The SGH Team gathered for our final “full team” breakfast at the Far Eastern Plaza Hotel in Tainan; because of a business meeting Saturday morning, Po-Chien needed to return to Taipei on Friday afternoon.
Over our breakfast deliberations, we determined that we had visited 12 of 25 sites with significant damage as identified by NCREE. We had yet to see the Wikuan Jinlong Complex, the large apartment collapse (that was now just a basement) or the King’s Town Bank collapse. These two sites are most prominent in local and international news, so we felt compelled to see them before we lost our guide. In addition to these well-known sites, Po-Chien recommended that we visit a building that was constructed by the same developer/contractor responsible for Wikuan Jinlong. But first on the list was a 24-story hotel near the Anping District in Tainan City.
When we arrived at the hotel, we first spotted an unintended coupling beam with significant cracking. We see many buildings in Tainan (most undamaged) that have free-spanning beams connecting floor levels at different story heights. In this instance, the addition of an interconnecting beam was not a good idea as it presented a rigid connection between two flexible buildings, focusing damage at the interface between building and beam. Exterior damage appeared to be facade failure associated with underlying concrete cracking. Based on the piles of debris near building exits, we assume that further damage exists inside the building. Unfortunately, we were unable to enter the building to confirm our assumption. Facade damage was also prevalent on the adjacent building, which was being repaired (no structural repair was evident). These buildings are located within 100 ft of a canal that runs through the Anping District. Many taller structures are located south of the canal and appear to be part of a major development push from the early 90s. Po-Chien indicated that these residential units are not as desirable as the smaller, more common three-story residential structures that are pervasive throughout Tainan and the surrounding area.
We next went to the Wikuan Jinlong Complex. Local construction crews have worked on this area constantly since the earthquake, clearing debris, demolition the collapsed building and rebuilding infrastructure. We observed the replacement of a 2000 mm water pipe, installation of new communication cables, road reconstruction, and final demolition and removal of building elements within the basement of Wikuan Jinlong. The neighbors of this area are all very much affected, but business seemed to be getting back to normal. A machine shop adjacent to the collapse site was fully functional with no evidence of equipment repair as a result of the earthquake. Very little of the collapsed building was available for us to view, but a few obvious issues contributed to the collapse, including some incredible reinforcing couplers on column bars. As is the case with most construction we visit, the column reinforcement is confined with small hoops, spaced approximately 8 in on-center and tied with short 90-degree hooks. These details were changed in the national building code after the Chi-Chi earthquake, but this building was constructed before that time.
We then visited a building built by the same contractor as the Wikuan Jinlong Complex. This building comprised of independent residential towers, interconnected by a plaza reinforced concrete slab over a subterranean basement/garage. The building(s) appeared to be generally undamaged, except for a few columns in the basement and a few inclined shear cracks in a wall forming the corner of the basement. One column had what appeared to be a localized vertical compression failure. Po-Chien was able to talk the building manager into letting us review the building drawings. The drawings did not have any structural information, but showed enough information for us to determine that the damaged column was one of two interior columns on a four column line supporting the exterior of one tower. There is no obvious reason for the “failure,” so Po-Chien will continue to pursue borrowing detailed drawings from the manager so that we can study the building in more detail.
Our next stop was the King’s Town Bank. This 10-story reinforced concrete building had an unbalanced layout of wall and columns, placing just two columns at the front of the building in a precarious position if the building were to see shaking in the short transverse direction. The building most likely responded in a torsional manner, failing the front two columns in shear, leading to confinement issues, bar buckling, and eventual collapse. The building demolition was well under way. Local business were significantly affected by the collapse as the debris covered a major thoroughfare, re-routing traffic and essentially closing shops on either side of the building. We observed government tax representatives noting affected businesses. Po-Chien learned that the closed businesses were promised a payment from the bank for their lost revenue. The community response to this event is very interesting and deserves focused study from experts in the sociology field.
Po-Chien then dropped us at our hotel, where we bid farewell and thanked him for his generosity and hospitality. In a future blog, we will provide a full biography of Po-Chien, he is a very impressive individual in addition to being a very nice guy.
The remaining SGH team (Andrew, Anindya, and Kevin) met with the Geotechnical Extreme Events Reconnaissance (GEER) team at the NCKU Civil Engineering building. GEER will be producing a report on their findings, specifically focused on observed liquefaction and related effects. SGH will contribute to the structural behavior/structural damage portion of their report. The collaboration opportunity brings both Taiwanese and US engineers closer together in the soil-structure interaction discussion. Tara Hutchinson (Professor of Structural Engineering at UCSD) is leading their efforts.