retrofitting of masonry buildings

Retrofitting of

Masonry Buildings

Submitted by-

MANISH SHARMA

Submitted to-

Dr. AKIL AHMAD

Retrofitting-

It is a technique for upgrade the strength

and structural capacity of an

existing/damaged structure to enable it to

safely withstand the effect of strong

earthquake in future.

Retrofitting techniques:-

Structural or global

retrofitting

1. Adding shear wall

2. Adding infill wall

3. Adding bracing

4. Adding wing wall/

buttresses

5. Wall thickening

6. Mass reduction

7. Supplemental damping

and Base isolation

Member or local

retrofitting

1. Jacketing of beams

2. Jacketing of columns

3. Jacketing of beam column

joints

4. Strengthening individual

footings

Failure mechanism of a masonry

building:-

Out-of- plane failure

In-plane failure

Connection failure

Diaphragm failure

Pounding

Failure due to opening in the walls

Non-structural component failure

Out-of- plane failure:-

Inadequate anchorage of wall into the roof

diaphragm.

Limited tensile strength of masonry.

More pronounced response at higher levels.

In-plane failure:-

In plane failures of walls in un-reinforced masonry

structure are due to excessive bending or shear.

Commonly it leads to form double diagonal shear

cracking.

Connection failure:-This type of failure is characterized by diagonal cracks disposed on both

the wall’s edge causing separation and collapse of the corner zone.

Diaphragm failure:-

Diaphragm failure is a rare phenomenon in the event of seismic

motion. In plane rotation of the diaphragm ends and absence of

good shear transfer between diaphragm and reaction walls account

for damages at corner of the walls.

Pounding:-

When adjacent roof levels of the two buildings and vertical brick

walls faces flush with one another ,the pounding action causes

structural distress due to out-of-plane vibrations.

Non-structural component failure:-

Parapet walls, partition walls, mumty, water tanks, projections and

staircase are non structural elements behave like cantilevers if they

remain unrestrained and are subjected to greater amplification as

compared to ground motion becoming prone to failure.

MASONRY CRACKING:-

GRADE

CRACKS

DAMAGE LEVEL DEFINATION FOR LOAD BEARING MASONRY

G0 Undamaged No visible damage

G1 Slight damage Hairline cracks

G2 Moderate damage Cracks 5-20 mm

G3 Heavy damage Cracks 20 mm or wall material dislodge

G4 Partial destruction Complete collapse of individual wall material

or roof support

G5 Collapse More than one wall collapsed or more than

half of roof

REPAIRING TECHNIQUES OF MASONARY:-

Jacketing:--

Most popular method for strengthening of buildings columns.

Types:-- 1.Steel jacket 2.Reinforced concrete jacket 3.Reinforced

polymer composite (RPC) jacket

Purpose of Jacketing:-

To increase shear strength.

To increase flexural strength

To increase concrete coinforment

Indian Codes for Earthquake Design:-

IS: 1893-2002 (part-1) Criteria for Earthquake Resistant Design of Structures

(Part 1 :General Provision and Buildings) - Code of Practice.

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 LowStrength

Masonary Buildings - Guidelines

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

Guidelines

Shaking table test:-

Conclusions:- Seismic Retrofitting is a suitable technology for protection of a variety of structure.

it has matured in the recent years to a highly reliable technology.

But, the expertise needed is not available in basic level.

The main challenge is to achieve a desired performance level at a min cost. Which can

be acheived through a detailed nonlinear analysis.

Optimization techniques are needed to known the most efficient retrofit for a particular

structure.

Proper design codes are needed to be published as code of practice for professionals

related to this field.

REFERENCES:-

Agarwal, P. and Shrikhande, M., 2006, Earthquake Resistant Design of

Structures, 2nd Edition, Prentice-Hall of India Private Limited, New Delhi.

Fastening for seismic retrofitting- state of art report, comite euro. International

Du Beton,Thomas Telford,UK,1995.

EERI, 1999, Lessons Learnt Over Time – Learning from Earthquakes Series:

Volume II Innovative Recovery in India, Earthquake Engineering Research

Institute, Oakland (CA), USA.

Murthy,C.V.R.,2004 IITK-BMTPC Earthquake Tip, New Delhi.

Thank You...