Final Project Topics

Seismic Control of Structures for

Dynamic Actions

A Brief Review of Fundamentals

of

Earthquake Resistant Design

Earthquake Engineering can be defined

as the branch of engineering devoted to

mitigating earthquake hazards. In this

broad sense, earthquake engineering

covers the investigation and solution of

the problems created by damaging

earthquakes, and consequently the work

involved in the practical application of

these solutions, i.e. in planning,

designing, constructing and managing

earthquake-resistant structures and

facilities.

Title: Roof-top water tank induced damage

Date: 2001

Earthquake: Bhuj, India earthquake, Jan. 26, 2001

Magnitude: 7.7

General Goals in Seismic-Resistant

Design and Construction

The philosophy of earthquake design

for structures other than essential

facilities has been well established and

proposed as follows:

a.To prevent non-structural damage in

frequent minor ground shaking

b.To prevent structural damage and

minimize non-structural damage in

occasional moderate ground shaking

c.To avoid collapse or serious damage in

rare major ground shaking

Title: Damage from out-of-plane deformation

Location: Turkey/ASIA/Western Asia

Earthquake: Izmit, Turkey earthquake, Aug. 17,

1999 Magnitude: 7.4

Building structures may be of many types and configurations and there is, of course,

no universal ideal configuration for any particular type of building. However, there

are certain basic or guiding principles of seismic-resistant design that can be used as

guidelines in selecting an adequate building configuration structural layout,

structural system, structural material and the non-structural components. These

basic guidelines are as follows:

1. Building (superstructure and

non-structural components)

should be light and avoid

unnecessary masses.

Superstructure should have the

largest possible number of

defense lines, that is, it should be

composed of different tough

structural subsystems which

interact or are interconnected by

very tough structural elements

(structural fuses) whose inelastic

behavior would permit the whole

structure to find its way out from

a critical stage of dynamic

response.

Plan view of the Banco de

America, Managua, Nicaragua.

This building generally

performed very well during the

1972 Managua Earthquake. Its

excellent performance can be

attributed to the symmetry

and uniformity of distribution

of the masses and structural

stiffnesses throughout the

building.

2. Building and its superstructure should be

simple, symmetric, and regular in plan and

elevation to prevent significant torsional

forces, avoiding large height-width ratio and

large plan area.

Hotel Terminal, Guatemala

City. Overall view of this 6-story

hotel, illustrating the torsional failure

of the second story during the 1976

Guatemala Earthquake.

Refer to type of irregularities in structures

3. Building and its superstructure should have

a uniform and continuous distribution of mass,

stiffness, strength and ductility, avoiding

formation of soft stories.

Commercial Building Casa

Micasa S.A., Managua,

Nicaragua. This 2-story

reinforced concrete frame

building suffered

significant lateral

displacement at the

second floor level during

the 1972 Managua

Earthquake.

Detailed view of the behavior of

one of the first and second story

columns in the building of Slide J72

during the 1971 San Fernando

Earthquake. Note the large

permanent distortion of the first

story column (because it was part

of the soft story at this

level). While the well-confined

concrete of the spirally reinforced

core of this column was capable of

holding the building up, the

unconfined concrete cover had

spalled off. Note also the shear

failure of the second story column,

induced by the shortening of this

column by the wall panels that

were placed at the top and bottom

of this story.

Olive View Hospital, Psychiatric Unit, San

Fernando, California. 1971 San Fernando

Earthquake. This unit was a 2-story reinforced

concrete building. The structural system was a

moment resisting frame. However, in the

second story there were masonry walls that

added significantly to the stiffness of this story.

4. The non-structural components

should either be well separated so that

they will not interact with the rest of

the structure, or they should be

integrated with the structure. On the

latter case, it is desirable that the

structure should have sufficient lateral

stiffness to avoid significant damage

under minor and moderate earthquake

shaking, and toughness with stable

hysteric behavior (that is, stability of

strength, stiffness and deformability)

under the repeated reversal of

deformations which could be induced

by severe earthquake ground motion.

The stiffer the structure, the less

sensitive it will be to the effects of the

interacting non-structural components,

and the tougher it is, the less sensitive

it will be to effect of sudden failure of

the interacting non-structural

elements.

Two-story reinforced concrete building, Managua,

Nicaragua, damaged in the 1972 Managua Earthquake.

The slide shows a reinforced concrete column which was

part of the structural system and which failed due to its

shortening because of the effect of the masonry wall. The

masonry walls were considered as non-structural elements.

Innovative Earthquake Resistant

Design and Control Methods

Motivation for Controlling of

Earthquake Forces

• Control earthquake forces in order to

• Obtain better building performances

• Controlling can be through design details,

passive control or active control

PED: Passive Energy Dissipation

An Example for a Passive Control

Seismic Isolation

� Seismic Isolation Technologies

� The basics – How it works?

� Design related issues

Seismic Performance GoalsOur goals are to Preserve Life Safety and Prevent Collapse

If collapse can be prevented, which level of damage is acceptable?

Local Failure

Permanent

Failure

L’Aquila Earthquake

2009 - Italy

Van Earthquake

2011 - Turkey

Total collapse

Seismic Performance Goals

In Earthquake Engineering the challenge is to build structures for different

performance levels (e.g.,):

� Life safety for strong eartquakes (rare events),

� Limited damage for design based eartquakes.

RESILIENT STRUCTURES

Ductility Design vs. Force

Control StrategyChallenges in “ductile design” strategy:

� Strong column – weak beam mechanism may not form due

to existence of wall,

� Shear failure of columns may occur due to wrong

proportioning or short-column effect,

� Construction difficulty at beam-column joints due to

complexity of steel reinforcement,

So, why not control the inertial forces

attracted to the structure?

Seismic Isolation – Controlling Forces

How It Works?

� The structure is decoupled

from the ground by isolators

with low horizontal stiffness,

� This results in fundamental

frequency that is much lower

than the fixed-base frequency,

� The first dynamic mode of the

isolated structure involves

deformation only in the

isolation system,

Seismic Isolation – Controlling Forces

How It Works?

� These higher modes do not

participate in the motion,

reducing drift (orthogonality),

� The isolation system does not

absorb the earthquake energy,

but rather deflects it through the

dynamics of the system.

Building with a Seismic Isolation

� Schematic representation of a

building with base isolation

system

Building with a Seismic Isolation

Seismic Isolation

�Smaller structural members

�Smaller foundations

�Smaller accelerations

With a seismically isolated structure, the seismic

forces are reduced, this leads to:

Seismic Isolation

How It Works? – A Demonstration!

Seismic Isolation

Requirements of a Base Isolated Device1. Isolating the building from the ground,

2. Supporting the weight of the structure,

Seismic Isolation

Requirements of a Base Isolated Device3. Damping of response amplitude,

4. Restoring to the original position after an earthquake,

Seismic Isolation

Isolated

Building

Increasing the period will reduce the

acceleration

Seismic Isolation

Isolated

Building

Increase in period will increase the displacements, therefore

high damping is needed!

Seismic Isolation

� Laminated elastomeric bearings,

Types of Isolators

Video

� Pendulums (low friction

sliders – stainless

steel/PTFE)

Types of Isolators

A Test Video of a Friction Pendulum

� Elasto-plastic devices

Types of Isolators

Devices at Bolu Viaducts

Application of anti-seismic

systemOver 10.000 new and existing structures:

� Bridge and viaduct

� Industrial plants and components

� Buildings including cultural heritage