Response Spectra Analysis of a Liquid Storage Tank 25-May-16 GT STRUDL Users Group
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Transcript Response Spectra Analysis of a Liquid Storage Tank 25-May-16 GT STRUDL Users Group
Response Spectra Analysis of a Liquid
Storage Tank
GT STRUDL Users Group
25-May-16
nd Annual Meeting
22
25-May-16
Double Tree Hotel
New Orleans, LA
June 23-26, 2010
Krishna Amirineni
WorleyParsons
Assoc. Structural Engineer
Contents
Introduction
•
Background
• Tank Geometry
• Problem Description
• Problem Approach
Pre-processing
•
Tank Wizard vs. Excel
• Joint Coordinates
• Element Incidences
• Applying Loads
Analysis
•
Sub dividing Input Files
Post-processing
•
P-M Interaction curves
• Export GT Strudl Output to Excel
• Secondary Loading (Thermal Load) Results
Background
Nuclear Power Plant
• 3 Units
• Pressurized Water Nuclear Reactor System
• 3 x Turbine Generators (1311, 1314 and 1247 MWe)
Refueling Water Tank
• Capacity – 750,000 Gallons
• Stores borated water for refueling
Tank Geometry
Tank Properties:
• Seismic Category
I
• Wall thickness
1’ - 9”
• Mat depth
4’ - 0”
• Wall height
68’ - 0”
• Water volume
750,000 gal
• Embedment
13’ – 10”
Problem Description
El. 129’
An additional 3’-0” of water required.
Overstress (Dead Load + EQ. Load)
• Vertical Reinforcing Steel @ wall base
mat junction (20%)
• Hoop Reinforcing Steel @ El. 129’ – 0”
(9.5%)
Problem Description (cont’d)
The seismic loading acting on the current tank three dimensional
model is defined, by hand computations, from a lumped mass model
Problem Approach
Perform Response Spectra Analysis of the three dimensional finite
element model
Contents
Background
•
Tank Geometry
• Problem Description
• Possible Approach
Pre-processing
•
Tank Wizard vs. Excel
• Joint Coordinates
• Element Incidences
• Applying Loads
Analysis
•
Sub dividing Input Files
Post-processing
•
P-M Interaction curves
• Export GT Strudl Output to Excel
• Secondary Loading (Thermal Load) Results
Pre processing
Use of GT STRUDL Tank Wizard vs. Excel
Triangular plate elements – NG for checking
reinforcement.
Basemat has the shape of the tank rectangular basemat not possible.
Basemat using Tank Wizard
Pre processing (cont’d)
Use of GT STRUDL Tank Wizard vs. Excel
Basemat using Excel
Rectangular basemat possible
Rectangular plate elements
possible
Customized plate element size
possible.
Pre processing (cont’d)
Excel as Pre processor – Generating Joint Coordinates
X = R Sin θ
Z = R Cos θ
Y - varies
Pre processing (cont’d)
Excel as Pre processor – Generating Element Incidences
X1
i = 0 to 35 290 + i
n = 1 to 23 290 + 36 x (n - 1) + i
X2
X3
X4
291 + i 327 + i 326 + i
Pre processing (cont’d)
Excel as Pre processor – Applying Loads
Loads considered
• Dead
• Hydrostatic
• Hydrodynamic
• Earthquake
• Thermal
Pre processing (cont’d)
Excel as Pre processor – Applying Hydrodynamic Loads
Fluid Motion in Tank
Dynamic Model
Pre processing (cont’d)
Excel as Pre processor – Applying Hydrodynamic Loads
Per TID-7024, “Nuclear Reactors and Earthquakes” Chapter 6
R
tanh 3
W
W
h
P0 u0
u0 0
R
g
g
3
h
P1 1.2W1h sin t
where
W1
R
h
0.318 tanh1.84
W
h
R
h 1.534
A1
h
tanh1.84
R
R
Pre processing (cont’d)
Excel as Pre processor – Applying Hydrodynamic Loads
P1 and P0 are point loads.
Hoop steel already overstressed at 9.5%.
El. 129’
Therefore, tried alternative approach.
Pre processing (cont’d)
Excel as Pre processor – Applying Hydrodynamic Loads
Distribute the Impulsive and Convective loads
per TID 7024, Appendix F:
Impulsive Pressure
Convective Pressure
Pre processing (cont’d)
Excel as Pre processor – Applying Impulsive Loads
Calculation of Impulsive Masses
The calculated Impulsive mass is applied as inertia
mass to the tank structure.
The GT Strudl Input file is generated using excel
macros.
Pre processing (cont’d)
Excel as Pre processor – Applying Convective Loads
The calculated Convective loads are applied as Forces in X
and Z directions separately on the tank structure.
The GT Strudl Input file is generated using excel macros.
Pre processing (cont’d)
72
64
56
Height
48
40
32
24
16
8
0
0.000
0.010
0.020
0.030
0.040
0.050
0.060
0.070
0.080
0.090
0.100
Pressure
Convective load on the tank walls
Convective and Impulsive load on
the tank basemat
Contents
Background
•
Tank Geometry
• Problem Description
• Possible Approach
Pre-processing
•
Tank Wizard vs. Excel
• Joint Coordinates
• Element Incidences
• Applying Loads
Analysis
•
Sub dividing Input Files
Post-processing
•
P-M Interaction curves
• Export GT Strudl Output to Excel
• Secondary Loading (Thermal Load) Results
Analysis
Analysis Split in to 4 parts:
•
Static Analysis
•
Eigen Value Analysis
•
Response Spectrum Analysis
•
Post Processing
Small input files help in managing the whole analysis
and also in debugging the input files.
Contents
Background
•
Tank Geometry
• Problem Description
• Possible Approach
Pre-processing
•
Tank Wizard vs. Excel
• Joint Coordinates
• Element Incidences
• Applying Loads
Analysis
•
Sub dividing Input Files
Post-processing
•
P-M Interaction curves
• Export GT Strudl Output to Excel
• Secondary Loading (Thermal Load) Results
Post processing
Tank Body
• Vertical Reinforcing steel
• Hoop Reinforcing steel
• Radial shear and
• Tangential shear
Basemat
• Reinforcing Steel in orthogonal
directions
• Section shear.
Post processing (cont’d)
Check Vertical and Hoop Reinforcing Steel
(P,M) sets are plotted on existing Interaction charts.
Post processing (cont’d)
Response Spectrum analysis gives the maximum peak values of
displacements and forces.
Stat
: Static Load
RS
: Response Spectra Load
Consider load cases:
Stat + RS
Stat - RS
PStat + RS
PStat – RS
MStat + RS
MStat – RS
Therefore, possible (P, M) pairs
(PStat+RS, MStat+RS)
(PStat+RS, MStat-RS)
(PStat-RS, MStat-RS)
(PStat-RS, MStat+RS)
Post processing (cont’d)
Export of GT Strudl Output to Excel
Post processing (cont’d)
Post processing (cont’d)
(P, M) Interaction Curves
Post processing (cont’d)
Primary Loading - Results
Tank Body
– Vertical Reinforcing Steel
OK
– Hoop Reinforcing Steel
OK
– Radial Shear
OK
– Tangential Shear
OK
Basemat
– Reinforcing Steel (N-S)
OK
– Reinforcing Steel (E-W)
OK
– Shear
OK
Post processing (cont’d)
Evaluation of Tank for Secondary Loading
(includes Thermal Loads)
Under thermal loading – concrete already cracked
Concrete sectional properties change
A second model used with changed sectional properties
Results from Primary loading and Thermal loading combined Externally.
Post processing (cont’d)
Post processing (cont’d)
Secondary Loading - Results
Tank Body
– Vertical Reinforcing Steel
OK
– Hoop Reinforcing Steel
OK
– Radial Shear
OK
– Tangential Shear
OK
Basemat
– Reinforcing Steel (N-S)
OK
– Reinforcing Steel (E-W)
OK
– Shear
OK
Post processing (cont’d)
Checking Soil Bearing Pressure – Node layout
Post processing (cont’d)
Checking Soil Bearing Pressure – Dead Load – Stress Contour
Post processing (cont’d)
Checking Soil Bearing Pressure – Seismic Load – Stress Contour
Post processing (cont’d)
Checking Soil Bearing Pressure – Seismic Load – Actual Stress Contour
Post processing (cont’d)
Checking Soil Bearing Pressure – Dead + Seismic Load – Stress Contour
Post processing (cont’d)
Checking Soil Bearing Pressure – Negative Soil Springs
=
+
Post processing (cont’d)
Checking Soil Bearing Pressure – No Tension Springs – Stress Contour
Results
No overstress in the tank (existing water level).
Tank can accommodate an additional 3 ft of water.
GT Strudl and Excel
GT STRUDL
– Technically solid
– Simple command structure
Helps creating input files easily
Command line gives more control over the analysis
– Database driven system
Helps dividing the analysis in to smaller portions
Helps in input file debugging
Saves time in debugging
Excel
– Ability to import large data and manipulate
– Macros help in data formatting and manipulation.
Questions ?