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Four earthquake-resistant constructions techniques





Soon after the 2005 earthquake, national policies specified reliable construction technique for self-builders. With the time and some people’s hard work, other options have been studied and acknowledged.

Reinforced Masonry

The first proposed technique was a set of (presumably) easy and (relatively) low-cost recommendations about contemporary masonry. The aim was to avoid use of too much concrete, which would have often exceeded self-builder’s budget.

The principle is as follows: the masonry (stone, brick or cement blocks) is bearing the weight, and reinforced horizontally every few feet (at plinth, sill, lintel, and tie beam level). Thus, the whole house works as a pile of self-bearing "rings" (as well-rings for instance), each such "ring" being able to resist horizontal stresses.

Vertical iron bars (at each corner and edging all openings) tie all "rings" together.

This technique is indeed rather easy and little costly, but the early explanations were so unclear that it discouraged most builders.

Confined Masonry

Then, the authorities in charge have proposed another masonry-based technique, more costly but also more traditional. The principle is to have a net of beams and columns framing all façades, all openings and dividing wide blind walls.

The process is easy and clever: the masonry is laid first, leaving gaps for columns and beams. Then easy formwork allows casting. Rough surface, connexion irons and specific weaving allow best collaboration of the two elements (masonry and concrete).

Thus, the concrete columns bear the house, the masonry helps and braces, and the horizontal framing elements link the whole.

Being traditional in our areas, this technique is most popular.

"Dajji"

Repeated demand for cement-less structures (for upper areas where no road access is available) has lead the authorities to propose a wood-and-stone technique, despite strong inner resistance (claimed to be for forest protection).

"Dajji" is traditional in Cashmere. It is probably the most efficient of all four earthquake-resistance techniques we teach.

A wooden frame is built without bracing. The empty rectangular or square "panels" are filled with a mesh of wood and stone cemented with mud. These panels work as bracing, but allow slight movement, and give elasticity to the whole structure. Thus, the house is able to move and to absorb the earthquake’s movement.

Another advantage of this technique is to be (comparatively) lightweight, and thus being less stressed by earthquakes.

In spite of its real simplicity and its effectiveness (not mentioning its low cost), this technique was received with very little enthusiasm in our area, for it is imported, and is felt as an attempt of acculturation. In addition to this general reason, some people criticize the thin walls, sometimes regarding to insulation, and more often regarding to safety (bullet proofing).

"Batar"

After a long struggle, we are on the verge of getting final approval on "batar", which is the local stone-and-wood construction technique. Opposed to the previous one ("dajji") where the wood was load bearing and the masonry was bracing, this technique is a masonry-borne house with wood reinforcement and bracing.

Reminding of the early time "Reinforce Masonry" (please see above), the principle is as follows: piling masonry (usually stone) "rings", each one made self-stable by horizontal wood reinforcement. Practically, we obtain a set of wood beams in a heavy thick stone wall. The latter being an advantage regarding to insulation and bullet safety, but a disadvantage for earthquake resistance.

People in our areas have long been urging for this "batar" technique to be approved. They will soon be allowed to start building. Actually, many who by no means could afford and manage concrete-based techniques have already built their houses in "batar", and now only expect to get fund and support for it.

Study of other countries (in particular a well-documented Greek island) lead us to strongly recommend two-stories houses with a "batar" ground flood and a "dajji" upper floor.

Oddly enough, both wood-and-stone techniques amount to quite precisely the same quantity of wood for similar constructions. In both cases, a firm nation-wide forestation program is needed in order to ensure the sustainability of this type of construction.