by David Gonzalez   Posted March 13, 2010 12:28 AM

Concepcion

Today, we started the day at the downtown area of Concepcion after a quick breakfast at the hotel. Luckily, our drivers made it to Concepcion. Traffic is heavy, a sign that things are slowly going back to normal. We were looking at a swimming pool on the 2nd floor of a condo building when we felt the aftershock just before noon. At the epicenter in Libertador O’Higgins, it was a 6.9 but it didn’t feel as strong in Concepcion. We finished looking at buildings around 2 pm and couldn’t find suitable places for lunch so we decided to head back to the hotel to see if the restaurants by the shopping center across the street were open.. bad idea! Because of the aftershock, a tsunami warning had been issued and it took us about 1.5 hours to get back to the hotel only to find the shopping center closed. We made it back to downtown in the mid-afternoon and had an opportunity to see many other buildings, including ongoing demolition of condemned buildings.

Today was Anuj’s birthday so we had agreed to do something a little special after our return. Red wine and torta (cake) after a quick dinner along with our Happy Birthday singing ended the day.

Based on what we have seen, it is likely we will change our itinerary slightly; and probably stay in Concepcion for the rest of our time here instead of going back to Santiago tomorrow. There is just too much for us to see here!

Bldg ID 3-11.1
Torre O’Higgins 241 Office Building (36⁰ 49′ 47″, 73⁰ 03′ 19″) (below)

• This modern towering office building of approximately 20 stories suffered extensive damage. There is risk of collapse and we had to photograph the building from a block away. The tower was inaugurated in mid-2009. Unfortunately, there appears to be a trend of severely damaged buildings constructed in the last few years.
• The structure has at least 3 levels of underground parking and 20 stories above ground. It is a reinforced concrete shear wall building with setbacks on at least two sides at about. Some of the shear walls are discontinuous landing at columns on two sides of the building.
• The building suffered a torsion irregularity and perhaps a soft-story condition at level 14 or 15. In addition, a regular pattern of spandrel beam shear damage can be observed. These conditions are observed on the East elevation only since the West elevation has a more regular shear wall layout. After the piers failed in shear, they lost the load-carrying capacity and a soft-story developed.
• The West elevation presents only minor damage.

Bldg ID 3-11.2
Obispo Salas – O’Higgins Ave & Salas St. Apartment Building (36⁰ 49′ 47″, 73⁰ 03′ 21″)(below)

• A reporter mentioned that this new apartment building, about a block away from Torre O’Higgins, has substantial damage in the lower levels. The access has been blocked off but we were able to observe shear failures in the concrete shear walls, in the East-West direction.
• The building was opened in December 2009 and suffered vertical deformations, according to one of the tenants that indicated the doors stuck after the earthquake and people couldn’t evacuate.
• The building is a reinforced concrete shear wall building with approximately 22 stories.There are several wings forming the floor plan, with setbacks about halfway up.
• The observed exterior damaged concentrated in the lower 2-3 levels with shear wall boundary element compression failure being the predominant damage. In addition, some widespread couple beam cracking in shear can be observed in some of the spandrel beams between shear walls. An interesting observation is that some of the vertical reinforcing in one of the boundary elements snapped or fractured.
• A homeowner indicated that there is severe nonstructural damage and that the owner has indicated they will repair the building. They were to be allowed to go inside today to retrieve personal belongings.

Bldg ID 3-11.3
Fire Station #1 – Salas #347 (36⁰ 49′ 49″, 73⁰ 03′ 18″)(below)
Our first fire station observed in this trip happened to be Fire Station #1 – San Carlos unit. They were the first responders to the Alto Rio Building collapse where they rescued some of the victims that had exited the building on their own. The firemen were then directed to assist with a chemical spill at a university campus nearby and then finally were routed to assist in a prison in the middle of gunfire due to some inmates that had escaped.

• The building is a two-story reinforced concrete building with concrete diaphragms. Substantial cracking of some of the shear walls, predominantly in the East-West direction, is present. In addition, some of the concrete roof slabs have cracking around the perimeter. This appears to indicate that the vertical acceleration component was very strong.
• There is some evidence of pounding in the North-South direction since there are no joints between the fire station and the adjacent buildings. Several of the buildings along this block may have worked together.
• The building has an open front to house the engine bays. The engines are not housed inside the fire station for now for fear they may get trapped in an aftershock. The firemen are now sleeping on tents on the street.

Bldg ID 3-11.4
City #1 Apartment Building – Chacabuco #333 (36⁰ 49′ 56″, 73⁰ 03′ 07″)(below)

• We were invited by a homeowner to come in and take a look at the building. The building is a 15-story shear wall structure with a couple levels of parking garage underneath. There doesn’t appear to be significant damage from the exterior. However, there is some damage in the staircase walls, garage shear walls and also in the lintel beams above most of the doorways. Some cracking was also observed on some interior concrete shear walls.
• The elevated pool is in a separate structure. We were walking around the pool when we felt the aftershock. No major damage occurred as the ground shaking in Concepcion was relatively low this time.

Bldg ID 3-11.5
La Araucana – Lincoyan #334 Office Building (36⁰ 49′ 64″, 73⁰ 03′ 03″)(below)

• 15-story above ground plus 3 underground parking garage levels. The structure is a concrete shear wall building, opened in 2009. The building serves retirees and provides services like: dental, medical clinic, spa, financial services, conference center, etc. There are no ramps to access the garage levels but rather a car elevator is used.

• The building has regular openings on three sides, the exception being the front side which is completely open to accommodate the storefront façade. The building is generally rectangular in footprint and has shear walls around the stair and elevator cores, and three perimeter walls. Metal panels and storefront form the skin of the building. There is a stiffness concentration on one side of the building which induced a torsional irregularity.
• One of the side walls exhibited severe damage at the third floor, apparently due to torsional effects. The amount of reinforcement appears to be similar to that of comparable buildings in the US. The aggregate provided good interlocking and the concrete of quality is good. The rebar detailing is generally good, with the exception of the 90-degree hooks for the horizontal bars that slipped loose. The floor dropped a few inches in all levels above the third level in the area adjacent to the damaged shear wall. The contractor representative indicated they were planning to cast a new 32-inch exterior concrete wall full height and then remove the existing damaged wall.
• Other structural damage included cracking in some of the interior core shear walls and spandrel beams.
• Nonstructural performance was generally good with the most severe damage consisting of one or two elevator counterweights rotating themselves out of the restraints and slamming against the doors. One mechanical unit that was not attached from its platform dislodged and fell. Ceilings performed a little better in this building that in those observed before. Some windows and door glazing broke but in general performed in a life-safety manner.
• At the end of our tour, the property manager gave us access to the original drawings in electronic format.

Bldg ID 3-11.6
Apartment Building – Lincoyan #440 (36⁰ 49′ 43″, 73⁰ 03′ 10″)

• 17-story concrete shear wall building. Shear wall arrangement appears to be in a cruciform layout of 2 walls in each direction. Compression failure of boundary elements was present throughout the height of the building. Most of the damage is in the East-West direction.



Miscellaneous Buildings
We observed multiple buildings from different vintages and structural systems with different levels of damage, ranging from minor nonstructural damage only to imminent collapse. Demolition of unrepairable buildings is proceeding very fast and haphazardly at times. We also took some close-up pictures of the damaged silos mentioned in log #4.

Throughout the day there have been at least nine aftershocks ranging from 4.9 to 5.5. Stay tuned for more tomorrow!




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