*What is earthquake resistance masonry structure
*stresses in masonry walls during earthquake ground
*Applied element modeling of masonry.
*Flow chart of AEM numerical analysis for masonry
*wall behavior analysis
*How buildings can be made more resistant to earthquakes
*Earthquake Resistant Features in Buildings
*Advantages of masonry building
WHAT IS EARTHQUAKE RESISTANCE
A structure which is constructed from the materials used by
masons, such as stone, brick, tiles, or the like is called massonary
Masonry structures are very weak to resist the earthquake
force as they have very less ductility.so to increase the ductility of
the masonry structures containment reinforcement are provided.
The structure made of the combination of the materials like
bricks , stones etc and containment reinforcement to resist the
earthquake forces is called earthquake resistance masonry
STRESSES IN MASONRY WALLS DURING
EARTHQUAKE GROUND MOTIONS
The walls of a masonry building offer resistance against lateral
dynamic loads by developing flexural and shear stresses, during
earthquake ground motions. In an attempt to identify the regions
in a masonry building where the flexural stresses and shear
stresses are a maximum during an earthquake, a linear dynamic
analysis has been carried out on a typical single storied masonry
building of plan dimensions 6.0m x 3.0m, when subjected to
earthquake ground motions.
It is assumed that the earthquake ground motion is
perpendicular to the cross walls of 6.0m length. Two openings
were provided in the cross-walls and none in the shear-walls.
The areas of maximum stress in single storied building when
subjected to the earthquake ground motions are given in the
The behavior of masonry buildings under lateral dynamic
loads is rather complicated basically due to complexities of
the walls such as orthotropy, presence of
openings, continuity at junctions of cross-walls and shearwall etc. However, all these can be conveniently modeled
using finite element technique.
• Wall Failure
• Shear Failure
APPLED ELEMENT MODELLING OF
In AEM, structure is assumed to be virtually divided into small
square elements each of which is connected by pairs of normal
and shear springs set at contact locations with adjacent elements.
These springs bear the constitutive properties of the domain
material in the respective area of representations (Fig.below).
Global stiffness of structure is built up with all element stiffness
contributed by that of springs around corresponding element.
Stress and strain are defined based on displacement of spring
end points of element edges.
As AEM so far has been used for homogeneous media like
concrete and soil, to develop an application of it for
multi-phase heterogeneous blocky material like masonry, it
requires development of some technique that can address the
particular features of masonry.
The flow as shown in chart 1 has been applied for the
FLOW CHART OF AEM NUMERICAL
ANALYSIS FOR MASONRY
WALL BEHAVIOR ANALYSIS
Cracking in wall started from very early
stage of loading initiating from loaded
diagonal corners of opening. The
cracks propagated towards the wall
corner points. However, when cracking
reached vicinity of corners where
enough compression has been
built, further propagation stopped and
new small cracks appeared at opposite
wall faces. After maximum resistance
was attained, those major cracks had
break through along the wall diagonal.
Though the cracks lie mainly in mortar
regions, there is also splitting of brick
units near left bottom corners .
The crack location and evolution obtained by analysis agrees well with reported observation.
Crack pattern observed in test and obtained through analysis
Flow of Stress
1. Through numerical analysis, it is observed that with the increment
of imposed displacement at top right corner, both compression
and tension stress level increase. Compression occurs in two
diagonal bands on either side of the opening and whereas tension
takes place in opposite corner locations and middle diagonal band.
Initial cracking takes place in those tension spots. As load increases
by virtue of increased displacement, compression stress
concentration takes place in four locations as marked in fig. below
apparently forming hinges.
2. when cracks passed throughout diagonal crossing high compression
zone, compression stress level does not increase and earlier high
level of tension is reduced. This may be due to sliding of upper
triangular part of wall over lower one through stepped cracks. In
this state, energy is dissipated through sliding and wall behaves in
Stiffness degradation starts when stress state lies on compression cap envelop
where shear resistance is reduced with increment in compression. Sliding of
upper part is represented by the flat plateau of load displacement curve. It is
observed that load-displacement behavior in experiment is well captured by
numerical analysis. From these observations, it is noted that though early
response of masonry shear wall is mainly due to de-bonding and friction
sliding, reduction in shear resistance in high compression governs the peak
load and post peak behavior.
HOW BUILDINGS CAN BE MADE MORE RESISTANT TO
• One of the most crucial physical features of earthquake resistant
buildings and structures is flexibility. Buildings and their foundations
need to be built to defy side to side movement
• Taller buildings are naturally more flexible than low rise buildings
Reinforced Walls, Beams and Trusses
Walls should also be strong enough to take the swaying load of an
earthquake. The walls must sway and go equally in both
directions. Reinforced beams and joints can also help prevent
deformity and collapse of buildings and structures during and
after an earthquake .
Foundational plates and cushions can be layered to let the sliding
movement and absorb the shock and movement during an
earthquake. These specially designed foundation plates and
cushions can help limit damage and help prevent collapse of
buildings and structures.
Progress in the field of structural engineering looks
promising. Advances in the field of structural engineering and
manufacturing of building materials are being done and new and
more superior construction materials are emerging. Earthquakeproof buildings and structures may soon be a reality.
SHOCK TABLE TEST FACILITY
Shock table test facility for evaluating seismic performance of buildings was
designed and constructed. The table is of size 3.5m by 2.5m and is supported
on 4 wheels with ability to move horizontally in one direction on rails. The
table can be subjected to shocks through a swinging pendulum of 600kg mass
with provision to increase the mass up to 1000kg. On the side of the table
opposite to the pendulum, provision is made to generate a reverse shock
through a reaction beam. The impulse force that can be given to the table can
be varied by changing the swing angle of the pendulum, mass of the
pendulum, the material to which the pendulum impacts. The reverse force to
the table can also be varied by changing the gap between the table and the
reaction beam before the start of the test. The photograph shows two brick
masonry building models with different earthquake resistant features on the
shock table with instrumentation to measure the table motion and the
response of the building models.
Shock Table Test Facility for Evaluating
Earthquake Resistant Features in Buildings
Research & Development
Peak table acceleration 1.1g
Indigenous design and fabrication of
Novel earthquake resistant features
for masonry buildings
Simulating failure patterns same as
those observed in buildings after an
(1.8m length & 600kg mass
Max. swing 400)
Table acceleration response for a swing
angle of 300
Fund. Freq. 90Hz
Behavior of building models after 13 shocks
Response after 5 shocks
One fourth scale models
Response at top of cross wall
(ERF as per
(ERF as per
R C band at
Sill level and
Response at top of cross wall
CONCEPT OF CONTAINMENT
It is well known that most of the structures tend to undergo large
deformations in the event of a strong earthquake. If the stresses caused due
to lateral forces experienced by the structures exceed its strength, the structure
yields, if it is ductile. If the structure is brittle, as in the case of un-reinforced
masonry, it will suffer brittle failure. The pattern of failure of masonry
buildings during an earthquake makes it clear that the prevention of sudden
flexural failure of masonry wall is critical to ensure an earthquake resistant
masonry structure. Again, since flexural tension can occur on both faces of
the wall due to reversal of stresses during an earthquake, there is a need to
provide ductile reinforcement on both faces. This can be accomplished by
placing vertical reinforcement either on the surface or close to the surface and
surrounding the wall, which is termed as “containment reinforcement”.
Containment reinforcement is not primarily intended to increase the lateral
strength of the wall, but to permit large ductile deformation and to avoid total
collapse. In other words, containment reinforcement will act as main energy
absorbing element of the wall which otherwise has poor energy absorption
Masonry with containment reinforcement and links/ties connecting them
through bed joints.
The use of materials such as brick and stone can increase the
thermal mass of a building.
Brick typically will not require painting and so can provide a
structure with reduced life-cycle costs.
Masonry is very heat resistant and thus provides good fire
Masonry walls are more resistant to projectiles, such as debris
from hurricanes tornadoes.
Masonry structures built in compression preferably with lime
mortar can have a useful life of more than 500 years as compared
to 30 to 100 for structures of steel or reinforced concrete.
Plate 4: Out-of plane failure of wall leading to collapse of lintel band (Bhuj)
Plate 3: Out-of-plane failure of sandstone in lime mortar masonry wall (Morbi)
Plate 6: Collapse of walls between openings (Khavda)
we conclude that the un-reinforced masonry structures are more vulnerable
to damage than the reinforced structure during an earthquake. The reinforced
structure can withstand greater magnitudes of earthquakes and more
earthquakes than the un-reinforced structures