Building and Town Planning

1. Subject name : Building And Town Planning
Subject code : 2140607
Guided by : Prof. Mehul gamit
Prof. Pinank Patel

2. Topic: Earthquake Resistant Building
Name Enrolment no.
Bhavik Deshmukh 151103106002
Yogesh Gain 151103106004
Jayveer kotila 151103106008
Aditya Mistry 151103106009
Dhrumil Pandya 151103106010

3. Outline
 What are Earthquake?
 Precautions while planning
 Non engineered masonary structure
 Failure mechanisms of masonary building
 Box action in masonary
 Suggestions for construction of new masonary building in earthquake sensitive area
 Water tank

4. What are Earthquake?
 A sudden and violent shaking of the ground, sometimes
causing great destruction, as a result of movements within
the earth's crust or volcanic action.

5. Precautions while planning
 Lightness
 Symmetry
 Regularity
 Simplicity
 Continuity
 Size of building

6. 1. Lightness:
 Since the earthquake force is a function of mass, the
building shall be as light as possible.
 Heavier structure means large inertia force and collapse
these structures results in heavier damage and loss of
lives.
 Thus, roofs and upper storey of buildings, in particular,
should be designed as light as possible.

7. 2. Symmetry
 The building as a whole or its various blocks should be
kept symmetrical about both the axes.
 The asymmetrical buildings are subjected to twist or
torsion during earthquakes.
 Twist in buildings causes different portions at the same
floor level to move horizontally by different amounts.
 Irregularities of mass, strength and stiffness in a building
can result in significant torsional response.
 Torsion arises from eccentricity In the building layout.

8. 3. Regularity:
 The building should have a simple rectangular plan. It is seen that
simple shapes behave better during earthquake than complex shapes
like L,T,E,H,U and C etc.
 It is seen that during earthquakes the building with re-entrant corners
have suffered great damage.
 Torsional effects of ground motion are pronounced in long, narrow
rectangular blocks.
 Separation of a large building into several blocks may be required so
as to obtain symmetry and regularity of each block.

9. 4. Simplicity:
 Ornamentation involving large cornices, vertical or
horizontal cantilever projections, facia stones and the like
are dangerous and undesirable from a seismic viewpoint.
Simplicity is the best approach.
 Where ornamentation is insisted upon, it must be
reinforced with steel which should be properly embedded
or tied into the main structure of the building.

10. 5.Continuity:
 The earthquake forces developed at different floor levels in a building need
to be brought down along the height to the ground by the shortest path.
 Any deviation or discontinuity in this load transfer path results in poor
performance of the building.
 Building with vertical setback (like the hotel building with a few storeys wider
than the rest) cause a sudden jump in earthquake forces at the level of
discontinuity.
 Some building have reinforced concrete walls to carry the earthquake loads to
the foundations.

11. 6. Size of building
 Buildings of great length or plan area may not respond to earthquakes
in the way calculated.
 Buildings that are two long in plan may be subjected to different
earthquake movements simultaneously at the two ends, leading to
disastrous results.
 As an alternate such building can be broken into a number of separate
square buildings.
 In a building with large plan area like warehouse , the horizontal
seismic forces can be excessive to be carried by column and walls.

12. Non-engineered masonry structure
 The advantage of masonry construction are as follows:
 Use of locally available materials.
 Need of less skilled labour.
 Easy and cheap repair.
 Good insulation against heat and sound.
 Less formwork.
 Possibility of easy alteration after construction.

13. The poor performance of masonry building in earthquake is
because of the following reasons:
 The material is brittle and its strength degrade due to repetitive loadings.
 Masonry has very low tensile strength and low shear strength specially with
poor mortars.
 Masonry has great weight weight because of thick walls. Consequently the
inertia force are large.
 Large stiffness of the material, which leads to large response to earthquake
waves of short natural period.
 The wall to wall connection and roof to wall connection is generally weak.
 In masonry construction, stress concentration occurs at corners of doors and
windows.
 Poor construction quality because of use of locally available materials and
unskilled labours.

14. Failure Mechanisms of Masonry Buildings:
 A masonry building may fail in various ways under the action of earthquake
forces. Some of the common modes of failure are:
 Out of plane failure
 In plane failure
 Connection failure
 Diaphragm failure
 Failure due to opening in walls
 Non-structural components failure

15. 1. Out of plane failure
 The force acting on the mass of the wall tends to overturn it.
 The seismic resistance of the wall is by virtue of its weight and tensile
strength of mortar and it is very small.
 This wall will collapse by overturning under the ground motion.
 The wall has very less resistance in this direction due to small depth.
 The bending of the wall results in development of tensile stress.
 The masonry is very weak in tension and hence it cracks.
 The cracking can lead to full or partial collapse of the wall.
 This type of failure is called out of plane failure.

17. In plane failure:
 The free standing wall fixed on the ground is subjected to ground motion on
its own plane.
 The damage modes if an unreinforced shear wall depend on the length to
width ration of the wall.
 A wall with small length to width ratio will generally develop a horizontal
crack due to bending tension and then slide due to shearing.
 A wall with moderate length-to-width ratio and bounding frame diagonally
cracks due to shearing.
 A wall with large length-to-width ratio, may develop diagonal tension at both
sides and horizontal cracks at the middle.

19. Connection Failure
 The ground shakes simultaneously in the vertical and two horizontal
directions during earthquakes .
 However, the horizontal vibrations are the most damaging to normal masonry
buildings.
 To ensure good seismic performance, all wall must be jointed properly to the
adjacent walls.
 In this way, walls loaded in their weak direction can take advantage of good
lateral resistance offered by walls loaded in their strong directions.
 Further, walls also need to be tied to the roof and foundation to preserve
their overall integrity.

21. Diaphragm Failure
 Consider a complete wall with enclosure with a roof on the top subjected to
earthquake force acting along with x-axis as shown in fig.
 The roof/slabs will transfer the earthquake force to the walls, causing
shearing and bending them.
 To transfer the forces the roof must have enough strength in bending in the
horizontal plane.
 This action is called diaphragm action.
 The roofs and floors which are rigid and flat are bonded to the walls properly,
do not show any sign of diaphragm failure.

23. Failure due to opening in walls:
 Openings are necessary in a building but the location and size of the opening
in walls affect the performance of masonry buildings during earthquake,
 During earthquake shaking, inertia forces act n the strong direction of some
walls and in weak direction of others.
 Walls shaken in weak direction seek support from other walls.
 Walls B1 and B2 seek support from walls A1 and A2 for shaking in the direction
shown in fig.
 Thus, walls transfer loads to each other at their junctions.
 Hence, the masonry courses from the walls meeting at corners must have
good interlocking.
 For this reason, opening near the wall corners are detrimental to good seismic
performance.

24. Non-structural components failure
 The non-structural damage is that due to which the strength and
stability of the building is not affected.
 Such damage occurs very frequently even under moderate intensities
of earthquakes.
 Some non-structural damages are:
 Cracking and overturning of masonry parapets, roof chimney, large
cantilever balconies and cornices.
 Falling of plaster from walls and ceiling.
 Cracking and overturning of partition walls.
 Cracking of glass panels.
 Falling of loosely placed objects, overturning of cupboards.

25. Box action in masonry buildings
 Brick masonry building have large mass and hence attract large
horizontal forces during earthquake shaking.
 They develop numerous cracks under both compressive and tensile
forces caused by earthquake shaking.
 The focus of earthquake resistant masonry building construction is to
ensure that these effects are sustained without major damage or
collapse.
 Appropriate choice of structural configuration can help achieve this.
 The structural configuration of masonry buildings include aspects like
 Overall shape and size of the building.
 Distribution of mass and lateral load resisting elements across like
building.

26. Suggestions for construction of new masonry
building in earthquake sensitive are:
 Site investigation must be carried out. Bearing capacity of soils should be
more than required safe bearing capacity.
 Construction work should be carried out by qualified civil engineer.
 Plan of building should be square or rectangular.
 Flat concrete roof is preferred.
 The thickness of wall should not be less than 230 mm.
 All the construction material like cement, steel, sand, aggregates, bricks,
stone, timber, tiles etc. Should be of good quality conforming to IS
specification.
 The proportion of cement: sand mortar should not be weaker than 1:4.
 First class bricks should be used. Minimum compressive strength of bricks
should not be less than 35 kg/cm^2.
 Number of stories should not be more than four.

27.  The total height of building should not exceed 15 m.
 Opening in wall should be minimum and centrally located. Total length of
opening in wall should not exceed 33% of the length of the wall.
 Vertical reinforcement must be provided at corners of walls and t door jambs.
 Proper R.C.C bands should be provided at plinth level, lintel level, caves
level, etc.
 At window sill level, U-shaped, 8 f bars should be provided t every sixth layer.
 Masonry work should be carried out in proper bond so that vertical joints are
broken.
 Horizontal dowel bars should provided t all T and L-junctions. Dowels are
placed in every fourth course or at 50 cm intervals. 8 mm dia bars used as
dowel bars.
 At T and L-junctions, toothed joints should be provided in masonry.

28. Water tank
 Elevated water tank contain huge mass t height supported on column or
circular RCC shft.
 It is an example of single degree of freedom.
 As large mss is supported at height, centroid of mss will be higher.
 During earthquakes inertia force produced due to mass will be higher.
 During earthquke inertia force produced due to mass of water and earthquake
acceleration my cause overturning of the tank. Inertia force= Mass *
acceleration
 Higher the mass, more will be the inertia force acting on the water tank, i.e.
mass of water.
 The columns or RCC shaft acts as stiffening member, providing stiffness
resistance during earthquake.

29.  The location of the water tank on roof slab should be carefully decided.
 It should be centrally located on the building.
 Water tank on edge or corner of a building may cause imbalance of mass,
resulting in overturning of tank.
 For small residential buildings, light weight PVC tanks are preferred to reduce
mass of the building.