Structural Control

Systems

By:

Vineet Kothari

Assistant Professor

Civil Engineering Department

Introduction

Ductile Concrete Moment

Resisting Frame Structure

(Parking Garage) that collapsed

during Northridge Earthquake

•Tremendous deformation Capacity in the Peripheral Columns

( Not Sufficiently Detailed to accommodate large Inelastic Deformations Demand…)

• So it is utmost important to have good and efficient structural control system.

Dynamic Forces

SEISMIC WIND

Mass Lower Mass Higher

Stiffness Higher Stiffness Higher

Damping Higher Damping Higher

WIND RESISTANT DESIGN

• Excitation is an applied Pressure or Force on the Facade

• Loading is Dynamic but Response is nearly Static for most Structures

• Structures deforms due to Applied force

• Deformations are monotonic (unidirectional)

• Structure is Designed to respond Elastically under Factored Loads

• The controlling Life Safety limit state is STRENGTH

EARTHQUAKE RESISTANT DESIGN

• Excitation is an Applied Displacement at the Base

• Loading and Response are Truly Dynamic

• Structural Systems deforms as a result of Inertial Forces

• Structure is designed to respond Inelastically under Factored Loads

• Controlling Life Safety limit is DEFORMABILITY

• Enough Strength is provided to ensure that Inelastic deformation demands do

not exceed deformation Capacity.

Structural Control Systems

• Energy absorption or dissipation devices

• by increasing stiffness (absorption)

• by improving dynamic performance (dissipation)

Methods to improve seismic response

conventional methods

1.Shear wall

2.Bracings Systems

3.Dual system

Structural Control Systems

Modern methods

1. Passive control systems

2. Active Control systems

3. Semi-active control systems

4. Hybrid control systems

Modern Methods

Base Isolation

• Introduces Flexibility in building

• Building is rested on flexible pads

• When earthquake strikes building does

not move

• It is suitable for hard soil only

Types of Base Isolator

Elastomeric and Lead Rubber Bearing

• Frequently used for base isolation

• Made of rubber sandwiched together within steel

• Very stiff and strong in vertical direction

• Flexible in horizontal direction

Types of Base Isolator

Spherical Sliding Isolation

• It uses bearing pads that have a curved surface and low

friction materials similar to Teflon

• During earthquake building is free to slide both

horizontally and vertically

• It returns to its original position as earthquake stops

Base Isolation

Most

Effective

Least

Effective

• Structure with Stiff Soil

• Structure with Low Fundamental Period

(Low Rise Buildings)

• Structure with Soft Soil

• Structure with High Fundamental Period

(High Rise Buildings)

Passive Energy Dissipation Devices

Passive energy Dissipation Devices

Viscous Fluid Damper

Visco-Elastic Damper

Metallic Damper

Tuned Mass Damper

Friction Damper

Viscous Fluid Damper

Visco-Elastic DamperEnergy Dissipation takes place due to shear deformation of material Sandwiched between

Steel Plates.

Friction Damper• Friction provides Excellent mechanisms for Energy Dissipation and has

been used from many years in automotive Brakes to dissipate KineticEnergy of Motion.

• The friction damper consists of diagonal brace elements with a friction interface at

their intersection point, which are connected together by horizontal and vertical link

elements.

• These link arms ensure that when the load is applied to a device via the braces is

sufficient to initiate slip on tension diagonal, then compression diagonal will also slip

an equal amount in opposite direction.

• The friction resistance of the device requires a normal force on the sliding interface,

and this is achieved through a bolt at the intersection of the diagonal arms.

Metallic DamperDissipation of energy input to a structure from an earthquake is through inelastic deformation of metals.

Metallic Damper

Thank YOU