SMK Negeri 9 School

October 18, 2009 by  
Filed under Structural Observations

The SMK Negeri 9 school is located in downtown Padang across the street from the damaged Ambacang Hotel. The school serves high school students in 3 main buildings on the campus. The largest of the three buildings, a 3-story structure built in 1996, suffered major damage in the earthquake. We were told by school personnel that 2 people died and 5 others were injured. The other two classroom buildings as well as the school mosque were relatively undamaged and continue to hold classes. Classes displaced by the collapsed building were being held inside a tent in the school’s front court, and workers were in the process of building a temporary wood building to house more classes.

The collapsed school building structure consisted of concrete moment frames with brick infill walls both around the perimeter and inside of the building. The primary failure was the collapse of the third floor slab at the north end of the building. This slab came down onto the second floor slab below and also brought down the wood framed roof. School personnel told us that the collapse occurred approximately 5 minutes after the start of the shaking.

The column bays at the third floor comprised mostly of solid walls while the bays below were mostly windows with short infill walls below. This may have contributed to the failure of the slab since there was extensive hinging in the columns at the third floor level, thus potentially forming a soft story mechanism at that level. There was also evidence of captive column hinging at the first floor as well, whereas the second floor structure fell more or less intact.

Like many other concrete framed buildings that failed in Padang, the columns were reinforced with smooth longitudinal bars and thin ties with only 90 degree hooks and a relatively wide spacing. This along with the apparent soft story condition at the third floor and the captive columns at the first floor appears to have contributed to the collapse. What is not apparent is what caused only the north end of the building to fail. There did not appear to be any significant difference in the structure between the north and south ends.

There were a number of interior brick infilled partitions that fell, including the partition at the second floor directly adjacent to the slab break. This partition appeared to have fallen out of plane as one rather than in pieces. The north stairwell was part of the section that collapsed. The south stairwell remained standing but sustained heavy damage including the loss of the walls surrounding the stairwell and pullout of the stair from the second floor slab.

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