LBA LIA (English Learning Center)

October 20, 2009 by nalexander
Filed under Uncategorized

LBA LIA was an afterschool English language learning center, built sometime after 2000, located in the city of Padang. The building was a 4-story reinforced concrete frame building with brick infill. After the September 30, 2009 earthquake, the first and second story of the building collapsed, resulting in 4 total fatalities. Based on local accounts, 11 were trapped in the collapsed building after the earthquake but 7 of them were able to be saved.

The typical beams and columns sizes used in the building are very small for supporting such heavy 4-story building. The typical interior columns were 16”x18” and the typical interior beams were 14”x18”. Notice that the partitions are brick walls, adding a lot more mass to the building. The reinforcement used throughout the building are smooth rebars. The concrete columns seem to lack adequate confinement for ductile detailing (Fig 6). “Short hooked anchors” (Fig 7) are also very common throughout the building. Notice that the short anchorage length does not satisfy the 12db requirement per ACI.

: Front view of the collapsed building

Side view of the collapsed building

Back view of the collapsed building

Third story columns shear failure at the stairs

The beams and columns sizes are very minimal for such a heavy 4-story building

Damaged joint exposing lack of confinement from the minimal ties

The hooked anchor commonly found in damaged buildings, which do not provide adequate anchorage length

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Ambacang Hotel

October 13, 2009 by nalexander
Filed under Structural Observations, Uncategorized

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This three star hotel has undergone several renovations over the past century. The original portion of the building was a Dutch-colonial style warehouse building facing North and was constructed early 1900. The structural system of the original 2-story building consisted of a reinforced concrete frame with masonry infill. Within the past three years, additions were added to the original building in different phases. Initially, an additional 3-story level was added on top of the existing construction. The structural system of the new upper addition consisted of a combination of steel gravity framing with concrete over metal deck and reinforced concrete frame with brick infill. Later on, a 1-story segment concrete structure with brick infill was added on Southwest of the original building, creating an L-shaped footprint. Finally, a 6-story steel frame structure was added south of the original building, creating a U-shaped footprint with an interior court used as a pool in between the two wings.

After the 7.6 earthquake in September 30, 2009, the second story of the back portion of the original building segment collapsed towards the pool followed by the 6-story south building segment also collapsing towards the pool. (Provincial Disaster Center reported 69 fatalities so far).

Many of the buildings that collapsed in Padang have quite a similar history where floor additions were added several times during the life of the building. The original segment of hotel Ambacang is an extreme case of such type of buildings, which is locally known as the ‘growing building’. So it is unclear how strict the code enforcement and quality assurance for inspection are being conducted.

Some structural deficiencies, such as defects in the concrete material and non-ductile detailing can be identified from the building damage. Non-ductile detailing was apparent from the lack of ties used in the concrete columns and poor detail practice observed from the exposed damage. The structural members are also very lightly reinforced. Poor splice detail between the addition structure to the existing structure also adds to the list of the structural vulnerabilities observed in the building. It is likely that the additional segments were added butt-up against each other without consideration of pounding during an earthquake.