Ambacang Hotel

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.

Figure 1. Front view of the main building showing the roof sagging downward and leaning towards the back.		Figure 2. Side view of the main building segment showing separation damage along the perimeter walls.		Figure 3. Side view of the main building segment with out of plane perimeter brick wall damage exposing the steel gravity framing system.
Figure 4. Back view of the main building segment – viewing west.		Figure 5. Poor detailing exposed at the building façade.		Figure 6. Another back view of the main building segment – viewing east.
Figure 7. Barely any reinforcing at the façade piers.		Figure 8. Close up front view of the main building segment showing the collapsed second floor.		Figure 9. 6-story south segment collapsed towards the pool.