I am searching for some facts about the strength of Afghan domes the case of earthquakes. To get my bachelor degree, I am about to write a manual entitled "Schoolbuilding in Afghanistan". I spent last autumn there building a school for a German relief organisation called Gruenhelme. Within the first 40 pages Islamic architecture in a broad perspective and Afghan architecture and building techniques as very special topics are presented.
I have a simple question. Can somebody provide me with facts about the adobe domes if an earthquake occurs? It would be very helpful. I attached a little picture of the school I designed.
Thanks in advance,
As long as the adobe dome is THICK enough at the base and preferable follows a NUBIAN curve, it should be safe. Very old buildings have survived earthquakes.
However for all practical purposes with current knowledcge of earthquake resistance, you need TIE ELEMENTS (TENSION MEMBERS) also to keep the COMPRESSIVE structure of dome in place. These tie beams/bands can come at various places. This also depends upon the size of the dome.
In large domes sometimes, the whole concept of having a compressive structure such as a dome or a vault itself is reduced to a mere face saving exercise. Only in hot climates like tropical climates, these compresive structures using adobe help keep inside temparature in control.
Thanks a lot for your contributions.|
Do you know somebody who did work in an earthquake lab doing some measuring on afghan domes? How stable are they and, on which level of the richter-scale do they collapse? I am attaching two sections of a typical Afghan dome.
A paralel line of thought would be to use the Hagia Sophia sections and compare those with your typical sections, they if I am not mistaken, belong to the same family, I am certain you will be able to find studies of that having been conducted by the Turkish Archeological authorities.
Also, at the very broadly, the dome shape looks safe. Except, that the walls may not be tapering enough (but may be they are thick enough). Whichever way, you will need beams/tensile BINDING members in Afghanistan (guess work because of Himalayas .... fault lines...??)
Nirup, I fail to see how the Hagia Sophia will be of help because a) it is not adobe b) it has the unique challenge of supporting a dome by two semi-domes on one axis and two grand arches on the other. The arches have the tendency to fall out because they are less strong then the semi-domes. Hence, the dome becomes an oval... and makes the building still moves). A Princeton University team directed by Ahmet Çakmak have been conducting analyses and restorations of this building since the mid 1990s.|
But, mentioning the Hagia Sophia highlights one point: That the stability of the dome is so instrinsically bound with the strength of the support system. (Basically, a dome wants to flatten out at the base, if not supported laterally).
I was working in Bam after the EQ, as an architect. The city was mainly built in adobe, and there were no domes or vaults left after the quake. At least right above the epicentre. The problem in Bam was, that the quake was right under the city, so it had a very strong vertical component, which lifted off whatever was on top, roof, vault, or dome. Then the walls shook and everything went down.
With regard to vaults: they are very bad under EQ conditions, because they are too stiff. Imagine that the quake lifts first one corner of the building (quake approaching diagonally). The stiff structure of the vault does not support such an excentric deformation.
Domes are better, theoretically. They are very stiff too, but the are homogeneous. The direction of the quake is not important. However, they are heavy structures and tend to remain in place, while the building below moves sideways under EQ influence. Therefore, they must be well anchored. In addition, they should be hold down by something, not to be lifted off (or made lighter) by the vertical component of the quake.
Thus the main problem is how the domes are fixed on the walls and how EQ resistant these walls are. It's best that you start checking right from the bottom of the building (and of the problem):
1. The layout of the building: is the form regular (not in a U shape like your school in Afghanistan, i.e. if its wings were connected to the central part instead of being separated by a serious 15-20cm empty joint)
2. Are the foundations rigid enough to make the whole building move in the same way?
3. How are the walls reinforced against EQs?
4. How is the dome fixed on the top of the walls? against lateral acceleration AND against vertical acceleration.
One of the things I have been thinking about is to use the vertical irons of the wall reinforcements to fix the dome against horizontal and vertical acceleration, and then add a chicken mesh over the dome, fixed to the reinforcement bars, to hold it down . The (heavy duty) chicken mesh must be imbedded in some plaster, mud or cement or whatever.
This proposal however isn't but a first guess. We are not ready to give a final answer. Some research has to be done first. It's quite a tricky problem, too difficult to solve for a bachelor degree. It would rather fit a PhD.
Hallo Sascha, Now you must have gained already your diploma. Are you still interested in adobe architecture, domes? I worked, like you, in the Herat region with Gruenhelme in 2003 and was not happy with our solutions for school buildings. We haven't had enough time and not open ears from the responsable persons to discuss better ideas. But at last a kind of mixed up building (carpenter workshop) was build in Qara Bagh. The walls as usual but the roof a dome. For details you should ask Heike Molsberger from Munich.
Did you find meanwhile good adobe school buildings in Afghanistan?
What is your approach to seismic detailing for these buildings?
Do you consult with an engineer who is familiar with the severe loading effects of earthquakes?
Often, these buildings will work for normal vertical gravity loads and will have good properties for thermal and other local needs but will form mass graves if built poorly - Look at the BAM earthquake in IRAN a few years ago.
I presume that earthquake engineering has been taken into account but it still amazes me how often visual aspects are considered in such detail with significant disregard to the Life safety performance aspect of such a building.
Kind Regards and I would be interested to know how others take earthquake engineering into account in their projects.
there are two points to discuss. One is the responsibility of architects and engineers considering the danger of earthquake in seismic vulnerable areas.
The other is to be conscious of modern architecture built in areas with no dangerous seismic activities but in traditional context without consideration of local material, building trade and resources. The western patent solution for fast success employed by good willing relief organizations. But this could be a topic for a new forum. Why not try to get the modern standards into the traditional concept?
could you please explain some more on your thoughts on the follwing you wrote recently?
"...The western patent solution for fast success employed by good willing relief organizations. But this could be a topic for a new forum. Why not try to get the modern standards into the traditional concept? "
Are you saying that a standard needs to be writen for traditional building types in earthquake prone areas?
Sorry for expressing myself not clear enough. I didn't ask for a new standard to be applied to traditional buildings in earthquake prone areas.
The new topic for the forum I thought about could be: Modern architecture in traditional context. This idea came in response to my own unsatisfied experience with a standard school building in an area with nearly 100 percent adobe traditional buildings.
Often there are new projects in poor countries with bad design. Traditional materials and techniques are abandoned in favour of the import of expensive and sometimes energy-inefficient materials and products. These imported materials benefit only the manufactures in more advanced economies. For example the concrete needs a lot of energy to be produced but in the end if it is badly used, it has not the desired results. The building is too warm in summer end too cold in winter... you need a lot of core iron, transport...
Please have a look to the Aga Kahan Award for Architecture 2006 for the METI school of Rudrapur, Bangladesh. This is a great example for a modern building in a traditional context.
Having been trained long ago as structural engineer, I am amaized about some of the responses, as they are misleading under structural safety aspects.
What has been shown are vaults, not domes.
A vault has a single sense of bending. It is rather weak in earthquakes, as the vault ( similar to an arch) can only be designed under pure compression for a single loadcase, normaly vertical loads. Earthquakes introduce always a considerable horizontal load. This load can only be taken by bending, but adobe is week in this, as it has little tension strength. Take a sheet of paper, bent into an arch form and push with your finger horizonatally. Then you can see how it deforms easily.
A dome is a spherical structure like the Hagias Sophia or a part of an egg.
It is much stronger, as it distributes the load in all directions using the curved structure in any direction. You can hardly smash an egg if you press it in your hand.
But this structure has also problems with non symmetrical loads. A true calculation requires special programms.
The most important structural element to make a dome safe is a tension belt at the bottom (a geometrical problem on square floor plans). Or you need other measures like tension bars or a very thick inclined supporting walls or a reinforced slab in the remaing part of the roof. Afghan domes are spherical structures, for details see for example Minke's publications.
The behavior of domes from temples in the Gujarat Earthquake in India was good. Even when the supporting structure collapsed, you could find intact domes laying on the ground.
Conclusion: forget about vaults in erthquake zones, but you may use domes, especilally when they are small in the range of below 8 m diameter. But you must provide enough horizontal resistance, which can rather simple be calculated using the Orange slices model.
Now in general about adobe and earthquake: You can make such buildings resistant if tension meber are introduced, traditionally it was wood. There is even a village in Iran not far away from Bam, that builds such safe houses, using wooden beams as reinforcement similar to the reinforcement of shear walls as per IAEE guidleines. The biggest problem is the realisation of tension resistant joints in a wooden construction. The adobe can then mainly act in compression (lattice structure model).