1. UNDERSTANDING RESPONSE SPECTRUM
&
PROVISIONS OF BNBC-2014

2. OUTCOME WHAT IS AN EARTHQUAKE RESPONSE SPECTRUM
AT THE END OF THIS TRAINING/WORKSHOP/DISCUSSION YOU WILL UNDERSTAND:
WHAT IS AN EARTHQUAKE RESPONSE SPECTRUM
RESPONSE SPECTRUM AS PER BNBC/14, AND
HAVE A DISCUSSION GROUP TO SHARE YOUR IDEAS AND CONFUSIONS

3. CONTENT PART – I UNDERSTANDING EARTHQUAKE RESPONSE SPECTRUM
PART – II RESPONSE SPECTRUM PROVISION OF BNBC/2014
PART – III : GROUND MOTION SIMULATION

4. RECAP - STRUCTURAL DYNAMICS

5. EQUATION OF MOTION
Summing forces along the x-axis is p(t) - fS – fD –fI = 0

6. EQUATION OF MOTION (Earthquake Excitation)
Single-Degree-of-Freedom System

7. NATURAL PERIOD OF VIBRATIONk
n 
rads/sec m
 2 T
sec n  n
 n f
cps (Hz) n 2

8. EFFECT OF DAMPING ON FREE VIBRATION
DAMPED FREE VIBRATION
EFFECT OF DAMPING ON FREE VIBRATION

9. EFFECT OF DAMPING ON THE NATURAL VIBRATION FREQUENCY
DAMPED FREE VIBRATION
EFFECT OF DAMPING ON THE NATURAL VIBRATION FREQUENCY

10. PART - I
UNDERSTANDING RESPONSE SPECTRUM

11. ORIGIN OF THE RESPONSE SPECTRUM METHOD
Response Spectrum Method began in 1932, in the doctoral dissertation of M.A. Biot (1905–1985)
The RSM remained in the academic sphere of research for many years and did not gain widespread engineering acceptance until the early 1970s.
First, the computation of the response of structures to earthquake ground motion led to “certain rather formidable difficulties” (Housner 1947), and,
second, there were only a few well-recorded accelerograms that could be used for that purpose.
Then, in 1971, with the occurrence of the San Fernando, California, earthquake, the modern era of RSM was launched. This earthquake was recorded by 241 accelerographs, and by combining these data with all previous strong-motion records it became possible to perform the first comprehensive empirical scaling analyses of response spectral amplitudes (Lee 2002).

12. TIME HISTORY DATA
THE MOST DIRECT DESCRIPTION OF AN EARTHQUAKE MOTION IN TIME DOMAIN IS PROVIDED BY ACCELEROGRAMS THAT ARE RECORDED BY INSTRUMENTS CALLED STRONG MOTION ACCELEROGRAPHS.
THE ACCELEROGRAPH RECORDS THREE ORTHOGONAL COMPONENTS OF GROUND ACCELERATION AT A CERTAIN LOCATION.
THE PEAK GROUND ACCELERATION, DURATION, AND FREQUENCY CONTENT OF EARTHQUAKE CAN BE OBTAINED FROM AN ACCELEROGRAMS. AN ACCELEROGRAM CAN BE INTEGRATED TO OBTAIN THE TIME VARIATIONS OF THE GROUND VELOCITY AND GROUND DISPLACEMENT.

13. El Centro ground motion (N-S Component)
TIME HISTORY DATA
El Centro ground motion (N-S Component)
May 18, 1940
Time, sec
Acceleration, g
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0.24
0.26
0.28
0.30

14. TIME HISTORY DATA CENTRAL DIFFERENCE METHOD
FOR EARTHQUAKE EXCITATION – i. ANALYTICAL SOLUTION IS NOT POSSIBLE; ii. NUMERICAL METHODS ARE EMPLOYED TO FIND OTHER QUANTITIES LIKE a. VELOCITY; b. DISPLACEMENT ETC. DIFFERENT NUMERICAL METHODS ARE:
CENTRAL DIFFERENCE METHOD
AVERAGE ACCELERATION METHOD
NEWMARK’S METHOD ETC.

15. TIME HISTORY DATA ANALYSIS

16. RESPONSE SPECTRUM

17. DEFORMATION RESPONSE SPECTRUM

18. VELOCITY RESPONSE SPECTRUM
Plot of V vs. TN

19. ACCELERATION RESPONSE SPECTRUM
Plot of A vs. TN

20. COMBINED D-V-A SPECTRUM
A  V   D n n
Tn A  V  2 D 2 Tn

21. RESPONSE SPECTRUM CHARACTERISTICS
Response spectrum ( = 0,2,5, and 10%) and peak values of ground acceleration, ground velocity, and ground displacement for El Centro ground motion.

22. RESPONSE SPECTRUM CHARACTERISTICS
Response spectrum for El Centro ground motion plotted with normalized scale A/ϋgo , V/ůgo , and D/ugo ;  = 0, 2 , 5 and 10%.

23. RESPONSE SPECTRUM CHARACTERISTICS
Response spectrum for El Centro ground motion shown by a solid line together with an idealized version shown by a dashed line;  = 5%

24. ACCELERATION RESPONSE SPECTRUM EL CENTRO EARTHQUAKE 5% DAMPING
IT IS NOT PRACTICALLY POSSIBLE TO CALCULATE EXACT STRUCTURAL PERIOD .
SPECTRAL ACCELERATION FOR SHORT PERIOD IS VERY IRREGULAR.
FOR PRACTICAL USE IT HAS TO MADE ‘SMOOTH’

25. DESIGN RESPONSE SPECTRUM

26. PART - II RESPONSE SPECTRUM PROVISIONS OF BNBC/14
[Part 6, chapter 2 – article 2.5.6]

27. DEVELOPMENT HISTORY
EARTHQUAKE ZONING MAP OF BANGLADESH

28. EARTHQUAKE ZONING MAP 1972 Adopted from East Pakistan Map
DEVELOPED BY METROLOGICAL DEPARTMENT OF BANGLADESH IN 1972
THE COUNTRY WAS DIVIDED IN FOUR ZONES
ZONE 1 : Seismic factor 0.2g ~ 0.1g
ZONE 2 : Seismic factor 0.1g ~ 0.067g
ZONE 3 : Seismic factor 0.067g ~ 0.05g
ZONE 4 : Seismic factor < 0.05g

29. ZONING MAP 1978 PREPARED BY GEOLOGICAL SURVEY OF BANGLADESH
THE COUNTRY WAS DIVIDED IN THREE ZONES
ZONE 1 : Seismic coefficient 0.08g
ZONE 2 : Seismic coefficient 0.05g
ZONE 3 : Seismic coefficient 0.04g

30. BNBC – 1993 Housing and Building Research Institute (HBRI)
FIRST SCIENTIFIC APPROACH ADOPTED IN PREPARING SEISMIC ZONING MAP
THE COUNTRY WAS DIVIDED IN THREE ZONES
ZONE 1 : Seismic coefficient 0.2g
ZONE 2 : Seismic coefficient 0.15g
ZONE 3 : Seismic coefficient 0.075g
PROBABILITY OF EXCEEDANCE 20% IN 50 YEARS.

31. BNBC – 2014 being updated Housing and Building Research Institute (HBRI)
SEISMIC ZONING MAP PREPARED FOR 2475 YEARS HAZARD LEVEL (PROBABILITY OF EXCEDENCE 2% IN 50 YEARS)
THE COUNTRY IS DIVIDED IN FOUR ZONES
ZONE 1 : Seismic coefficient 0.36g
ZONE 2 : Seismic coefficient 0.28g
ZONE 3 : Seismic coefficient 0.20g
ZONE 4 : Seismic coefficient 0.12g

32. EARTHQUAKES

33. EARTHQUAKES
Historical earthquakes of 1973~2013 (source superimposed on proposed on BNBC seismic zoning map

34. BNBC/14 EARTHQUAKE DEFINITION
2% Probability of Exceedence in 50 Years (2,475 Year Return Period) – MAXIMUM CONSIDERED EARTHQUAKE (MCE)
Design Ground Motion 2/3rd of MCE
Design Ground Motions are Set at 2/3rd of MCE Ground Motion Levels, With The Reasoning That Any Structure Designed With The Provision Shall Have A Minimum Margin Against Collapse of 1.5

35. PEAK GROUND ACCELERATION (PGA)
AN INFINITELY RIGID STRUCTURE
HAS ZERO NATURAL PERIOD (T=0)
DOES NOT DEFORM:
NO RELATIVE MOTION BETWEEN ITS MASS AND ITS BASE
MASS HAS SAME ACCELERATION AS OF THE GROUND
HENCE, PEAK GROUND ACCELERATION REPRESENTS STRUCTURAL RESPONSE OF A STRUCTURE OF ZERO PERIOD

36. PARAMETERS DEFINING ELASTIC RESPONSE SPECTRUM

37. ACCELERATION RESPONSE SPECTRUM
TB = Lower limit of the period of the constant spectral acceleration branch as a function of site class (Table )
TC = Upper limit of the period of the constant spectral acceleration branch as a function of site class (Table )
TD = Lower limit of the period of the constant spectral displacement branch as a function of site class (Table ).

38. PARAMETERS DEFINING ELASTIC RESPONSE SPECTRUM
Table 2.5.4: Site dependent soil factor and other parameters defining elastic response spectrum
Soil type S
TB(s)
TC(s)
TD(s) SA
1.00
0.15
0.4
2.0 SB
1.20
0.5 SC
1.15
0.20
0.6 SD
1.35
0.8 SE
1.40
MAY BE THIS VALUE IS WRONG !!!!!!!!!!!!

39. ELASTIC RESPONSE COEFFICIENT, CS
SOIL TYPE = SA (ROCK)
DAMPING = 5%
ZONE = DHAKA (0.2g)

40. DESIGN RESPONSE SPECTRUM

41. STRUCTURE IMPORTANCE FACTOR, AS DEFINED IN SECTION 2.5.7.1
Table Importance Factors for Buildings and Structures for Earthquake design
OCCUPANCY CATEGORY
IMPORTANCE FACTOR, I
I OR II
1.0
III
1.25 IV
1.5

42. RESPONSE REDUCTION FACTOR

43. AN EXAMPLE
Table 2.5.4: Site dependent soil factor and other parameters defining elastic response spectrum
Soil type S
TB(s)
TC(s)
TD(s) SA
1.00
0.15
0.4
2.0 SB
1.20
0.5 SC
1.15
0.20
0.6 SD
1.35
0.8 SE
1.40

44. AN EXAMPLE - Continued
ELASTIC SEISMIC RESPONSE COEFFICIENT FOR “0” PERIOD (PGA FOR THE SITE)
ELASTIC SEISMIC RESPONSE FOR SHORT PERIOD
ELASTIC SEISMIC RESPONSE COEFFICIENT FOR CONSTANT ACCELERATION ZONE
ELASTIC SEISMIC RESPONSE COEFFICIENT FOR VELOCITY SENSITIVE ZONE
ELASTIC SEISMIC RESPONSE COEFFICIENT FOR DISPLACEMENT SENSITIVE ZONE

45. AN EXAMPLE - Continued ELASTIC RESPONSE COEFFICIENT, CS T CS 0.000
1.150
0.100
2.013
0.150
2.444
0.200
2.875
0.300
0.400
0.500
0.600
0.700
2.464
0.800
2.156
0.900
1.917
1.000
1.725
1.100
1.568
1.200
1.438
1.300
1.327
1.400
1.232
1.500
1.600
1.078
1.700
1.015
1.800
0.958
1.900
0.908
2.000
0.863
ELASTIC RESPONSE COEFFICIENT, CS
TB = 0.2 sec
TC = 0.6 sec
TD = 2 sec

46. AN EXAMPLE - Continued

47. DESIGN RESPONSE SPECTRUM, Sa
Original (Rock site)
Soil Amplication
Design, Sa (Reduced by R)
0.000
0.133
0.153
0.031
0.100
0.267
0.268
0.054
0.150
0.333
0.326
0.065
0.200
0.383
0.077
0.300
0.400
0.500
0.600
0.222
0.700
0.190
0.329
0.066
0.800
0.167
0.288
0.058
0.900
0.148
0.256
0.051
1.000
0.230
0.046
1.100
0.121
0.209
0.042
1.200
0.111
0.192
0.038
1.300
0.103
0.177
0.035
1.400
0.095
0.164
0.033
1.500
0.089
Amplified for Soil Type
Original on Rock
Reduced by Response Reduction Factor, R

48. PART - III
GROUND MOTION SIMULATION

49. SEISMIC INSTRUMENTATION ERA, BANGLADESH
ONE ANALOGUE SEISMOGRAPH WAS INSTALLED IN 1954 IN BALU-BAGAN CHITTAGONG.
INSTRUMENTATION ERA STARTED BY INSTRUMENTATION OF JAMUNA BRIDGE. JAMUNA MULTIPURPOSE BRIDGE AUTHORITY COMPLETED THE INSTRUMENTATION WORK IN 2003.
SIXTY MORE ACCELEROGRAPHS WERE OBTAINED FROM SAFER CITIES PROJECT OF COSMOS—WSSI TO DEPLOY IN THE FREE-FIELD AT DIFFERENT LOCATION OF BANGLADESH.
THIRTY FOUR (34) STRONG MOTION ACCELEROGRAPHS (SMA) ARE INSTALLED IN DIFFERENT LOCATIONS OF PWD OFFICE AND BUET CAMPUS IN 2006.
NO TIME HISTORY DATA AVAILABLE

50. BANGLADESH STRONG MOTION DATA at Station ID: ALTUS S/N Channel 1: EW 07/05/ :55:52 (GMT) – AT NATORE

51. GROUND MOTION SIMULATION SPECTRUM COMPATIBLE TIME HISTORY DATA GENERATION
STANDARD PROCEDURES AVAILABLE
Linear scaling
Frequency content modification
Frequency domain techniques
Time domain techniques
COMPUTER ROUTINE NEEDED TO CALCULATE THE MATCHING. COMMONLY AVAILABLE SOFTWARE ARE
RspMatch
SeismoMatch
SIMQKE
SYNTH
EZ-FRISK

52. GROUND MOTION SIMULATION
1. LINEAR SCALING OF A KNOWN STRONG MOTION DATA
EL-CENTRO EARTHQUAKE STRONG MOTION DATA HAS BEEN SCALED DOWN BY A FACTOR OF TO MAKE MAXIMUM ACCELERATION OF 0.133g

53. RESPONSE SPECTRUM OF THE SCALED STRONG MOTION DATA

54. COMPARISON OF SCALED DATA – BNBC/14 SPECTRUM

55. STRONG MOTION SIMULATION
2. SPECTRA MATCHING IN FREQUENCY DOMAIN TECHNIQUES
EL-CENTRO SPECTRUM PLANNED TO MATCH WITH THE BNBC SPECTRUM

56. SPECTRUM MATCHED

57. COMPARES OF THE SPECTRUMS

58. MATCHED TIME HISTORY GRAPH

59. WELCOME TO OPEN DISCUSSION
THANKS
&
WELCOME TO OPEN DISCUSSION