Goals of Earthquake Resistant Design
It is economically not feasible for ordinary buildings to be designed as absolute earthquake proof.
However, the goals for EQRD are shown below.
Serviceability level Earthquake
•Frequent and minor earthquakes
•Building should not be damaged and continue to remain in service
•Expected ten times during the life of building
Damageability level Earthquake
•Occasional moderate earthquakes
•No structural damage is expected
•Non structural damage should not lead to any loss of life
•Expected once or twice during the life of building
Safety level Earthquake
•Rare major earthquakes
•Building should not collapse
•Non structural & structural damage should not lead to any loss of life.
In symmetrical building plan the distance between Centre
of Mass [CoM] & Stiffness Centre / Centre of Resistance
[CoR] is less compared to asymmetrical plans.
Irregular Building configuration results in twisting (torsion or
rocking) when subjected to seismic forces.
Direction of ground motion
Inertia Force due to
Earthquake act through
Internal resistive Force
due to Structural Element
configuration act through
Plan of building
Elevation of building
Geometrical Asymmetry - Plan
Asymmetrical buildings undergo large amount of
torsion and hence extreme corners are subjected to
Avoid asymmetrical buildings like: I, L,U, and T shape
As CoM & CoR coincide in plan twisting will not occur
due to earthquake. Building will need to resist the
horizontal inertia force only.
Symmetrical plans like Rectangular, Square,
Polygonal or Circular are favourable.
Geometrical Asymmetry - Elevation
In vertical directions, sudden change in stiffness or mass creates instability. It attracts more forces
and hence undergo large deflections. Excessive deflection induces large bending moment and shear force
in the structural members.
Gradual change in lateral stiffness and
building floor mass in vertical direction
can be provided
Geometrical Asymmetry – Building Joint
Typical problem occurs in the junction areas
as two neighbourhood block strikes each
other and try to separate out in a periodic
During earthquake three blocks undergo
twist in three different orientations
Building blocks can be separated by seismic
Gaps. The individual building blocks now
vibrate in plan separately. The Stress
concentration in block joints can be avoided.
Difference in CoM & CoR
will invite Torsion Couple,
which produce instability
•The resisting inertia force in the super structure
causes uplift and compression in the flat foundation at
•The tilting of foundation due to uplift force initiate the
failure of foundation of building
Three main prerequisites for liquefaction :
1.A layer of relatively loose sand or silt.
2.A water table high enough to submerge a layer of
3.An intensity of ground shaking sufficient to increase
the water pressure between soil particles to cause the
soil-water mixture to liquefy.
•The pressures generated during large earthquakes
with many cycles of shaking can cause the liquefied
sand and excess water to force its way to the ground
surface from several meters below the ground.
•The phenomenon may incorporate both flow of already
liquefied sand from a layer below ground and a
•Individual footings should be
interconnected with tie-beams or a structural
slab to prevent any relative horizontal
movement occurring during earthquake
•As the raft has a common base and it
equally and uniformly distribute the super
structure load to the sub soil.
•It spreads concentrated loads onto a larger
area and makes the structure tolerant of
minor ground subsidence.
•It mobilizes the entire weight of the building
to resist inertia-induced overturning
Techniques for making Earthquake-Resistant
Currently, there are several design philosophies in earthquake engineering, making use of
experimental results, computer simulations and observations from past earthquakes to
offer the required performance for the seismic threat at the site of interest. There are five
broad categories of structural systems which are taken into account when designing
earthquake resistant buildings.
Bearing wall systems,
Building frame systems,
Moment-resisting frame systems,
Cantilever column systems
1. Bearing Wall Systems
•Structural walls located throughout the structure provides primary vertical support for the
building’s weight and that of its contents as well as the building’s lateral resistance.
•Bearing wall buildings are commonly used for residential construction, warehouses, and
low-rise commercial buildings of concrete, masonry, and wood construction.
•Unlike standard masonry walls which are solid, the interlocking mortar-less masonry
blocks allow slight movement and lock tighter over time, aided by an innovative
application of steel reinforcement. This construction technique is also better at dissipating
the energy of a seismic wave than traditional masonry.
2. Bearing Frame Systems
•For buildings constructed of structural steel and concrete Lateral resistance is provided
either by diagonal steel members (termed braces) that extend between the beams and
columns to provide horizontal rigidity or by concrete, masonry, or timber shear walls that
provide lateral resistance but do not carry the structure’s weight.
•In some building frame structures, the diagonal braces or walls form an inherent and
evident part of the building design. In most buildings, the braces or walls may be hidden
behind exterior cladding or interior partitions.
3. Moment-Resisting Frame
•Used for both structural steel and reinforced concrete construction.
• The horizontal beams and vertical columns provide both support for the structure’s
weight and the strength and stiffness needed to resist lateral forces.
•Stiffness and strength are achieved through the use of rigid connections between the
beams and columns that prevent these elements from rotating relative to one other.
•Moment-resisting frame systems are popular because they do not require braced frames
or structural walls, therefore permitting large open spaces and facades with many
unobstructed window openings
4. Dual Systems
•Dual systems is an economical alternative to moment-resisting frames, are commonly
used for tall buildings.
•Dual system structures feature a combination of moment-resisting frames and concrete,
masonry, or steel walls or steel braced frames.
•The moment-resisting frames provide vertical support for the structure’s weight and a
portion of the structure’s lateral resistance while most of the lateral resistance is provided
either by concrete, masonry, or steel walls or by steel braced frames..
Earthquake Building Codes in Japan
Japan is a seismically active country and has some of the most rigorous earthquake
building standards in the World.
1924: Earthquake resistant construction regulations were introduced.
Cause:1923 Kanto Earthquake
Effect: Regulations for wooden beams, reinforced concrete used in construction
in town areas
1950: The introduction of the Building Standards Act “kyu-taishin”
Cause: 1948 Fukui earthquake
Effect: Regualtions were no longer limited to town areas.
1971: Amendments to the Act
Shearing reinforcements and reinforced concrete foundations
1981: New Earthquake Resistant Building Standard Amendment“Shin-taishin”
Cause: 1978 Miyagi Earthquake
Effect: Buildings should not suffer during a mid-size
earthquake, and a buiding shold not collapse during l
Case Study: Shigeru Ban's Paper Tube School
Shigeru Ban along with a team of Chinese and Japanese students, built
temporary but resilient schools out of plywood and recycled cardboard
a. Recycled paper tubes are molded into load-bearing columns,
bent into trusses and rapidly assembled.
b. Can be made waterproof and fire resistant.
c. Various thickness and diameters of paper can be added to a
structure to support more weight as necessary
d. Can build structures a few stories high.
Framework -made from paper tubes
Walls –cheap material, easy to produce
Roofs -made of plywood, and used polycarbonate as
Feasibility: Uses materials that are available anywhere in the world and is also structurally