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Conflict and Natural Disasters
 
Building strength in earthquakes
Given that the mass of a building is probably a millionth of the mass of the earth. Then the maximum stress from an earthquake must happen at the junction between earth and building. (Note: For the basic case I am excluding high-rise because of the whiplash effect stresses at the top of a high-rise building.

Therefore, there is a need to reinforce the structure of the ground floor, not only to take the weight of the upper floors, but also to be able to stand under the impact of an earthquake.

No doubt I am writing nothing new, but as Ozgur wrote that in Turkey, building blocks with shops on the ground floor collapsed, most probably because shops usually have glass-walled fronts and sides and so at the plane of maximum stress there was less support (in the form of brick or concrete walls) than on the floors above.

Here in Turkey I can watch building work continually because a great many buildings are built slowly one floor at a time, sometimes with delays of years.

But it seems there is no difference either in the number and thickness of these columns from one floor to the next and this concerns me, because if there is no extra support on the ground floor to offset (a) the lack of brick and concrete walls, and (b) the weight of the other floors from above, then the building is practically garanteed to collapse in an earthquake.

Another point is that the bare concrete block buildings I see have concrete floors, concrete stairs but no concrete structural walls. Whereas, in Britain block buildings have structural fire-safety walls for stairs and lifts.

These structural fire-safety walls act to give strength to the building and it may be an idea to retro-fit both more concrete reinforcement (either as walls or columns) on the ground floor and to enclose stairs with structural walls.
Frank John Snelling
Responses
 
Building strength in earthquakes
Prashant, Thank you. :) Yes, "retro-fitting" of earthquake reinforcement can and should be seen as an aesthetic challenge rather than as a barrier.

In other words how to absorb more mass while keeping to the original design?

If extra columns and walls are placed edge-on to the "viewer in the street", then the column width is minimal while the column depth is maximal.

Another way for thinner and aesthetic columns, is using two smaller ones (one behind the other) for a thick column.

And for designs which have serious structural problems; both solid and flying buttresses as an exo-skeleton.
Frank John Snelling
Building strength in earthquakes
Hello again Frank

Mmmmm... Columns behind columns are very interesting; sounds like a wall of steel and concrete to me, let's expand this a bit more.

Now that we have come to look at the structural integrity of a building that is built using columns and beams and infill walls, consisting of bricks and plaster and glass panel walls for the view, it is necesary to look at how a building reacts in a moving situation. Regardless of how big the shake, all buildings built of unflexible stone, whether it be natural or man-made, i.e. concrete, brick or concrete block with mortar. The fact remains that the these materials will crack and give way under preasure.

The use of structural load carrying walls made using some flexible resilient material within the wall, will stand a much better chance of remaining in one piece than a stack of bricks mortared togeather, or a concrete block wall infilled only with concrete grout. In order to enable these wall types to survive movement, one needs to install reinforcing steel in both the horizontal and vertical plane and tie this all together to the foundations. Now, the more extreme form of these walls is found in the buildings that will survive earthquakes. Look at New Zealand, Japan and North America: They have designed systems that use concrete panels with diagonal steel reinforcing within the precast wall panels and these 'bracing' walls are set at right angles to each other and provide a rigid, braced perimeter wall for the structure. Likewise, in lightweight construction methods -- timber frame and light weight steel frame, as I use-- diagonal bracing elements triangulate and tie the opposite corners together to form an X and the lower points are affixed to the foundations/floor slab with a predetermined restraint value, normally a minumum of 5kN and sometimes 10kN (kN is kilo Newtons) at each corner. The resultant wall can withstand the presures applied to a bulding during a shake, by bracing the wall.

Now, the claddings on framed structures are varied, from cavity brick cladding, to concrete board panels, to weather boards, to monilithic plasters over a variety of backings. These claddings do little to stop the movement of the building structure themselves and are sometimes damaged while the frame structure survives. If the building is as a lot of commerical shops are built (with glass frontages and only parallel walls from front to back with no cross bracing walls across the frontage), another way of introducing bracing walls is to place them above the glass window wall openings.

Anyway, let this discussion look at the real solutions and not the make believe. Happy new year gentlemen. Ciao for now,
David Michael James Davies
Building strength in earthquakes
Dave, if you read my starting entry. You will see I was looking at probable causes of collapses and probable ways of retro-fitting and I was thinking in terms of "reinforced concrete".

Obviously retro-fit work is not ideal, but neither does it have to be ugly.

If a retro-fitted building saved lives which would otherwise have been lost, surely this better than none, because the object is to save lives rather than worry about whether or not the building needs to be knocked down post-disaster.

Yes, "double-diagonal rod or wire ties" to brace walls or between columns would work and as this format was frequently used by Victorian engineers. But, where there is not the resources or money to buy the modern equivalents then other ways need to be considered, such as:-

If you look at both "shelter domes for disaster areas" and my "hexagon plan buildings for earthquake safety", I put forward the use of hexagonal or zigzag walls with three-way wall junctions as being stronger than straight walls. Plus, the honeycomb shape is non-directional.

Both (a) the design shape and (b) the materials used are important. If buildings and building practices in Pakistan and Northern India are similar to Turkey, then there will not be any sizable import of modern materials and designs into the Kashmir and that means having to work with what is available and economic.

Towards a better New Year, :)
Frank John Snelling
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