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Since my city Karnal lies in seismic zone, I tried to look into aspects realted to safety in the event of any seismic tremour. However, I found that the citizens have poor knowledge about the importance of retrofitted buildings. Also I tried to convince the importance of mock drill in schools for I do think that preparedness is the key to check casualty in the event of disaster. The points I discussed at different times are given below.

Adjacent to Kurukshetra the city of Karnal is an important trade centre which is said to have been founded by Raja Karna, a central character in the Mahabharata war. This is the same Karna, who was the eldest son of Kunti and thus Karnal is called the city of Daanvir Karna. It has been a walled town as far as its history can be traced and it may have had a citadel at one time.

Karnal sprang into prominence in 1739 when Persian emperor Nadir Shah defeated and captured the Mughal ruler Muhammad Shah in the Battle of Karnal. Raja Gopal Singh of Jind seized Karnal in 1763, and the Marathas established themselves at Karnal in 1785. Skirmishes followed between the Marathas and the Sikhs and in 1795, the Marathas finally wrested the city from Raja Bhag Singh of Jind and made it over to the British-Irish military commander George Thomas, who took part in the fight. The British established a cantonment in 1811 but abandoned it after 30 years due to an outbreak of malaria. The fort which had been built by Raja Gajpat Singh of Jind, was taken over by the British and converted into a residence for Dost Mohammad Khan, Amir of Kabul. The fort was used as a jail, as quarters for native cavalry and as a poorhouse. In 1862, it was made over to the Education Department, when the district school was moved into it from the city.

There is an interesting story that links Karnal with the birth and early history of Pakistan. History suggests that the person who dragged back Quaid-i-Azam Mohammad Ali Jinnah into politics was from Karnal and lived in Kalandri Gate. The district of Karnal has given a lot of big political figures to Pakistan and Nawab Liaqat Ali Khan, the first Prime Minister of Pakistan, ranks foremost amongst them. Liaqat Ali Khan was the Nawab of Kunjpura and his palace has now been converted into a Sainik School and it is situated at a distance of 10 kilometers from the city of Karnal.

(Source: Wikipedia)

The details of sectors are given in the following map:

Land Use proposals are given as below:-

Land Use

Area within Controlled area (hectare)

Area within Municipal Limits (hectare)

Total Area (hectare)

Percentage Total

1. Residential

1452

1129

2581

43.75

2. Commercial

267

99

366

6.20

3. Industrial

163

146

209

5.24

4. Transport & Communication

20

206

448

7.59

5. Public Utility

90

33

123

2.09

6. Public & Semi Public

774

687

1461

24.76

7. Open Space (including Green Belt)

439

173

612

10.37

Total

3407

2493

5900

100.00

The Three Components of Retrofit Design

The three areas of retrofit reinforcement are:

· Bolting - attachment of the mudsill to the foundation

· Shear walls - bracing of the cripple walls

· Shear transfer ties - attachment of the floor framing to the top of the cripple wall

The illustrations below show where each of these areas is located. If these illustrations are not clear to you, see the drawings at Retrofit Terminology.

If any one of these three areas fails in an earthquake, the building could suffer serious structural damage and maybe even total collapse. A retrofit must therefore resist base shear forces in each of these three damage areas. This means a properly designed retrofit for the house in our engineering example must resist a minimum of 13,000 pounds of force where it is sits on the foundation, AND a minimum of 13,0000 pounds against the cripple walls, AND a minimum of 13,000 pounds of force where the floor sits on top of the cripple wall or mudsill.

Components of retrofit design

The three areas of retrofit reinforcement are:

· Bolting - attachment of the mudsill to the foundation

· Shear walls - bracing of the cripple walls

· Shear transfer ties - attachment of the floor framing to the top of the cripple wall

The illustrations below show where each of these areas is located. If these illustrations are not clear to you, see the drawings at Retrofit Terminology.

The 3 areas of retrofit are in pink.

If any one of these three areas fails in an earthquake, the building could suffer serious structural damage and maybe even total collapse. A retrofit must therefore resist base shear forces in each of these three damage areas. This means a properly designed retrofit for the house in our engineering example must resist a minimum of 13,000 pounds of force where it is sits on the foundation, AND a minimum of 13,0000 pounds against the cripple walls, AND a minimum of 13,000 pounds of force where the floor sits on top of the cripple wall or mudsill.

It is an engineering principle that earthquake resisting elements (bolts, shear walls, etc.) can resist only those forces Base shear forces.that are generated parallel to the foundation. In the illustration at the right, this means earthquake forces generated in the east-west direction will be resisted by the bolts, plywood, and other hardware that are installed along foundation walls A and C. Forces generated in the north-south direction will be resisted by bolts and other hardware installed in foundations B and D.

This information allows us to calculate how much hardware and plywood is needed to protect these three weak areas. All bolts, nails, plywood, shear transfer ties, etc. are rated in terms of the amount of shear force they can resist. For example, a 1/2-inch bolt with a plate washer can resist 1000 pounds of force. Each linear foot of high capacity plywood bracing can resist approximately 500 pounds of force. Good shear transfer ties can also resist around 500 pounds of force.

Basic Terminology of Seismic Retrofit

This first illustration shows the basic structures under a house before it has been retrofitted.

Unreinforced crawlspace

1-Crawl space - The appropriately named space between the ground under the house and the floor you walk on. How much space you have to crawl in depends on how tall your cripple wall is. (see #5) The retrofit contractor does almost all of his work in this crawl space area. To see a photo of a crawl space area, click here.

2-Floor - This is the area you walk on.

3-Foundation - This is the cement structure that supports the house and gives it stability. The primary goal of seismic retrofit is to attach the house to the foundation so it doesn´t fall off the foundation during an earthquake.

4-Mudsill - This is a piece of wood that rests on top of the concrete foundation. The entire house rests on it. When an earthquake hits, the mudsill can be jolted off the foundation causing the house to collapse.

5-Cripple wall - Not all houses have a cripple wall. If you go up a set of stairs to enter your home, you probably have one. Un-reinforced cripple walls are the weakest part of a house because they readily collapse in an earthquake. In the photograph at the top of this webpage, the cripple wall of the house collapsed. The entire house had to be jacked up, the cripple wall rebuilt, and the house placed back on top of it. To see a photo of a cripple wall, click here.

6-Floor framing - also called floor joists. In an earthquake, the floor framing can be jerked off the cripple wall, causing the floor of the house to collapse.

7-Top plate - This is made of 2x4 lumber lying on top of the cripple wall. The floor framing is nailed into this.

The next illustration shows the same structures as above but after the house has been retrofitted.

Reinforced crawlspace


Bolts - These attach the mudsill to the foundation. There are several types, but basically they are long threaded steel rods that pass through the mudsill and deep into the foundation. Bolt strength is greatly affected by the type of washer that is used.

Mudsill plates - These are specially designed square washers that increase the strength of a bolt by 60%. Newer homes can be significantly strengthened by merely changing the traditional washers to mudsill plates.

Shear wall - This protects and strengthens the cripple wall. Basically, it is a sheet of plywood nailed onto the wood framing of the cripple wall to prevent it from collapsing in an earthquake. Specifics like the type of nail used, nail spacing, type of plywood used, the spacing of the framing and many other factors effect the strength of a shearwall.

Shear transfer ties - These are specially designed pieces of steel hardware that securely attach the floor framing to the cripple wall.

Views: 243

Comment by Patricio Buenrostro-Gilhuys on April 20, 2010 at 5:14am
Great data, Historical context and clever retrofit solutions!!!
Comment by Pradip Dey on April 20, 2010 at 7:29am
Thank you so much Patricio for nice comments and encouragement through a +KS to my blog post Resilience strategy of Karnal.
http://www.urgentevoke.com/profiles/blogs/resilience-strategy-of-ka...
With regrads,
Pradip Dey
Comment by Cecilia Rossiter on April 26, 2010 at 9:02am
I have been curious about this. Thank you for the clarity.
Comment by Pradip Dey on April 26, 2010 at 9:22am
Thanks Cecilia for your nice comment "I have been curious about this. Thank you for the clarity" and encouragement with a +KS to my blog post Resilience strategy of Karnal.
http://www.urgentevoke.com/profiles/blogs/resilience-strategy-of-ka...
With regards,
Pradip Dey

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