1st International Conference on Modern Design, Construction and Maintenance of Structures, 10-11 December 2007, Hanoi, Vietnam
Seismic Performance of Special Moment Resisting Frames Designed In
Accordance to the Indonesian Concrete and Earthquake Codes.
B. Lumantarna, P. Pujisuryadi, M.C. Adinata, F.R. Doly
(Civil Engineering Department Petra Christian University, Surabaya, Indonesia)
Abstract: The design provision for column reinforcement of a Special Moment Resisting Frames in the new
Indonesian Concrete Code SNI 03-2847-2002, is adopted from ACI 318M-99. This new provision is less stringent
than the previous code SNI 03-2847-1992. This study checks the seismic performance of Special Moment Resisting
Frames designed in accordance to the new concrete code. Two symmetrical buildings, six and ten stories are
considered and subjected to nonlinear static pushover and nonlinear time history analysis. The load pattern used in the
nonlinear static pushover analysis is derived from an inverted triangular first mode, while the ground acceleration used
in the nonlinear time history analysis is a spectrum consistent ground acceleration generated from El Centro 18 May
1940 North-South component in accordance to SNI 03-1726-2002. It is shown that due to 500 years return period
earthquake some upper columns of the six story building develop plastic hinges although still in a very preliminary
stage, with damage indices in the range of 0.02 to 0.04
Keywords: Seismic Performance; Special Moment Resisting Frames; Indonesian Concrete Code; Column
design
1 Introduction
The design provision for column reinforcement of a Special Moment Resisting Frames in the new Indonesian
Concrete Code SNI 03-2847-2002 [1] is adopted from ACI318M-99 [2], which is less stringent than the previous code
SNI 03-2847-1992 [3]. In the new code, the nominal moment of the columns should satisfy the following condition:
Mc 
6
Mg
5
(1)
In which:
Mc = sum of moments at the center of the joint, corresponding to the nominal flexural strength of the columns
framing into that joint. Column flexural strength shall be calculated for the factored axial force, consistent
with the direction of the lateral forces considered, resulting in lowest flexural strength.
Mg = Sum of moments at the center of the joint, corresponding to the nominal flexural strengths of the girders
(including participating slab reinforcement) framing into that joint.
While in SNI 03-2847-1992 [3]:
M u ,k  0.7  d  M kap,b
(2)
where:
Mu,k
= sum of required ultimate moment of columns
ωd
= dynamic magnification factor = 1.3
Mkap, b
= flexural moment capacity of beam
The relation between the nominal strength (1) and the required ultimate moment (2) of the column is:
M c  M u ,k /  k
(3)
where k is the capacity reduction factor, while the capacity of the beam
M kap ,b  M n ,b
in which  the overstrength factor.
__________________________
B. Lumantarna, Professor
Correspondence to B. Lumantarna; E-mail: bluman@petra.ac.id
(4)
Assuming that the capacity reduction factor, k, is 0.65 and the overstrength factor, , is 1.25, it can be shown that the
column reinforcement required in accordance to the SNI 03-2847-2002 is 30 percent less than SNI 03-2847-1992 [4].
In this study the seismic performance of Special Moment Resisting Frames designed in accordance to the new
concrete code is studied. Two symmetrical office buildings, six and ten stories are considered and subjected to
nonlinear static pushover and nonlinear time history analysis. The load pattern used in the nonlinear static pushover
analysis is derived from an inverted triangular first mode, while the ground acceleration used in the nonlinear time
history analysis is a spectrum consistent artificial ground acceleration generated from El Centro 18 May 1940 NorthSouth component in accordance to the design spectrum given in SNI 03-1726-2002 [5].
2 Performance Criteria
Asian Concrete Model Code [6] suggests three level performance criteria as shown in Figure 1. The buildings
objective are grouped into; basic objective such as offices, essential/hazardous objective such as hospitals, and safety
critical objective such as nuclear power plant. In the basic objective group, the structure should satisfy the
serviceability limit state if subjected to minor earthquake, the damage control limit state to moderate earthquake, and
the safety limit state to severe earthquake.
An additional performance criteria related to the capacity design method is the so called strong column weak
beam criteria resulting in a beam side sway mechanism as shown in Figure 2. It is expected that no plastic hinge
should appear anywhere in the columns except at the base of the building.
Fig. 2 Beam side sway mechanism, strong column weak
beam
Fig. 1 Performance level [6]
For the performance evaluation, the drift will be obtained from the static nonlinear pushover analysis employing
ETABS nonlinear [7] and from the nonlinear time history analysis employing Ruaomoko [8]. The damage indices will
be obtained from the nonlinear time history analysis using the following criteria:
DI 
m  1
u  1
(5)
where:
 m = ductility required
 u = ultimate ductility.
3 Structures Considered and Analysis Result
Figures 3 and 4 show respectively the plan of the six and ten story building considered in this study. Columns
and beams sizes are shown in Table 1. This structure is designed as Special Moment Resisting Frames (SMRF) in
accordance to the new Indonesian Concrete Code SNI 03-2847-2002 [1] and the old SNI 03-2847-1992 [3]. The
buildings are assumed to be built on soft ground located in Zone 2 of the Indonesian Earthquake Code SNI.03-17262002 [5]. Buildings designed in accordance to SNI 03-2847-2002 are labelled as SMRF-6-02 and SMRF-10-02 for the
six and ten story building respectively, while SMRF-6-92 and SMRF-10-92 respectively stand for six and ten story
building designed in accordance to SNI 03-2847-1992. Table 2 shows comparison of typical column reinforcement. It
can be seen that the old SNI 03-2847-1992 [3] requires much more reinforcement that the new SNI 03-2847-2002 [1],
details can be seen in reference [4].
These buildings are then subjected to a nonlinear static pushover and time history analysis due to artificial
ground acceleration with various return periods. The load pattern used in the nonlinear static pushover analysis is
shown in Figure 5, while the artificial ground acceleration used in the nonlinear time history analysis is shown in
Figure 6. This artificial ground acceleration is a spectrum consistent ground acceleration generated from El Centro 18
May 1940 North-South component (Figure 7) using RESMAT, a program developed at Petra Christian University [9].
The response spectra of the ground accelerations and the design spectrum are shown in Figure 8. The peak ground
accelerations of various return periods for Zone 2 of Indonesian seismic map are shown in Figure 9 [10].
Fig. 3 Plan of the six story building (SMRF-6)
Fig. 4 Plan of the ten story building (SMRF-10)
10
6
9
5
8
7
6
Story
Story
4
3
5
4
2
3
2
1
1
0
0
0
500
1000
0
1500
500
1000
Load (kN)
1500
2000
2500
Load (kN)
(a) Six story building, SMRF-6
(b) Ten story building, SMRF-10
Fig. 5 Load patern for nonlinear static pushover analysis
El Centro 18 May 1940 North-South Component Modified
El Centro 18 May 1940 North-South Component
0,4
0,3
0,3
0,2
0,2
Acceleration (g)
Acceleration (g)
0,4
0,1
0
-0,1
-0,2
0,1
0
-0,1
-0,2
-0,3
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20
-0,3
Waktu (detik)
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20
Time (detik)
Fig. 6 Artificial ground acceleration used in nonlinear time
history analysis
Fig. 7 El Centro 18 May 1940 North-South component
Response Spectra El Centro 18 May 1940 North-South Componentand
Peak Ground Acceleration Factor
1,40
1
0,9
1
Artificial
0,7
1,00
PGA Factor
Acceleration (g)
0,8
0,6
0,5
0,4
1,275
1,20
El Centro
Design spectrum
0,3
0,86212
0,71204
0,80
0,54379
0,60
0,343
0,40
0,2
0,21635
0,20
0,1
0,11765
0
0,00
0
1
2
3
0
100
200
300
Periode(T)
400
500
600
700
Fig. 8 Response spectra of the artificial ground acceleration,
El-Centro, and design spectrum
Tab.1 Beams and columns sizes
SMRF-6
Number of floors
6
10
40 x 40 m2
3.5 m
64 x 64 m2
3.5 m
500 x 700 mm2
500 x 700 mm2
Floor plan
Floor to floor
Beam
SMRF-10
( floor 1-3)
620 x 620 mm2
( floor 1-4)
700 x 700 mm2
( floor 4-6)
570 x 570 mm2
( floor 5-7)
600 x 600 mm2
( floor 8-10)
Floor thickness
120 mm
550 x 550 mm2
120 mm
Concrete grade (fc’)
Reinforcement
Stirrups
25 MPa
400 MPa
240 MPa
25 MPa
400 MPa
240 MPa
Table 2.: Comparison of column reinforcement six story building SMRF-6.
level
location
6
top
bottom
top/bottom
top/bottom
top/bottom
top
bottom
top
bottom
5
4
3
2
1
interior column SMRF-6-02
longitudinal
stirrups
8
12
12
12
16
16
28
28
20
D
D
D
D
D
D
D
D
D
25
25
25
25
25
25
25
25
25
4
4
4
4
4
4
4
4
4
Ø
Ø
Ø
Ø
Ø
Ø
Ø
Ø
Ø
12
12
12
12
12
12
12
12
12
exterior column SMRF-6-02
longitudinal
stirrups
interior column SMRF-6-92
longitudinal
stirrups
12
20
20
20
24
24
40
40
16
D
D
D
D
D
D
D
D
D
25
25
25
25
25
25
25
25
25
4
4
4
4
4
4
4
4
4
Ø
Ø
Ø
Ø
Ø
Ø
Ø
Ø
Ø
10
10
10
10
10
10
10
10
10
level
location
6
top
8
D
25
4
Ø
12
16
D
25
4
Ø
10
bottom
12
D
25
4
Ø
12
20
D
25
4
Ø
10
5
top/bottom
12
D
25
4
Ø
12
20
D
25
4
Ø
10
4
top/bottom
12
D
25
4
Ø
12
16
D
25
4
Ø
10
3
top/bottom
12
D
25
4
Ø
12
20
D
25
4
Ø
10
2
top/bottom
12
D
25
4
Ø
12
24
D
25
4
Ø
10
top
12
D
25
4
Ø
12
24
D
25
4
Ø
10
bottom
8
D
25
4
Ø
12
8
D
25
4
Ø
10
1
900
1000
Fig. 9 Peak ground acceleration, 500 yr return period is
scalled to 1.0 g [10]
DATA
Column
800
Return Period (x, year)
.
exterior column SMRF-6-92
longitudinal
stirrups
The pushover analysis on SMRF-6-02 shows plastic hinges appearing in some upper columns in the exterior
frames due to 500 years return period earthquake (Figure 10), which is not the case with SMRF-6-92 (Figure 11),
SMRF-10-02, and SMRF10-92. The same phenomena are also detected in the nonlinear time history analysis as
damage indices bigger than zero (Figure 12 and 13) although the locations are not the same with the plastic hinges
shown in the pushover analysis. In Figure 12 and 13; numbers above beam lines are the damage indices, numbers
below the beam lines are beam numbers, numbers on the right of column lines are damage indices, and numbers on
the left are column numbers.
Fig. 10 Plastic hinges on columns in the exterior frame,
SMRF-6-02, 500 yrs return period
Fig. 11 Plastic hinges in exterior frame, SMRF-6-92, 500 yrs
return period
Fig. 12 Damage indices in the exterior frame, SMRF-6-02, 500 yrs return period
Fig. 13 Damage indices in exterior frame, SMRF-6-92, 500 yrs return period
6
6
5
5
4
4
Story
Story
Figures 14 and 15 show respectively typical results of the lateral displacement and drift of structures designed in
accordance to SNI 03-2847-2002 compared to the one designed in accordance to SNI 03-2847-1992. Figure 15 shows
that the lateral displacement and drift of SMRF-10-02 and SMRF-10-92 are practically the same, there is no plastic
hinge appearing in the columns of both buildings. The performance matrices are shown in Figures 16 to 19. Figure 16
shows the performance matrix of SMRF-6, while Figure 17 is the performance matrix of SMRF-10 both using drift as
the performance criteria. Figure 18 and 19 show respectively the performance matrices of SMRF-6 and SMRF-10
using individual member damage index as the performance criteria.
3
3
2
2
1
SMRF-6-02
1
SMRF-6-02
SMRF-6-92
SMRF-6-92
0
0
0
0,05
0,1
0,15
Displacement (m)
(a) Displacement of SMRF-6
0,2
0
0,005
0,01
Drift
(b) Drift of SMRF-6
Fig. 14 Displacement and Drift of SMRF-6, 500 yrs Retirn Period
(a) Displacement of SMRF-10
(b) Drift of SMRF-10
Fig. 15 Displacement and drift of SMRF-10, 500 yrs retirn period
0,015
Return
period
(yrs)
20
100
200
500
1000
Earthquake Performance Level
SMRF-6-02
SMRF-6-92
SMRF-6-02
SMRF--92
SMRF-6-02
SMRF-6-92
SMRF-6-02
SMRF-6-92
SMRF-6-02
SMRF-6-92
Serviceability
0.153
0.153
0.473
0.473
Damage Control
Safety Limit State
0.652
0.640
0.950
0.942
1.292
1.270
Drift
0.5
1.0
2.0
Fig. 16 Performance matrix of SMRF-6, using drift as performance criteria
Return
period
(yrs)
20
100
200
500
1000
Earthquake Performance Level
SMRF-10-02
SMRF-10-92
SMRF-10-02
SMRF-10-92
SMRF-10-02
SMRF-10-92
SMRF-10-02
SMRF-10-92
SMRF-10-02
SMRF-10-92
Serviceability
0,190
0,187
0,490
0,470
Damage Control
Safety Limit State
0,720
0,716
1,041
1,021
1.446
1.399
Drift
0.5
1.0
2.0
Fig. 17 Performance matrix of SMRF-10, using drift as performance criteria
Return
period
(yrs)
500
SMRF-6-02
SMRF-6-92
1000 SMRF-6-02
SMRF-6-92
Maximum DI
Earthquake Performance Level
Serviceability
Damage Control
0.1-0.25
0.25-0.4
Safety Limit State
0.515
0.553
0.685
0.694
0.4-1.0
Fig. 18 Performance matrix of SMRF-6, using maximum damage index as performance criteria
Return
period
(yrs)
500
SMRF-10-02
SMRF-10-92
1000 SMRF-10-02
SMRF-10-92
Maximum DI
Earthquake Performance Level
Serviceability
0.1-0.25
Damage Control
0.308
0.306
0.415
0.400
0.25-0.4
Safety Limit State
0.4-1.0
Fig. 19 Performance matrix of SMRF-10, using maximum damage index as performance criteria
4 Discussions and Conclusions
The design provision for column reinforcement of a Special Moment Resisting Frames in the new Indonesian
Concrete Code SNI 03-2847-2002 is less stringent than the previous code SNI 03-2847-1992. A study of the seismic
performance of Special Moment Resisting Frames designed in accordance to the new concrete code (SMRF-6-02 and
SMRF-10-02) and the old code (SMRF-6-92 and SMRF-10-92) shows that both passed the performance evaluation as
shown in the performance matrices (Figures 16 to 19). However a very important finding needs to be noted in this
study. It is shown that due to 500 years return period earthquake some upper columns of the six story building
designed in accordance to SNI 03-2847-2002 (Figures 10 and 12), while the ones designed in accordance to SNI 032847-1992 (Figures 11 and 13) do not show the same phenomena. The formation of these plastic hinges although still
in a very preliminary stage, with damage indices in the range of 0.02 to 0.04, raise some concern that an unsafe failure
mechanism could developed in special moment resisting frames designed in accordance to the new code SNI 03-28472002.
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