Earthquake Proof Buildings
Earthquake Proof Buildings: 4 Must-Read Facts
Ancient and modern history have been canvasses for impressive, towering structures, only for them to buckle under the wrath of nature.
Engineers work to ensure buildings remain structurally sound, even in the face of destructive calamities. Yet, even so, human-made buildings are no strangers to destruction.
Earthquakes are one such destructive force. Seismic waves and vibrations can topple down structures and destroy even the sturdiest of buildings.
In response, engineers are introducing new designs and materials to erect earthquake proof buildings. These buildings are now more commonplace than ever to prevent collapse, expensive repairs, and losses of lives.
1. How Do Earthquakes Affect Buildings?
Before understanding the distinct features of earthquake proof buildings, let’s understand how natural disasters affect artificial structures.
Earthquakes occur when tectonic plates in the ground brush against or collide. This results in a destructive seismic energy release, sending shockwaves throughout the earth in multiple directions.
Most buildings are generally designed to withstand vertical forces. However, they cannot withstand earthquakes due to side-to-side seismic forces.
Seismic forces, or horizontal forces, lead to destructive vibrations on floors, bearings, beams, rafters, columns, walls, and other structures. Traditional buildings cannot handle lateral forces leading to extreme stress and eventually collapse.
2. What Are The Features Of Earthquake Proof Buildings?
Designing earthquake resistant buildings is all about adding reinforcements to the structure. The added reinforcements can counter potential seismic forces coming from an earthquake.
And, since earthquakes produce energy pushing on buildings from one direction, earthquake resistance involves counteracting these directional forces.
Cross braces are one of the most commonly used structural elements in designing earthquake proof buildings.
A cross bracing system keeps buildings stable against extremely heavy wind guests and earthquakes.
In addition, cross braces reduce lateral loads on the building, minimising damage to the entire building.
Cross braces are usually made of steel frames, tubes, or rods. Diagonal steel components are arranged in an X-shaped pattern and installed near building columns. They may also be hidden using non-structural wall systems.
Diaphragms are another distinct feature of earthquake proof buildings. These structural components transfer inertial forces from the floor to the vertical walls.
Diaphragms are flat, structural units, also acting like metal beams. While they usually apply to roofs and floors, shear walls, for instance, can be cantilevered diaphragms.
Most earthquake proof buildings have these components on the deck. They’re further reinforced to “share” the lateral loads with vertical structures.
Moment Resisting Frames
Moment resisting frames refer to a rectilinear arrangement of beams and columns. Rectilinear refers to a structure made of straight lines.
Moment resisting frames include beams which are rigidly fixed to columns. They resist lateral forces through rigid frame action against bending and shear force.
Aside from their earthquake resistance capabilities, these frames offer engineers more flexibility. They allow the construction of exterior walls, ceilings, and arrangement of other building components.
Trusses provide added strength to the diaphragm, especially where the deck is the least stable.
They are diagonal substructures attached to the building’s frames.
Lightweight roofing is another prominent feature of earthquake resistant buildings. Many engineers use profiled steel cladding or lightweight steel purlins. They may also use double-skin metal roofs built with insulators and purlins.
Other lightweight roofing materials include aluminium, fibreglass shingles, composites, modified bitumen, or wood shakes.
One effective way of resisting ground forces due to seismic activity is lifting the foundation through a base isolation technique.
Base isolated buildings include foundations made of flexible steel, rubber, and lead pads. The isolators produce vibrations when the foundation moves during an earthquake, while the overall structure remains stable.
A base isolation system can absorb seismic waves and prevent them from travelling through the different parts of the building.
Continuous Load Path
Continuous load paths are crucial in earthquake proof structures because they assist in redistributing external pressures or forces caused by heavy winds and earthquakes.
Structural and non-structural building components are tied together to remove inertial forces that may cause cracks and damage.
Sturdy Shear Walls
Engineers install shear walls in earthquake proof buildings to minimise movement sway during earthquake activity.
Shear walls provide stiffness to the building’s structural frame and the cross brace system.
Damping refers to the suppression of building vibrations due to seismic forces. Dampers are connected with the building frame and foundation. They act as shock absorbers which reduce the magnitude and pressure on the building.
Damping can be achieved through pendulum power and vibrational control devices:
- Pendulum Power – Pendulum power dampening is typically used for skyscrapers. Engineers will attach a large ball to steel cables connected to a hydraulic system. As soon as the buildings start swaying, the ball serves as a pendulum, moving in the opposite direction.
- Vibration Control Devices – Vibration control devices or seismic dampers are installed between columns and beams on every building level. Each damper has a piston, where vibrational energy is transferred during an earthquake. This energy converts into heat, effectively minimising the vibrations.
Regularity refers to the building’s movement when it’s pushed laterally or side-to-side. Engineers and designers need the building to move equally to reduce destructive energy.
Meanwhile, an irregular building cannot withstand lateral forces. The weaknesses become especially apparent during seismic activity.
3. New Techniques For Earthquake Resistant Buildings
Aside from standard techniques to improve building stability during earthquakes and disasters, new practices have also emerged, making buildings even more resistant to damage.
We’ll discuss a few of them below.
Many buildings topple during earthquakes due to weak joints. So, engineers will naturally want to strengthen the joints to provide added resistance.
One way to strengthen joints is by adding haunches. Haunch retrofitting stiffens beam-column joints, providing more stability to the entire structure.
Hollow Box Foundations
Hollow boxes or floating foundations are used to construct earthquake proof buildings on weak or soft soil.
These foundations are designed to act as buoyant substructures for the net load over them. They help reduce load intensity over the soft soil.
Some hollow-type foundations also contain water to dampen an earthquake’s destructive impacts. Or, it may also be filled with other viscous substances to withstand earthquakes and their damaging effects further.
Conclusion About Earthquake Proof Buildings
Earthquakes are a type of natural disaster which causes a sudden shaking of the ground. This generates powerful seismic waves that can significantly damage tall and low-rise buildings without proper earthquake proofing.
Many methods have emerged in the construction industry, targeted at reducing and ultimately minimising an earthquake’s effects on a building.
These techniques include reinforcing the concrete foundation, adding vibration dampeners, using lightweight materials, and many others.
Despite such efforts, building a 100% earthquake proof building remains impossible. This is due to the unpredictable intensity and magnitude of natural occurrences.
Nevertheless, earthquake resistant structures have been instrumental in reducing costly damage and grave loss of life.
For more information on earthquake proof construction materials, get in touch with Pollisum at +65 67557600.
Frequently Asked Questions About Earthquake Proof Buildings
Wood and steel are the favoured construction materials for buildings situated on fault lines.
Safety experts say brittle concrete frames aren't ideal for earthquake proofing. They pose deadly risks, especially during major earthquakes.
Yes. In addition to strict compliance with building codes and regulations, high-rise structures and tall buildings remain safe during an earthquake. Engineers consider seismic and wind loads during high-rise construction, unlike small houses and low-rise buildings.
Contrary to popular understanding, there's no direct relationship between displacement/velocity and lower and upper floors. Furthermore, earthquakes have two types of waves: S and P.
S waves are more dangerous than P waves due to the higher amplitude. They also produce vertical and horizontal motions on the ground.