How to create Earthquake resistant buildings? – Part 1
Earthquakes can occur at any point of time and those ranking high on the Richter scale can leave behind an unimaginable loss of life and property. Throughout, our history we have seen impressive structures and whole communities lose the battle against the seismic waves of earthquakes. From Sichuan earthquake of 2008 which left 5 million people homeless to the Haiti earthquake of 2010 which displaced an estimated 1.5 million survivors. With more and more skyscrapers taking to new heights it is now apparent that strong measures need to be taken to ensure that the building is able to withstand the effects of earthquake.
In past few decades engineers have introduced new designs and building materials to better equip the buildings to handle the effects of an earthquake. In the two parts of this article we will be looking at what happens to a building during an earthquake, what are the possible measures that can be taken to prevent the collapse of the building, and finally how can BIM Services be used to more efficiently design such buildings.
What happens to the building during an earthquake?
During an earthquake there are shockwaves which are sent in short rapid intervals in all different directions. The buildings are ideally equipped to handle the vertical force, which occurs due to their weight and Earth’s gravity but they cannot handle the side to side force caused by the quakes. An earthquake affects and vibrates walls, floors, columns, beams etc. The difference between the conflicted force on the top and bottom of the building puts extreme pressure on the supporting frame causing a rupture and resulting in the collapse of the whole building.
The side to side load is much worse when the shocks come in waves, which is more likely to happen when the building is built on deep soft ground. Additionally, when the weight has been added to the building or the structure at a higher level, small cracks can appear in the concrete increasing the chances of the building being impacted by the earthquake.
What can be done to build an earthquake proof building?
The logic behind designing an earthquake proof building is to reinforce the structure and counteract the earthquake’s force. The earthquake releases an energy that pushes the building from one direction, the strategy involves creation of design that would push the building from the other side. The engineers take the following measures:
1. Base Isolation:
One method of resisting the forces of Earthquake involves floating a building above its foundation. This is done by using a system of bearings, springs and padded cylinders. This basically lifts the building’s foundation above Earth. Thus, when the earthquake hits, the base vibrates but the structure does not move.
2. Install Damping Systems:
Damper Systems are designed and manufactured in order to protect the structural integrity of the building by absorbing seismic energy and by reducing deformation in the structures. Seismic Damper permits the structure to resist any severe energy input and reduces harmful deflations, forces and accelerations. There are two ways in which damping is done:
3. Vibrational Control Device:
Here a damper is placed at each level of the building between a column and beam. These dampers consist of piston heads inside a cylinder which is filled with Silicone oil. Thus, when the earthquake occurs it pushes the vibration energy into piston, pushing it against the oil.
4. Pendulum Power:
This is a damping method significantly used in skyscrapers. Here, a large ball with steel cables and a system of hydraulics is suspended at the top of the building. When the earthquake hits, the ball acts as a pendulum moving in the opposite direction to stabilize the building.
5. The Building Design:
Steel Detailing Servicescan be used to add vital reinforcement to keep the structure standing through the earthquake. Steel cross braces can be used to frame the exterior of the building in an X shape. These steel crosses can transfer the force back to the ground and the impact of the building is significantly reduced. Shear walls can be added to building design to add stiffness to the frame and thus enabling the building resistance.
6. Earthquake-Resistant Materials:
If the materials used in the building construction have high ductility, then the building itself can have some capacity to dissipate or damp the energy. Ductility refers the material’s capacity to undergo large plastic deformations. Brick and concrete have low ductility and can absorb very little energy. Structural steel on the other hand can withstand the forces of the earthquake much better because the embedded steel increases the ductility of the material.
The engineers and scientists are looking at various different materials that have the ability to endure the forces of the earthquake. Certain materials that can be used are shape memory alloys that can withstand heavy strain and then revert to their original shape. Fiber-reinforced plastic wrap which is made of variety of polymers can be wrapped around columns to provide more strength and ductility.
Above we have looked at all the possible ways in which engineers can design buildings which can resist the force of Earthquakes. In the consequent article we will be taking specifically about Building Information Model, and how this new method of construction can be useful in creating safer and earthquake resistant structures.
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