Dear Editor,

I note with interest the photo in the June 25, 2021 edition of the Jamaica Observer on page 23.

The collapsed section of the building, now rubble, is situated to the left of centre. Looking at the remaining structure I would surmise that the protruding section to the left was mirrored on the right. The open space at the ground level to the left, with just three columns supporting an entire stack of rooms, and likely lots of open lobby areas is what is called in earthquake engineering a “soft storey” (See pages 159 -161, The Seismic Design Handbook, Farzad Naeim editor.)

There are not many tall buildings in Jamaica, thank goodness, which have this type of configuration, because our engineers have mostly recognised the danger of this type of building in an earthquake zone.

Assuming that the building was sort of “U” shaped at the side facing the camera, and noticing that the lower left of centre of the photo shows a layered pile of rubble, each layer being a collapsed floor, because if you look closely you can see the balcony handrails, I would surmise that since the rubble is so configured that this layered rubble was the upper floors which rode the collapsing building down, relatively intact and slid outwards on top of the pancaked lower floors to end up so far away.

If the collapse had started in the upper half of the building, the layered stack of rubble would not have occurred, but, rather, a jumbled mass, because the re-bar strands in the floors would have held long enough before snapping, to act like hinges, rolling over the falling rubble and falling close to the base of the building where the balcony handrails would be buried.

So, most likely, the collapse initiated in the lower half of the building, and most probably where the ground floor columns are. As well, since the rubble is more to the left of centre, suspicion would be that the lower left column on that side of the building failed somehow.

Proper design would not have such critical supports without redundancy. Such columns, exposed to the possibility of vehicular damage, should normally be designed to have any one removed and the building still stays up. Or, such columns should be protected from damage.

I wonder what design considerations are being taken with the newer tall buildings being built nowadays in Jamaica with car parking on the lowest floor. Is there sufficient redundancy and strength so that the “soft storey” effect is avoided? Interesting, eh? A teaching moment.

Howard Chin, PE

Member

Jamaica Institution of Engineers

hmc14@cwjamaica.com