Prepared by S.SELVAPRAKASH AP/CIVIL GNANAMANI COLLEGE OF ENGINEERING

SMART STRCTURES

DEFINITION

A "Smart Material" refers to a material that has one or more property that can be altered through the application of an external stimulus.

A "Smart Structure” is a system that incorporates particular functions of sensing and actuation to perform smart actions in an ingenious way.

Five components of a smart structure

Data Acquisition

Data Transmission

Command and Control Unit

Data Instructions

Action Devices

Data Acquisition The aim of this

components is to collect the required raw data needed for an appropriate sensing and monitoring of the structure

Data Transmission The purpose of this

part is to forwarded the raw data to the local and/or central command and control units.

Command and Control Unit

The role of this unit is to manage and control the whole system by analyzing the data, reaching the appropriate conclusion, and determining the actions required

Data Instructions

The function of this part is to transmit the decisions and the associated instruction back to the members of the structure

Action Devices

The purpose of this part is to take actions by triggering the controlling devices/units

SMART STRUCTURES

CONTROL

ACTUATIORSENSOR

DATA INSTRUCTIONS

DATA TRANSMISSION

BUILDINGS AND BRIDGES

Skyscrapers and long bridges are subject to resonance created by high winds and seismic activity

In order to mitigate the resonance effect, it is important to build large dampers into their design to interrupt the resonant waves

If these devices are not in place, buildings and bridges can be shaken to the ground

DAMPERS

Dampers are used in machines that you likely use every day, including car, bike suspension systems

If you take a look the How suspension systems work, you'll learn that damping systems use friction to absorb some of the force from vibrations

A damping system in a building is much larger and is also designed to absorb the violent shocks of an earthquake

The size of the dampers depends on the size of the building

DAMPENING SYSTEMS

Passive

Requires no input power to operate

They are simple and generally low in cost

They are uncontrollable

Active

Require a great deal of power

They are fully controllable

Semi-Active

Combines features of passive and active damping.

They are fully controllable yet require little input power

Magneto-Rheological fluid (MR fluid) dampers are semi-active devices

That can change their damping level by varying the amount of current supplied to an internal electromagnet that controls the flow of MR fluid.

A full-scale

MR fluid

damper that is

1-meter long

and weighs

250 kilograms.

This one

damper can

exert 20 tons

of force on a

building

Inside the MR fluid damper, an electromagnetic coil is wrapped around three sections of the piston.

Approximately 5 liters of MR fluid is used to fill the damper's main chamber.

During an earthquake, sensors attached to the building will signal the computer to supply the dampers with an electrical charge.

This electrical charge then magnetizes the coil, turning the MR fluid from a liquid to a near-solid.

Now, the electromagnet will likely pulse as the vibrations ripple through the building.

This vibration will cause the MR fluid to change from liquid to solid thousands of times per second, and may cause the temperature of the fluid to rise.

A thermal expansion accumulator is fixed to the top of the damper housing to allow for the expansion of the fluid as it heats up.

This accumulator prevents a dangerous rise in pressure as the fluid expands.

BUILDINGS EQUIPPED WITH MR FLUID DAMPERS WILL

MITIGATE VIBRATIONS DURING AN EARTHQUAKE

Depending on the size of the building, there could be an array of possibly hundreds of dampers.

Each damper would sit on the floor and be attached to the chevron braces that are welded into a steel cross beam.

As the building begins to shake, the dampers would move back and forward to compensate for the vibration of the shock.

When it's magnetized, the MR fluid increases the amount of force received in dampers

WHAT IS MR FLUID

MR fluid doesn't seem like such a revolutionary substance.

It's a gray, oily liquid that's about three times denser than water.

It's not too exciting at first glance, but MR fluid is actually quite amazing to watch in action.

MR Fluid Composition

Carbonyl Iron Particles -20 to 40 percent of the fluid is made of these soft iron particles that are just 3 to 5 micrometers in diameter. A package of dry carbonyl iron particles looks like black flour because the particles are so fine.

A Carrier Liquid -The iron particles are suspended in a liquid, usually hydrocarbon oil. Water is often used in demonstrating the fluid.

Proprietary Additives -The third component of MR fluid is a secret, but Lord says these additives are put in to inhibit gravitational settling of the iron particles, promote particle suspension, enhance lubricity, modify viscosity and inhibit wear.

MR FLUID

AFTER MAGNETIZED

Principle of a MRF

ADVANTAGES

This structure cut downs a lot of material cost incurred in using under reamed pile and factor of safety.

India has 25% of area prone to earth quake. This smart technology will help in saving a lot of men and material.

The health monitoring of structures will help in forecasting failure and will provide time for rehabitation.

35% of deccan pleateau has black cotton soil, the use of this technology can ensure safe and economical construction over there.

As the structure is constantly maintained the service life increases and the need for repair decreases.

RELATED PROJECT

Mitigation of wind-rain-induced cable vibration in cable-stayed bridges using adjustable fluid dampers

Control of wind-rain-induced cable vibration of Dongting Lake Bridge using magneto-rheological dampers

Semi-active tuned liquid column dampers using magneto rheological fluids for vibration control of tall buildings

Wind-rain-induced vibration control of stay cables in the Dongting Lake Bridge

THANK YOU