Advanced seismic analysis of building-م.54-مبادرة#تواصل_تطوير-أ.د.ناجى أبو شادى

Advanced Seismic Analysis
and Design of Buildings (1)
Nagi Abo-Shadi, PhD, SE, PEng

2
Advanced Seismic Analysis and
Design of Buildings (1)
Nagi Abo-Shadi, PhD, PE, SE, PEng
Structural Engineering Center, Inc

Seismic Analysis of Structures (Buildings)
This is about the determination of the expected
deformation of structures and the developed forces,
strains and stresses during an earthquake event.
3

4
Seismic Performance of Buildings is based on:
Site
- Seismicity (location)
- Soil properties
Building
- Structural system
- Size and weight of building
- Construction materials

5
Seismicity
Right-Lateral Strike-Slip
Fault
Left-Lateral Strike-Slip
Fault
Divergent Boundary (Normal Fault)
Fault
Convergent Boundary (Thrust Fault).
Fault

8
Multi Degree of Freedom System (MDOF)
Single Degree of Freedom System (SDOF)
Building

Equation of Motion (E.O.M.)
Equations describing dynamic equilibrium of a system
in terms of D.O.F.s
𝐹 = 0 = 𝐹𝐼 + 𝐹𝑠𝑝
0 = 𝑚 𝑥 + 𝑘 𝑥
𝑀 = 𝑚 and 𝐾 = 𝑘
E.O.M. → 0 = 𝑀 𝑥 + 𝐾 𝑥 ( Undamped Free Vibration)
9
𝑥
𝑥
𝐹 𝐷
𝐹 𝐷 is ignored here

10
0 5 10 15 20 25 30 35 40
Time (sec)
-2.00
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
2.00
Displacement(in)
T
Damped SDOF
Undamped SODF
 = 5%
= 20%
Xn Xn+1

11
In general, take the undamped free vibration form of
the E.O.M.
0 = 𝑀 𝑥 + 𝐾 𝑥
1
𝑀
0 = 𝑥 +
𝐾
𝑀
𝑥
0 = 𝑥 + 𝜔 𝑛
2
𝑥
𝜔 𝑛 =
𝐾
𝑀
(Note that 𝐾 ≠ 𝑘 always, and M ≠ 𝑚 always)

12
Fundamental Period (𝑻 𝒏)
Represents the time for one complete cycle of
vibration (s)
𝑇𝑛 =
2𝜋
𝜔 𝑛
= 2 𝜋
𝑀
𝐾
Frequency
𝑓𝑛 =
1
𝑇𝑛
=
1
2 𝜋
𝐾
𝑀

13
0 10 20 30 40 50 60
Time (sec)
-0.50
-0.40
-0.30
-0.20
-0.10
0.00
0.10
0.20
0.30
0.40
0.50
Acceleration(g)
1940 El-Centro-270
o
PGA = 0.35g
0 10 20 30 40 50 60
Time (sec)
-0.80
-0.60
-0.40
-0.20
0.00
0.20
0.40
0.60
0.80
Acceleration(g)
1940 El-Centro-270
SDOF - T=0.7 sec
o
Sa = 0.69 g
 = 5 %
0 10 20 30 40 50 60
Time (sec)
-0.80
-0.60
-0.40
-0.20
0.00
0.20
0.40
0.60
0.80
Acceleration(g)
1940 El-Centro-270
SDOF - T=1.0 sec
o
Sa = 0.51 g
 = 5 %
Response Spectra
El-Centro Ground Acceleration
Structural Response for
T = 0.7 Sec and  = 5%
Structural Response for
T = 1.0 Sec and  = 5%

14
Response Spectra for  = 5%
F = m x Sa
Where:
m = Structure mass
Sa = Spectral acceleration
F = Elastic force
Spectral force
Unreduced force

15
Seismic Design of Buildings
Seismic design of buildings follows the following codes:
2018 International Building Code, IBC
2019 California Building Code, CBC
2020 City of Los Angeles Building Code, LABC
2020 County of Los Angeles Building Code, LACBC
which adopts the ASCE7-16 document for the design forces

16
𝜇 =
𝛥 𝑢
𝛥𝑦
Displacement Ductility
𝑉 =
𝑚 𝑆 𝑎
𝑅

17
Stiff Bracing Elements:
Appropriate for controlling the building drift.
- Concentric Braced Frames
- Eccentric Braced Frames
- Steel shear walls
- Reinforced concrete shear walls
- Masonry shear walls
- Light-framed shear walls (wood or sheet metal)

18
Concentric Braced Frames
For the concentric braced frames, the energy dissipation occurs
in the brace itself through the compression reversals. These
compression forces cause buckling of the frame braces.
Concentric braced frames with K-Bracing are prohibited in high
seismic zones since losing one brace will result in column failure..

19
Concentric Braced Frames

20
Eccentric Braced Frames
The link beam in the eccentric braced frames is exposed to high
shear forces and dissipates the energy through shear yielding.

21
Eccentric Braced Frames

22
Typical Connection Detail and Link Beam for an EBF

23
Reinforced concrete shear walls

24
Reinforced concrete shear walls

25
Concrete Confinement
Concrete confinement is provided at specific locations of the
seismic force resisting member. These locations are exposed
to high strains beyond that can be taken by the unconfined
concrete.
The purpose of providing
the confinement is to
enhance the concrete
properties including the
strength, f’c and the
ultimate concrete strain,
εcu.

26
Reinforced concrete masonry shear walls

29
Light-Framed (wood) shear walls

30
Flexible Bracing Elements:
Ductile and appropriate for reducing the design base shear.
- Steel moment frames
- Reinforced concrete frames

31
The pre-Northridge earthquake connection demonstrated poor
performance. The weld at the interface between the beam and
column fractured. The figure below shows fractured weld at the
interface between the frame beam and frame column.

32
The figure shows a
pre-Northridge
earthquake moment
frame connection at
which the maximum
moment and hence
the maximum strain
occurs at the beam-
column interface.

33
Typical Beam-
Column Connections
for Special Moment
Resisting Frames
Typical Coverplated
Connection

34
Typical Beam-
Column Connections
for Special Moment
Resisting Frames
Typical Reduced
Beam Section (RBS)
Connection

35
Bearing Wall System
Building Frame System

36
Moment Frame Building
Moment Frame Building (Y)
and Dual System (X)

37
Moment Frame System
Building Frame System

38
Moment Frame Building (X)
and Dual System (Y)
Dual System (X) and
Dual System (Y)

39
Seismic Design
Prescriptive Design
Method(s)
Performance-Based
Design Method(s)

40
Prescriptive Design
Method(s)

41
)I/R(
S
C DS
s 
)I/R(T
S
C 1D
maxs 
Equivalent Lateral Force Procedure (ASCE 12.8)
The ASCE 7-16 includes static equivalent lateral force procedure to
determine the earthquake forces on building structures as follows:
V = CS W (ASCE 12.8-1)
Cs-min = 0.044 SDS I
Seismic Weight (ASCE 12.7.2)
W = D (self weight) + 1) 25% of the storage load
2) Partition wt. or 10 psf min.
3) Permanent equipment A/C, generators, etc.
4) 0.2 snow load if snow load Pf > 30 psf

50
Performance-Based
Design Method(s)

51
Featured Project
Aqua Condominiums
AKA “Ocean Villas”

54
Tallest Concrete Shear Wall Building in the West Coast
Height = 220 feet (code permits 160 feet)
21 stories: Two 18-story residential towers atop 3
levels of partially enclosed parking
556 Residential Units
723,000 sf (residential)
264,000 sf (parking)
85,000 sf (plaza)
$150 million

55
Structural System
Specially Reinforced Concrete Bearing
Wall
8-inch and 6-inch shear walls spaced at
12 to 16 feet
Cast-in-Place concrete with tunnel form
construction
Support a 5½-inch one way slab

Advantages of Using Tunnel Form Construction
Faster Completion
High Quality Construction
Reduced Maintenance & Insurance Expense
Reliable Completion Dates
Cost Savings on Construction
Built-In Accuracy and Tolerances
Noise Reduction & Fire Resistance
https://www.youtube.com/watch?v=5vD62cZN4LE
https://www.youtube.com/watch?v=Me0uouvePG8

0.00 1.00 2.00 3.00 4.00 5.00 6.00
Period (sec)
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80Acceleration(g)
1.7 (El-Centro 270 )
El-Centro, 270
Site Specta
o
o

0.00 1.00 2.00 3.00 4.00 5.00 6.00
Period (sec)
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80Acceleration(g)
2.0 (El-Centro 180 )
El-Centro, 180
Site Specta
o
o

EQ # EARTHQUAKE RECORD FILENAME Case Norm. FactorMin. Max. Max.
IMPERIAL VALLEY EARTHQUAKE - EL CENTRO
MAY 18, 1940, 2037 PST
CORRECTED ACCELEROGRAM, 270 DEGREES, CALTECH IIA001
ISEE, UC BERKELEY, CALIFORNIA
IMPERIAL VALLEY EARTHQUAKE - EL CENTRO
MAY 18, 1940, 2037 PST
CORRECTED ACCELEROGRAM, 180 DEGREES, CALTECH IIA001
NORTHRIDGE EARTHQUAKE - SYLMAR COUNTY HOSPITA
JANUARY 17, 1994 04:31 PST
CORRECTED ACCELEROGRAM, CHANNEL (90 DEG), CDMG QN94A514
NORTHRIDGE EARTHQUAKE - SANTA MONICA CITY HALL GROUNDS
JANUARY 17, 1994 04:31 PST
CORRECTED ACCELOGRAM, CHANNEL 1, 90 DEGREES, CDMG QN94A538
NORTHRIDGE EARTHQUAKE - ARLETA and NORDHOFF FIRE STATION
JANUARY 17, 1994 04:31 PST
CORRECTED ACCELOGRAM, CHANNEL 1, 90 DEGREES, CDGM QN94A087
-9.57 10.5
10.5
0.83%
5 NRIDGE3.ACC NR3 1.45
-2.18 2.51
2.51
0.20%
-10.5 9.29
10.45
0.83%
0.85%
2 IMPVAL1.ACC ELC180 2 -7.33 7.9
7.9
0.63%
EARTHQUAKE INFORMATION Normalize to Site SpectraDisplacement (in)
1 IMPVAL1.ACC ELC270 1.7 -10.1 10.7
10.66
Max Disp. = 10.66 in

0 10 20 30 40 50 60
Time (sec)
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
Displacement(in)
1.7 El-Centro 270
Linear Analysis
0 10 20 30 40 50 60
Time (sec)
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
Displacement(in)
2.0 El-Centro 180
Linear Analysis
Structural Linear
Performance

1
2
3
4
5
6
7
8
9
10
0 10 20 30 40 50
Spectral Analysis (ETABS)
Spectral lateral load distribution
T = 0.89 sec
Spectral Disp. = 10.54 Drift 0.84%

0 10 20 30 40 50 60
Time (sec)
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
Displacement(in)
2.0 El-Centro 180
Non-Linear Analysis
0 10 20 30 40 50 60
Time (sec)
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
Displacement(in)
1.7 El-Centro 270
Non-Linear Analysis Structural Non-Linear
Performance

Min. Max. Max. Abs.
1 ELC270 1.7 -6.2 7.5 7.5
2 ELC180 2 -7.04 7.56 7.56
3 NR1 (Sylmar) 0.85 -7.33 3.86 7.33
4 NR-2 (Santa Monica) 0.55 -2.18 2.51 2.51
5 NR-3 (Arleta) 1.45 -8.6 5.72 8.6
EQ # Case Norm. Factor
Displacement (in)
Max Disp. = 8.6 in
Non-Linear Analyses Results

Ocean Villas Reinforcing Program
12-inch Shear Wall:
10#9 Jamb Bars w/ #7@12 EWEF
8-inch Shear Wall:
Bottom: 10#8 Jamb Bars w/ #5@12 EWEF (Grnd – 7th)
Top: 10#8 Jamb Bars w/ #4@12 EWEF (14th – Roof)
6-inch Shear Wall:
6#8Jamb Bars w/ #5C12 EW

Pushover Analysis
PERFORM 2D
Spectral Lateral Load
Distribution

Advanced seismic analysis of building-م.54-مبادرة#تواصل_تطوير-أ.د.ناجى أبو شادى

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