Return to index: [Subject] [Thread] [Date] [Author]

RE: FAQ on earthquake resistant construction - your technical com ments invited

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Ok, I'm going to be picky but there are some exceptions to your answers as noted below.
 
Also, this reads more like a sales brochure for shear walls than a ERC FAQ.  There are other methods of earthquake resistant construction.
 
Mark Jones
-----Original Message-----
From: bhagavan [mailto:bhagavan(--nospam--at)eth.net]
 <snip>
 
EARTHQUAKE RESISTANT CONSTRUCTION (ERC) 
 
It is a session of FAQ on ERC
 
* Do earthquakes kill people?
No - not directly!
This depends on how you define directly.  A person could be next to a fault when it opens, thereby falling into the fault and dying either by the fall or getting crushed.
 
* But, how people are killed during earthquakes?
Collapse of building structures in which they live, during the earthquake kills people. Hence, the real culprits are our construction practices and poor quality of construction. The conventional buildings instantly collapse without any warnings, during the unpredictable and sudden earthquakes. 
 
Agreed, you also have the stupid people who go back into buildings that leaning 20+ degrees to get things. 
 
* Is it possible to build totally earthquake proof building structure?
-It is not feasible and economical to design and construct totally earthquake proof building structures, particularly to withstand very severe earthquakes of magnitude above 8.0 (Richter Scale) 
 
The correct answer is, "You could but you wouldn't want to pay for it".  Cheyenne Mountain, site of the United States' air defense command (or some such) is built to withstand 9.0+ earthquakes, nuclear bombs and chemical and biological attacks.  It is built on giant springs to withstand the earthquakes.  While Cheyenne Mountain is not practical for other uses, the Transamerica Tower in San Francisco uses a similar methodology with its springs and is a great example of uses active techniques to "earthquake-proof" a building.
 
- But it is very much possible to design and construct earthquake resistant building structures, though they may suffer huge damage for severe earthquakes, which will not kill people
 
Hence, the current change in US design philosophy.
 
*What is the best building construction practice to resist earthquakes?
Shear wall concept!
 
Nope, WOOD.  It's very flexible.  IF DESIGNED RIGHT, it doesn't even have to absorb the energy of the earthquake.  However, their are other limits to wood construction.
 
* What is shear wall concept in building construction practice?
In this concept the walls are not only designed to resist gravity / vertical loads (due to its self weight and other living / moving loads), but they are also designed for lateral loads of earthquakes / cyclones. The walls are structurally integrated with roofs / floors (diaphragms) and other lateral walls running across at right angles.
 
* How is it structurally superior to the conventional construction practices of load bearing masonry structures and / or Reinforced Cement Concrete (RCC) framed structure(of concrete beams, columns and slabs)?
- The load bearing masonry is very brittle material. Due to different kinds of stresses such as shear, tension, torsion, etc., caused by the earthquakes, the conventional unreinforced masonry collapses instantly during the unpredictable and sudden earthquakes! 
- The RCC framed structures are slender, when compared to shear wall concept of box like three-dimensional structures. Though it is possible to design the earthquake resistant RCC frame,  it requires extraordinary skills at design and construction levels, which can not be anticipated in all constructions projects!
- On the other hand even moderately designed shear wall structures are comparatively ductile. In safety terms it means that, during earthquakes they will not suddenly collapse causing death of people. They give enough indicative warnings such as widening structural cracks, yielding rods, etc., offering most precious moments for people to run out off structures, before they totally collapse.