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The earth's crust consists of several so-called tectonic plates, which all move slowly with a few centimeters each year. This movement is caused by convective currents between the core of the earth and the mantle. The edges of these plates are called fault lines.

 

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Millions of years ago the Indian Subcontinent has collided with Tibet. India has slipped under and the Tibetan Plateau is pushed up. This way the Himalayas came into existence and this is why Mount Everest still grows with 2 centimeters per year.

 

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Nepal is situated directly above the fault line between these two plates! As a result of all this pushing, huge amounts of energy are stored down in the ground. At some point those forces need to be released, by means of a sudden jolt. This discharge of energy is translated in huge and devastating waves that make their way up to the surface of the earth; this is an earthquake!

 

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Buildings have to cope with enormous dynamic forces and have to resist all kinds of deformations.

 

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But when the building is not made according to certain earthquake resistant principles...

 

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...the chance is that it will collapse, regardless of the way of construction or the materials used.

 

Basic Principles of Earthquake Resistant Construction

 

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Before we start with our projects, we give extensive training to the villagers, masons and carpenters, with many pictures and movies.

 

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First make sure that you build on a flat surface, with sufficient distance to edges and slopes. De school on the left picture is at risk of sliding down during an earthquake.

 

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Make simple and symmetric building shapes. Square, rectangular, round and oval shapes behave well during an earthquake, but difficult configurations such as L- and T-shapes may twist and crack.

 

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We advice to cut difficult shapes into several smaller building volumes, and make a gap of 5 to 7 centimeter between them.

 

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The maximum ratio between width and length of a building is 1 is to 3. Ensure enough stability inside the building by placing walls or buttresses at a maximum distance of 6 meters.

 

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Then we will hold our small building volumes together, by tying them up like small packages. Horizontally we include continuous beams and corner stitches, which can be made of wood or reinforced concrete.

 

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In case of masonry with bricks or blocks, we reinforce the corners and T-sections vertically as well, by inserting vertical steel rods. These rods we also include next to the doors and windows.

 

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The doors must always open to the outside, in order to create safe exits during an emergency. In Phalangkot (picture left) the door was blocked when an interior wall collapsed.

 

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In case of construction with mountain stones, it is very important to create a good bonding in the masonry; The stones must grip into each other. Also with school builidngs we use cement mortar instead of mud. The picture on the left shows how it defenitely should not be done... Here 3 walls are being built istead of one solid wall. Also the vertical steel in the corners is not necessary with these heavy structures, it will make the connections even weaker!

 

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The last recommendation is to make light roofs, such as tin sheets. When constructing with mountain stones, we also recommend not to build higher than the ground floor. A raise in height halfway the building, as can be seen on the right picture, is very dangerous to do!

 

Correct Use of Materials

 

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Now that we know how to make our building earthquake resistant, it is important to execute it correctly! We start with some practical training in the villages about the correct handling of materials.

 

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We show them how to mark your building with straight and perpendicular lines. This can easily be done with the Pythagorean theorem. Also we explain how to make good connections with for example hollow cement blocks.

 

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Reuse of materials is an important feature of Smart Shelter Foundation! The main part of the stones from the old schoolbuildings can be recycled into the foundation, walls and floor filling of the new building.

 

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We train the masons how to bend and apply the steel correctly, that goes into the reinforced concrete tie beams.

 

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Rough sand is suitable for construction purposes, and fine sand can be used for plastering.

 

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Old cement should not be used. Also we train the masons how to apply the water and mix the concrete properly, and we teach them that freshly made concrete should be used within 45 minutes. After that it will rapidly loose its strength.

 

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This is how concrete is normally made in Nepal, and this is something that we will defenitely not accept! Here a lot of money has been invested in expensive cement, steel, sand and pebbles, but in the end these beams have zero strenght. So we introduce two simple tricks about how to make good concrete:

 

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First of all we make use of a measuring box. This box has the exact volume of a bag of cement. so when we need to make concrete in the ratio 1:2:4, we open 1 bag of cement, and we add two boxes of rough sand and 4 boxes of correctly sized pebbles. This way the mixture is always corrrect!

 

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The second trick is to use spacers, that we tie to the steel bars. Then we place the formwork, but this way we can assure that there is sufficient concrete covergae on the steel.

 

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And this is our secret weapon for transferring the knowledge to the villages... We paint all the earthquake resistant features in the outside of the buildings!

 

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The text on one of the sides of the building says: 'This school is earthquake resistant. If you want to construct your house in the future, please contact SEED Foundation for technical assistance'. The building has become a life-size advertisement billboard for earthquake resistant construction!

 

 

 

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After levelling the land we start with digging of the foundation trenches.

 

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The steel bars are placed in the bottom of the foundation and we start the masonry of the foundation with mountain stones and stabilized mud mortar.

 

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On the foundation we cast the first continous ringbeam of reinforced concrete. Between seperate building volumes we make a gap of 5 centimeters.

 

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Then we lay the first blocks for the masonry. As soon as these are placed on the correct height, at the correct distance and after making them level, it is quite easy to place the blocks in between.

 

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Under and above the doors and windows we make more concrete ring beams, which improve the stability of the building.

 

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In the lintel we include galvanised steel wire. With these wires we connect the roof structure firmly to the walls.

 

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As soon as the tin sheets are placed, it is just a matter of finishing, plastering and painting.

 

 

Earthquake Resistant Construction with Mountain Stones

 

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The foundation with this type of construction is a bit different. We don't need to include vertical steel rods and we prefer to do the masonry with cement mortar instead of mud.

 

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The steel is being cut and applied for the first ring beam, which comes on top of the foundation.

 

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As soon as the beam is cast, the door frames are placed.

 

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Most stones of the old school buildings can be reused and the masons are busy with cutting and preparing the stones for the new walls. Most important is to make a proper bonding. Every 50 centimeter we include so-called through stones, which are placed over the complete width of the walls. The masonry is done with cement mortar.

 

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At certain levels we include the continuous ring beams. Also here, between the building volumes we make a gap of 5 centimeters.

 

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In the lintel we tie the galvanised steel wire to the horizontal bars, which will later hold the roof in place.

 

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After finishing the building the schools are officially inaugurated with many festivities and ceremonies.

 

Confined Masonry for Multiple Storey Buildings

 

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In Nepal most buildings are constructed with reinforced concrete columns and beams, with an infill of bricks or blocks. During an earthquake these two systems will move independently and behave differently from each other.

 

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The result is that either the columns explode, or the masonry will crack at many places. Often it is a combination of both.

 

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And that may even result in the total collapse of the building. As this way of construction is expensive, but not too safe, we construct our buildings differently!

 

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We construct according to the confined masonry principle. That means that we build our walls first, and that we cast the columns between them later.

 

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These tie-columns, in combination with the ring beam on the walls, tie the walls firmly to the foundation.

 

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This way the columns work together with the walls and the forces are more evenly distributed through the loadbearing system. This way of construction is not even better, it is also cheaper than the type on the left. Check our project 'Hostel for Blind Students' to see an example of confined masonry.