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Republic of the Philippines

Polytechnic University of the Philippines

COLLEGE OF ARCHITECTURE

AND FINE ARTS

Department of Architecture

Sta. Mesa, Manila

BUILDING TECHNOLOGY 5

SEISMIC DESIGN

SUBMITTED BY:

GAVARRA, KRISTINE V.

MARASIGAN, KAMILLE S.

MUSNI, DYAN ALYSSA R.

NOBLEZA, MA. CARMELA D.

PORRAS, CHERRY FAITH V.

BS ARCH 4-2

SUBMITTED TO:

ARCHT. EMILIE T. GARCIA

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SEISMIC JOINTS

Seismic joints are used for seismic frames around

windows, gaps between external precast panels,

thermal expansion joints on large slabs, and gaps

between internal partition walls and the supporting slab

above. Buildings of irregular shape such as an L shape

are split up into simpler separate structures so that the

different parts can move freely in an earthquake. This

strategy of separate parts to a building is also often

used when adding a new section to an existing building.

A seismic joint typically creates a separation

between the adjacent buildings or parts of buildings

that include separation of walls, floors, and roof and, in

the case of joints within the same building, may also

include separation, or accommodation for movement of

piping, HVAC ducts, and other elements that have a

functional need to cross the joint.

Seismic joints or separations between buildings have been used for many years. However, over the years the

required width, and subsequently the cost, of the separations have grown. Seismic joints, within a single building, have

been introduced by engineers, in the past, either to simplify analysis or to reduce the seismic effects of building

irregularities. The requirements for structural function, weather tightness, fire separation, appearance, and services

distribution performance need to be all met.

Seismic joints must accommodate movement in both orthogonal directions simultaneously and their spacing is

not typically affected by building length or size.

HISTORY:

The earliest use of seismic joints did not

recognize them as joints at all. They were merely the

space between adjacent buildings. As seismic analysis

evolved to the level of the static analysis methods of

the 1950s and 60s, structural engineers began to

recognize that certain building shapes resulted in

potentially undesirable effects, such as torsion or high

collector forces at reentrant corners, that their analysis FIGURE: SEISMIC WALL JOINTS

FIGURE: PARTS OF A SEISMIC JOINT

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methods were not yet adequate to deal with. It became a common practice to introduce seismic joints to divide a

complexly shaped building into a group of smaller buildings with simple shapes that were easy to analyze and had

predictable seismic performance.

Another place where seismic joints have often been introduced is at locations where diaphragms are recognized

to be weak, and it is felt to be better to introduce a joint than to suffer the damage that might occur during a seismic

event.

Movement can occur in the horizontal, vertical, lateral and axial directions. Two parts of a building side by side

can move towards and away from each other, move from side to side, or

have a difference in height as they deform.

If access is required between two buildings or two separate

structures in a building then a physical link is required between the two.

This will require connections for walls, floors, ceilings and roofs. Floors

of a building are generally fire separations which require the floor to

ceiling junction and any expansion joint to be fire rated.

Internal walls for separate fire cells and safe path corridors are

required to be fire rated. These are subject to differential movement

where they cross a seismic floor joint. There will be differential seismic

movement between the slab and the top and bottom of the wall,

requiring a gap which must be fire rated. External walls often have gaps

between the structural frame and the cladding of masonry or precast

concrete. These gaps need to be fire rated to prevent fire spread to

adjacent buildings or from floor to floor.

Architects have a strong dislike for seismic joints, with good reason. The joints require very significant design

effort by the architect and, ultimately, no matter how well they are done, they are expensive and unattractive features

of the building.

SAFETY CLADDING

This topic discusses the issues related to the protection of the building envelope,

including the concrete cladding, glass and metal panels and roofing system from

seismic or earthquake forces. It also tackles the performances of the building envelope

in terms of its capability to resist from earthquake.

Seismic Performance

Heavy cladding systems

FIGURE: SEISMIC FLOOR JOINTS

Figure 1: Falling concrete panels

(Source: wbdg.org)

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The performance of heavy cladding systems has been good, despite of the severe threat to life safety of possible

falling and detachment of concrete panels and glass breakage.

Metal and glass curtain walls

These materials have performed well, because of the inherent strength of

the glass, the flexibility of the framing assembly, the resiliency of the glass

retention materials and relatively small size of the glass panels. However, seismic or

earthquake forces causes the building to drift, resulting to deformation and/or

breakage of glass panels.

Heavy roof tiles

Roof tiles may vulnerable to breakage due to deficient workmanship and

inadequate design.

Heavy cladding systems

Heavy cladding systems consist of precast concrete, and may also have

additional materials like ceramic tiles or natural stone. Seismic codes require that

heavy cladding systems have sliding or ductile connections. However, sliding

connectors are rarely used in high seismic zones, because of the possibility of incorrect

adjustments when bolts are used, jamming or binding due to unwanted materials left

after installation and jamming due to geometrical

change of the structural frame under horizontal

forces.

What are ductile connectors?

Ductile connectors are also known as push-pull

connectors. It provides a simple and reliable method of de-coupling the panel from the

structure. The generic connection method consists of supporting the panel by fixed

bearing connections to a structural element at one floor to accommodate the gravity

loads, and using ductile "tie-back" connections to a structural element at an adjoining

floor.

The tie-back connection is designed to deform under lateral forces and thus does

not transmit racking forces to the panel. The tie-back must be capable of

accommodating the out-of-plane forces on the panel, including wind.

The bearing connections may be located at the top or at the bottom of the panel. Deep spandrel connections

have fixed and ductile connections, to prevent deformation of the support under severe seismic forces.

Figure 2: Glass damage

during an earthquake (Source:

wbdg.org)

Figure 3: Illustration of

sliding and ductile connectors

(Source: wbdg.org)

Figure 4: Typical floor to

floor "push-pull'' panel connectors

(Source:wbdg.org)

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Column covers are also supported by

fixed and ductile connections, to accommodate

possible deformations in the columns.

The push-pull connection also represents

one of the simplest ways of obtaining

installation adjustments that are necessary for

panel alignment, irrespective of seismic

requirements. Connections must be designed

for safe temporary support while the panel is

being adjusted, leveled vertically and horizontally

and correctly spaced in relation to adjoining

panels. In high-rise building, however, it is common to provide temporary

placement for a large number of panels, before another crew returns to adjust and

make final connections. Since the panel connections, of which there may be

hundreds or even thousands, are relatively expensive, designers sometimes reduce the number of connections

necessary by varying to shape of the panels.

Another technique for reducing the number of panels and connection is to support a number of facing panels on a

metal frame that is attached to the building structure. The frames can be shop welded: a number of facing panels are

attached at the site and the entire assembly is then lifted up and attached to the structure.

Glass Fiber Reinforced Concrete Cladding Systems

Glass fiber reinforced concrete products

are manufactured using cement/aggregate

slurry reinforced throughout with alkali resistant

glass fibers. GFRC architectural panels generally

weigh from 10 to 25 pounds per square foot (48

kg/m to 121 kg/m) depending on surface

finish, panel size, shape and arrangement of

the steel stud or tube framework.

Light-Weight Panel Systems

Lightweight cladding is generally designed to move with the structural frame

and must be able to accommodate design drifts. In the case of a full metal and glass curtain wall system the opaque

portions will often use the same glazing as the transparent areas, with reflective or dark glass backed-up by insulation.

Another common type of light-weight cladding is that of horizontal alternating bands of glazing and metal insulated

Figure 6: "Push-pull"

connections on deep precast

spandrel system (Source: wbdg.org)

Figure 5: Panel design layouts

(Source: wbdg.org)

Figure 7: Typical GFRC panel

(Source: wbdg.com)

Figure 8: Relationship between

curtain wall and structural drift (Source:

wbdg.org)

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panels. The latter may be a spandrel wall built on site from steel studs with metal facing, or it may consist of factory

fabricated panels, with exterior facing, insulation and interior finish assembled into an integrated panel.

Windows and Curtain Walls

Earthquake forces cause the structure to drift,

and in a typical curtain wall in which the framing is

rigidly attached to the structure framing system

deforms and corners of the glass may impact the metal

frame.

Glass is retained within the frame by flexible

gaskets and clearance between glass and frame is maintained by inserting small rubber

block spacers. The flexible gaskets and rubber spacers

allow for considerable movement of the glass within the

frame and the rubber blocks must be compressed before

the glass impacts the metal.

BUCKLING RESTRAINED BRACE

HISTORY:

The concept of BRBs was developed in Japan at the

end of the 1980s.

It appeared in the United States after the Northridge earthquake (MAGNITUDE 6.7, Intensity 11) in 1994 and it is

now accepted with its design regulated in current standards as a displacement dependent lateral load resisting solution.

DEFINITION:

Buckling restrained braces are made to prevent buckling under axial compression when there are seismic events.

It can absorb significant amount of energy during cyclic loadings.

It is composed of a steel core and a casing.

COMPONENTS

steel core

Bond-preventing layer - decouples the casing from the core.

Figure 10 (Source:

wbdg.org)

Figure 9: Elevation of glazing

installed on a metal frame (Source:

wbdg.org)

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Casing - typically made of concrete filled steel tubes.

CHARACTERISTIC

An extremely dissipative structure can be designed using BRBs.

CONNECTIONS

Usually three kinds of connections are used for BRBs:

welded connection

pinned connection

bolted connection

STRUCTURES WITH BRB

ADVANTAGES:

Superior ductile and energy dissipative behavior

Lower demand on foundations specially, the arising tension loads are drastically decreased,

Easy to adopt in seismic retrofitting

Easy post-earthquake investigation and replacement if needed.

PARKING STRUCTURE: JOHN WAYNE AIRPORT REAL SALT LAKE STADIUM

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FRICTION PENDULUM BEARINGS

Friction Pendulum Bearings is a type of base isolation system in

which the superstructure is isolated from the foundation using specially

designed concave surfaces and bearings to allow sway under its own

natural period during the seismic events.

Seismic isolation bearings are structural joints that are installed

between a structure and its foundation support columns. The purpose is

to minimize damage caused by large lateral displacements observed during earthquakes.

Bearings can be designed to accommodate different

magnitudes of displacement simply by adjusting the

curvature and diameter of the bearing surface. Typically

Friction Pendulum bearings measure 3 feet in diameter, 8

inches high, and weigh 2000 pounds.

Friction Pendulum Bearing is selected simply by choosing the radius of curvature of the concave surface.

It is independent of the mass of the supported structure. The damping is selected by choosing the friction

coefficient. Torsion motions of the structure are minimized because the center of stiffness of the bearings

automatically coincides with the center of mass of the supported structure. The bearings period, vertical load

capacity, damping, displacement capacity, and tension capacity, can all be selected independently. For the

Triple Pendulum bearing, three effective radii and three friction coefficients are selected to optimize

performance for different strengths and frequencies of earthquake shaking. This allows for maximum design

flexibility to accommodate both moderate and extreme motions, including near-fault pulses.

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The Single Pendulum Bearing maintains constant friction, lateral stiffness, and dynamic period for all

levels of earthquake motion and displacements. In the Triple Pendulum bearing, the three pendulum

mechanisms are sequentially activated as the earthquake motions become stronger. The small displacement,

high frequency ground motions are absorbed by the low friction and short period inner pendulum. For the

stronger Design Level Earthquakes, both the bearing friction and period increase, resulting in lower bearing

displacements and lower structure base shears. For the strongest Maximum Credible Earthquakes, both the

bearing friction and lateral stiffness increase, reducing the bearing displacement.

The Triple Pendulum Bearing offers better seismic performance, lower bearing costs, and lower

construction costs as compared to conventional seismic isolation technology. The properties of each of the

bearings three pendulums are chosen to become sequentially active at different earthquake strengths. As the

ground motions become stronger, the bearing displacements increase. At greater displacements, the effective

pendulum length and the effective damping increase, resulting in lower seismic forces and bearing

displacements.

The Triple Pendulum bearings inner isolator consists of an inner slider that slides along two inner

concave spherical surfaces. Properties of the inner pendulum are typically chosen to reduce the peak

accelerations acting on the isolated structure and its contents, minimize the participation of higher structure

modes, and reduce structure shear forces that occur during service level earthquakes.

The two slider concaves, sliding along the two main concave surfaces, comprise two more independent

pendulum isolators. Properties of the second pendulum are typically chosen to minimize the structure shear

forces that occur during the design basis earthquake. This reduces construction costs of the structure.

Properties of the third pendulum are typically chosen to minimize bearing displacements that occur during the

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maximum credible earthquake. This reduces the size and cost of the bearings, and reduces the displacements

required for the structures seismic gaps.

Put simply, the bearings literally isolate the structure from the moving ground below by permitting the

building to move up to 30 horizontally and 2 vertically in an earthquake.

To prevent the building from moving more than 30 horizontally and literally falling off its foundation,

large shock absorbers or viscous dampeners are connected to the structure and to embed set within the

foundation.

BASE ISOLATION

HISTORY OF BASE ISOLATION

ANCIENT

Tomb of Cyrus is said to be the oldest base-isolated structure in the world

Cyrus the Great Tomb

Pasargadae, southeast of Iran, built in 550 BC, several layers of smoothed stone without any mortar or sticky

material between them actually form a kind of base isolation.

Orthostat Stone Layers

-In earthquake prone areas, some flat small stones like pillow were laid to absorb the first shock of earthquake

forces on the pre-prepared soil under foundations.

-Then, some big foundation stone layers were put over these small stones where normal construction of the walls

was built.

-The number of layers in most of the times was three and no mortar was used.

-These large foundation stones are called Orthostat stones.

Even though the stones are over each other without any mortar or sticky material, the mechanism is in such a

manner that actually no sliding occur; or better say, they may slide a little but they come back to their original position

following the earthquake.

CYRUS THE GREAT TOMB

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Erechtheion Temple on the north side of the Acropolis of Athens in Greece (built between 421 and 407 BC). Source: Google Images

Research on Base Isolation

The Earthquake Engineering Research Centre (EERC), now known as the Pacific Engineering Research Centre

(PEER), of the University of California at Berkeley, was the first institution in the United States to conduct a study on the

feasibility of using raw rubber bearings as base isolators to defend buildings from earthquakes. This was in 1976. The

study undertaken was a combined effort between the EERC and the Malaysian Rubber Producers Research Association

(MRPRA) from the United Kingdom. In the beginning, this study program was fully financed by the MRPRA and latter on

by the National Science Foundation and the Electric Power Research Institute.

Quite simply, the idea underlying the technology is to detach the building from the ground in such a way that the

earthquake motions are not transmitted up through the building, or are at least greatly reduced. Seismic isolation is

most often installed at the base level of a building and is called base isolation. This new concept meets all the criteria for

a classic modern technological innovation: the necessary imaginative advances in conceptual thinking, new materials

available to the industry, and as can be seen in the World Housing Encyclopedia (WHE) reports using isolators,

simultaneous development of the ideas worldwide.

Principle and concept

The principle of seismic isolation is to introduce flexibility at the base of a structure in the horizontal plane, while

at the same time introducing damping elements to restrict the amplitude of the motion caused by the earthquake.

The concept of seismic isolation became more feasible with the successful development of mechanical energy

dissipators and elastomers with high damping properties. Seismic isolation can significantly reduce both floor

accelerations and inter story drift and provide a viable economic solution to the difficult problem of reducing

nonstructural earthquake damage.

Intuitively, the concept of separating the structure from the ground to avoid earthquake damage

is quite simple to grasp. After all, in an earthquake the ground moves and it is this ground

movement which causes most of the damage to structures. An airplane flying over an earthquake

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is not affected. So, the principle is simple. Separate the structure from the ground. The ground

will move but the building will not move. As in so many things, the devil is in the detail. The

only way a structure can be supported under gravity is to rest on the ground. Isolation conflicts

with this fundamental structural engineering requirement. How can the structure be separated

from the ground for earthquake loads but still resist gravity

Suitability of seismic isolation

Earthquake protection of structures using base isolation technique is generally suitable if the following conditions

are fulfilled:

1. The subsoil does not produce a predominance of long period ground motion.

2. The structure is fairly squat with sufficiently high column load.

3. The site permits horizontal displacements at the base of the order of 200 mm or more.

4. Lateral loads due to wind are less than approximately 10% of the weight of the structure.

BASE ISOLATION TECHNOLOGY

Definition:

Base isolation systems detach the building from its foundation in a way that allows the building to separate itself

from an earthquakes shock wave. While the building still rests firmly over its foundation, it is separated from it by a

distinct layer of material that acts as a shock absorber. When an earthquake occurs, the building can rely on this layer of

shock absorption to counteract and dampen any movement as a result of the earthquake's shock waves and therefore

maintain its structural integrity.

BASIC ELEMENTS

1. A vertical-load carrying device that provides lateral flexibility so that the period of vibration of the total system

is lengthened sufficiently to reduce the force response,

2. A damper or energy dissipater so that the relative deflections across the flexible mounting can be limited to a

practical design level, and

3. A means of providing rigidity under low (service) load.

Base isolation system consists of isolation units with or without isolation components, where:

1 Isolation units are the basic elements of a base isolation system which are intended to provide the

aforementioned decoupling effect to a building or non-building structure.

2 Isolation components are the connections between isolation units and their parts having no decoupling effect of

their own.

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FIXED VERSUS BASE ISOLATED BUILDING

A.)CONVENTIONAL STRUCTURE B.)BASE ISOLATED BUILDING

In a conventional structure, acceleration on the ground is amplified on the higher floors and the contents are

damaged, while in a base isolated building, earthquake movement takes place on the level of the isolators. Floor

accelerations are low, the building, its occupants and the loads are safe.

TWO BASIC TYPES

1. ELASTOMERIC BEARING

Natural Rubber Bearing

Low Damping Rubber Bearing

High Damping Rubber Bearing

Lead Rubber Bearing

2. SLIDING SYSTEM

Spherical Sliding Bearing

Friction Pendulum System

A.) ELASTOMERIC BEARING

The building is supported by bearing pads that have a curved surface and low friction. During an earthquake the

building is free to slide on the bearings. Since the bearings have a curved surface, the building slides both horizontally

and vertically. The forces needed to move the building upwards limits the horizontal or lateral forces which would

otherwise cause building deformations. Also by adjusting the radius of the bearings curved surface, this property can be

used to design bearings that also lengthen the buildings period of vibration.

Low Damping Rubber Bearing

High Damping Rubber Bearing

Natural/Synthetic Rubber Bearing

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Lead-rubber bearings are the frequently- used types of base isolation bearings. A lead rubber bearing is made

from layers of rubber sandwiched together with layers of steel. In the middle of the solid lead plug. On top and

bottom, the bearing is fitted with steel plates which are used to attach the bearing to the building and foundation. The

bearing is very stiff and strong in the vertical direction, but flexible in the horizontal direction.

B.) SLIDING SYSTEM

These are formed of horizontal layers of natural or synthetic rubber in thin layers bonded between steel plates.

The steel plates prevent the rubber layers from bulging and so the bearing is able to support higher vertical loads with

only small deformations. Under a lateral load the bearing is flexible.

1. Spherical Sliding Isolation

Curved surface sliders use gravity as a reentering force; the operating principle is the same as the pendulum.

Energy dissipation is ensured by the friction of the main sliding surface. The parameters for the bilinear constitutive

bond depend on the bending radius and friction coefficient.

It uses bearing pads that have a curved surface and low friction materials similar to Teflon

During an earthquake, the building is free to slide both horizontally and vertically

It will return to its original position after the ground shaking stops

2. FRICTION PENDULUM BEARING

Based on three aspects:

A. Articulated Friction Slider

B. Spherical concave sliding surface

C. Enclosing cylinder for lateral displacement

The second type is the friction pendulum system or sliding system. This type of system consists of a stainless steel

concave bowl and a self-lubricating slider. The slider is a post that supports the weight of the building and sits within the

steel bowl. When seismic movement occurs the building is free to move in the dish and return to the center once the

movement is complete. In this design the buildings weight is used to dampen the seismic loads by transferring the

horizontal movement to a vertical movement. Think of a skateboarder in the middle of a half pipe if you move the half

pipe rapidly, he will roll up the sides and return to the center once the movement has stopped. The only difference is the

FPS can move 360 degrees.

BENEFITS

The benefits of using seismic isolation and energy dissipation devices (isolators for simplicity) for earthquake-

resistant design are many:

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1. Isolation leads to a simpler structure with much less complicated seismic analysis as compared with

conventional structures;

2. Isolated designs are less sensitive to uncertainties in ground motion;

3. Minor damage at the design level event means immediate reoccupation;

4. The performance of the isolators is highly predictable, so they are much more reliable than conventional

structural components (e.g. some ductile walls in the Christchurch earthquakes); and finally,

5. Even in case of larger-than-expected seismic events, damage will concentrate in the isolation system, where

elements can be easily substituted to restore the complete functionality of the structure.

DISADVANTAGES

1. Uneconomical. It would be too expensive; it cannot be done for a normal office, apartments, and a normal

house.

BUILIDINGS WITH BASE ISOLATION SYSTEM

University of Southern California Teaching Hospital

The University of Southern California Teaching Hospital in east Los

Angeles (1991) had a severe test in 1994, when the Northridge earthquake hit.

Though it was only 23 miles from the epicenter, the horizontal acceleration in

the building was three or four times less than thepeak acceleration outside: the

building was effectively isolated from the motions that caused significant

damage to buildings nearby.

Source: Google Images

Emergency Operations Center

City of Los Angeles (Base

Isolated)

Owner: City of Los Angeles

Architect: Fluor/HOK

Saiful Bouquet is the Engineer of Record for the new Los Angeles Emergency Operations Center, (EOC). The new

EOC is the focal point for coordination of the Citys emergency planning, training, and response and recovery efforts for

major disasters such as fires, floods, earthquakes, and acts of terrorism. The EOC houses the emergency management

department, a new fire dispatch center, fire department operations center, and police department RACR division and

SOURCE: GOOGLE IMAGES

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operations center. The structural design is complete on the 2-story 83,000 gsf new state-of-the-art City of Los Angeles

EOC located in downtown Los Angeles. The building is designed as a base isolated facility to allow for critical operations

to continue immediately following a major regional earthquake. The structure itself is designed as a steel construction

with eccentric brace frames as its seismic bracing system.

SBI was very proactive from the beginning in developing multiple structural schemes and worked very closely with

the architect and the owner. This interactive collaborative effort led to the selection of the final structural and base

isolation system that was not only very cost-effective but also provided the architectural and functional layout flexibility.

Unlike typical base isolated facilities, this building only has a handful of steel braces, which resulted in significant savings

in structural steel. This was achieved through a combination of the use of the state-of-the-art advanced seismic analysis

along with an innovative base-isolation system (tension-restrained friction pendulum system).

Tohoku Electric Power Company, Japan.

Currently the largest base-isolated building in the world is

the West Japan Postal Computer Center, located in Sanda, Kobe

Prefecture. This six-story, 47,000 m square (500,000 ft square)

structure is supported on 120 elastomeric isolators with a number

of additional steel and lead dampers. The building, which has an

isolated period of 3.9 sec, is located approximately 30 km (19

miles) from the epicenter of the 1995 Hyogoken Nanbu (Kobe)

earthquake, and experienced severe ground motion. The peak

ground acceleration under the isolators was 400 cm/sec square (0.41 g) but was reduced by the isolation system to 127

cm/sec square (0.13 g) at the sixth floor. The estimate of the displacement of the isolators is around 12 cm (4.8 in.). A

fixed-base building adjacent to the computer center experienced some damage, but there was no damage to the

isolated building.

The use of isolation in Japan continues to increase, especially in the aftermath of the Kobe earthquake. As a result

of superior performance of the West Japan Postal Computer Center, there has been a rapid increase in the number of

permits for base-isolated buildings, including many apartments and condominiums.

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DAMPING TECHNOLOGY

DEFINITION:

These are mechanical devices to dissipate a portion of structural input energy, thus reducing structural responses and

possible structural damage.

Dampers are huge concrete blocks or steel bodies mounted in skyscrapers or other structures, and moved opposition to

the resonance frequency oscillations of the structure by means of springs, fluid or pendulums.

HISTORY:

In the early 1860s, the evolution of large dampers began with the advent of large loaded canons. The British army was

said to be the first to use hydraulic recoil dampers on the gun carriages in 1862. The first mass produced hydraulic recoil

damper was used on the 75mm French field gun, Model M1897. And by the end of World War I, fluid dampers were

being used on the field artillery pieces of, naval guns, coastal guns and railway guns.

In 1920s and 1930s were a period when the dominant feature of American culture are automobiles. While the earliest

damping were simple carried over from horse drawn wagons.

In 1925, Ralph Peo of Houdaille Company in NY, USA invented a solution by redesigning the damper to use rotating

piston rod and vane assembly.

In

1960s, during the Cold War, shock isolation became apparent because of the enemys missile attacks. The successful

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use of Fluid Dampers and Liquid Spring Dampers on Land Based Missile Facilities became an extremely powerful yet

compact isolation.

The transition of Defense Technology to the Private Sector was introduced by the Taylor Devices, Inc wherein defense

products were used by commercial outlets in 1987.

In general, it was found that adding 20% damping to a structure will triple its earthquake resistance, without increasing

stress or deflection.

PASSIVE ENERGY DISSIPATION DEVICES

DAMPING Devices are also called Energy Dissipation Devices. Considering the vast production of dampers that have

been developed, it can be grouped into THREE BROAD CATEGORIES:

1. FRICTION DAMPERS

- These utilize frictional forces to dissipate energy

2. YIELDING DAMPERS/ METTALIC DAMPERS

-Utilize the deformation of metal elements within the damper

3. VISCOUS DAMPERS

-Utilize the force movement (orificing) of fluids within the damper

FRICTION DAMPERS

Friction dampers are designed to have moving parts that will slide over each other during a strong earthquake. When

the parts slide over each other, they create friction which uses some of the energy from the earthquake that goes into

the building.

In 1980s, Pall and Marsh pioneered passive friction dampers on the basis of the model of Friction brakes

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IMPACT ABSORPTION FRICTION DAMPER Damptech dampers absorb the impact of a moving load and thereby reduce the transmission of potentially damaging shocks to equipment and vehicles, by converting the kinetic energy of the impact load into heat.

ROTATIONAL FRICTION DAMPER Undesired vibration are made when bridge cables are subjected to strong winds

ROTATIONAL FRICTION DAMPER Based on rotational friction concept, it consists of several steel plates with friction pads a placed in between. The motion of the damper creates relative rotation in the joints, causing friction sliding between the plates.

METALLIC YIELD DAMPERS

Metallic Dampers are usually made from steel. Designed to deform when the building vibrates during an earthquake

that they cannot return to their original shape. This permanent deformation is called INEALSTIC DEFORMATION, and it

uses some of the earthquake energy which goes into the building.

In 1970s, conceptual and experimental work on metallic yield devices began.

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VISCOUS DAMPERS

Viscous fluid dampers are similar to shock absorbers in a car. They consist of a closed

cylinder containing a viscous fluid like oil. The piston rod, connected to the piston

head, can move in and out of the cylinder. As it does this, the oil is forced to flow

through holes in the piston head causing friction.When the damper is installed in a

building, the friction converts some of the earthquake energy going into the moving

building into heat energy.

Basic Parts of a Fluid Damper:

Piston Rod Highly polished on its outside diameter, the piston rod slides through the

seal and seal retainer.

Cylinder The damper cylinder contains the fluid medium and must accept pressure

vessel loading when the damper is operating.

Fluid Dampers used in structural engineering applications require a fluid that is fire-

resistant, non-toxic, thermally stable, and which will not degrade with age.

Piston Head The piston head attaches to the piston rod, and effectively divides the

cylinder into two pressure chambers.

Seal Retainer Used to close open ends of the cylinder, these are often referred to as

end caps, end plates, or stuffing boxes.

Accumulator The purpose of the accumulator is to allow for the volumetric displacement of the piston rod as it

enters or exits the damper during excitation.

Orifices The pressurized flow of the fluid across the piston head is controlled by orifices.

DID YOU KNOW?

Millenium Bridge, London, UK

The eight suspension cables are tensioned to pull with a force of 2,000

tons against the piers set into each bank enough to support a working

load of 5,000 people on the bridge at one time.

Also known as wobbly bridge until 2001 wherein the oscillations

movement was given solution by placing 37 fluid-viscous dampers and

vibrations hasnt felt ever since.

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TUNED LIQUID DAMPERS

Another type of dynamic absorber for structural vibration suspension. In TLD, water or some other liquid serves as the

mass in motion. TLDs were initially applied in ships, and their application for vibration control of engineering structures

began in 1980s.

Dampens the vibration produced by the earthquake through fluid inertia. It is made up of a tank partially filled with

water, divided into segments by louvers that prevent turbulence.

TWO TYPES OF TLD:

1. Sloshing Damper 2. Column Damper

TUNED MASS DAMPER

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Tuned mass damper (TMD), also known as Harmonic Absorber, a device mounted in structures to reduce the amplitude

of mechanical vibrations. It is the most popular and extensively used device ranging from small rotating machinery to tall

civil structures.

The application of a Tuned Mass Damper suspends a large internal lumped mass at the uppermost floors of a tall

building, supporting the mass with cables, steel arms, or springs combined with air/fluid/mechanical slider bearings.

DID YOU KNOW?

Taipei 101 has the largest TMD sphere in the world and weighs 660 metric tons with a

diameter of 5.5 meters and costs US$4 million (total structure costs US$ 1.80 billion).

NEW TECHNOLOGY

MAGNETORHEOLOGICAL FLUID DAMPERS

Shock absorbing devices containing a liquid that becomes more vicious when a magnetic field is applied.

At first, it would normally feel like a thick fluid, but magnetic field is applied it becomes more vicious that it transform

into a peanut butter consistency.

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REFERENCES:

www.earthquakeprotection.com

rebuildingmphs.wordpress.com

en.wikipedia.org/wiki/Earthquake_engineering wbdg.org

http://en.wikipedia.org/wiki/Buckling_restrained_brace

http://www.corebrace.com/products.html

mceer.buffalo.edu/education/bridge.../Bruneau_presentation.pdf

www.dhsteel.co.nz/star_seismic_brb.html

http://seismicdesignzone.com/designing-around-base-isolation/

http://www.slideshare.net/vaignan/base-isolation-topic-as-per-jntu-syllabus-for-mtech-1st-year-structures

http://www.ehow.com/info_8695094_base-isolation-systems.html

http://www.brighthubengineering.com/structural-engineering/42793-base-isolation-in-seismic-engineering/

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB4QFjAA&url=

http%3A%2F%2Fwww.cibw114.net%2Fsymposium2009%2Fpdf%2FOS09_Ahmad_Naderzadeh.pdf&ei=sVLnU9rGK

tTh8AXKnICgDg&usg=AFQjCNH2WsU-E9qwZnI4aQXO4XZkGIS3BA&sig2=3XK8-EKJGOMqQHE1gdWhvQ

http://civil-engg-world.blogspot.com/2011/05/usc-university-hospital-california.html

http://taylordevices.com/papers/history/design.htm

http://theconstructor.org/earthquake/dampers-for-seismic-resistant-structures/8332/

https://www.youtube.com/watch?v=Hn_g7Uxzlr4&list=PL27E643948F34874E

http://link.springer.com/article/10.1007/s40091-014-0046-5#page-2

http://en.wikipedia.org/wiki/Millennium_Bridge,_London

http://books.google.com.ph/books?id=93ysnbMf8oQC&pg=PA22&lpg=PA22&dq=yielding+damper&source=bl&ot

s=3dUtk0-IG-

&sig=D5RMmKrQryN1fthabNEQnuwjLqU&hl=en&sa=X&ei=NXcDVMiPObGvigLj4oH4CQ&ved=0CE4Q6AEwCw#v=o

nepage&q&f=false

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