A contact on Facebook posts photos of his "dream home," located in earthquake-prone Philippines. Problem is, it's all concrete hollow block (CHB / CMU / concrete masonry unit) walls. Filled and reinforced, I'm sure. But, no reinforced concrete columns? Based on what I know, this kind of construction is not safe at all, specially in earthquake-prone countries. Or even if it had (and it didn't) have reinforced concrete columns, they still require proper seismic design. These all-masonry wall systems are just bound to collapse when the next big one happens. What do I do? Do I become the bearer of bad news? Do I give unsolicited advice? The problem also is that who knows when the next big one will happen, right? If nothing big occurs during our lifetime, then, well it would seem I am wrong, after all, no? What to do, what to do.
Please share your thoughts in the comments.
civil, structural, typhoon, wind, earthquake, and structural dynamics engineering
8 comments:
Hi ronjie, if this is a friend you care about, then I suggest to give them a little talk, that the dream home may not have been design adequately for seismic forces, due to the lack of lateral force resisting system.
If they follow your advice to consider some adjustment on the plans, then that would be great, and if not then at least you made your duty, as friend & as a professional engineer, to inform them regarding the safety of their future home.
The thing about structural engineering is that most people fail to appreciate it. Unlike doctors, artist, or lawyers people can gauge the level of work of these professionals because their work is outright tested. When the doctor treats a patient and he is healed then he is a good doctor. or when a lawyer defends a client and win then he is a good lawyer.
But structural engineering is not like that. Because how often does a magnitude 7 or higher EQ occur to test the design of the engineer? once in 50 yrs? The public is not aware which structure is designed properly and which is not, unless the worst have already come.
The approving authorities can also vindicate you if they reject the plans that don’t have adequate lateral force resisting system.
elfili pinoy, thanks for your comment. We're not really close friends, and yes I've felt it necessary I tell him, but I don't know how he'll take it. It would be a dream-shattering unsolicited advice. If it were a friend telling me, I'd understand, but not everyone is like that.
And good points about the structural engineering profession. Maybe that's one other thing -- maybe he won't trust one as much as he would a doctor or a lawyer. But should I still try? Or, what about telling him indirectly, through a common cotact that I'm more close friends with?
Regarding the approving authorities -- this is a rather big project that clearly has gone through the "approval" process. That's the one other issue, do these "authorities" even know anything? It's a big problem.
Hi Ron, conveying your concerns to a closer friend to tell the owner, is a good idea.
I am not sure if masonry design & construction as a structural member is practiced in your area. In other countries, CMU walls can resist seismic forces if it was designed properly.(using masonry codes etc.)
Most concerning here is the approving authorities, because they hold the key to public safety. The approving authorities must be competent enough to know the basic requirement structural engineering, otherwise their existence is useless.
elfili, in the Philippines, i can't really say that masonry design & construction is done with enough seismic considerations. i know in seismic regions, they have the proper codes in place. i have analyzed some CMU-wall construction in seismic regions myself and those still need at least a few reinforced concrete supporting elements.
Can't do that with ordinary blockwork (fc'= ~7 MPa), unless:
1. the supplier has specifically made them for structural purpose.
2. it's brickwork. Then that's different.
Thanks for your input, Sarce. That is true for CHBs in the Philippines (fc'=~7 MPa). Definitely not brickwork.
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