Earthquake Resistant Structures | Engineering Tips

Architect — Tue, 15 Jun 2010 00:20:22 +0000

Earthquakes are a major geological phenomena. Man has been terrified of this phenomena for ages, as little has been known about the causes of earthquakes, but it leaves behind a trail of destruction. There are hundreds of small earthquakes around the world everyday. Some of them are so minor that humans cannot feel them, but seismographs and other sensitive machines can record them. Earthquakes occur when tectonic plates move and rub against each other. Sometimes, due to this movement, they snap and rebound to their original position. This might cause a large earthquakes as the tectonic plates try to settle down. This is known as the Elastic Rebound Theory.

Haiti Earthquake 2010

Every year, earthquakes take the lives of thousands of people , and destroy property worth billions. The 2010 Haiti Earthquake killed over 1,50,000 people and destroyed entire cities and villages. Designing Earthquake Resistant Structures is indispensable. It is imperative that structures are designed to resist earthquake forces, in order to reduce the loss of life. The science of Earthquake Engineering and Structural Design has improved tremendously, and thus, today, we can design safe structures which can safely withstand earthquakes of reasonable magnitude.

Index of all posts on Earthquake Resistant Structures

Design Earthquake Resistant Buildings | Engineering Tips

Earthquakes and Natural Calamities

Types of Seismic Waves

Hazardous Effects of Earthquakes

Effect of Earthquakes on Structures

Building Stiffness and Flexibility | Earthquake Engineering

Inertial Forces in a Structure

Effects of Deformations in Structures

Horizontal and Vertical Shaking of a Structure

Flow of Inertia Forces to Foundations

How Earthquakes affect Reinforced Concrete Buildings

Building Planning | Earthquake Resistant Buildings

Earthquake Resistant Structures by Planning and Design Approach

Design Philosophy of Earthquake Resistant Designs

Building Construction Materials for Earthquake Resistance

Concept of Earthquake Resistant Engineering

Seismic Base Isolation Technique for Building Earthquake Resistance

Energy Dissipation Devices for Earthquake Resistant Building Design

Active Control Devices for Earthquake Resistance

Energy Dissipation Devices for Earthquake Resistant Building Design

Architect — Tue, 15 Jun 2010 00:03:47 +0000

Another approach for controlling seismic damage in buildings and improving their seismic performance is by installing Seismic Dampers in place of structural elements, such as diagonal braces. These dampers act like the hydraulic shock absorbers in cars – much of the sudden jerks are absorbed in the hydraulic fluids and only little is transmitted above to the chassis of the car. When seismic energy is transmitted through them, dampers absorb part of it, and thus damp the motion of the building.

Energy Dissipation Devices

Commonly used Seismic Dampers

Viscous Dampers (energy is absorbed by silicone-based fluid passing between piston cylinder arrangement),
Friction Dampers (energy is absorbed by surfaces with friction between them rubbing against each other),
Yielding Dampers (energy is absorbed by metallic components that yield).
Viscoelastic Dampers (energy is absorbed by utilizing the controlled shearing of solids).

Thus by equipping a building with additional devices which have high damping capacity, we can greatly decrease the seismic energy entering the building.

How it Works?

How Dampers Work

The construction of a fluid damper is shown in (fig). It consists of a stainless steel piston with bronze orifice head. It is filled with silicone oil. The piston head utilizes specially shaped passages which alter the flow of the damper fluid and thus alter the resistance characteristics of the damper. Fluid dampers may be designed to behave as a pure energy dissipater or a spring or as a combination of the two.

A fluid viscous damper resembles the common shock absorber such as those found in automobiles. The piston transmits energy entering the system to the fluid in the damper, causing it to move within the damper. The movement of the fluid within the damper fluid absorbs this kinetic energy by converting it into heat. In automobiles, this means that a shock received at the wheel is damped before it reaches the passengers compartment. In buildings this can mean that the building columns protected by dampers will undergo considerably less horizontal movement and damage during an earthquake.

Fluid Viscous Dampers

New Breed of Energy Dissipation Devices

The innovative methods for control of seismic vibrations such as frictional and other types of damping devices are important integral part of seismic isolation systems as they severe as a barrier against the penetration of seismic energy into the structure. In this concept, the dampers suppress the response of the isolated building relative to its base.

The novel friction damper device consists of three steel plates rotating against each other in opposite directions. The steel plates are separated by two shims of friction pad material producing friction with steel plates.

When an external force excites a frame structure the girder starts to displace horizontally due to this force. The damper will follow the motion and the central plate because of the tensile forces in the bracing elements. When the applied forces are reversed, the plates will rotate in opposite way. The damper dissipates energy by means of friction between the sliding surfaces.