demolition or repairs could be made. The former Caledonian Hall had been reduced to a mass of rubble.
Damage to older reinforced concrete structures dating from before the latest codes were issued was widespread. For example, a building at the corner of Colombo and Peterborough Streets that appears to be 1960s construction (smooth bars were used in at least some columns) shows column failures in the first floor (soft-story?) along with large damage to non-structural walls. More modern buildings such as TV3 Building on Kilmore Street show only tensile cracking on the columns. The nearby PGC building, dating from the 1960s, is another, now infamous, example of the potential brittleness of older RC structures.
We spent the day tagging all the buildings in this block, including small houses that had suffered severely from improperly tied walls and chimneys to foundation shifts due to liquefaction.
Sunday, Feb. 27
I took the day off and attended services at St. Barnabas Anglican Church on Fendalton Road. Beautiful service outside under sunny skies and warm sun, as the church was damaged and still awaiting an evaluation. The congregation was extremely welcoming as well as hopeful for the future of the city. The indomitable Kiwi spirit means that this city will rise again.