It is said that a home is an earthquake resistant building when it is designed and constructed with adequate structural configuration, with components of appropriate dimensions and materials with a sufficient proportion and resistance to withstand the action of forces caused by frequent earthquakes.
Even if a home is designed and built in compliance with all the requirements of the design and construction standards earthquake resistant homes, there is always the possibility of an earthquake even stronger than those that have been planned and that must be resisted by the home without any total or partial collapses in the building.
Among the consideration we must take at the time we build earthquake resistant homes we have:
It is necessary to find places where the ground is stable, where there is no possibility of slipping or falling rocks in the event of an earthquake. Avoid placing yourself in the riverbed.
The dwelling must be built away from slopes of which there is doubt of its stability or stabilization and protection of the slope. Do not build on loose hillside soils, as during an earthquake you can easily release and drag the house. If the slope of the hillside is greater than 30%, the advice of a floor engineer and a structural engineer must be sought.
- Geometry: Walls must be built in two perpendicular directions, housing geometry must be regular and symmetrical. A well built, symmetrical housing, better resists the action of earthquakes. It should be avoided to build dwellings with elongated and narrow forms where the length of the dwelling is greater than 3 times its width.
- Resistance: it is necessary to guarantee uniformity in the use of the materials in the walls, structures, roofs and others. This allows an integral response of the building in the event of an earthquake. The House must be firm and maintain the equilibrium when it is subjected to the vibration of the earthquake. Unsound and unstable housing can tip or slip.
- Rigidity: It is desirable that the elements that make up the structure of the house are monolithically spliced as a unit and that little form is formed when the house moves to the action of an earthquake.
- Continuity: For a building to withstand an earthquake its structure must be solid, symmetrical, uniform, continuous or connected. Abrupt changes in its dimensions, its rigidity, lack of continuity, a disordered structural configuration or excessive overhangs falicitan the concentration of harmful forces, torsions and deformations that can cause serious damage or the collapse of the building.
The materials must be of good quality to guarantee an adequate resistance and capacity to absorb and dissipate the energy that the earthquake gives it when the building is shaken.
- Cement: The cement must be in its original, fresh packaging and when used it must be insured that it retains its characteristics of fine powder without lumps.
- Aggregates: gravel and sand should not be soiled or mixed with organic matter (Earth), swamp and clay. This causes the concrete’s resistance to decrease considerably or produce a large amount of cracks in the mortars.
Dosage of Concrete
It must be done in a very careful way. It is recommended to consider the dosage according to the structural element to be built. As far as possible, the amount of water must be half the amount of cement. The parts should be measured in the same container as bucket, jar or drawer. To obtain a good quality concrete you have to control the amount of water added to it.
It is recommended to measure the sand parts and empty them on a clean and flat floor. Add the corresponding parts of cement and mix until a uniform color is obtained. Then add the parts of gravel and water properly measured.
Once the concrete has been placed on the site, it must be chuzar with a smooth straight rod with a rounded tip.
The concrete vibrating must be done to eliminate the air bubbles in the concrete and to avoid future anthills or gaps in the structural elements that weaken their resistance, stiffness and continuity.
Concrete needs curing time, because not all of its particles react and harden at the same time. The curing time, usually, is one week. During this time the concrete must be protected from wind and sun and kept as moist as possible especially for the first three days.
The steel should preferably be used corrugated. This improves the adhesion between concrete and steel. Before emptying the concrete, check that the reinforcement is clean of rust and grease.
If bricks are used to build the walls, they must be placed completely moist or saturated with water, and by the accountant they use concrete blocks, they must be placed completely dry.
The volume dosage should not be less than 1 unit of cement per four of sand, i.e. never less than 1:4 (cement: Sand). Lime does not replace cement but improves mixture. The lime should be mixed with water (4 kg of lime per 55 gallons of water). About 48 hours after use, the good quality mortar is left to scratch with a nail while the poor quality is crumbling.
Finally we will see other considerations when constructing earthquake resistant homes. Watch this video!