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Rehabilation of Seismically Damaged Structures

Bringing back life to the structures

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“Earthquakes Don’t Kill People, Buildings Do” In 1994 MIn 1994 Mww 6.7 Northridge earthquake 6.7 Northridge earthquake

struck Los Angeles urban area.struck Los Angeles urban area.

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Structural Failure

I-5 & State HW14 Interchange Collapse of the 2500-car parking structure, Cal State University-Northridge campus

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Structural Failure

Partial collapse of Olive View Hospital during 1971 M 6.7 San Fernando earthquake

Rebuilt Olive View Hospital again subjected to strong shaking in the 1994 Northridge earthquake. The rebuilt structure sustained no serious damage.

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Damages to Wood Buildings

Failure of cripple wall

Chimney damage Overturned bookcases

Major damage by house moving off the foundation

Weak first story

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Earthquake’s Other Damages…

Trans-Alaska oil pipeline was subjected to the 2002 Mag. 7.9 Denali Fault earthquake.

In this photo of Northridge earthquake, ground failure ruptured two gas lines that burned five houses.

This photo shows fires in San Francisco’s Marina District following the 1989 Mag. 6.9 Loma Prieta earthquake.

Broken gas line in Los Angeles following 1994 Northridge earthquake.

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Damages to bridges

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Performance of Structures in EarthquakesPerformance of Structures in Earthquakes

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India, Gujarat earthquakeJan 26, 2001

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Wind action on bridges

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WHY IS REHABILITATION DONE.

Revision of design codes is a continuing process world Revision of design codes is a continuing process world over and usually results in up-gradation of seismic over and usually results in up-gradation of seismic hazard and increase in design forces. hazard and increase in design forces.

In India also several regions have been upgraded in In India also several regions have been upgraded in terms of seismic zones thereby rendering buildings terms of seismic zones thereby rendering buildings unsafe according to new code. unsafe according to new code.

All these factors make the rehabilitation of existing All these factors make the rehabilitation of existing structures necessary. structures necessary.

The retrofitting may also be required if change in usage The retrofitting may also be required if change in usage of a building takes place or there is a major of a building takes place or there is a major alteration/extension of building.alteration/extension of building.

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The level of retrofitting of a building depends on the The level of retrofitting of a building depends on the seismic zone in which building is situated and the level of seismic zone in which building is situated and the level of performance desired from the building. performance desired from the building.

Important buildings are desired to have a higher Important buildings are desired to have a higher performance level during future earthquakes. The seismic performance level during future earthquakes. The seismic zone governs the design earthquake forceszone governs the design earthquake forces

Not only member forces and strength and the stiffness of Not only member forces and strength and the stiffness of the members are important, but also the nonlinear the members are important, but also the nonlinear deformations and ductile capacity of members are also deformations and ductile capacity of members are also important for seismic safety of building and need to be important for seismic safety of building and need to be evaluated and examined.evaluated and examined.

Level of rehabilitation required

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Rehabilitation ObjectivesRehabilitation Objectives

Unacceptable Performance

(for New Construction)

Basic Objective

Essential/Hazardous

Objective Safety Critical

Objective

Earthquake Performance Level

Fully Operational

Operational Life Safety

Near Collapse

Earthquake Design Level

Very Rare(970 years)

Frequent(43 years)

Occasional(72 years)

Rare(475 years)

Inelastic RangeElastic Range Collapse

Du

ctil

ity

Str

eng

th

Sti

ffn

ess

Lateral Load

Deflection

Collapse PreventionServiceability Life Safety

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It is very evident from the It is very evident from the graph that if the deflection graph that if the deflection vs the lateral load curve is vs the lateral load curve is with in the elastic range with in the elastic range

then only the stiffness of the then only the stiffness of the structure should be structure should be

increased by rehabilitation increased by rehabilitation so as to enhance its so as to enhance its

serviceability.serviceability.  

Now if the deflection vs the Now if the deflection vs the lateral load curve goes lateral load curve goes

beyond the elastic range but beyond the elastic range but is with in the inelastic range is with in the inelastic range then both the stiffness and then both the stiffness and

the strength of the structure the strength of the structure has to be enhanced by has to be enhanced by rehabilitation so as to rehabilitation so as to

enhance both its enhance both its serviceability as well as its serviceability as well as its

life.life.  Now if the deflection vs the lateral load curve goes beyond the inelastic range Now if the deflection vs the lateral load curve goes beyond the inelastic range

and reaches the collapse range then the stiffness, the strength and ductility and reaches the collapse range then the stiffness, the strength and ductility should be increased by rehabilitation so as to enhance both its serviceability as should be increased by rehabilitation so as to enhance both its serviceability as

well as its strength and to prevent it from collapsing.well as its strength and to prevent it from collapsing.  

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GOALS OF REHABILITATION : Structure survivability. The structure may require extensive repair Structure survivability. The structure may require extensive repair

(but not replacement) before it is generally useful or considered safe (but not replacement) before it is generally useful or considered safe for occupation. This is typically the lowest level of retrofit applied to for occupation. This is typically the lowest level of retrofit applied to bridges. bridges.

Structure usability. The structure is retrofitted to retain or enhance Structure usability. The structure is retrofitted to retain or enhance its utility. This type of retrofit is applied to its utility. This type of retrofit is applied to fire fire fighting fighting stationsstations, , transportation infrastructure such as rail and highway roadways, transportation infrastructure such as rail and highway roadways, bridges, and tunnels, water supplies used for fire fighting - bridges, and tunnels, water supplies used for fire fighting - reservoirs, water lines, and hydrantsreservoirs, water lines, and hydrants

Public safety only. The goal is to protect human life, ensuring that Public safety only. The goal is to protect human life, ensuring that the structure will not collapse upon its occupants or passers by, and the structure will not collapse upon its occupants or passers by, and that the structure can be safely exited. that the structure can be safely exited.

Structure unaffected. This level of retrofit is preferred for historic Structure unaffected. This level of retrofit is preferred for historic structures of high cultural significance so as to aid their preservation structures of high cultural significance so as to aid their preservation for years to come. for years to come.

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Framework for Seismic Rehabilitation Framework for Seismic Rehabilitation (3)(3)

• Rehabilitation Rehabilitation StrategyStrategy

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Design ParametersDesign Parameters

StrengthStrength DuctilityDuctilityStiffnessStiffness

Ductility Ductility eenhancementnhancementB

ase

shea

r rehabilitated structure

Δu

displacement

existing structure

Stiffness & StrengthStiffness & Strength eenhancementnhancement

existing structure

ΔV

rehabilitated structure

Bas

e sh

ear

displacement

Stiffness, Strength Stiffness, Strength & Ductility& Ductility eenhancementnhancement

displacement

Bas

e sh

ear

Δu

ΔV

existing structure

rehabilitated structure

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Rehabilitation Schemes for RC StructuresRehabilitation Schemes for RC Structures

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Intervention TechniquesIntervention Techniques

• RC jacketingRC jacketing

• Addition of RC wallsAddition of RC walls

• External buttressesExternal buttresses

• Steel bracingSteel bracing

• Base isolationBase isolation

GlobalGlobalLocalLocal

• Injection of cracksInjection of cracks

• Shotcrete (Gunite)Shotcrete (Gunite)

• Steel Plate AdhesionSteel Plate Adhesion

• Steel JacketingSteel Jacketing

• FRP JacketingFRP Jacketing

SelectiveSelective• Stiffness-onlyStiffness-only

• Strength-onlyStrength-only

• Ductility-onlyDuctility-only

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DIFFERENT PROCESSES OF REHABILITATION FOR VARIOUS CASES OF STRUCTURE FAILURES DUE EARTHQUAKES

1. Reinforcement1. Reinforcement The most common form of seismic The most common form of seismic

rehabilitatoin to building is adding strength to rehabilitatoin to building is adding strength to the existing structure to resist seismic forces. the existing structure to resist seismic forces. The strengthening may be limited to The strengthening may be limited to connections between existing building elements connections between existing building elements or it may involve adding primary resisting or it may involve adding primary resisting elements such as walls or frames, particularly elements such as walls or frames, particularly in the lower stories.in the lower stories.

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Connections between buildings and their expansion additions

Frequently, building additions will not be strongly connected to Frequently, building additions will not be strongly connected to the existing structure, but simply placed adjacent to it, with only the existing structure, but simply placed adjacent to it, with only minor continuity in flooring, siding, and roofing. minor continuity in flooring, siding, and roofing.

As a result, the addition may have a different resonant period than As a result, the addition may have a different resonant period than the original structure, and they may easily detach from one the original structure, and they may easily detach from one another. another.

The relative motion will then cause the two parts to collide, The relative motion will then cause the two parts to collide, causing severe structural damage.causing severe structural damage.

Proper construction will tie the two building components rigidly Proper construction will tie the two building components rigidly together so that they behave as a single mass.together so that they behave as a single mass.

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failure in lowest storey 

Using modern design methods, it is possible to take a weak lower story into account.

the weak story is reinforced to make it stronger than the floors above by

1. adding shear walls or moment frames.

2. Moment frames consisting of inverted U bents are useful in preserving lower story garage access.

3. while a lower cost solution may be to use shear walls or trusses in several locations, which partially reduce the usefulness for automobile parking but still allow the space to be used for other storage.

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Wooden floor failures 

Floors in wooden buildings are usually Floors in wooden buildings are usually constructed upon relatively deep spans constructed upon relatively deep spans of wood, called of wood, called joistsjoists, covered with a , covered with a diagonal wood planking or diagonal wood planking or plywoodplywood to to form a subfloor upon which the finish form a subfloor upon which the finish floor surface is laid.floor surface is laid.

To prevent the beams from tipping over To prevent the beams from tipping over onto their side, blocking is used at each onto their side, blocking is used at each end,end,

For additional stiffness, blocking or For additional stiffness, blocking or diagonal wood or metal bracing may be diagonal wood or metal bracing may be placed between beams at one or more placed between beams at one or more points in their spans. points in their spans.

As part of a retrofit the blocking may As part of a retrofit the blocking may be doubled, especially at the outer edges be doubled, especially at the outer edges of the building. of the building.

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Reinforced concrete column burst

One simple rehabilitate is to One simple rehabilitate is to surround the column with a surround the column with a jacket of steel plates formed jacket of steel plates formed and welded into a single and welded into a single cylinder. The space between cylinder. The space between the jacket and the column is the jacket and the column is then filled with concrete, a then filled with concrete, a process called grouting. process called grouting.

Where soil or structure Where soil or structure conditions require such conditions require such additional modification, additional modification, additional pilings may be additional pilings may be driven near the column base driven near the column base and concrete pads linking and concrete pads linking the pilings to the columns the pilings to the columns are fabricated at or below are fabricated at or below ground level. ground level.

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Brick wall resin and glass fiber reinforcement

Brick building structures have been Brick building structures have been reinforced with coatings of glass reinforced with coatings of glass fiber and appropriate resin (epoxy fiber and appropriate resin (epoxy or polyester). or polyester).

In lower floors these may be applied In lower floors these may be applied over entire exposed surfaces, while over entire exposed surfaces, while in upper floors this may be confined in upper floors this may be confined to narrow areas around window and to narrow areas around window and door openings. door openings.

This application provides tensile This application provides tensile strength that stiffens the wall strength that stiffens the wall against bending away from the side against bending away from the side with the application. with the application.

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Reinforced concrete post to beam connections

Examination of failed structures often reveals failure at the corners, where vertical posts join horizontal beams.

These corners can be reinforced with external steel plates, which must be secured by through bolts and which may also offer an anchor point for strong rods, as shown in the image at left.

The horizontal rods pass across the beam to a similar structure on the opposite side, while the vertical rods are anchored after passing through a grouted anti-burst jacket.

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2. Use of Ferrocement2. Use of Ferrocement  In In IndiaIndia, ferrocement is used often because , ferrocement is used often because

the constructions made from it are the constructions made from it are better resistant against better resistant against earthquakesearthquakes..

AdvantagesAdvantagesThe advantages of a well built The advantages of a well built

ferrocement construction are the low ferrocement construction are the low weight, maintenance costs and long weight, maintenance costs and long lifetime in comparison with steel lifetime in comparison with steel constructions. However, meticulous constructions. However, meticulous building precision is considered crucial building precision is considered crucial here. Especially with respect to the here. Especially with respect to the cement composition and the way in cement composition and the way in which it is applied in and on the which it is applied in and on the framework.framework.

When a ferrocement sheet is mechanically When a ferrocement sheet is mechanically overloaded, it will tend to fold instead overloaded, it will tend to fold instead of crack or rupture. The wire of crack or rupture. The wire framework will hold the pieces framework will hold the pieces together, which in some applications together, which in some applications (boat hull, ceiling, roof) is an (boat hull, ceiling, roof) is an advantage.advantage.

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      3. Isolation3. Isolation Generally required for large masonry Generally required for large masonry

buildings, excavations are made around buildings, excavations are made around the foundations of the building and the the foundations of the building and the building (in piecemeal fashion) is building (in piecemeal fashion) is separated from the foundations. Steel separated from the foundations. Steel or reinforced concrete beams replace or reinforced concrete beams replace the connections to the foundations, the connections to the foundations, while under these, layered rubber and while under these, layered rubber and metal metal isolating padsisolating pads replace the replace the material removed, these in turn are material removed, these in turn are attached below to new or existing attached below to new or existing foundations. These allow the ground to foundations. These allow the ground to move while the building, restrained by move while the building, restrained by its its inertialinertial massmass, remains relatively , remains relatively static. The pads absorb energy, static. The pads absorb energy, transforming the relative motion transforming the relative motion between the ground and the structure between the ground and the structure into heat. While the pads tend to into heat. While the pads tend to transmit some of the ground motion to transmit some of the ground motion to the building they also keep the building the building they also keep the building positioned properly over the positioned properly over the foundation. foundation.

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4. Dampers4. Dampers  

Dampers absorb the Dampers absorb the energy of motion and energy of motion and convert it to heat, thus convert it to heat, thus ""dampingdamping" resonant " resonant effects in structures effects in structures that are rigidly that are rigidly attached to the attached to the ground.  ground.  

During an earthquake, tension in one brace will force the plate in the damper to slip. In response, the damper shortens the other brace and keeps

the tank’s frame from buckling.

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5.Slosh tanks5.Slosh tanks  

A large tank of water may be A large tank of water may be placed on an upper floor. During placed on an upper floor. During a seismic event, the water in this a seismic event, the water in this tank will slosh back and forth, tank will slosh back and forth, but is directed by baffles - but is directed by baffles - partitions that prevent the tank partitions that prevent the tank itself becoming resonant; itself becoming resonant; through its mass the water may through its mass the water may change or counter the resonant change or counter the resonant period of the building. Additional period of the building. Additional kinetic energy can be converted kinetic energy can be converted to heat by the baffles and is to heat by the baffles and is dissipated through the water . dissipated through the water .

Hotel Cosima.

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6.Shock absorbers6.Shock absorbers  

Shock absorbersShock absorbers, similar to , similar to those used in those used in automotive suspensionsautomotive suspensions, may be , may be used to connect portions of a used to connect portions of a structure that are free to move structure that are free to move relative to each other and that relative to each other and that may collide during an may collide during an earthquake. The shock earthquake. The shock absorbers allow the relative absorbers allow the relative motion to be restrained by motion to be restrained by transferring and dissipating transferring and dissipating energy. This can be especially energy. This can be especially effective if the two structures effective if the two structures have differing fundamental have differing fundamental frequencies of resonance. frequencies of resonance. 

  

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7.Tuned mass dampers7.Tuned mass dampers  

Tuned mass dampersTuned mass dampers employ employ movable weights with dampers. movable weights with dampers. These are typically employed to These are typically employed to reduce wind sway in very tall, reduce wind sway in very tall, light buildings. light buildings. A tuned mass damper is a device mounted in structures to prevent discomfort, damage or outright structural failure by vibration. Typically, the dampers are huge concrete blocks mounted in skyscrapers or other structures, and moved in opposition to the resonant frequency oscillations of the structure by means of springs, fluid or pendulums.

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8.Active damping with fallback8.Active damping with fallback   Very tall buildings, when built Very tall buildings, when built

using modern lightweight using modern lightweight materials, might sway materials, might sway uncomfortably (but not uncomfortably (but not dangerously) in certain wind dangerously) in certain wind conditions. A solution to this conditions. A solution to this problem is to include at some problem is to include at some upper story a large mass, upper story a large mass, constrained, but free to move constrained, but free to move within a limited range, and within a limited range, and moving on some sort of bearing moving on some sort of bearing system such as an air cushion or system such as an air cushion or hydraulic film. Hydraulic hydraulic film. Hydraulic pistonspistons, , powered by electric pumps and powered by electric pumps and accumulators, are actively driven accumulators, are actively driven to counter the wind forces and to counter the wind forces and natural resonances. These may natural resonances. These may also, if properly designed, be also, if properly designed, be effective in controlling excessive effective in controlling excessive motion - with or without applied motion - with or without applied power - in an earthquake. power - in an earthquake.   

Landmark Tower. Shinjuku Park Tower.

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9.Rehabilitation of natural gas lines

Natural gasNatural gas and and propanepropane supply pipes to structures often prove especially supply pipes to structures often prove especially dangerous during and after earthquakes. The ductile iron pipes transporting dangerous during and after earthquakes. The ductile iron pipes transporting the gas within the structure may be broken, typically at the location of the gas within the structure may be broken, typically at the location of threaded joints. The gas may then still be provided to the pressure regulator threaded joints. The gas may then still be provided to the pressure regulator from higher pressure lines and so continue to flow in substantial quantities; it from higher pressure lines and so continue to flow in substantial quantities; it may then be ignited by a nearby source such as an electrical connection.may then be ignited by a nearby source such as an electrical connection.

There are two primary methods of automatically restraining the flow of gas There are two primary methods of automatically restraining the flow of gas after an earthquake, installed on the low pressure side of the regulator, and after an earthquake, installed on the low pressure side of the regulator, and usually downstream of the gas meter.usually downstream of the gas meter.

A caged metal ball may be arranged at the edge of an orifice. Upon seismic A caged metal ball may be arranged at the edge of an orifice. Upon seismic shock, the ball will roll into the orifice, sealing it to prevent gas flow. The ball shock, the ball will roll into the orifice, sealing it to prevent gas flow. The ball may later be reset by the use of an external may later be reset by the use of an external magnetmagnet. This device will respond . This device will respond only to ground motion. only to ground motion.

A flow-sensitive device may be used to close a valve if the flow of gas exceeds a A flow-sensitive device may be used to close a valve if the flow of gas exceeds a set threshold .This device will operate independently of seismic motion, but will set threshold .This device will operate independently of seismic motion, but will not respond to minor leaks which may be caused by an earthquake. not respond to minor leaks which may be caused by an earthquake.

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Reinforced Concrete Jacketing Reinforced Concrete Jacketing

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DIFFERENT TECHNIQUES OF REHABILITATION FOR DAMAGED STRUCTURES

35 Demokritus University of ThraceDemokritus University of Thrace10/22

Local interventionLocal interventionSide JacketingSide Jacketing

Reinforced Concrete Jacketing Reinforced Concrete Jacketing (2)(2)

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Fibre Reinforced Polymers (FRPs) JacketingFibre Reinforced Polymers (FRPs) Jacketing

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ColumnsColumns BeamsBeams

Shear strengtheningShear strengthening**

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COLUMN WRAPING PROCESS with steel plates

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Large capacity isolation bearings and dampers

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Wall Failure

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 Using of steel bolts for retrofitting of walls  

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Using steel braces

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STRUCTURES TO BE REHABILITATEDExpansion JointsExpansion Joints

Many bridges are statically anchored at Many bridges are statically anchored at one end and attached to joint at the other. one end and attached to joint at the other. This expansion joint gives vertical and This expansion joint gives vertical and transverse support while allowing the transverse support while allowing the bridge span to expand and contract with bridge span to expand and contract with temperature changes. The change in the temperature changes. The change in the length of the span is accommodated over a length of the span is accommodated over a gap in the roadway by these gap in the roadway by these expansion jointsexpansion joints.. During severe ground motion the rockers During severe ground motion the rockers may jump from their tracks or be moved may jump from their tracks or be moved beyond their design limits, causing the beyond their design limits, causing the bridge to unship from its resting point and bridge to unship from its resting point and then either become misaligned or fall then either become misaligned or fall completely.completely.Motion can be constrained by adding Motion can be constrained by adding ductile or high-strength steel restraints that ductile or high-strength steel restraints that are friction-clamped to beams and designed are friction-clamped to beams and designed to slide under stress while limiting the to slide under stress while limiting the motion relative to the anchorage.motion relative to the anchorage.

1.Bridges

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Lattice beams Obsolete riveted lattice Obsolete riveted lattice beams shown in the beams shown in the figure.figure.

Lattice beams consist Lattice beams consist of two "I"-beams of two "I"-beams connected with a criss-connected with a criss-cross lattice of flat cross lattice of flat strap or angle stock. strap or angle stock. These can be greatly These can be greatly strengthened by strengthened by replacing the open replacing the open lattice with plate lattice with plate members. This is members. This is usually done in concert usually done in concert with the replacement with the replacement of hot of hot rivetsrivets with bolts. with bolts.

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2. Tunnels2. Tunnels

    Unless the tunnel penetrates a fault Unless the tunnel penetrates a fault likely to slip, the greatest danger to likely to slip, the greatest danger to tunnels is a landslide blocking an tunnels is a landslide blocking an entrance. Additional protection entrance. Additional protection around the entrance may be applied around the entrance may be applied to divert any falling material (similar to divert any falling material (similar as is done to divert snow as is done to divert snow avalanchesavalanches) ) or the slope above the tunnel may be or the slope above the tunnel may be stabilized in some way. Where only stabilized in some way. Where only small- to medium-sized rocks and small- to medium-sized rocks and boulders are expected to fall, the boulders are expected to fall, the entire slope may be covered with wire entire slope may be covered with wire mesh, pinned down to the slope with mesh, pinned down to the slope with metal rods. This is also a common metal rods. This is also a common modification to highway cuts where modification to highway cuts where appropriate conditions exist.appropriate conditions exist.

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4.Fill and overpass4.Fill and overpass   If the soil fails where a bridge If the soil fails where a bridge

terminates, the bridge may become terminates, the bridge may become disconnected from the rest of the disconnected from the rest of the roadway and break away. The retrofit roadway and break away. The retrofit for this is to add additional for this is to add additional reinforcement to any supporting wall, reinforcement to any supporting wall, or to add deep caissons adjacent to the or to add deep caissons adjacent to the edge at each end and connect them edge at each end and connect them with a supporting beam under the with a supporting beam under the bridge.bridge.

Another failure occurs when the fill at Another failure occurs when the fill at each end moves in bulk, in opposite each end moves in bulk, in opposite directions. Addtional shelf and ductile directions. Addtional shelf and ductile stays may be added to attach the stays may be added to attach the overpass to the footings at one or both overpass to the footings at one or both ends. The stays, rather than being fixed ends. The stays, rather than being fixed to the beams may instead be clamped to the beams may instead be clamped to them. Under moderate loading these to them. Under moderate loading these keep the overpass centered in the gap keep the overpass centered in the gap so that it is less likely to slide off its so that it is less likely to slide off its founding shelf at one end. founding shelf at one end.

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5.Viaducts5.Viaducts    Large sections of roadway may consist Large sections of roadway may consist

entirely of viaduct, sections with no entirely of viaduct, sections with no connection to the earth other than connection to the earth other than through vertical columns. When concrete through vertical columns. When concrete columns are used, the detailing is critical. columns are used, the detailing is critical. Typical failure may be in the toppling of a Typical failure may be in the toppling of a row of columns due either to soil row of columns due either to soil connection failure or to insufficient connection failure or to insufficient cylindrical wrapping with rebar.cylindrical wrapping with rebar. Such Such columns are reinforced by excavating to columns are reinforced by excavating to the foundation pad, driving additional the foundation pad, driving additional pilings, and adding a new, larger pad, well pilings, and adding a new, larger pad, well connected with rebar along side of or into connected with rebar along side of or into the column. A column with insufficient the column. A column with insufficient wrapping bar, which is prone to burst and wrapping bar, which is prone to burst and then hinge at the bursting point, may be then hinge at the bursting point, may be completely encased in a circular or completely encased in a circular or elliptical jacket of welded steel sheet and elliptical jacket of welded steel sheet and grouted as described above.grouted as described above.

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6.Wood frame

The lowest plate rails of walls are bolted The lowest plate rails of walls are bolted to a continuous foundation, or held down to a continuous foundation, or held down with rigid metal clips bolted to the with rigid metal clips bolted to the foundation. foundation.

Selected vertical elements, especially at Selected vertical elements, especially at wall junctures and window and door wall junctures and window and door openings are attached securely to the openings are attached securely to the steel plate. steel plate.

In two story buildings using "western" In two story buildings using "western" style construction, the upper walls are style construction, the upper walls are connected to the lower walls with tension connected to the lower walls with tension elements. In some case connections may elements. In some case connections may be extended vertically to include be extended vertically to include retention of certain roof elements. retention of certain roof elements.

Low Low cripple wallscripple walls are made shear are made shear resistant by adding plywood at the resistant by adding plywood at the corners and by securing corners from corners and by securing corners from opening with metal strapping or fixtures. opening with metal strapping or fixtures.

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7.Retaining Wall The retaining wall is used both to The retaining wall is used both to retain the soil and also to transfer retain the soil and also to transfer the weight of the span directly the weight of the span directly downward to footings in downward to footings in undisturbed soil. If these walls are undisturbed soil. If these walls are inadequate they may crumble inadequate they may crumble under the stress of an under the stress of an earthquake's induced ground earthquake's induced ground motion.motion.

One form of retrofit is to drill One form of retrofit is to drill numerous holes into the surface of numerous holes into the surface of the wall,. Additional vertical and the wall,. Additional vertical and horizontal bar is then secured to horizontal bar is then secured to the new elements, a form is the new elements, a form is erected, and an additional layer of erected, and an additional layer of concrete is poured and the surface concrete is poured and the surface of each hole coated with epoxy of each hole coated with epoxy adhesive. This modification may adhesive. This modification may be combined with additional be combined with additional footings in excavated trenches footings in excavated trenches and additional support ledgers and additional support ledgers and tie-backs to retain the span and tie-backs to retain the span on the bounding walls.on the bounding walls.

    

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Effect of Rehabilitation on Global ResponseEffect of Rehabilitation on Global Response

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Bas

e sh

ear

Roof displacement

Accurate assessment of the retrofitted structureAccurate assessment of the retrofitted structure

Accurate modeling at local levelAccurate modeling at local level

FRPs Jacketing

RC Jacketing

Δu

ΔV

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ADVANTAGES OF RETROFFITING

1.Damage and collapse of bridges can be prevented with proper seismic design and detailing.

2.Understanding plastic concepts can produce more economical foundations.

3. Utilizing the latest seismic guidelines produces safe and state-of-the-art designs.

4. Traffic congestion and interruption to commerce can be minimized if bridges remain in service following a seismic event.

5. Higher strength/weight ratio. 

6. Higher oriented strength. 

7. Better design flexibility. 

8. Lower maintenance and long term durability. 

9. Better dimensional stability. 

10. Protection of various building components can be accomplished . 

11. Will enable us in better protection of life and property. 

12.Will help us to preserve various historic monuments for years to come.

Release of hazardous materials with associated environmental impacts.

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THANK YOU FOR THE KIND LAYOUT OF YOUR PRECIOUS TIME

Let us all work together to make this earth a Let us all work together to make this earth a better place to live in in which ever fashion better place to live in in which ever fashion we can. we can.