Is it possible to do an assessment of buildings post earthquake by photos?
This question is posed in relation to responses to an early question about whether lay-people could assess whether a building is safe to re-enter after an earthquake.
My original response was that it could be risky for a lay-person (by which I mean not a civil or structural Engineer) to do such an assessment, but after some reflection, I wondered whether a very experienced Engineer (CEng PEng) could do an assessment remotely, using photographs sent by a lay-person on the ground.
About eighteen months ago I did building assessments of garment factories in Dhaka as a response to the Rana Plaza collapse. Doing these assessments made me realise that even a very limited (in terms of time and investigation) inspection could enable worthwhile judgements to be made.
As as experienced Engineer who has worked on many buildings (large and small, low-rise, high-rise, concrete, masonry, timber), I very much know what I am looking at with respect to the structural safety of a building. I am also aware that a lay-person can see a crack and either
a) panic b) be far too cavalier about significant structural flaws.
So, if an Engineer were to inspect buildings from photographs, what could be a possible methodology?
1) Start with a description. Low-rise, high-rise, masonry, concrete. From a description, an Engineer could assess the level of risk. E.g. a high-rise building would impact more people if it collapsed. So, at this point, it could be that a remote inspection is deemed inappropriate.
2) Sketch location and topology. A building on a slope is having to deal with more onerous ground conditions and therefore might be put under more stress than a building on a flat site. There may be slope stability issues very locally to the building.
3) Ask the lay-person to take photos of elevations, floors, roofs and to put key dimensions on the photographs. For example, a masonry building has more inherent strength if cross-walls are frequent. A concrete framed building is often stronger if the floors are beam and slab construction as opposed to flat slab.
4) Ask the lay-person to take photos of any cracks over 3mm (or it could be 2mm, or 5mm); vertical cracks, horizontal cracks, diagonal cracks.
At this point, the Engineer might be able to conclude that the building is in very precarious state.
5) Ask the lay-person to photograph wall and floor/roof junctions, asking them to describe as much as possible what the support to each floor/roof is. E.g. is there a good bearing for a floor joist or concrete slab floor.
6) Ask the lay-person to measure floor thicknesses. For example, if there is a very thin flat slab spanning large distances, this might be a warning sign.
7) Ask the lay-person to judge whether there is any 'lean' or 'tilt'.
I am sure that there are many more questions that could be asked, so suggestions would be welcome.
The final point is that the Engineer needs to have the ... (more)
I'm an Agricultural Engineer, not a Structural person, but I have had a lot of experience in doing remote project work. My biggest frustration is always that I may have a photo of what I need to look at, but it doesn't show the detail I need.
I would agree with the above, If the process could be created to be 80% effective, then it might be worth it, but at what point does it loose it's value - 50/50?
The problem with relying on a lay person to provide a photo is that, as obvious as it sounds, if they don't know what they are looking for, then they don't know what to take a photo off. It's easy to think that they can just take a photo of the crack, but if it's too dark, or from the wrong angle, or not close enough, you can't see the detail that you want.
I guess the ultimate concern is that you have to be 100% sure that the will not ignore a vital piece of evidence that shows an otherwise sound looking building is actually in very bad condition. You have to be 100% sure that you can effectively train and communicate with whoever is doing the inspections. In my experience that is almost impossible, even when you are on the ground training them in person - as soon as you include cross cultural communication, and second languages, such things become significantly more difficult.
This might work if you were using a junior engineer to do the inspections - they have the training to understand what to look for, but not the experience to make the call.
There are considerations of to "Duty of Care", and potential liability. As CEng, IntPE, Eur Ing my views may not be shared by humanitarian colleagues expressing that urgency overrides normal technical process. My reply is from some 20+ years in on the ground responses to conflicts and natural disasters in developing countries, initially a seismic structural engineer and years as a DVN, Lloyds, CSWIP certified structural inspector and NDT tester of offshore structures. I have also spent quite a period in Bangladesh and live in Cambodia so am well familiar with the failing of indigenous construction and compliance. Seismic responses are unlike most other responses in the cyclic and progressive nature can create various levels of visible, invisible patent and latent defects. Even experienced engineers can have difficultly identifying some latent damage - a holistic approach is imperative to look for clues, that may lead you to look for other symptoms ... (more)
Dear Ruth, Thankyou for your submission and thoughtful approach. One thing that jumps out at me immediately is that in my experience lay persons can not always see a lean or tilt or misalignment as effectively as an Engineer to whom it may be glaringly obvious. A spirit level and straight piece of timber could be used against each wall, or plumb line of course to assist the identification of such structural defects. Also where possible , video footage via mobile phone technology may help, as well as of course any video conferencing. I appreciate this may not reflect the resources available at point of use in emergency situations, as no doubt telecomunications and energy supplies are usually effected. Any further comments much appreciated, Regards Pauline RedR
My 2 cents. It all very much depends on the lay person's capability to see what is there. But I think this brings us to another point/s:
- could some lay people in "at risk locations" be trained to do fairly good assessments?
- could this type of training be created to be part of some basic training for people sent to disaster areas?
- could a process be created to address the 80/20 rule? If such trainees can clear (or condemn) 80% of the damaged buildings then one might be "4 times better off" (80/20=4) than waiting and condemning people to the open air while experts arrive/are available.
This is a bit like training lay-women to deliver babies in remote areas where nothing else is available. Comments? 'nando
I would not accept the conclusions of a structural assessment based on photos alone, and would consider such an assessment as to be worthless. Photo's in the hands of an experienced, knowledgeable structural engineers would be useful to plan a detailed assessment, but in situ assessment by someone with the requisite knowledge of structural mechanics and local building codes are absolutely necessary to allow credible conclusions to be reached.
For low rise domestic buildings the required skills and experience can be accessed via using suitably experienced local contractors. For more complicated public buildings I would am certain that the Nepalese Earthquake DRR codes would specify the required knowledge and experience required of an individual undertaking such an assessment, and may even include a register of qualified individuals.
The scale of the humanitarian needs in Nepal should not be used as a justification for short cuts in the assessment and ... (more)
Hello all and thank you for your comments.
I have to confess, as an Engineer I pretty much agree with you all about asking lay-people to get involved. E.g. it's not a very good idea.
Equally, I am interested in Aios Nando's 80/20 rule and comparison with training local women to deliver babies in remote areas.
One thing I am sure of is that Engineers need to be more embedded in aid organisations and government...we have so much to contribute. We can solve problems from first principles, design and build infra-structure, and think of appropriate alternatives.
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