2. Kobe Earthquake Japan 1995 Structures in Kobe built since 1981 had been
designed to strict seismic codes. Most of these buildings withstood the earthquake. In
particular, newly built ductile-frame high rise buildings were generally undamaged.
http://www.vibrationdata.com/earthquakes/kobe.htm
4. What do Architects do?Architects design buildings and structures. They advise individuals, property
owners and developers, community groups, local authorities and commercial
organizations on the design and construction of new buildings, the reuse of
existing buildings and the spaces which surround them.
Architects work closely with other members of the construction industry
including engineers, builders, surveyors, local authority planners and building
control officers. Much of their time is spent visiting sites assessing the
feasibility of a project, inspecting
building work or managing the
construction process. They will
also spend time researching old
records and drawings, and
testing new ideas and construction
techniques. Society looks to
architects to define new and better
ways of living and working, to
develop innovative ways of using
existing buildings and creating new
ones. Architects can be extremely
influential as well as admired for their
imagination and creative skills.
www.architecture.com
www.cnn.com
5. What do Structural Engineers do?
Structural engineering's combine their
Knowledge of science and design making as
they construct better framework for buildings
and other structures to safely resist natural
and made-made forces.
They are involved in physical testing,
mathematical modeling, computer
simulation all of which support decisions that
Aid in the creation and maintenance of safe
and economical structures.
http://www.seaint.org /
http://cee-ux49.cee.uiuc.edu/strweb/home.html
www.earthscience.org/.../geopro/seismic/seismic.html
6. What is Earthquake Engineering?
Earthquake engineers are concerned
with creating earthquakes resistant
designs and construction techniques
to build of all kinds
of bridges, roads and buildings.
Earthquake engineers are faced with
many uncertainties and must be
smart in their decisions in developing
safe solutions to challenging
problems. They rely on state-of-the-
art technology, materials science,
laboratory testing and field
monitoring.
www.sciencedaily.com
7. Earthquake-Resistant Structure
Building designed to prevent total collapse, preserve life, and minimize damage
http://nisee.berkeley.edu/elibrary/getpkg?id=GoddenD50-69
http://www.infinityfoundation.com/mandala/t_es/t_es_agraw_quake.htm
11. Liquefaction is a type of ground failure in which water saturated sediment turns from a
solid to a liquid as a result of shaking, often caused by an earthquake or even a volcanic
eruption. In order for the liquefaction to occur the sand grains must be fine grain sand
that are not closely packed together nor must it be held but some sort of cohesion. The
intense shaking causes the strength of the soil to become weak and the sand and water
begin to flow.
www.scieds.com
12. Nepal Develops Earthquake Resistant Architecture
A plan for safer houses in rural areas
Nepal has a history of being devastated by major
earthquakes every 75 to 100 years, with the first recorded
as early as 1255 AD. In 1934 Nepal experienced a deadly
earthquake that resulted in the death of 8,500 people
and destruction of 20 percent of valley structures, at a
time when the population was far less than at present.
Seismologists are predicting the occurrence of a large
earthquake of this kind in the near future, which is likely
to be most intense in the urban core.
http://www.archidev.org/rubrique.php3?id_rubrique=273
13. Ninety percent of Nepalese houses are made of stone and
unfired bricks. The Structural Engineers in Nepal are
retrofitting current structures for about $25/home. By creating a one-
meter square grid of punched holes in the stone wall covered with a 10
cm mesh of bamboo on the inside and outside the homes become
earthquake resistant. This net is Secured to the wall by means of 12-gauge
Gabion wire, (a form of riprap contained in a wire cage that is very
useful in erosion control.), which is inserted through the holes and
fastened strongly. It is covered with a stucco of mud, which is used in rural
areas in order to ensure longer life for the bamboo mesh.
14. Building Design
After the earthquake in Mexico City, Mexican officials adopted a new design that can protect the buildings from earthquakes. This
design was developed by some engineers at the University of California at Berkeley.
Looking at the diagram below you can see that the braces form an X which are anchored in concrete blocks at the base and on the
roof of the building.
In diagram A we have conventional steel bracing. Under the stress of the earthquake one of the braces collapses under the stress. If
all the braces begin to snap then the structural integrity of the building fails.
Now in diagram B, the engineers at Berkely used a hydraulic jack to pull or stretch the rods. Once the rods are prestressed they can
now be anchored to the base and to the roof of the building. The braces now have some room to contract thereby strengthening the
structural integrity of the building.
15. Factors governing effect of Earthquake
on structure
• Intensity of earthquake
• Type of earthquake waves
• Type of structure
• Type of design
• Shape of structure both in plan & elevation
• Type of soil
• Type of foundation
• Type of material used for construction
• Load of structure
16. Seismic designing
• Planning stage
– Plan building in symmetrical way (both axis)
– Avoid weak storey and provide strong diaphragms.
– Don’t add appendages which will create difference in Centre of mass and
centre of rigidity
– Conduct soil test to avoid soil liquefaction
– Steel to be used of having elongation of 14% and yield strength of 415 N/mm2
• Design stage
– Avoid weak column and strong beam design.
– Provide thick slab which will help as a rigid diaphragm. Avoid thin slab and
flat slab construction.
– Provide cross walls which will stiffen the structures in a symmetric manner.
– Provide shear walls in a symmetrical fashion. It should be in outer boundary to
have large lever arm to resist the EQ forces.
• Construction stage
– Compact the concrete by means of needle vibrator.
– Cure the concrete for at least a minimum period.
– Experienced supervisor should be employed to have
good quality control at site
17. CONVENTIONAL METHODS
The concept is to strengthen the building.
Have stiffness and inelastic deformation capacity.
18. CONVENTIONAL METHODS
Some of the general design concepts:
Follow current earthquake standards and codes.
Provide strong foundation.
Use best quality materials.
Avoid irregular shaped structures and framing system.
Maintain integrity by providing seismic bands:
At the plinth level of the building.
At the levels of lintels of doors and windows.
Vertical reinforcing bars at all wall junctions.
Introduce shear walls to transfer seismic loads down to
the bottom of foundation.
19. CONVENTIONAL METHODS
Remedial measured for soft storey buildings.
(a) bracings in columns of open ground storey, (b) Providing R.C. shear wall and (c)
Providing brick infills between columns.
20. Methods Of creating Earthquake Resistant
Structure
• Increase natural period of structures by Base Isolation like :
– Lead Rubber Bearing
– Laminated Rubber Bearing
– High Damping Rubber Bearing
– Spherical Sliding Bearing
– Friction Pendulum System
• Increase damping of system by Energy Dissipation Devices like :
– Viscous dampers
– Friction dampers
– Yielding dampers
– Visco elastic dampers
• By using Active Control Devices like :
– Sensors
– H/w & S/w
– Actuators
21. How to Reduce Earthquake Effects on Buildings?
Two basic technologies are used to protect
buildings from damaging earthquake effects.
The Base Isolation Devices
Seismic Dampers.
The idea behind base isolation is to detach (isolate) the
building from the ground in such a way that earthquake
motions are not transmitted up through the building, or
at least greatly reduced. Seismic dampers are special
devices introduced in the building to absorb the energy
provided by the ground motion to the building.
22. Types of seismic dampers:
viscous dampers
energy is absorbed by silicone-based fluid passing
between piston-cylinder arrangement.
friction dampers
energy is absorbed by surfaces with friction between
them rubbing against each other.
yielding dampers
energy is absorbed by metallic components that
yield.
How to Reduce Earthquake Effects on
Buildings?
23. Diaphragms
Diaphragms are horizontal resistance elements,
generally floors and roofs, that transfer the lateral forces between the vertical resistance
elements (shear walls or frames). Basically, a diaphragm acts as a horizontal I-beam.
That is, the diaphragm itself acts as the web of the beam and its edges act as flanges.
Shear Walls
Shear walls are vertical walls that are designed to receive lateral forces from
diaphragms and transmit them to the ground.
The forces in these walls are predominantly shear forces in which the fibers
within the wall try to slide past one another.
(fig. 2)
When you build a house of cards, you design a shear wall structure, and you soon
learn
that sufficient card "walls" must be placed at right angles to one another or the
house
will collapse. If you were to connect your walls together with tape, it is easy to
see that
the strength of this house of cards would significantly increase. This illustrates a
very
important point, in which the earthquake resistance of any building is highly
dependent
upon the connections joining the building's larger structural members, such as
walls,
beams, columns and floor-slabs.
Shear walls, in particular, must be strong in themselves and also strongly
connected to
each other and to the horizontal diaphragms. In a simple building with shear
walls at
each end, ground motion enters the building and creates inertial forces that
move the
floor diaphragms. This movement is resisted by the shear walls and the forces are
transmitted back down to the foundation.
24.
25.
26. Approach to ERC construction
• Conventional Approach:-
– Design depends upon providing the building with
strength, stiffness and inelastic deformation capacity
which are great enough to withstand a given level of
earthquake generated force.
• Basic Approach:-
– Design depends upon underlying more advanced
techniques for earthquake resistance is not
to strengthen the building, but to reduce
the earthquake generated forces
acting upon it.
27. ADVANCED METHODS
Basic approach is to reduce the earthquake
generated forces acting upon the building;
rather than strengthening it.
Two main techniques:
Base isolation
Energy dissipation devices
28. BASE ISOLATION DEVICES
Spherical Sliding Isolation Systems
Lead rubber bearings
Base Isolation Devices - separate building from
building foundation by bearing pads.
29. BASE ISOLATION DEVICES
Supported by a series of bearing pads which are placed
between the building and the building's foundation.
In case of an earthquake:
Fixed base building deform
and are damaged.
Base isolated building rocks
back and forth like a boat.
Shaking is reduced
by
as much as 5 times
30. TECHNIQUES UNDER RESEARCH
SHAPE MEMORY ALLOYS
Bounce back after experiencing large loads.
Used in bearings, columns and beams and connecting
elements.
Most common alloys used are copper-zinc-aluminum-
nickel, copper-aluminum-nickel or nickel-titanium.
31. TECHNIQUES UNDER RESEARCH
MUSSEL FIBERS
Elastomeric fibers combine stiffness and flexibility which helps
mussel to attach to hard surfaces.
Construction materials made of a similar blend of firm and
flexible parts could help buildings withstand high-stress forces
during an earthquake.
Ratio of stiff-to-flexible
fibers = 80:20.
32. TECHNIQUES UNDER RESEARCH
VISCO-ELASTIC DAMPERS CST30
Two layer of high damping rubber sandwiched between
steel plates.
Absorb energy produce from vibrations.
33. TECHNIQUES UNDER RESEARCH
VISCO-ELASTIC DAMPERS CST30
Advantages over traditional damping system.
Effective utilization of interior space.
Improvement in the degree of freedom of design.
Accepts different vibration types.
High performance and high quality.
Environmental friendliness.
Maintenance free.
34. TECHNIQUES UNDER RESEARCH
RUBBER CLOAKING DEVICE
Rubber 'cloaking device' could make buildings immune to
earthquakes.
Waves can be made to bend their path by various techniques.
Seismic waves can also be redirected. This is called ‘cloaking’.
