Source: Maps Of IndiaVisit link (click) for updates.
Source: AssortedWednesday, October 5, 2011
Sunday, July 24, 2011
Some earthquake feelers by Structural Engineers
Photos. Typical Reinforced Masonry buildings in India The earth’s surface is under continuous movement, in other words is always vibrating. However, these vibrations are so low in magnitude that they are not felt by us humans at all; unless they are large in size, which happen during events such as earthquakes.
One of the methods which earthquake experts apply to understand earthquakes and these vibrations is by classifying these in the form of waves. These waves which are generated inside the earth’s crust during an earthquake have their movement in all directions. Known as seismic waves, these waves can be categorized in to two types- 1. Body, and 2. Surface. While the Body wave would move through the body of the earth; the surface wave would take a little longer route because it has to make its way to the nearest earth’s surface first, and thereafter travels as a surface wave. See some simple educational websites Website 1, Website 2 which provide simplified understanding of these earthquake waves.
The science of structural engineering is concerned how these waves travel and when they hit, have an impact on the building.
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In recent last one year history has seen two unfortunate earthquake events, with some significant aftershocks. New Zealand and Japan, faraway places were in news. Last year significant damage was noted in other places such as Chile as well. See what the Structural Engineers have to say about what they felt:
New Zealand (22nd Feb 2011)
Roberto T. Leon, president of the Structural Engineering Institute, ASCE has an interesting blog on being present in Christchurch, New Zealand when the 2nd earthquake had unexpectedly stuck there. The whole blog is an interesting read, where in a portion he summarizes a comparison with the Chilean event.
It was eerily different for me because my most recent recollections are from the large Chilean earthquakes that I experienced last year. The Chilean ones “build up” slowly and last a very long time. This one seemed to be three or four very sudden, violent jerks, with a strong vertical feel, and lasting probably no more than 15 seconds or so.
Japan (11th March 2011)
Balaji, a friend and a structural engineer, was in the fourth floor his ten storey office building in Tokyo when the earthquake stuck. Pretty much inland where the Tsunami could not reach, a few days later he told me over Skype [http://skype.com] how he first felt the body wave which came stinging in no time and took him off ground, and then he waited for the surface waves to arrive. While he prepared himself for a floor dance, for the surface wave would arrive in no time, next moment he saw his colleague flying away and his back curved hitting the wall. It was a nasty bump but thankfully both are safe. The buildings their colleagues designed ensured they are.
***
Ten years back, I personally felt the Gujarat, India earthquake (26th Jan 2001), because it lasted for approximately two minutes. Halfway, it woke me up from my sleep; and the ground plus two building I was in, a typical Reinforced Cement Concrete (RCC) confined structure [See pictures] took the shaking well. One can contend such buildings, which are a typical design for institutional buildings across India, therefore take building movements and uncertainties into consideration when designing/constructing one. Otherwise, many buildings which are built keeping only enclosure in mind were not that lucky. Many had collapsed. A structural engineer colleague of mine, when we were students, in all this chaos, was wise in saying,
… either you design the building so stiff that nothing happens to it, or make it so flexible that you can bend or twist it endlessly anywhere, or you make the joint so ductile that no matter what the earthquake force or duration is, let it be endless, the joint shall never ever snap out.
***
Website 1: http://www.matter.org.uk/schools/content/seismology/pandswaves.html
Website 2: http://earthquake.usgs.gov/learn/topics/?topicID=63
ASCE President blog: http://www.asce.org/PPLContent.aspx?id=12884904978
Skype: http://skype.com
Pictures of Typical Reinforced Cement Concrete (RCC) confined structure
Wednesday, June 29, 2011
Recent notification by National Disaster Management Authority (NDMA) and the Reserve Bank of India (RBI) on disaster resilient construction
Thanks to Anup Karanth for providing an update on a significant move by the National Disaster Management Authority (NDMA) and the Reserve Bank of India (RBI) towards making buildings and infrastructure more disaster resilient. Please refer below an e-mail I received from Anup Karanth (Anup is a Civil Engineer and Planner working extensively in Disaster Management and Capacity Building sector) for more details on this development. It is indeed encouraging that the RBI has come out with a notification on this issue, which may go a long way in ensuring that the NDMA Guidelines are taken more seriously.
One can download the document here (In English, directly from Government of India NDMA Website - or from our website.
In verbatim below:
From: Anup Karanth [mailto:anup.karanth@gmail.com]
Sent: 01 June 2011 12:42
To: undisclosed-recipients:
Subject: National Disaster Management Guidelines on Ensuring Disaster Resilient construction of Buildings and Infrastructure (NDMA, GoI)
The National Disaster Management Authority (NDMA), Government of India has formulated guidelines on ensuring disaster resilient construction of buildings and infrastructure financed through banks and other lending institutions. The NDMA has observed that in the context of disaster resilience there are certain critical gaps and the guidelines aim at addressing these gaps in the current process of approving the loan applications. It has been observed that the structural design of the proposed buildings and structures are not completed before submitting the application for a bank loan and no processes are in place at the banks to ensure that disaster resilience has indeed been incorporated in the assets during the design process at least before the construction begins. A copy of National Disaster Management Guidelines on Ensuring Disaster Resilient construction of Buildings and Infrastructure, September 2010 is enclosed.
Monday, June 20, 2011
India’s National Building Code on Staircases in Educational Buildings (Some Safety Clauses)
image source: http://supercoloring.com
During emergencies, most school buildings and educational facilities in India appear to be critical at staircases- many appear structurally questionable, as well as like bottlenecks to an otherwise safe passage.
The National Building Code (NBC) by Bureau of Indian Standards (BIS), also known as SP-7:2005 contains useful clauses on staircases, which apply to educational buildings, and are implementable across the country. We have extracted some information and have simplified it. The following information can be used as a checklist also.
***
Design from a particular floor to evacuate in 2.5 min (Type 1), 1.5 min (Type 2), 1 min (Type 3), Not specified for Type 4
For buildings greater than 15 m height and 500 m2 in each floor:
o Minimum 2 staircases
o These should be of enclosed type
o At least one staircase on exterior wall as a facility outside also
Exit doors:
o No exit doorway to be less than 1000mm in width
o Exit doors to open outward
o Exit door shall not open immediately upon a flight of stairs, a landing equal to at least the width of the door shall be provided in the stairway at each doorway; the level of landing shall be the same as that of the floor which it serves
o Exit doorways shall open from the side, to serve without the use of a key
Where stairways discharge through corridor and passage ways, the height of corridors and passage ways shall not be less than 2.4m
Ensure all means of exit, such as lobbies, passages, staircases are well-ventilated
Internal staircases should:
o be of non combustible material
o be a self contained unit, enclosed, and with one side made of external wall
o not be arranged around a lift shaft
o not be of hollow combustible construction
o not have gas piping or electrical panels along the stairway
o can have ducting if it provides 1hour of fire rating.
o have dimensions of:
- minimum staircase width = 1.5 m
- minimum tread width = 300mm
- maximum riser height = 150mm
- maximum 15 risers per flight
- handrail height = 1.0m
- minimum head room = 2.2m
o one flight between landings shall be designed for maximum number of people occupying that floor
o not have any fire risk spaces opening directly on to staircase
o have their external exit door at ground level, and should open directly to open spaces, or large lobby, if necessary
o Main stairs to be continuous from ground to terrace
o Should not have any combustible decoration
o have clearly visible Exit signs
o show individual floors
Pressurization of staircases should be thought of, which means that although fire spread is controlled by compartmentalization of staircases in design, ingress of smoke and toxic gasses perhaps cannot be avoided. Exclusion of smoke and toxic gases from protected route is important for safe passage. Therefore, in high rise buildings air can be injected in order to raise the pressure of the stair compartment.
External staircases are desirable for high rise buildings, and when provided shall comply to the following:
o All external staircases should be directly connected to ground
o Entrance to external staircase shall be separate and remote from internal staircase
o No door or window opening shutter shall obstruct the staircase
o Should be kept in sound operable conditions
o Should be kept obstruction free
o The external staircase shall be constructed of non combustible materials, and any doorway leading to it shall have the required fire resistance
o No external staircase, used as a fire escape, shall be inclined at an angle greater than 45 deg. From the horizontal
o Some dimensions
- Staircase flight width = 1250mm
- Minimum tread = 250mm
- Maximum riser = 190mm
- Maximum risers per flight = 15
o Spiral staircase can be employed but should be
- limited to a building not higher than 9m
- designed for a low occupant load
- not less than 1500 in diameter
- designed for an adequate headroom
The above are points directly quoted by the Indian National Building Code, and should be useful in designing safer staircases for evacuation in educational buildings.
Some clauses in the code, like this one, need changing. Improvements are endless and like other international codes can be issued as amendments.
The National Building Code (NBC) by Bureau of Indian Standards (BIS), also known as SP-7:2005 contains useful clauses on staircases, which apply to educational buildings, and are implementable across the country. We have extracted some information and have simplified it. The following information can be used as a checklist also.
***
Design from a particular floor to evacuate in 2.5 min (Type 1), 1.5 min (Type 2), 1 min (Type 3), Not specified for Type 4
For buildings greater than 15 m height and 500 m2 in each floor:
o Minimum 2 staircases
o These should be of enclosed type
o At least one staircase on exterior wall as a facility outside also
Exit doors:
o No exit doorway to be less than 1000mm in width
o Exit doors to open outward
o Exit door shall not open immediately upon a flight of stairs, a landing equal to at least the width of the door shall be provided in the stairway at each doorway; the level of landing shall be the same as that of the floor which it serves
o Exit doorways shall open from the side, to serve without the use of a key
Where stairways discharge through corridor and passage ways, the height of corridors and passage ways shall not be less than 2.4m
Ensure all means of exit, such as lobbies, passages, staircases are well-ventilated
Internal staircases should:
o be of non combustible material
o be a self contained unit, enclosed, and with one side made of external wall
o not be arranged around a lift shaft
o not be of hollow combustible construction
o not have gas piping or electrical panels along the stairway
o can have ducting if it provides 1hour of fire rating.
o have dimensions of:
- minimum staircase width = 1.5 m
- minimum tread width = 300mm
- maximum riser height = 150mm
- maximum 15 risers per flight
- handrail height = 1.0m
- minimum head room = 2.2m
o one flight between landings shall be designed for maximum number of people occupying that floor
o not have any fire risk spaces opening directly on to staircase
o have their external exit door at ground level, and should open directly to open spaces, or large lobby, if necessary
o Main stairs to be continuous from ground to terrace
o Should not have any combustible decoration
o have clearly visible Exit signs
o show individual floors
Pressurization of staircases should be thought of, which means that although fire spread is controlled by compartmentalization of staircases in design, ingress of smoke and toxic gasses perhaps cannot be avoided. Exclusion of smoke and toxic gases from protected route is important for safe passage. Therefore, in high rise buildings air can be injected in order to raise the pressure of the stair compartment.
External staircases are desirable for high rise buildings, and when provided shall comply to the following:
o All external staircases should be directly connected to ground
o Entrance to external staircase shall be separate and remote from internal staircase
o No door or window opening shutter shall obstruct the staircase
o Should be kept in sound operable conditions
o Should be kept obstruction free
o The external staircase shall be constructed of non combustible materials, and any doorway leading to it shall have the required fire resistance
o No external staircase, used as a fire escape, shall be inclined at an angle greater than 45 deg. From the horizontal
o Some dimensions
- Staircase flight width = 1250mm
- Minimum tread = 250mm
- Maximum riser = 190mm
- Maximum risers per flight = 15
o Spiral staircase can be employed but should be
- limited to a building not higher than 9m
- designed for a low occupant load
- not less than 1500 in diameter
- designed for an adequate headroom
The above are points directly quoted by the Indian National Building Code, and should be useful in designing safer staircases for evacuation in educational buildings.
Some clauses in the code, like this one, need changing. Improvements are endless and like other international codes can be issued as amendments.
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