LBA LIA (English Learning Center)

Jembatan Siti Nurbaya (large concrete bridge south of the city)

The construction on Jembatan Siti Nurbaya began in 1994, was stopped due to a bad economy, and eventually completed in 1999. Jembatan Siti Nurbaya is the most substantial bridge over the Batang Arau, located at the South of the city center spanning roughly 70m. The bridge is approximately 10m wide and is a standard concrete box girder. The bridge itself faired very well in the September 30th earthquake with no apparent damage. The approaches, which consist of soil confined by concrete retaining walls, held up during the earthquake but sustained damage. The sidewalk on the South West approach separated and settled from the concrete retaining wall approximately 12”, as a result of an earthquake in 2007. This same location settled an additional 18” in the recent earthquake. In addition to the measurable separation, the south approach suffered damage in that the entire approach dropped relative to the bridge and the pavement split in two clear cracks forming deep longitudinal voids. Additionally, the North approach currently has about a two-inch crack spanning the entire width of the bridge just a few feet from the bridge-approach connection.

This bridge could serve as a key component for tsunami evacuation for two reasons: the bridge sits approximately 26 feet above the road below therefore the bridge is approximately 30 ft above sea level, which could potentially act as an evacuation site; the second use of the bridge is to facilitate numerous pedestrians, motorbikes and even cars, over the bridge to grant access to higher ground.

Photos to follow.

Ambacang Hotel

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.

STBA Junior College Performance Report

Link to File:  STBA Junior College Performance Report (DOC)

Lake Maninjau Landslides

Lake Maninjou is a volcanic crater with an average rim to lake elevation change of 2000 ft.  The southern quarter of the lake experienced much greater ground motion than the rest of the lake , and this resulted in major
landsliding on the southern rim of the crater.  Approximately 25% of the southern rim experienced slides, burying parts of villages and displacing at least 2000 residents.

Most of the slides were not extremely powerfull and did not reach the lake shore, but at least 3 slides carried debris all the way to the shore. The largest slide was approximately 200 feet wide and buried 6 houses.

Heavy rains the night after the earthquake caused additional mudslides that damage more housing.

Mitsubishi car showroom

This Mitsubishi car showroom in Padang was built in 2006 and began operating in 2007.  The building is a reinforced concrete frame with masonry infill.  Earthquakes in 2007 caused some minor cracks in the building, which were later patched over.  It appears that the September 30, 2009 earthquake did not damage the concrete frame itself, but the nonstructural features (e.g. façade, infill) were unable to deflect with the frame and were therefore significantly damaged.  In particular, many of the infill walls failed in shear.  The showroom is closed because of the extensive damage to the nonstructural features.  Fortunately, the car showroom was closed during the time of the earthquake and therefore there were no casualties.  The building owner is planning to demolish and rebuild the structure since it is insured for earthquakes.  It is currently being guarded by one of the security guards since nine of the ten deposit boxes are still in the building.

BAPPEDA – City Planning Provincial

This BAPPEDA building (provincial planning) was constructed in 1980.  The structural system is reinforced concrete with masonry infill.  The architectural features of the building created a larger mass on the top floors.    The first floor appears to have a smaller floor plan with a rim of exterior columns around the building supporting the floors above.  It was a soft first story building and that it went from a 4 story to 3 story building; specifically, the North East corner of the building completely collapsed on the first floor.  The exterior columns on the first floor were approximately 20”x20” in dimension, with large, smooth bars and rather small stirrups.  The bar spacing was anywhere from 2.5 to 3.75 inches and alarmingly large aggregate was found.  Smooth river rocks were used for the aggregate and some of the pieces found were up to 5”.  Approximately, 80 persons were inside the building during the earthquake – 50 ran out immediately, 30 stayed on the upper floors and two were killed near the entrance on the first floor.  The two victims were both crushed as the first floor came crashing down.  At the back of the building, several infill falls fell out and various contents from within the building fell onto the pavement below.  Planning documents were found among the debris, including tsunami preparation and planning booklets.

Sentral Pasar Raya

Built approximately three years ago, Sentral Pasar Raya is located in the dense city center of Padang.  Sentral Pasar Raya contained many small shops within the four-story building.  The top floor consisted of a modest food court in the center and an open roof.  The building is a reinforced concrete moment frame with masonry infill.  The earthquake occurred at 17:16 on a Wednesday, and it is unclear as to how many people were inside when the ground shaking began.  Various people recounted a number of deaths ranging from 3 to 36; currently the precise number is unknown.  The earthquake caused a partial collapse, with a large extent of the damage occurring at the back of the building.  A few cooling towers were located on the roof at the back of the building.  It is likely that the uneven weight distribution accounts for the abundance of column failure that can be found at the back of the building.  The first story completely collapsed at the back, and the second story partially collapsed.  In addition, several columns/beams/floors/stairs appear to or may have failed throughout the entire building, although the extensive damage is centralized at the back.  The column located at the back of the building (the North East corner) failed extensively and clearly displayed stirrups tied to a meager 90° (rather than the US standard of 135°).  Additionally, every stirrup in the column was oriented along the same corner of the cage, rather than staggered about all corners.  The columns and beams throughout the building contained deformed bars, approximately size #6.

Basko Mall Performance Evaluation

Link to File: Basko Mall Performance Review (DOC)

Key Drivers of Structural Damage

Link to File: Padang – Key Drivers of Structural Damage (DOC)

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