ultratech_mailer_ tips to construct earthquake resistant buildings (1)

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Introduction Experience in past earthquakes has demonstrated that many buildings with conventional methods of construction lack basic resistance to earthquake forces. In most cases this resistance can be achieved by following simple, inexpensive principles of earthquake resistant construction. Adherence to these simple rules will minimise damages during moderate or large earthquakes. But life threatening collapses should be prevented, and damage limited to repairable proportions under all circumstances. Seismic Zone Map of India The Indian subcontinent has a history of devastating earthquakes. The major reason for the high frequency and intensity of the earthquakes is that the Indian plate is driving into Asia at a rate of approximately 47 mm/year. As per the Geographical statistics, almost 59% of the land in India is vulnerable to earthquakes The seismic zoning map of India assigns four levels of seismicity for India in terms of zone factors. India is divided into 4 seismic zones, viz. Zone 2, Zone 3, Zone 4 and Zone 5 Zone 5 is highly prone to the earthquake with the highest level of seismicity whereas Zone 2 is associated with the lowest level of seismicity. Tech Mailer Vol. 02 No. 04 Oct 2015 Dear Reader, Earthquakes are the most feared natural disasters. Unpredictable and sudden, earthquakes can strike anytime, anyplace, resulting in loss of life and property. Also, the lack of any foolproof early warning systems to predict earthquakes makes the situation even more complex. With about 59% of our country's landmass precariously resting above active seismic zones (i.e. areas prone to earthquakes) besides structural collapse. Earthquake also causes human casualties. In an effort to disseminate the basic concepts of earthquake resistant buildings, UltraTech Cement Ltd. has compiled a few proven construction tips that will help in making buildings earthquake resistant. So, come, explore the tips and start building a safer abode to live in. We hope you find the mailer informative and useful. Happy Reading!!

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Page 1: UltraTech_Mailer_ Tips to Construct Earthquake Resistant Buildings (1)

Introduction Experience in past earthquakes has demonstrated that many buildings with conventional methods of construction lack basic resistance to earthquake forces. In most cases this resistance can be achieved by following simple, inexpensive principles of earthquake resistant construction. Adherence to these simple rules will minimise damages during moderate or large earthquakes. But life threatening collapses should be prevented, and damage limited to repairable proportions under all circumstances. Seismic Zone Map of India The Indian subcontinent has a history of devastating earthquakes. The major reason for the high frequency and intensity of the earthquakes is that the Indian plate is driving into Asia at a rate of approximately 47 mm/year. As per the Geographical statistics, almost 59% of the land in India is vulnerable to earthquakes The seismic zoning map of India assigns four levels of seismicity for India in terms of zone factors. India is divided into 4 seismic zones, viz. Zone 2, Zone 3, Zone 4 and Zone 5 Zone 5 is highly prone to the earthquake with the highest level of seismicity whereas Zone 2 is associated with the lowest level of seismicity.

Tech Mailer Vol. 02 No. 04 Oct 2015

Dear Reader, Earthquakes are the most feared natural disasters. Unpredictable and sudden, earthquakes can strike anytime, anyplace, resulting in loss of life and property. Also, the lack of any foolproof early warning systems to predict earthquakes makes the situation even more complex.

With about 59% of our country's landmass precariously resting above active seismic zones (i.e. areas prone to earthquakes) besides structural collapse. Earthquake also causes human casualties.

In an effort to disseminate the basic concepts of earthquake resistant buildings, UltraTech Cement Ltd. has compiled a few proven construction tips that will help in making buildings earthquake resistant.

So, come, explore the tips and start building a safer abode to live in.

We hope you find the mailer informative and useful. Happy Reading!!

Page 2: UltraTech_Mailer_ Tips to Construct Earthquake Resistant Buildings (1)

Tips to Construct EARTH QUAKE RESISTANT BUILDINGS

1. Shape of the Building

Ø Buildings should be rectangular and symmetrical in plan.

Ø Projections in the buildings should not exceed 1/5th the dimension of the building in the direction of projection.

Ø In case of large extensions or portions of different height, it is advisable to separate the buildings with a gap of

minimum 25mm.

2. Protecting Masonry Units/walls

Ø All walls must be joined properly to the adjacent walls using L- shaped dowel bars or Toothed masonry joints at the

edges of the wall.

Ø Ensure good interlocking of the masonry courses at the junctions.

Ø Blocks/bricks must be soaked in water before use.

Ø Cement-Lime- Sand or Cement-Sand mortar of 1: 1: 6 or 1: 4 respectively, is the most suitable. Do not use mud mortar.

Ø Joint thickness should generally not be more than 10mm.

Ø Provide Lintel and Sill bands above and below openings.

Ø Vertical rod shall have to be embedded in to the masonry at corners, junction and at the vertical edges of the opening.

Ø Vertical rod shall be of minimum 10mm diameter for single storey and 12mm for 2 storey building.

Ø Ensure that the vertical rods are taken right down into the foundation and must be placed inside the loop formed by the

rods of horizontal band.

Page 3: UltraTech_Mailer_ Tips to Construct Earthquake Resistant Buildings (1)

3. Right Ways To Provide Openings In The Walls

Ø Sizes of door and window openings need to be kept small.

Ø Do not keep door and window openings close to a corner. Opening should be at least 600mm away from a corner.

Ø Distance between two openings on a same wall should be minimum 500mm.

Ø In single storey building, if the room width is 3m, the total width of opening should not exceed 1.2m.

4. Importance Of Horizontal Bands

Ø Provide Horizontal RCC bands at Plinth, Sill, Lintel and Roof level.

Ø Roof band is not required in case of RCC flat roof. Roof and Gable band should be provided for Gable Roofs.

Ø Minimum grade of concrete for bands shall be M20.

Ø The Band shall cover the entire width of masonry and minimum depth shall be 75mm. It shall have two rods of 10mm

diameter tied with 6mm diameter stirrups at a spacing of 150mm.

Ø For 2 storeyed building, the bands in the ground floor shall be of minimum 150mm depth having 4 rods of 12mm

diameter tied with 6mm diameter stirrups at a spacing of 150mm.

Ø The bars in the bands at corners and junctions should be bent and taken to a distance of at least 750mm.

Page 4: UltraTech_Mailer_ Tips to Construct Earthquake Resistant Buildings (1)

5. Earthquake Resistant RC Beams

Ø The width of the beam shall be 1/3rd the depth of the beam or 200mm or, whichever is more.

Ø The depth of the beam shall be maximum 1/4th of the span (length between the supports).

Ø At the ends of beams, the amount of steel provided at the bottom is at least half of that at top.

Ø The diameter of stirrup must be at least 6mm; in beams more than 5m long, it must be at least 8mm.

Ø Both ends of the stirrups should be bent into a 135° hook as shown.

Ø Maximum spacing of stirrups shall be less than half the depth of the beam.

Ø For a distance of 2 times the depth of beam from column face stirrups shall be very closely spaced. It shall be lesser of

• 8 times the diameter of the beam bar

• 1/4th depth of beam

Ø If bars are to be lapped, it shall be done at a distance of 1/4th the span from face of column.

Ø Ensure that stirrups in the lap zone are closely spaced.

Page 5: UltraTech_Mailer_ Tips to Construct Earthquake Resistant Buildings (1)

6. Earthquake Resistant RC Columns

Ø Width of Column shall be minimum 300mm. A column width of up to 200mm is allowed if unsupported length is less

than 4m and beam length between the columns is less than 5m.

Ø The ties shall be provided at closer spacing above and below the beam-column junction to a height not less than

• larger dimension of the column

• one-sixth the column height or

• 450mm.

Ø At beam-column junction, the spacing of ties in columns above and below the junction shall not exceed 1/4th of the

smallest dimension of the column. This spacing shall be between 75mm and 100mm.

Ø Spacing of the ties at other locations shall not be more than ½ the smallest dimension of the column. It is preferable to

provide some ties within the junction also as shown.

Ø In columns where the spacing between the corner bars exceeds 300mm, additional links with 180° hook shall have to be

provided. The links should go around both vertical bars and horizontal closed ties as shown.

Ø The bars shall be lapped only in the middle half of the column and not near its top and bottom. Only half the vertical

bars are to be lapped at a time in any storey.

Ø Closer ties must be provided along the length of the lap as shown.

Page 6: UltraTech_Mailer_ Tips to Construct Earthquake Resistant Buildings (1)

7. Foundation of the Building

Ø Foundations shall rest on firm ground; if soil is soft it shall be firmed by proper and adequate compaction.

Ø Foundation shall be laid on Plain Cement Concrete bed of minimum 100 mm thickness.

Ø After constructing the foundation, it is advisable to back fill the foundation trench by compacted sand or granular

material.

Ø Reinforced plinth band shall be provided between the bottom of the wall and top of foundation.

Ø In case of isolated footings, they shall be connected in both directions by reinforced concrete tie beams. Tie beams shall

have a minimum dimension of 200 mm X 200 mm and shall have 4 rods of minimum 12mm diameter with 6 mm

stirrups at spacing of 150 mm.

PERSONAL SAFETY TIPS

F When you are indoors, drop to the floor, take cover under a sturdy wooden table or cot and hold on to it firmly.

F If there is no shelter near you, cover your face and head with arms and couch at a corner inside the building.

F If you are in bed during an earthquake, stay there and protect your head with a pillow.

F Stay away from exterior walls, glass doors, glass panes, windows, lighting fixtures, kitchen cabinets or anything that could fall on you.

F If trapped under debris, do not shout as you may inhale dust; knocking or tapping is better. Shout only as a last resort.

F During an earthquake, the safe place is an open space. Stay there till shaking stops. But, do not stand near buildings, trees, lamp posts, high tension electricity wires etc.

F If in a moving vehicle, quickly stop to the side of road, set parking brakes and stay inside the vehicle. Do not stop the vehicle under a bridge, utility wires or trees.

References:

• How to Construct Earthquake Resistant Buildings – By Pradipta Banerji & Shirish Patel. • IITK-BMTPC – Earthquake Tips – By CVR Murthy. • Earthquake Safe Construction of Masonry Buildings - By Prof. Anand S Arya & Jnananjan Panda, National Disaster Management

Division. • IS 1893 (Part 1):2002 - Criteria for Earthquake Resistant Design of Structures. • IS 4326: 1993 (Reaffirmed 1998) Edition 3.2 (2002-04) – Earthquake Resistant Design and Construction of Buildings – Code of Practice.

• To Talk to our Mobile Concrete Expert* • For Technical/General Assistance • For RMC Bookings

Call Toll Free No. 1800 425 2525

CENTRAL MARKETING OFFICE: Mumbai – UltraTech Cement Limited, A-Wing Ahura Centre, 1st Floor Mahakali Caves Road, Near M.I.D.C Office, Andheri (East), Mumbai – 400 093 Tel.(022)66917360. ZONAL OFFICES: Bengaluru- ‘Industry House’ 5th Floor, Fair Field Layout, 45, Race Course Road, Bengaluru – 560 001. Tel. (080) 22250748/49. Chennai – 23, Anna Salai, Little Mount, Saidapet, Chennai – 600 015. Tel. (044) 42328018. New Delhi – 12th Floor, Ambadeep Building, K.G. Marg, Connaught Place, New Delhi – 110 001. Tel. (011) 23315007/10. Kolkata – Constantia 7th Floor, 11, Dr. U.N.Brahamachari Street, Kolkata – 700 017. Tel. (033) 30214100, 30214400. Mumbai - A-Wing Ahura Centre, 1st Floor Mahakali Caves Road, Near M.I.D.C Office, Andheri (East), Mumbai – 400 093 Tel.(022)66928400

In the event of an earthquake, Stay calm and advise others not to panic. Do not believe or spread rumours.

Tech Mailer Team -Dr. M R Kalgal, Prasad YTVV, Vaishnavi V