Visited SIRVE, an engineering company specializing in base isolation and advanced structural/geotechnical issues. It is an offshoot of the Catholic University. Jack and I are being hosted primarily by Juan Carlos De la LLera, Rafael Riddell, and Karl Luders . They gave us a brief overview of the damage that they have observed. Since 2003, all building over three stories and significant occupancy erected in Chile have to be subject to peer review, done mostly by academics who have consulting firms like SIRVE. Thus, these people have a very good grasp of the state-of-the-art in structural design in Chile.
We discussed how to arrange the teams and we were introduced to several students who will go with us on the visits. The rest of the team will meet them on Sunday. Meeting interrupted about 11:10AM by:
Highlight of the day: the three shocks we felt – the main one seem to have lasted about 45 seconds… it is been a while (about 18 years to be precise) since I had felt one that long. We were in the third floor of a 22 story building and it was quite a ride. People remained calm and did not try to run out of the building. A very organized and calm precautionary evacuation of the building followed the second shock.
Visited several sites that afternoon in and around the Parque Empresarial area, a large complex of new buildings to the North of downtown that suffered significant damage. As in many other locations, soil conditions seem to have played a role. Unconfirmed reports say it was the site of an old lagoon. In addition, it is encircled by mountains so some other interesting seismological/geotechnical issues could be at work here.
Visited a new precast concrete frame-wall building, apparently the first of its type in Chile. The building was under construction and the first five stories (precast concrete) were undamaged. The building had two steel floors on top that were being erected at the time (these floors was a last minute change to the original plan). Several steel beams collapsed as they were not tied in any way to the building. Some anchor bolts failed in the columns in the top floor but these columns were basically flexible flagpoles. Little to be learned for steel here, but lots about precast. The resident engineer shared all details but we were unable to enter the structure. It was relatively unstable and after the morning earthquake no workers were willing to enter it (nor was the owner wanting them to) – this was the case at almost all other buildings on Thursday.
Saw several of the buildings on the Parque Empresarial but were unable to enter them. The Parque Mayor complex had three buildings severely damaged, of which two I think could be total losses (the city had closed them earlier in the day and not even business owners could enter). A similar fate will probably will befall the adjacent Radisson Hotel. All were wall buildings with poorly confined boundary zones. Several other glass covered buildings around were externally undamaged but showed major non-structural damage and had been emptied. As per my previous report, important damage is disappearing fast as owners are implementing repairs very quickly. There is an air of normalcy that is being cultivated; most owners are looking forward and implementing repairs as fast as they can (not necessarily the best strategy, probably, but it makes economic sense to them).
Day 5 – (Friday, March 12) Santiago
Jack and I separated. Jack went to look at some heavily damaged or collapsed buildings (Maipu) and I went looking for damaged industrial facilities and steel buildings.
Visited the Plaza Norte Mall, a modern, heavily damaged mall located near the Parque Empresarial and the collapsed bridges on the Vespucio Norte toll road – again, the level of damage would indicate some ground amplification (not my area, but the damage patterns appear consistent with some soil effects). Three main damaged areas:
A large “new” composite steel floor collapsed due to poor anchorage of the steel beams to the “existing” concrete columns.
A large central, four story courtyard had serious problems due to poor attention to detailing during construction.
A large outside wall (four storied by about 150 ft., long) was leaning due to pounding from the floors and improper anchorage.
Visited a large warehouse/distribution center on Carretera 5. The first floor, used for distribution is a massive precast concrete frame/wall building that was undamaged. The second story, the warehouse, had precast wall panels that collapsed and steel horizontal roof cables that failed. The connection details between the precast wall units and the precast columns were not adequate. Visited extremely fancy new buildings in the Parque Hipico area. Some very large non-structural damage to the plaster walls, evidence of shear failures in some external walls, crushed columns in the bottom story where walls sat on columns.
Only new, severely damaged structure from yesterday’s aftershock is a church downtown Santiago – the archbishop is very worried: will try to find some details on that.
