that strange serendra blast

what intrigued me most, looking at the photos, was that the explosion from inside unit 501 blew off only the exterior walls of only that unit, and so cleanly, with hardly any jagged edges, and the exterior walls of the units beside, above, and below it are hardly damaged except for shattered glass windows and the like.  it didn’t make sense, unless, unless, aha, the walls are pre-fab?!?  googled it and, yes!  “precast wall” it’s called.  this is how they’re made, and this is how they’re “installed.”

so, i wonder what industry people are saying.  mabuti na lang that those walls were precast, otherwise they would not have been blown away so easily?  had those walls been made of poured concrete (buhos) with rebars and all, they would have been thicker,  maybe they would not have been blown away, and damage to the interior would have been greater?  maybe the ceiling and floor and inner walls would have been first to give way, and casualties would have been from inside the building?  unless of course that explosion was directed at, and meant to blow off, those walls.  but why?

so yes, we need to find out what and who caused that explosion.  and, certainly, whether precast walls are safe, or should passers-by beware?

Comments

  3. faux_ph

    That is the problem of having to use a structural system without relying on the stiffness of the precast walls: the precast walls have minimal positive connection to main structural system (i.e. columns, beams). Thus, when a blast or even a high pressure wind gust from storm/typhoon or god forbid an earthquake, the entire precast panel are blown away easily. That’s what you get for a shoddy and cheap engineering design.

    Blast coming from gas leaks is likely since Fort Bonifacio is the only place in the country where a centralised LPG (LNG?) distribution system exist. Since most builders here in the country really don’t have much of an experience for this type of gas distribution system to buildings, it is highly likely that this is the culprit. What amazes me is the magnitude of blast radius reaching up to the eaves of the rooftop, it must have been a really big explosion!

    Nevertheless, if the residents of Serendra or the developer (Ayala) really want to know what happened and potential mitigation solutions to avoid repeating this type of incident, they should seek help/advice from independent professionals who are into security and risk consulting, particularly those firms who designs facilities with high risk/security requirements such as embassies.

    June 5, 2013 at 12:52 pm
    Reply
  4. faux_ph

    angela,

    the use of a precast wall system is an accepted global construction industry practice. However, special attention to its use is given when it is used to provide as a structural lateral resisting system (i.e. resistance to wind/earthquake) for buildings or containment to gas/liquids.

    Blast effects is highly likely NOT considered in the design of the Serendra building since more often than not, the probability of having an explosion is very low (unless by terrorist act) for a residential use. But even if is the case, the risk of explosion coming from the gas distribution system is mitigated if an HSE (Heakth, Safety & Environment) risk assessment is done in the first place. A risk assessment would have had an influence in the design of the building and the way LPG/LNG gas is distribution to the building.

    regards,
    faux_Ph

    June 5, 2013 at 1:06 pm
    Reply
    • angela

      hello, faux_ph, at last, confirmation that precast walls are not made to withstand gas explosions and earthquakes and maybe even very strong winds (thank god we dont have tornados, though i dont know that climate change won’t bring that in some future). i wonder how pinas-made precast walls compare with those made in other countries. ganoon lang ba talaga kanipis? clearly now, there are risks, and maybe they should redesign, including the attachment to main structure? that corner post was obviously made of stronger stuff, buti na lang.

      June 5, 2013 at 1:24 pm
      Reply
    • faux_ph

      depending on its intended use and function, precast walls can be designed to the thinnest section possible, limited by installation requirements such as lifting the panel on one point without cracking/breaking. I suspect that the precast walls used in Serendra is really just intended to be a barrier against environmental effects (sunlight,wind,rain); nothing more, nothing less…

      June 5, 2013 at 5:00 pm
      Reply
  6. baycas

    According to Raymund Fortun, lawyer of the burned victim and the condo unit owner, “the renovation (of Unit 501B) was not that extensive” and that “the only things that were moved in that area were the washer and dryer cabinet” (Mornings@ANC, June 6, 2013).

    Serendra Unit-owner Robin Leonard at allfamousdotcom captured an image of SOCOs examining a blown-out appliance, which appeared to be a dryer. The appliance was found near the bushes at the sidewalk below the blast site.

    Was the clothes dryer a gas-powered one? It might have been the source of the explosion if it is indeed a gas dryer.

    Edward Wilson, a 63-year-old homeowner living at 515 Anderson Avenue, Akron, Ohio, had an experience with a gas dryer explosion in April 2012. He never smelled gas in his house prior to the explosion.

    http://www.newsnet5.com/dpp/news/local_news/akron_canton_news/gas-dryer-causes-house-explosion-on-anderson-avenue-in-akron

    June 7, 2013 at 12:46 am
    Reply
    • baycas

      [Fortun says before San Juan was taken
      to the hospital, he was able to talk to Herminia Ochoa,
      the aunt of Cayton, who was also in Serendra.

      “He said: ‘I touched the door handle.
      I heard the explosion. I was thrown to the ground and
      I felt I was electrocuted.‘”]

      — Mornings@ANC, June 6, 2013

      The static electricity (electrostatic discharge or ESD) might have been produced when San Juan touched the doorknob.

      ESD may cause a fire or an explosion in a flammable atmosphere such as a room filled with gas vapor or dust clouds.

      The “gas dryer”, as thought above, might have been the source of the gas leak as it might have been improperly reinstalled during the renovation of Unit 501B.

      June 7, 2013 at 2:10 am
      Reply
  7. manuel buencamino

    Bakit walang amoy yun gas? In other countries, gas companies are mandated by law to mix very strong doors with the gas para nga maamoy kung meron gas leak. Dito ba meron ganyang batas? Kung meron dapat i-check ng authorities yun tanke ng supplier kasi obviously walang naamoy yung occupant ng unit. Kaso yan against the gas supplier.

    June 7, 2013 at 8:39 pm
    Reply
          • baycas

            the scientists disclosed that they were only a parallel expert opinion and were not part of the investigation. they excluded b omb explosion and ruled in gas explosion because the magnitude of the Serendra blast may also be consistent with gas explosion, similar to natural gas (methane) blasts that happened elsewhere.

            dust explosion must also be ruled out by investigators in a systematic manner similar to what they did with the b omb theory.

            in a legal battle, ideas may be advanced to cast reasonable doubt to an opponent’s testimony.

            June 11, 2013 at 7:54 am

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