Analysis of LSA by OpenSees

1
Analysis of LSAby OpenSees

• GSR Tae-Hyung Lee
• PI Khalid M. Mosalam

2
Objective

• 2-D linear analysis (phase 1)
• 2-D nonlinear analysis (phase 2)
• 3-D nonlinear analysis (phase 3)

• Current status in the middle of phase 2

3
Outline

• 2-D structural model description
• Eigenvalue analysis
• Available EQ data
• Linear elastic analysis
• Nonlinear analysis
• Future study

4
Structural Model

• Member types beams, columns, shear walls, and
  coupling beams
• nonlinearBeamColumn element in OpenSees
• Fiber descretization of cross section

5
Structural Model (contd)

• Two different boundary conditions Fixed and
  Pinned
• Fixed rigid soil
• Pinned very soft soil
• Actual foundation
• Mat foundation with 38 depth

6
Outline

• 2-D structural model description
• Eigenvalue analysis
• Available EQ data
• Linear elastic analysis
• Nonlinear analysis
• Future study

7
Eigenvalue Analysis- Fixed Boundary
T1 0.31 sec
T2 0.12 sec
T3 0.11 sec
8
Eigenvalue Analysis- Pinned Boundary
T1 0.38 sec
T2 0.13 sec
T3 0.11 sec
9
Earthquake Data

• Three levels by the return period 2, 10, and
  50 in 50 yrs
• 10 EQ records at each level in transverse
  direction
• Totally, 30 EQ records

10
Outline

• 2-D structural model description
• Eigenvalue analysis
• Available EQ data
• Linear elastic analysis
• Nonlinear analysis
• Future study

11
Elastic Analysis

• 60 simulations were performed 3 EQ levels 10
  data 2 B.C. 60
• Mean max. roof displacement (in.)

12
Outline

• 2-D structural model description
• Eigenvalue analysis
• Available EQ data
• Linear elastic analysis
• Nonlinear analysis
• Future study

13
Nonlinear Analysis- Material Models
s
s
Confined
Unconfined
e
e
Concrete (modified Kent-Park model)
Steel
14
Nonlinear Analysis- Solution Strategy

• Integrator Newmark beta method with g 0.5, b
  0.25
• Solution algorithm Modified Newton-Raphson
• Time step 10 times smaller than EQ record
  (0.0005 0.001 sec)

15
Nonlinear Analysis- 50 in 50 yrs
1.5
Pinned
1

0
Fixed
Roof displ. (in.)
-1

• Livermore Fagundes Ranch

-2
0
5
10
15
20
Time (sec)
16
Nonlinear Analysis- 10 in 50 yrs
8
Pinned
6
4
2
0
-2
Roof displ. (in.)
Fixed
-4
-6
-8

• Erzican, Turkey

-10
-12
0
10
20
Time (sec)
17
Nonlinear Analysis- 10 in 50 yrs
4
x 10
3
Turkey
2
1
0
-1

• Coupling beam M - k history

-2
-3
-1.5
-1
-0.5
0
0.5
1
-3
x 10
18
Nonlinear Analysis- 10 in 50 yrs
4
Turkey, Fixed
3
Linear elastic
2
1
0

• Roof displ. (in.)

-1
-2
Nonlinear
-3
-4
-5
0
5
10
15
20
Time (sec)
19
Nonlinear Analysis- 2 in 50 yrs
5
10 in 50 yrs
0
-5
Roof displ. (in.)
2 in 50 yrs
-10
-15
Turkey, Fixed
-20
0
5
10
15
20
Time (sec)
20
Nonlinear Analysis- Summary

• Local failure caused numerical problems in large
  EQs (e.g. 2 in 50 yrs EQ)
• Coupling beams and columns were modeled as
  elastic beam-column elements in these cases

21
Nonlinear Analysis- Summary
Roof
Level 6
Level 5
Floor displacement (in.)
Turkey, Fixed 10 in 50 yrs
Level 4
5
Level 3
0
-5
5
Level 2
0
-5
5
Level 1
0
-5
0
2
4
6
8
10
12
14
16
18
20
Time (sec)
22
Future Tasks

• Resolve numerical problems in OpenSees Consult
  developers
• Investigate other available nonlinear material
  models in OpenSees
• Investigate role of soil flexibility (?)
• 3-D nonlinear analysis (Major Task!)
• Probabilistic analysis considering material
  variability