What is Earthquake Engineering?
Earthquake construction is an important discipline that contributes to minimizing damage by using pile foundations, base isolation, and other techniques. Evaluation of soil conditions is also important.
What Is Earthquake Construction?
Earthquake construction ensures that structures resist earthquake shocks by the integration of seismic designs throughout their expected life, in conformity with the building codes applicable in the region. Earthquakes destabilize buildings either by direct effects of the seismic waves, or indirectly through soil liquefaction and landslides.
Most structures fail laterally by an earthquake, meaning the the walls may fall down, or movement of the walls may cause displacement of the roofs, and result in the collapse of the structure. Therefore, to ensure safety of human life and property, earthquake-resistant techniques should be used, including the utilization of proper design and materials.
The condition of soil at the site of construction
is an important factor, since the state of soil can significantly alter the motions of an earthquake. The condition of the soil should be thoroughly evaluated. Soils that consist of loose sand and gravel possess poor earthquake-resistant characteristics, and should be reinforced. Seismic waves are amplified in soils that are saturated with water, and change the form of soil from a solid to a liquid upon the occurrence of earthquakes.
Such soils acquire the characteristics of quicksand and make the ground incapable of supporting a foundation due to cracks and weakening. Deep and firm soils are good since they allow only minor vibrations to be transferred from the foundation to the construction above.
Pile foundations are a structural part used for the transfer of the structure load to the solid ground located at some depth. Piles are extended and thin elements that transmit the load to a lower soil of greater bearing capability, penetrating the shallow soil. Piles can be used in earthquake construction to minimize earthquake effects, especially with soft surface soils that may easily liquefy, by resisting vertical and lateral loads.
A structure is raised on piles if the soil is unstable, weak, does not possess sufficient bearing capacity, and the likely settlement is not advisable. The design of the piles should be proper, by binding the pile caps with reinforced concrete slabs that can function in tension as well as compression, so that the foundation may perform as a unit. In addition, the piles should be designed to carry axial, shear, and bending loads that may be occur because of the horizontal movements between the layers in the soil.
Base isolation techniques are a recent development in the structural design of buildings and bridges in highly seismic regions. They function on the principles of oscillation and damping. Rubber isolation bearings are used that minimize the earthquake damage to the buildings by decoupling the building from the horizontal component of the ground movement.
This is achieved by making the bearings rigid in the vertical direction and elastic in the horizontal direction. The earthquake energy is not absorbed by the base isolation techniques but is deflected due to the system. Rubber bearings can be manufactured easily, do not have any moving parts, and are not affected by time or the environment.