SCIENCE & TECHNOLOGY


Quake code to be revised
Jagvir Goyal
After the Bhuj catastrophe, a constant focus on making the buildings earthquake resistant has brought new aspects to light and IS 1893, the code for Earthquake Resistant Design of Buildings and other structures, is slated to undergo another revision. The code was last revised in 2002 as the Bhuj earthquake had forced the structural engineers to review their design methods.

Download, print your toothbrush
Andrew Buncombe
F
orgotten your toothbrush? Never mind, just print out a new one! What may seem science fiction is in fact scientific fact and these 3-D printers are just a couple of years from being affordable home accessories, according to industry insiders.


Prof Yash Pal

Prof Yash Pal

THIS UNIVERSE
PROF YASH PAL
How do flies die? I haven’t seen any dead fly
A fly could die in many ways. You might swat it. It might come under your foot, even though it is very unlikely. It might fall into a cup of milk or get trapped in honey. I suppose these are not the answers you seek.



Top









Quake code to be revised
Jagvir Goyal

A typical failure mode in a reinforced concrete frame
A typical failure mode in a reinforced concrete frame. The column concrete is well-confined where the beams frame into the joint, but above the beams, large reversals of shear and bending moment have caused spalling of the concrete cover.

After the Bhuj catastrophe, a constant focus on making the buildings earthquake resistant has brought new aspects to light and IS 1893, the code for Earthquake Resistant Design of Buildings and other structures, is slated to undergo another revision. The code was last revised in 2002 as the Bhuj earthquake had forced the structural engineers to review their design methods.

Generally, codes are not revised at such a frequent interval. However, the Bhuj earthquake resulted in a sharp increase in awareness among public to make their buildings earthquake proof. As the occurrence and magnitude of earthquakes has so far remained unpredictable, it is not possible for now to construct earthquake-proof buildings. Of course, these can be made earthquake resistant by adopting proper design methodology and by taking certain precautions.

There can be no guarantee however as you can never judge the intensity with which an earthquake may hit a region or zone. If we begin designing the buildings for maximum intensity, these will become too uneconomical. A sane approach shall therefore be to divide a country into seismic-sensitive zones based on the past seismic history and lay design methods accordingly. That’s what the Bureau of Indian Standards is trying to do.

Prior to 2002, there had been no revision of IS 1893, the code on earthquake resistant design for 18 years, as the last revision was done in 1984. There existed only one volume of it. In 2002, this volume underwent its fifth revision and it was divided into five parts. The code was made structure-specific and separate guidelines were laid for different types of structures. Separate parts for buildings, dams and embankments, industrial structures and stacks, liquid retaining structures and bridges were planned. However, only the code for buildings could be released at that time as the others were under framing stage.

What the new revision is trying to do is to provide more detailed guidelines for the construction of RCC framed structures having masonry filled in the spaces created by beam column frames. There has been a spurt in building RCC framed structures along the full length and breadth of our country as the flat culture is spreading fast. These guidelines are therefore urgently required to be released.

Soft storey parameters are also being revised in the new edition. As the degree of redundancy of a building plays an important role in its seismic design, its definition and values have also been explained. Strength of masonry infill in buildings having height more than 12 metres is also undergoing a revision.

A general advice given in favour of making the buildings earthquake resistant is to keep them symmetrical, to avoid irregularities in them and to restrict the size of openings. However, the humans always crave to have unique facades, most complex architectural elevations and widest possible openings-a symbol of inbuilt sense of freedom, in their buildings. The new revision therefore tries to provide specific treatment for irregular buildings and torsional effects that irregularities and openings cause.

Saturated cohesionless soils like sand suffer peculiar damage during earthquakes as they tend to behave like liquids and all their shear strength reduces to zero. This phenomenon called liquefaction is also being covered in the new revision.

This most important factor for earthquake resistant design is also undergoing significant changes in view of studies and feedback of last five years.

Studies made by the International Code Council, USA, the Federal Emergency Management Agency, USA and the Standards Association of New Zealand have been particularly studied for the new revision of Indian code. These international bodies have made elaborate studies for seismic design of buildings. BIS has shown no hesitation in seeking the assistance of various publications by these bodies and this is a good sign for future.

The new revision, now in its final stage of checking is expected to be released in August.

Top

Download, print your toothbrush
Andrew Buncombe

Forgotten your toothbrush? Never mind, just print out a new one! What may seem science fiction is in fact scientific fact and these 3-D printers are just a couple of years from being affordable home accessories, according to industry insiders.

Using halogen lamps that melt powered nylon and technology that allows customers to download plans for such designs online, it will soon be possible to produce everything from a toothbrush to a pair of flip-flops.

Such printers have been used in industrial design stores for the last decade where they have been used to test designs for parts before being sent for manufacture en masse. But such machines cost around $ 100,000. In recent years that price has fallen to around $ 15,000 but in just a matter of a year or two such printers are expected to be available for around $ 2,000.

Later this year, California-based IdeaLab will start selling its Desktop Factory machine for $ 4,995.

Chairman Bill Gross told the New York Times that the price could fall to $ 1,000 in four years. “The really powerful thing about this idea is that the fundamental engineering allows us to make it for $ 300 in materials,” he said.

The printers, sometimes called rapid prototypers, build objects using specks of liquid or powdered plastic in much the same way as a traditional printer creates imagines out of dots of ink. The object is created out of a stack of very thin layers of the plastic that can be hardened.

Hod Lipson, a professor at Cornell University, who has led a project that produced a design for a $ 2,000 3-D printer, said: “In the future, everyone will have a printer like this at home. You can imagine printing a toothbrush, a fork, a shoe. Who knows where it will go from there?” — The Independent

Top

THIS UNIVERSE 
PROF YASH PAL

How do flies die? I haven’t seen any dead fly

A fly could die in many ways. You might swat it. It might come under your foot, even though it is very unlikely. It might fall into a cup of milk or get trapped in honey. I suppose these are not the answers you seek. Perhaps you want to know about the life span of a fly. I have looked through some literature and I am overwhelmed. There are so many species of flies. Some rather benign, in the sense that they only suck juices or lick on things they like.

There are others who sting and bite. But I will like to come back to your question. It seems they do not live too long after reaching adulthood. Life spans vary from weeks to months, and at the very maximum a year. If there are so many flies dying all around, where are their dead bodies? The reason we don’t see their corpses is that they are not left around very long; very soon, insects descend on them and finish them off.

Ants drag them away if they cannot consume them on the spot. Indeed, there is no dearth of sanitary workers — insects, birds and of course, bacteria. A dead fly, like dead anything, is high quality food for many species.

Can electric charges and magnets distort space the way gravitation is said to distort space?

After Einstein, gravitation has acquired a special role. Gravity defines the structure of space. All matter and energy, no matter what its charge or quantum number, is subservient to gravity. It has only one sign; there is no negative gravity. This is not true of electric and magnetic fields. They belong to a different species of fundamental forces.

There is a quest to get to a theory that will encompass all forces of nature. This has been nearly accomplished for the three other forces. Gravitation has still to be brought into this unification. You might think about your question in another way. As the mass increases, its gravitational force goes on increasing.

If the charge were to increase, it would disperse very soon because of mutual repulsion of the particles. You cannot go on increasing the charge and have a stable configuration.

And if we add particles of the opposite charge in equal number, the mass would increase but the net charge remains zero.

The large-scale electric field disappears. It is meaningless to talk about distortion of space by nothing.
Top


HOME PAGE