PREPARED BY:-

Shlok Patel

Mansukh Prajapati

SANKALCHAND PATEL COLLEGE OF ENGINEERING,VISNAGARCIVIL ENGINEERING DEPARTMENT

ULTRATECH SPARKLING STARS

RETROFITTING OF CONCRETE STRUCTURE

Flow of presentation

Why retrofitting is required ? What is a retrofitting ? Objectives of retrofitting. To retrofit or not ? Retrofitting techniques. Materials to be used in local retrofitting. Existing retrofitted structure in gujarat. Critical remarks. References.

Why retrofitting is required ?Problem faced in concrete structure

■ Damage to structural members.

■ Excessive loading.

■ Errors in design or construction.

■ Modification of structural system.

■ Seismic damage.

■ Structural cracks.

■ Corrosion due to penetration-

honey combs.

What is a retrofitting ?

■ Retrofitting is the seismic strengthening of existing damaged or undamaged structures.

■ It is an improvement over the original strength when the evaluation of the building indicates that the strength available before the damage walls insufficient and restoration alone will not be adequate in future quakes.

Objectives of retrofitting

■ Increasing the lateral strength in one or both directions, by reinforcement or by increasing wall areas or the number of walls and columns.

■ Giving unity to the structure by providing a proper connection between its resisting elements.

To retrofit or not ?

SEISMIC LOAD CAPACITY VERSUS RISK OF BUILDING COLLAPSE

Retrofitting techniques

Adding shear wall ■ Used for non ductile reinforced concrete frame buildings.

■ A new shear wall can be cast in-situ or precast concrete elements.

■ It can be placed at the exterior wall of building, however it may cause in the appearance.

■ Increase the lateral strength, ductility and stiffness of the building substantially.

SHEAR WALLS

Adding infill wall

■ This is the brick masonry infill wall.

■ Installed tight to surrounding concrete elements.

■ The lateral stiffness of a storey increases with infill wall.

■ Due to ‘strut action’ of the infill walls, the flexural and shear forces and ductility demand on the ground storey columns are substantially reduced.

■ Do not increase the ductility of structure.

BRICK MASONRY INFILL WALL RETROFITTING

Adding steel bracing■ An effective solution when large openings are required.

■ Increase in strength, ductility and stiffness.

■ Opening for natural light.

■ Adds much less weight to the existing structure.

Wall thickening techniques■ Increase the thickness by adding bricks, concrete and steel

reinforcement.

■ It can bear more vertical and horizontal loads.

■ Does not cause sudden failure of the wall.

WALL THICKENING BY REINFORCE CONCRETE

Adding wing wall or buttress■ To increase lateral strength, ductility and stiffness of structure.

■ The wing wall are placed on the exterior side of an existing frame.

QUADRA ELEMENTRY SCHOOL, CANADA

Mass reduction■ In this process removing one or more storey of building as shown in

figure.

■ Decrease the load at foundation.

■ Increase the life and strength.

MASS REDUCTION BY REMOVING ONE STOREY

Base isolation■ Isolation of superstructure from the foundation is known as base isolation.

■ It is the most powerful tool for passive structural vibration control techniques.

■ Isolates building from ground motion lesser seismic loads, hence lesser damage to the structure, minimal repair of superstructure.

■ Building can remain serviceable throughout construction.

■ Does not involve major intrusion upon existing superstructure.

BASE ISOLATION OF BUILDING

Jacketing of structural elements

■ This is the most popular method for strengthening of concrete building elements like as

1. Beams

2. Columns

3. Beam column Junctions

■ Due to jacketing, enhancing the shear strength, concrete confinement, flexural strength.

Materials to be used Steel plates

Fiber reinforce polymer (FRP wrap)

Carbon fiber reinforce polymer (CFRP)

Glass fiber reinforce polymer (GFRP)

Steel reinforced concrete

RETROFITTING AT JUNCTION BY STEEL PLATE

RETROFITTING OF COLUMN BY CFRP WRAP

GFRP WRAP AND WRAPPED STRUCTURE

RETROFITTING BY STEEL REINFORCE CONCRETE

Existing retrofitted structure in gujarat

MANI MANDIR, MORBI

Critical remarks

■ Increase in the capacities( strength, stiffness, ductility, stability and integrity) of concrete structure.

■ The reduction in loss of lives, damage of the essential facilities and functional continuity of life-span of structures.

■ Decrease the working space of concrete structure due to extension in structural elements and affect the appearance.

■ Increase in lateral stiffness with high shear concentration near wall.

■ Increase in overturning moment at foundation.

References■ Handbook on retrofit of building by Indian Institute Of Technology Madras (Civil

Engineering Department).

■ Earthquake resistant design of structure” by pankaj agrawal and shrikhande.

■ IS: 1893-2002 (part-1) Criteria for Earthquake Resistant Design of Structures (Part 1 : General Provision and Buildings) – Code of Practice

■ IS: 4326-1993 Earthquake Resistant Design and Construction of Buildings – Code of Practice

■ IS: 13920-1993 Ductile Detailing of Reinforced Concrete Structures subjected to Seismic Forces – Code of Practice

■ IS: 13935-1993 Repair and Seismic Strengthening of Buildings – Guidelines

■ IS: 13828-1993 Improving Earthquake Resistance of Low Strength Masonry Buildings – Guidelines

■ IS: 13827-1993 Improving Earthquake Resistance of Earthen Buildings – Guidelines

Thank you…