Earthquake Engineering Key Point

1. Earthquake Engineering
Key points of Earthquake Basics and Earthquake resistant Masonry features
1. The earth consists of the inner core radius is 1290 km.
2. The earth consist of the outer core radius is 2200 km.
3. The earth consist of the mantle thickness is around 2900 km.
4. The thickness of the crust layer of earth is around 5 to 40 km
5. The inner core of earth is solid.
6. At the core of earth, the temperature is estimated to be around 2500 °C.
7. At the core of earth, the pressure is estimated to be around _4 million atmospheres.
8. At the core of earth, the density is estimated to be around _13.5 gm/cc.
9. Conventional currents develop in the viscous mantle, because of prevailing High temperature
and pressure gradient between the crust and the core.
10. Sliding of earth’s mass takes place in pieces called as Tectonic plates.
11. The surface of the earth consists of 7 major tectonic plates.
12. The plate in the front is slower, then the plate behind it comes and collides and mountains are
formed, this type of inter plate interactions are known as convergent.
13. Himalayas is an example of transform.
14. Energy released during the 2001 Bhuj earthquake is about 400 times that released by the 1945
Atom Bomb dropped on Hiroshima.
15. When the earthquake occur along the boundaries of the tectonic plates are called as Intra plate
earthquake.
16. A number of earthquakes occur within the plate itself away from the plate boundaries its called
as Intra plate earthquake.
17. During intra plate and inter plate earthquake the slip generated at the fault during earthquakes
is along both vertical and horizontal direction is called as Dip slip.
18. During intra plate and inter plate earthquake the slip generated at the fault during earthquakes
is along lateral direction is called as Strike slip.
19. The point on the fault where slip starts is known as Focus.
20. The point vertically above the hypocenter on the surface of the earth is known as epicentre.
21. The depth of focus from the epicenter called as Focal depth.
22. Most of the damaging earthquakes have shallow focus with focal depths less than about 70 km.
23. The distance from epicenter to any point of interest is called as Epicentral distance.
24. A number of smaller size earthquake take place before and after a big one is called ad
Foreshocks and the ones after is called as aftershocks.
25. Magnitude of an earthquake is a measure of its size.
26. India lies at the end of the Indo – Australian plate.
27. January 2001, Bhuj earthquake has magnitude is around M7.7.
28. Based on the levels of intensities sustained during the damaging past earthquakes, the 1970
version of the zone map subdivided India into 5 zones.
29. The Indian standards provides the first seismic zone map in 1962.
30. Masonry buildings are brittle structures.
31. In brick masonry structures, the walls are most vulnerable to damage caused by horizontal
forces due to earthquake.
32. Horizontal vibrations are the most damaging to normal masonry buildings.
33. Bricks with low porosity are to be used for brick masonry construction work.

2. 34. The earthquake response of masonry walls depends on the relative strengths of Brick and
mortar.
35. A 10 mm thick mortar layer is generally satisfactory from practical and aesthetic consideration
for brick masonry construction.
36. Brick masonry buildings have large mass and hence attract Large horizontal forces during
earthquake shaking.
37. 4 types of bands are provided in any typical masonry building.
38. Lintel band is the most important band in any masonry building.
39. The Gable band is employed only in buildings with pitched or sloped roofs.
40. In buildings with flat reinforced concrete or reinforced brick roofs the roof band is not
required.
41. In building with pitched roof, the roof band is very important.
42. plinth bands are primarily used when there is concern about uneven settlement of foundation
soil.
43. lintel band also reduces the unsupported height of the walls and thereby improving their
stability in the weak direction.
44. During the Latur earthquake the intensity of shaking in Killari Village was IX on MSK scale.
45. During earthquake shaking, the lintel band undergoes bending and pulling actions.
46. When wooden bands are used, the cross-section of runner is to be at least75 mm X 38 mm.
47. When RC bands are used, the minimum thickness is 75 mm and at least two bars of 8 mm
diameters are required.

3. Earthquake Engineering
Key points of Design Philosophy
1. Minor shaking of earthquake occurs frequently.
2. Moderate shaking of earthquake occurs occasionally
3. Strong shaking of earthquake occurs rarely.
4. On average annually about 800 earthquakes of magnitude 5.0 – 5.9 occur in the world.
5. On average annually only about 18 earthquakes of magnitude 7.0 – 7.9 occur in the world.
6. In Minor type of earthquake shaking the building will be fully operational within a short time
and the repair costs will be small.
7. In Moderate type of earthquake shaking the building will be operational once the repair and
strengthening of the damaged main members is completed.
8. In Strong type of earthquake shaking the building may become dysfunctional for further use
but will stand so that people can be evacuated, and property recovered.
9. In minor earthquake the earthquake is Less than to design basic earthquake.
10. In moderate earthquake the earthquake is Equal to design basic earthquake.
11. In major earthquake the earthquake is Greater than to maximum consider earthquake.
12. Normally, design basic earthquake is half of maximum considered earthquake.
13. Hospital building we can consider as important building during earthquake.
14. The behaviour of the building depends critically upon Shape and size of the building.
15. At the planning stage, Architect and Structural engineer must work together to ensure good
building configuration.
16. In tall buildings with large height-to-base size ratio, the horizontal movement of the floors
during ground shaking is Large.
17. In short but very long buildings, the damaging effects during earthquake shaking are
Many.
18. In buildings with large plan area like warehouses, the horizontal seismic forces can be
Extreme to be carried by columns and walls.
19. Square shape type of building layout perform good during earthquake.
20. Separation joints make a complex plan into simple plan.
21. When two buildings are too close to each other, they may pound on each other during strong
shaking.
22. Masonry can carry loads that cause compression during earthquake.

4. 23. Concrete is used in buildings along with steel reinforcement bars, that composite material is
known as RCC.
24. The amount and location of steel in a member should be such that the failure of the member
is by steel reaching its strength in tension before concrete reaches its strength in compression.
This type of failure is known as ductile.
25. For making the structure earthquake resistant Strong column weak beam type of design is
more suitable.
26. Value of time period depends upon the building mass and flexibility both.
27. More the flexibility, the longer is the time.
28. Taller buildings are more flexible and have larger mass, and therefore have a longer time.
29. Low rise buildings generally have time period less than 0.4 sec.
30. Elevated water tank has time period is around 4 sec.
31. Generally reinforced concrete chimney has 2sec time period.
32. Laxman Jhula type of bridge has time period is around 6 sec.
33. Earthquake shaking of the ground has waves whose periods vary in the range of 0.03-33sec.
34. Title of IS: 13920 (1993) is Indian Standard Code of Practice for Ductile Detailing of
Reinforced Concrete Structures Subjected to Seismic Forces.
35. Equation of design base shear is VB = Ah .W.
36. If the size of the floor is 10 m x 5 m and the intensity of the dead load is 10 kN/m2
then the
weight of floor is 500 kN.
37. For a three-story building, the lumped mass of roof is 960 kN, lumped mass on each floor is
1120 kN then the total seismic weight of the building is 3200 kN.

5. Earthquake Engineering
Key point of Earthquake Resistant Design of a Four-storey RC building based on IS 13920-1993
1. The continuous bar having a 135° hook with a 10-diameter extension at each end.
2. The factored axial stress on the member under earthquake loading shall not exceed 0.1 fck
3. The member shall preferably have a width to depth ratio of more than 0.3.
4. The width of the flexural member shall not be less than 200 mm.
5. The depth D of the flexural member shall preferably be not more than 1/4 of the clear span.
6. The top as well as bottom reinforcement shall consist of at two bars throughout the member length.
7. The tension steel ratio on any face at any section shall not be less than 0.24 .
8. The maximum steel ratio on any face at any section shall not exceed 0.025.
9. The positive steel at a joint face must be at least equal to 1/2 the negative steel at that face.
10. The steel provided at each of the top and bottom face of the member at any section along its length
shall be at least equal to 1/4 of the maximum negative moment steel provided at the face of either
joint.
11. In an external joint, both the top and the bottom bars of the beam shall be provided with anchorage
length, beyond the inner face of the column, equal to the development length in tension plus 10
times the bar diameter minus the allowance for 90 degree bends.
12. The longitudinal bars shall be spliced only if hoops are provided over the entire splice length, at a
spacing not exceed 150 mm
13. The lap length shall not be less than the bar development length in tension.
14. In flexural beam, note more than 50% of the bars shall be spliced at one section.
15. The minimum diameter of the bar forming a hoop shall be 6mm according to IS 13920 (1993).
16. The first hoop shall be at a distance not exceeding 50mm from the joint face.
17. In frames which have beams, with centre to centre span exceeding 5m or columns of unsupported
length exceeding 4m, the shorter dimension of the column shall not be less than 300 mm.
18. The ratio of the shortest cross-sectional dimension to the perpendicular dimension shall preferably
not be less than 0.4.
19. The parallel legs of rectangular hoops shall be spaced not more than 300 mm centre to centre.
20. The spacing of hoops shall not exceed ½ the least lateral dimension of the column, except where
special confining reinforcement is provided.
21. When a column terminates into a footing or mat, special confining reinforcement shall extend at
least 300 mm into the footing or mat.
22. The thickness of any part of the shear wall shall not be less than 150 mm.
23. The minimum reinforcement shall be 0.0025 of the gross area in each direction.
24. If the shear wall thickness exceeds 200 mm, reinforcement shall be provided in 2 curtains, each
having bars running in the longitudinal and transverse directions in the plane of the wall.
25. The diameter of the bars to be used in any part of the shear wall shall not exceed /10 of the
thickness of that part.
26. Deformed pattern of any object at a specific frequency is known as mode shape.
27. 0.187 sec will be the natural period (T) if the natural frequency ω is 33.49 rad/sec.
28. 0.522 sec will be the natural period (T) if the natural frequency ω is 12.04 rad/sec.
29. 33.49 rad/sec will be the natural frequency if the natural period is 0.187 sec.
30. 12.04 rad/sec will be the natural frequency if the natural period is 0.522 sec.
31. 0.255 sec will be the natural period (T) if the natural frequency ω is 24.574 rad/sec.
32. 0.911 sec will be the natural period (T) if the natural frequency ω is 6.895 rad/sec.
33. 0.368 sec will be the natural period (T) if the natural frequency ω is 17.04 rad/sec.
34. 24.574 rad/sec will be the natural frequency if the natural period is 0.255 sec.
35. 2π/T will be the equation of fundamental natural frequency.
36. 2 π/ ω will be the equation of natural time period.