Sap example

SAP2000®
Integrated
Finite Element Analysis
and
Design of Structures
VERIFICATION MANUAL
COMPUTERS &
STRUCTURES
INC.
Computers and Structures, Inc.
Berkeley, California, USA
Version 6.1
Revised July 1997
1

COPYRIGHT
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rest with Computers and Structures, Inc. Unlicensed use of the program
or reproduction of the documentation in any form, without prior written
authorization from Computers and Structures, Inc., is explicitly prohib-
ited.
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2

DISCLAIMER
CONSIDERABLE TIME, EFFORT AND EXPENSE HAVE GONE
INTO THE DEVELOPMENT AND DOCUMENTATION OF
SAP2000. THE PROGRAM HAS BEEN THOROUGHLY TESTED
AND USED. IN USING THE PROGRAM, HOWEVER, THE USER
ACCEPTS AND UNDERSTANDS THAT NO WARRANTY IS EX-
PRESSED OR IMPLIED BY THE DEVELOPERS OR THE DIS-
TRIBUTORS ON THE ACCURACY OR THE RELIABILITY OF
THE PROGRAM.
THE USER MUST EXPLICITLY UNDERSTAND THE ASSUMP-
TIONS OF THE PROGRAM AND MUST INDEPENDENTLY VER-
IFY THE RESULTS.
3

Table of Contents
Introduction 1
Example 1 Two-Dimensional Frame — Static and Dynamic Loads 3
Example 2 Bathe and Wilson Frame — Eigenvalue Problem 13
Example 3 Three-dimensional Frame — Dynamic Loads 17
Example 4 ASME Frame — Eigenvalue Problem 23
Example 5 Three-dimensional Braced Frame — Dynamic Loads 29
Example 6 Beam — Steady-State Harmonic Loads 35
Example 7 Two-dimensional Truss — Static Loads 39
Example 8 Three-dimensional Building — Dynamic Loads 43
Example 9 Patch Tests — Prescribed Displacements 47
Example 10 Straight Beam — Static Loads 51
Example 11 Curved Beam — Static Loads 59
Example 12 Twisted Beam — Static Loads 63
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Example 13 Beam On Elastic Foundation — Static Loads 67
Example 14 Rectangular Plate — Static Loads 71
Example 15 Cantilever Plate — Eigenvalue Problem 75
Example 16 Scordelis-Lo Roof — Static Loads 79
Example 17 Hemispherical Shell — Static Loads 83
Example 18 Portal with P-delta 87
Example 19 Pounding of Two Planar Frames — Nonlinear Time-History
Analysis 91
Example 20 Friction-Pendulum Base-Isolated 3D Frame — Nonlinear Time-
History Analysis 95
ii
SAP2000 Verification Manual
6

Introduction
This manual presents a set of example problems solved using the SAP2000 struc-
tural analysis program. These examples demonstrate many of the capabilities of the
SAP2000 program. For purposes of verification, key results from these examples
are compared with theoretical or published results from other computer programs,
where such are available. The verification problems cover each type of element and
include both static and dynamic examples.
For each example, this manual contains:
• A short description of the problem
• A list of significant SAP2000 options activated
• A description of the input data used to create the model
• A comparison of key results with theoretical results or results from other com-
puter programs, if available
Some examples are solved using several different elements, mesh sizes and/or
boundary conditions. Key results from these different solutions are presented for
comparative purposes.
The data files and selected output files associated with the example problems are
provided in subdirectory EXAMPLES of the SAP2000 directory. For each exam-
ple, the following files may be provided:
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• The SAP2000 model file, with extension .SDB. This file can be accessed in
SAP2000 using the Open command under the File menu
• The input data text file, with extension .S2K. This is an alternative to the .SDB
file and can be accessed in SAP2000 using the Import command under the File
menu
• Binary results files, with various extensions. If these files are provided, analy-
sis results can be viewed in SAP2000 without running the analysis
Some of the examples have more than one model file corresponding to the use of
different element types or mesh sizes in the creation of the model. The filenames as-
sociated with a particular problem are identified (without extension) in each exam-
ple.
Note that not all examples can be run with every version of the program. For exam-
ples, time-history analyses require the PLUS or Nonlinear version, and the nonlin-
ear examples require the Nonlinear version.
2
8

E x a m p l e 1
Two-Dimensional Frame —
Static and Dynamic Loads
Description
This is a seven-story two-dimensional frame structure, subjected to static lateral
and vertical loads and dynamic lateral loads due to earthquakes. The structure is
analyzed once using earthquake loads specified as a response spectrum, and once
using earthquake loads specified as a base acceleration time history. A solution to
this problem using another computer program is documented in Reference [1]. The
framing and the static loads are shown in Figure 1-1. The earthquake excitation is
shown in Figure 1-8. It is the N-S component of the 1940 El Centro earthquake. The
framing and the loads are all identical to the ones used in Reference [1].
Significant Options of SAP2000 Activated
• Two-dimensional frame analysis
• Diaphragm constraints
• Lateral joint loads
• Vertical span loads
• Response-spectrum analysis
• Time-history response to base excitation
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9

Input Data
The computer model used is shown in Figures 1-1 and 1-2. Kip-inch units are used.
Two different input files are used. The first file is to analyze the structure for static
vertical and lateral loads and response spectrum dynamic loads. The input data file
for this analysis is FRAME. The second file is to repeat the dynamic analysis but
using base acceleration time-history as a loading. The input data file for this analy-
sis is FRAMETH and the digitized base acceleration is given in file ELCENTRO.
This is shown in Figure 1-8.
The file FRAME is described first. Vertical loads input as Load Case 1 are specified
as span loading on beams. Static lateral loads input as Load Case 2 are specified as
joint loads. The lateral (Y) displacements of the columns at each story level are con-
strained together using a separate Diaphragm Constraint for each floor. Also,
masses are specified only in the lateral (Y) direction at each story level. These are
common modeling techniques used to reduce the size of the equation system and
are also utilized in the analysis reported in Reference [1]. The Diaphragm Con-
straints eliminate all axial deformations in the beam. This, and the absence of mass
specification in the vertical direction reduces the dynamic problem to seven natural
modes of vibration. All seven modes are included in the analysis.
It should also be noted that the AISC section properties in the database file SEC-
TIONS.PRO are not used in this example and the required properties are explicitly
entered. This is intentional as most of the sections shown are older sections not in
the current AISC database.
The input file FRAMETH is identical to file FRAME for the structural model.
However, no static or response spectrum loads are specified. Instead the base accel-
eration is specified in the Y direction. The acceleration data is discretized in une-
qual time steps. The output sampling time used is 0.02 seconds and the response is
calculated for the first eight seconds. A damping value of 0.05 is used for all modes.
Comparison of Results
Reference [1] presents results only for the static lateral load analysis and the dy-
namic analysis. A comparison of key results for these analyses is presented in Fig-
ures 1-3, 1-4 and 1-5. The static results and the time periods are identical for the two
programs. The comparison is excellent for the response spectrum results and good
for the time-history results. Explicit time integration, not dependent on the size of
the time steps, is used in SAP2000.
For the response-spectrum results, the program of Reference [1] uses the square
root of the sum of the squares (SRSS) method of modal combination. SAP2000
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allows both the SRSS method and the complete quadratic combination (CQC)
method of modal combination. The CQC method is the default for SAP2000 and is
generally recommended. Figure 1-5 presents two sets of results for SAP2000 re-
sponse spectrum analysis: the default CQC results, and the SRSS results.
Plots of the deformed shape of the structure under the static lateral loads and of the
sixth mode shape are shown in Figures 1-6 and 1-7. A plot of time versus displace-
ment at the top of the structure is given in Figure 1-9.
References
1. Static and Dynamic Analysis of Multistory Frame Structure Using DY-
NAMIC/EASE2, Engineering Analysis Corporation and Computers/Structures
International.
5
Example 1 Two-Dimensional Frame — Static and Dynamic Loads
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6
Figure 1-1
Two-dimensional Frame Example
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7
Figure 1-2
Two-dimensional Frame Example Model
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8
Quantity SAP2000 Reference [1]
Lateral Displacement
at Node 22
1.450764 1.450764
Axial Force
in Member 1
69.99 69.99
Moment in
Member 1
at Node 1
2324.68 2324.68
Figure 1-3
Comparison of Results for Static Lateral Loads
Mode SAP2000 Reference [1]
1 1.2732 1.2732
2 0.4313 0.4313
3 0.2420 0.2420
4 0.1602 0.1602
5 0.1190 0.1190
6 0.0951 0.0951
7 0.0795 0.0795
Figure 1-4
Comparison of Results for Periods of Vibration
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9
Quantity
SAP2000 Reference [1]
Response
Spectrum
(CQC)
Response
Spectrum
(SRSS)
Time
History
Response
Spectrum
(SRSS)
Time
History
Lateral Dis-
placement
at Node 22
5.431 5.437 5.486 5.438 5.46
Axial Force
in Member 1
261.5 261.7 263.0 261.8 258.0
Moment in
Member 1
at Node 1
9916 9864 9104 9868 8740
Figure 1-5
Comparison of Results for Dynamic Analyses
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10
Figure 1-6
Deflection Due to Lateral Loads
Figure 1-7
Mode Shape 6
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11
Figure 1-8
El Centro Ground Acceleration Input
Figure 1-9
Lateral Displacement of Joint 22
17

E x a m p l e 2
Bathe and Wilson Frame —
Eigenvalue Problem
Description
This is a ten-bay, nine-story, two-dimensional frame structure solved in Reference
[1]. The framing and the material and section properties are shown in Figure 2-1.
The mass per unit length and other properties used are consistent with References
[1] and [2], to which the results are compared. The first three eigenvalues are com-
puted.
• Eigenvalue analysis
Input Data
The computer model used is shown in Figure 2-1. Kip-foot units are used. Mass per
unit length of the members is specified. The program automatically computes the
joint masses to be used in the eigenvalue analysis.
The input data file for this example is FRAMEBW.
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19

A comparison of the first three eigenvalues computed by SAP2000 with results
from References [1] and [2] is presented in Figure 2-2. The comparison is excel-
lent.
References
1. Bathe, K. J. and Wilson, E. L.
Large Eigenvalue Problems in Dynamic Analysis, Journal of the Eng. Mech.
Div., ASCE, Vol. 98, No. EM6, Proc. Paper 9433, Dec. 1972.
2. Peterson, F. E.
EASE2, Elastic Analysis for Structural Engineering, Example Problem
Manual, Engineering Analysis Corporation, Berkeley, California, 1981.
14
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15
Example 2 Bathe and Wilson Frame — Eigenvalue Problem
Figure 2-1
Bathe and Wilson Frame Example
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16
Mode SAP2000 Reference [1] Reference [2]
1 0.589541 0.589541 0.589541
2 5.52696 5.52695 5.52696
Figure 2-2
Comparison of Eigenvalues
22

E x a m p l e 3
Three-dimensional Frame —
Dynamic Loads
Description
This is a two-story, three-dimensional frame structure with rigid diaphragm floors.
The problem is the same as the one solved in Reference [1]. The framing is shown
in Figures 3-1 and 3-2. The structure is doubly symmetric in plan, except that the
center of gravity at each story level is eccentric and is given by coordinates X = 38
feet and Y = 27 feet, represented in Figure 3-1 by joints 28 and 29.
• Three-dimensional frame analysis
• Rigid diaphragm modeling
• Response spectrum analysis
Input Data
The computer model used is shown in Figures 3-1 and 3-2. Kip-foot units are used.
An additional joint is added to each story at the center of gravity, and all story mass
is given at these two joints.
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Two rigid Diaphragm constraints are defined, one each for Stories 1 and 2. All
joints on story 1 are constrained together, including the joint at the center of gravity.
Similarly, all joints for story 2 are constrained together. For each story, the X and Y
displacements and the Z rotations for all joints are dependent upon each other.
Masses at the centers of gravity are specified in the X and Y directions. No rota-
tional mass inertia is used for consistency with Reference [1]. It should be noted
that the problem has only four natural modes. All four modes are used in the analy-
sis.
The input data file for this example is FRAME3D.
A comparison of the SAP2000 results with Reference [1] results for the four natural
periods of vibration and the X-deflection at Joint 29 is presented in Figure 3-3. The
comparison is excellent.
Reference
1. Peterson, F. E.
EASE2, Elastic Analysis for Structural Engineering, Example Problem Man-
ual, Engineering Analysis Corporation, Berkeley, California, 1981.
18
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19
Example 3 Three-dimensional Frame — Dynamic Loads
Figure 3-1
Three-dimensional Frame Example: Dimensions
25

20
Figure 3-2
Three-dimensional Frame Example: Element Properties
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21
Example 3 Three-dimensional Frame — Dynamic Loads
Period, Mode 1 0.2271 0.2271
Period, Mode 2 0.2156 0.2156
Period, Mode3 0.0733 0.0733
Period, Mode 4 0.0720 0.0720
X Deflection, Joint 29 0.0201 0.0201
Figure 3-3
27

E x a m p l e 4
ASME Frame —
Eigenvalue Problem
Description
This is a single-story, single-bay in each direction, three-dimensional frame struc-
ture made of 2-inch steel pipe segments and 2.75-inch steel cubes as shown in Fig-
ure 4-1. The frame is the same as modeled in References [1] and [2] and is Problem
1 from the ASME 1972 Program Verification and Qualification Library (Reference
[3]).
• Use of rigid end offsets on Frame elements
• Ritz vector analysis
Input Data
The computer model used is shown in Figure 4-2. The pipe segments are modeled
using Frame elements. For consistency with Reference [1], masses are specified at
the nodes instead of using the Frame member mass per unit length specification and
additional nodal masses only for the solid cubes. Masses identical to those used in
23
29

Reference [1] are specified. Since masses at 14 nodes are specified in three direc-
tions, this problem has 3 x 14 = 42 dynamic degrees of freedom. The first 24 modes
are calculated using both eigenvectors and Ritz vectors. The Ritz vectors are calcu-
lated using ground acceleration in the three global directions as the starting load
vectors. The input data file for this example using Ritz vector analysis is FRA-
MASME. For eigenvector analysis, just change the type of modes requested.
Comparison of Output
A one-to-one comparison of SAP2000 results with References [1] and [2] results
for this problem is not possible. This is because both References [1] and [2] use the
Guyan reduction method to reduce the 42 dynamic degrees of freedom problem to
24. This introduces approximations into the solution. A comparison of the results is
presented in Figure 4-3 for the first 12 natural frequencies. Two sets of results are
presented for SAP2000: one using Ritz vector analysis, and one using eigenvector
analysis.
The comparison between SAP2000 and References [1] and [2] is good considering
the modeling differences between the different solutions. The SAP2000 eigenvec-
tor and Ritz-vector results are essentially the same for the first 11 modes, but begin
to differ in the higher modes. In general, only the eigenvectors represent the natural
modes of the structure. The Ritz vectors are a better basis for response-spectrum
and time-history analyses, but may not have the same frequencies and mode shapes
as the eigenvectors.
References
1. Peterson, F. E.
2. DeSalvo, G. J. and Swanson, J. A.
ANSYS, Engineering Analysis System, Examples Manual, Swanson Analysis
Systems, Inc., Elizabeth, Pennsylvania, 1977.
3. Program Verification and Qualification Library, ASME Pressure Vessel and
Piping Division, Committee on Computer Technology, 1972.
24
30

25
Example 4 ASME Frame — Eigenvalue Problem
Figure 4-1
ASME Frame Example
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26
Figure 4-2
ASME Frame Model
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27
Example 4 ASME Frame — Eigenvalue Problem
Mode
SAP2000
Ritz Analysis
SAP2000
Eigen Analysis
Reference [1] &
Reference [2] *
1 114 114 112
2 119 119 116
3 141 141 138
4 222 222 218
5 399 399 404
6 422 422 423
7 450 450 452
8 550 550 554
9 774 774 736
10 800 799 762
11 909 909 853
12 955 946 894
* Both results are based upon Guyan reduction from
42 to 24 dynamic degrees of freedom.
Figure 4-3
Comparison of Modal Frequencies
33

E x a m p l e 5
Three-dimensional Braced Frame —
Dynamic Loads
Description
This is a three-story, L-shaped braced frame structure. The floors act as rigid dia-
phragms. The framing consists of four identical frames and the frame members
carry only axial loads. The problem is identical to the one solved in Reference [1].
The framing is shown in Figure 5-1.
• Axial-load-only frame members
• Response spectrum analysis
Input Data
The computer model used for Frame 1 is shown in Figure 5-2. Kip-inch units are
used. The models for Frames 2, 3 and 4 are identical except that node numbers are
incremented by 12 and member numbers by 21, for each successive frame. It must
be noted that the common column between Frames 2 and 3 is modeled twice, once
for each frame. This is done for consistency with the modeling in Reference [1].
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35

Joints 49, 50 and 51 are specified at the center of gravity of stories 1, 2 and 3, re-
spectively. X- and Y-direction masses and the mass moment of inertia about the
Z-axis are specified at these joints. All joints on a given story are connected to-
gether using a Diaphragm constraint.
The modeling is identical to that used in Reference [1]. Also, only the first two
modes are used in the response spectrum analysis. The input data file for this exam-
ple is FRAMBRAC.
Key results from the SAP2000 analysis are compared with the Reference [1] solu-
tions in Figure 5-3. The comparison is excellent.
Reference
1. Peterson, F. E.
30
36

31
Example 5 Three-dimensional Braced Frame — Dynamic Loads
Figure 5-1
Three-dimensional Frame Example
37

32
Figure 5-2
Three-dimensional Braced Frame Example — Model of Frame 1
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33
Example 5 Three-dimensional Braced Frame — Dynamic Loads
Period, Mode 1 0.326887 0.326887
Period, Mode 2 0.320640 0.320640
Axial Force,
Member 1
279.47 279.48
Axial Force,
Member 4
194.50 194.50
Axial Force,
Member 5
120.52 120.52
Figure 5-3
Comparison of Results for Three-dimensional
Braced Frame Example
39

E x a m p l e 6
Beam — Steady-State Harmonic Loads
Description
This is a fixed-end beam in two dimensions subjected to a uniformly distributed
load which varies harmonically with respect to time. The beam is shown in Figure
6-1. The problem is the same as given in Reference [1]. The beam is solved twice,
once using the undamped, steady-state analysis option and once using the periodic
loading, time-history analysis option.
• Steady-state analysis
• Time-history analysis for periodic loading
Input Data
The computer model used is shown in Figure 6-1. Pound-inch units are used.
For the steady-state option the frequency of the forcing function is provided in cy-
cles per second. The input data file for this option is BEAM.
35
41

For the time-history option the time function (sine wave) portion of the loading is
discretized at 37 points at equal intervals covering one complete cycle of loading.
See Figure 6-2. The input data file for this example is BEAMTH.
Reference [1] computes the deflection at the center of the beam to be -0.0541 sin
300t. The SAP2000 result for the amplitude of this deflection for the steady-state
option is -0.054535. It should be noted that Reference [1] uses only the first five
mode shapes of the beam for its computation. The SAP2000 results for the time-
history option are shown in Figure 6-3. The maximum amplitude being reported is
-0.05440. The comparison of results for both methods of analysis in SAP2000 with
the theoretical results is excellent.
Reference
1. Paz, M.
Structural Dynamics, Theory and Computations, Van Nostrand Reinhold,
1985.
36
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37
Example 6 Beam — Steady-State Harmonic Loads
Figure 6-1
Beam Example
43

38
Figure 6-2
Time Variation of Loading
Figure 6-3
Center Span Displacement
44

E x a m p l e 7
Two-dimensional Truss —
Static Loads
Description
This is a two-dimensional truss structure. All members can carry only axial loads.
The truss is shown in Figure 7-1.
• Two-dimensional truss analysis
• Vertical joint loads
Input Data
The computer model used is shown in Figure 7-1. Truss members are modeled us-
ing frame elements with zero moments of inertia. Load case 1 is live load, and Load
case 2 is dead load. Load combination 1 is dead load plus live load.
The input data file for this example is TRUSS.
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45

This example is included as a sample only. Other results for comparison are not
available.
40
46

41
Example 7 Two-dimensional Truss — Static Loads
Figure 7-1
Two-dimensional Truss Example
47

E x a m p l e 8
Three-dimensional Building —
Dynamic Loads
Description
This is a two-story, three-dimensional framed building. The structure is shown in
Figure 8-1. The floors act as rigid diaphragms. The building is unsymmetrical and
is subjected to lateral dynamic loads along two horizontal axes at a 30o angle to the
building axes.
• Response-spectrum analysis in two directions
Input Data
The computer model used is shown in Figure 8-1. Kip-foot units are used. Joints 19
and 20 are specified at the center of gravity of Stories 1 and 2, respectively, and the
X- and Y-direction masses and the mass moment of inertia about the Z axis is de-
fined at these joints only. All six modes of the structure are used for the dynamic
analysis. The response spectra are defined for two horizontal axes at a 30o angle to
the building axes.
43
49

The input data file for this example is BUILDING.
This example is included as a sample only. Other results for comparison are not
available.
44
50

45
Example 8 Three-dimensional Building — Dynamic Loads
Figure 8-1
Three-dimensional Building Example
51

E x a m p l e 9
Patch Tests — Prescribed
Displacements
Description
This is a rectangular plate with irregularly-shaped elements and subjected to pre-
scribed displacements at the edges. The plate is shown in Figure 9-1. The location
of the inner nodes and the prescribed displacements are the same as suggested in
Reference [1]. The problem is solved using both Plane Stress elements and Shell
elements.
• Plane stress analysis using 4-node Plane elements
• Displacement specification
• Plate bending and membrane analysis using Shell elements
Input Data
The computer model used is shown in Figure 9-1. The prescribed displacements at
the edges are calculated as:
u = 10 ( x +
y
2
)
-3
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v = 10 ( y +
x
2
)
-3
w = 10
( x + xy + y )
2
-3
2 2
Θx
-3
= 10 ( y +
x
2
)
Θy
-3
= 10 ( - x -
y
2
)
These represent constant stress fields.
For the Plane element solution, only the X- and Y-translations are unrestrained. All
other degrees of freedom are restrained. For the Shell element solution, all six de-
grees of freedom are unrestrained because the membrane formulation of this shell
element gives rotational stiffness components about a direction normal to the plane
of the shell.
For this example, the input data file using the Plane element is PATCHPLN, and
that using the Shell element is PATCHSHL.
The theoretical results for the problem are Sxx
= Syy
= 1333 and Sxy
= 400 for the
membrane components; and Mxx
= Myy
= 1.111 x 10
-7
and Mxy
= 0.333 x 10
-7
for the
plate bending components. These theoretical results are reproduced by SAP2000.
Reference
1. MacNeal, R. H. and Harder, R. C.
A Proposed Standard Set of Problems to Test Finite Element Accuracy, Finite
Elements in Analysis and Design 1 (1985), pp. - 20, North-Holland.
48
54

49
Example 9 Patch Tests — Prescribed Displacements
Figure 9-1
Patch Test Example
55

E x a m p l e 1 0
Straight Beam — Static Loads
Description
This is a straight cantilever beam of proportions shown in Figure 10-1. The beam
has unit forces at the tip in the three orthogonal directions and a unit twist, each
modeled as a separate Load case. The beam is modeled using different mesh geo-
metries as suggested in Reference [1]. The problem is solved using Shell elements,
nine-node Plane stress elements ,and Solid elements.
• Shell element analysis
• Plane element analysis with plane-stress option
• Solid element analysis with and without incompatible bending modes
Input Data
Several mesh geometries are used and key results for these are presented. The fol-
lowing data files are provided:
• STRBMSHL for the rectangular mesh of Shell elements.
• STRBMPLN for the rectangular mesh of Plane elements.
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57

• STRBMSOL for the rectangular mesh of Solid elements with incompatible
bending modes.
Figures 10-1 to 10-3 represent the models used for the Shell, Plane and Solid ele-
ments.
The unit forces at the tip are applied as 1/2 at each node for the Shell element; 1/6 at
each corner node and 4/6 at the midside node for the Plane element; and 1/4 at each
node for the Solid element. This represents a consistent set of forces for the ele-
ments. The unit twist for the Shell and Solid elements is applied as a couple.
For the model using Shell elements the nodes at the fixed end are restrained in the
axial direction, in the out-of-plane direction, and for rotations that cause out of
plane bending. The transverse, in-plane direction is restrained only at one node so
as not to cause local Poisson’s effect. The other node is, however, provided with the
transverse reaction as a load.
For the model using Plane elements the nodes at the fixed end are restrained in the
axial direction and one of them is also restrained in the transverse, in-plane direc-
tion for the same reason as for the Shell element. The other nodes are, however, pro-
vided with the transverse reactions as loads. All rotations and the out-of-plane di-
rection for all nodes are also restrained.
For the model using Solid elements the nodes at the fixed end are restrained in the
axial direction and one of them is also restrained in the two transverse directions for
the same reason as for the Shell element. This , however, does not make the model
stable, so an additional node is restrained in the vertical direction to prevent rotation
about the axial direction. The other nodes are, however, provided with the trans-
verse reactions as loads.
The displacements at the tip in the direction of the load is compared for each type of
element and the different meshes with the theoretical results in Figures 10-4, 10-5,
and 10-6.
The results for the Shell element are good except for the in-plane shear results for
the irregular meshes and the results for the unit twist. The twist results are too stiff.
The element is too thick compared to the width for the thin plate twisting behavior
the Shell element is capable of modeling. The irregular mesh behavior in in-plane
shear can be improved by decreasing the skewness and aspect ratio of the elements
and using more elements.
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58

The results for the nine-node Plane element for all mesh geometries is excellent.
The four-node Plane element is too stiff in bending and a finer mesh would be re-
quired to accurately capture the bending behavior.
The results for the Solid element with a rectangular mesh and using incompatible
bending modes are good except for the case with the unit twist. To capture the twist-
ing behavior accurately, more elements are needed across the beam section. The
Solid element model without incompatible bending modes is too stiff in the bend-
ing mode. A finer mesh along the length of the beam would give better results.
Reference
Elements in Analysis and Design 1 (1985), pp. 3-20, North-Holland.
53
Example 10 Straight Beam — Static Loads
59

54
Figure 10-1
Straight Beam Example - Shell Element Models
60

55
Figure 10-2
Straight Beam Example - Plane Stress Element Model
Figure 10-3
Straight Beam Example - Solid Element
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56
Load
Direction
SAP2000
Theoretical
Rectangular
Mesh
Trapezoidal
Mesh
Parallelogram
Mesh
Extension 3.000x10-5
3.000x10-5
3.000x10-5
3.000x10-5
Out-of-plane
Shear
0.4263 0.4266 0.4266 0.4321
In-plane Shear 0.1072 0.0221 0.0790 0.1081
Twist 0.00233 0.00233 0.00233 0.00321
Figure 10-4
Comparison of Tip Displacements Using Shell Elements
Load
Direction
SAP2000
TheoreticalRectangular
Mesh
4-Node
Element
Rectangular
Mesh
9-Node
Element
Trapezoidal
Mesh
9-Node
Element
Parallelo-
gram
Mesh
9-Node
Element
3.000x10-5
3.000x10-5
3.000x10-5
3.000x10-5
In-plane Shear 0.0101 0.1076 0.1063 0.1065 0.1081
Figure 10-5
Comparison of Tip Displacements Using Plane Stress Element
62

57
Load
Direction
SAP2000
Theoretical
Rectangular
Mesh with
Incompatible
Bending Modes
Rectangular
Mesh without
Incompatible
Bending Modes
3.000x10-5
3.000x10-5
Out-of-plane Shear 0.4283 0.0109 0.4321
In-plane Shear 0.1072 0.0101 0.1081
Twist 0.00286 0.00286 0.00321
Figure 10-6
Comparison of Tip Displacements Using Solid Elements
63

E x a m p l e 1 1
Curved Beam — Static Loads
Description
This is a curved cantilever beam of proportions shown in Figure 11-1. The beam is
loaded with unit shears at the free end. The problem is the same as suggested in Ref-
erence [1]. The problem is solved using Shell elements and Plane elements.
• Shell element analysis
• Plane element analysis using plane- stress option
Input Data
The input data file for the Shell element example is CRVBMSHL, and for the Plane
element example is CRVBMPLN.
The displacement at the free end in the direction of the load is compared with theo-
retical results (Reference [1]) for both element types in Figure 11-2.
For the Plane element, more elements along the length of the beam would give bet-
ter results. The aspect ratio of the element is quite large in this model.
59
65

For the Shell element, the in-plane (membrane) results are good; the out-of-plane
(bending) results are not as good. This is because of the stiffer twisting behavior
when the thickness is large compared with the width.
Reference
60
66

61
Example 11 Curved Beam — Static Loads
Figure 11-1
Curved Beam Example — Shell Element Model
67

62
Load
Direction
SAP2000
Theoretical9-Node
Plane Stress
Element
Shell
Element
In-plane
Shear
0.0775 0.0851 0.0873
Out-of-plane
Shear
0.4518 0.5022
Figure 11-2
Comparison of Tip Displacements
68

E x a m p l e 1 2
Twisted Beam — Static Loads
Description
This is a twisted cantilever beam of proportions shown in Figure 12-1. Unit loads
are applied at the free end. The problem is the same as suggested in Reference [1].
The problem is solved using Shell elements.
• SHELL element analysis
Input Data
The computer model used is shown in Figure 12-1. The input data file for this ex-
ample is TWSBMSHL.
The displacements at the tip in the direction of the loads are compared with theoreti-
cal results (Reference [1]) in Figure 12-2. The comparison is excellent.
63
69

Reference
1.1. MacNeal, R. H. and Harder, R. C.
64
70

65
Example 12 Twisted Beam — Static Loads
Figure 12-1
Twisted Beam Example
Load
Direction
SAP2000 Shell
Element
12x12 Mesh
Theoretical
In-plane Shear 0.005413 0.005424
Out-of-plane Shear 0.001770 0.001754
Figure 12-2
Comparison of Tip Deflections
71

E x a m p l e 1 3
Beam On Elastic Foundation —
Static Loads
Description
This is a simply supported beam on an elastic foundation. Half of the beam is mod-
eled as shown in Figure 13-1. The geometry and the loads are the same as used in
Reference [1].
• Plane element analysis using the plane stress option
• Spring supports representing elastic foundations
Input Data
The computer model used is shown in Figure 13-1. Pound-inch units are used.
Nine-node Plane elements with the plane stress option are used. Half of the beam is
modeled using 10 elements and symmetry is utilized to obtain the boundary condi-
tions. Springs are used to model the elastic foundation.
The input data file for this example is BEAMONFN.
67
73

The transverse displacements along the center of the beam and the maximum bend-
ing stress (using the average of the values at the top and bottom fiber) are compared
with theoretical results (Reference [1]) in Figure 13-2. The comparison is good.
Reference
1. Peterson, F. E.
68
74

69
Example 13 Beam On Elastic Foundation — Static Loads
Figure 13-1
Beam on Elastic Foundation Example
75

70
Axial
Station
Transverse
Displacements
Maximum
Bending Stress
SAP2000 Theoretical SAP2000 Theoretical
0 1.0458 1.0453
6 18029 18052
12 1.0336 1.0331
18 17751 17773
24 0.9973 0.9967
30 17183 17206
36 0.9373 0.9367
42 16304 16327
48 0.8546 0.8541
54 15082 15106
60 0.7507 0.7502
66 13476 13501
72 0.6275 0.6270
78 11436 11462
84 0.4874 0.4870
90 8902 8930
96 0.3335 0.3331
102 5810 5839
108 0.1695 0.1693
114 2089 2119
120 0.0002 0.0000
Figure 13-2
76

E x a m p l e 1 4
Rectangular Plate — Static Loads
Description
This is a rectangular plate as shown in Figure 14-1. This problem is solved using
two different aspect ratios: one square plate of 2 x 2, and another rectangular plate
of 2 x 10. Two Load cases are used: Load case 1 for a concentrated load at the cen-
ter and Load case 2 for uniform load. Also, the problems are solved once with the
edges clamped, and once with the edges simply supported. The problem is modeled
using both Shell and Solid elements. The geometry, properties and loads used are
those suggested in Reference [1].
• Plate bending analysis using Shell elements
• Plate bending analysis using Solid elements
• Static load analysis
Input Data
The computer model using Shell elements is shown in Figure 14-1. For both types
of elements, a 6 x 6 mesh is used on a quarter of the plate, with symmetry conditions
applied to represent the remainder of the plate. Incompatible bending modes are in-
cluded for the Solid element solutions.
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77

The input data file for the model using Shell elements with clamped edges is
RCPLTSHL. The input data file for the model using Solid elements with simple
supports is RCPLTSOL. Both are for a rectangular (2 x 10) plate.
Two different thicknesses are used in models using Solid elements. One is 100
times thicker than the model using Shell elements, the other is 1000 times thicker.
The loads for each model are inversely proportional to the cube of the thickness so
that all displacements are of the same order of magnitude.
The central deflection results for the various boundary conditions, loading condi-
tions, and element types are compared in Figure 14-2 with the theoretical results.
The comparison is good. The thicker model using SOLID elements gives better re-
sults because of the improved aspect ratio.
Reference
72
78

73
Example 14 Rectangular Plate — Static Loads
Figure 14-1
Rectangular Plate Example
79

74
Loading
Boundary
Condition
Aspect
Ratio
(b/a)
SAP2000
Theoreti-
cal
0.0001
Thick
Shell
Element
0.01 Thick
Solid
Element
0.1 Thick
Solid
Element
Uniform
Simply
Supported
1.0 4.061 3.175 4.084 4.062
5.0 12.92 9.37 12.91 12.97
Clamped
1.0 1.29 0.83 1.30 1.26
5.0 2.60 1.83 2.61 2.56
Concen-
trated
Simply
Supported
1.0 11.77 8.76 11.89 11.60
5.0 17.74 6.40 15.97 16.96
Clamped
1.0 5.76 3.44 5.87 5.60
5.0 7.80 1.78 6.39 7.23
Figure 14-2
Comparison of Deflection at Center
80

E x a m p l e 1 5
Cantilever Plate — Eigenvalue Problem
Description
This is a square cantilever plate and the first five eigenvalues are computed. The
plate is shown in Figure 15-1.
• Shell elements for plate bending analysis
• Large capacity analysis — over 4900 dynamic degrees of freedom
Input Data
Three different mesh sizes are used: a 10 x 10 mesh, a 19 x 19 mesh, and a 40 x 40
mesh. The computer model used for the 19 x 19 mesh is shown in Figure 15-1.
Kip-inch units are used. Unit mass for the plate is specified to generate the mass
matrix.
The input data file is PLATE for the 19 x 19 mesh and LARGEPLT for the 40 x 40
mesh.
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81

Comparison of Output
Reference [1] gives results for the first five natural frequencies of a square cantile-
ver plate obtained by using the Ritz method with beam mode shapes. A comparison
of the SAP2000 results with the Reference [1] results is given in Figure 15-2.
The comparisons of the periods of vibration for the first, third and fourth modes are
excellent; however, the comparisons of the periods of vibration for the second and
fifth modes are not as good because the results of Reference [1] involve approxi-
mating plate mode shapes with beam mode shapes.
The SAP2000 results using three different mesh sizes are very close.
Reference
1. Harris, C. M. and Crede, C. E.
Shock and Vibration Handbook, McGraw-Hill, 1976.
76
82

77
Example 15 Cantilever Plate — Eigenvalue Problem
Figure 15-1
Cantilever Plate Example
83

78
Mode
SAP2000
Reference [1]*40 x 40 19 x 19 10 x 10
MESH MESH MESH
1 0.01779 0.01781 0.01787 0.01790
2 0.00647 0.00648 0.00654 0.00732
3 0.00284 0.00285 0.00288 0.00292
4 0.00221 0.00223 0.00228 0.00228
5 0.00186 0.00187 0.00190 0.00201
* Using Ritz’s method with beam mode shapes
Figure 15-2
Comparison of Natural Periods of Vibration
84

E x a m p l e 1 6
Scordelis-Lo Roof — Static Loads
Description
This is a reinforced concrete single span cylindrical roof as shown in Figure 16-1.
The roof is to be analyzed for gravity loads. The problem solved is the same as sug-
gested in Reference [1].
• Three-dimensional shell analysis
• Gravity load analysis
• Large capacity analysis — 7991 static degrees of freedom
Input Data
Two different mesh sizes are used for this problem: one, a 6 x 6 mesh used on a
quarter of the roof as shown in Figure 16-1; another, an 18 x 72 mesh used on half
the roof. Pound-foot units are used. Symmetry boundary conditions is used to rep-
resent the omitted parts of the structure. Unit weight is specified to apply the uni-
formly distributed loading.
The input data file for the 6 x 6 mesh is ROOF. The input data file for the 18 x 72
mesh is LARGEROF.
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85

The theoretical vertical deflection at the center of the free edge is 0.3086, and Ref-
erence [1] suggests a value of 0.3024 for comparison of finite element behavior.
SAP2000 gives a value of 0.3068 for the 6 x 6 mesh and 0.3012 for the 18 x 72
mesh. The comparison is excellent.
A comparison of SAP2000 displacement and bending moment results using the 6 x
6 mesh, and theoretical results provided in Reference [2] using the theory presented
in Reference [3], is given in Figures 16-2 and 16-3. The theoretical results are meas-
ured from the figures given in Reference [2]. Nodal averages are used for the
SAP2000 bending moments shown. The comparison is good.
References
1. MacNeal, R. H. and Harder, R. L.
2. Zienkiewicz, O. C.
The Finite Element Method, McGraw-Hill, 1977.
3. Scordelis, A. C. and Lo, K. S.
Computer Analysis of Cylindrical Shells, Journal of the American Concrete In-
stitute, Vol. 61, May 1964.
80
86

81
Example 16 Scordelis-Lo Roof — Static Loads
Figure 16-1
Scordelis-Lo Roof Example
87

82
Location
Axial Deformations
at Support
Vertical Displacements
at Central Section
SAP2000 6x6
Mesh Theoretical
SAP2000 6x6
Mesh Theoretical
0° 0.0000 0.0004 0.046 0.045
6.67° 0.0005 0.0009 0.031 0.027
13.33° 0.0018 0.0020 -0.013 -0.018
20.00° 0.0029 0.0030 -0.078 -0.082
26.67° 0.0024 0.0021 -0.155 -0.155
33.33° -0.0017 -0.0016 -0.234 -0.241
40.00° -0.0118 -0.0120 -0.307 -0.309
Location
Transverse Moments
at Central Section
Twisting Moments
at Support
SAP2000 6x6
Mesh Theoretical
SAP2000 6x6
Mesh Theoretical
0° -2099 -2090 -91 0
6.67° -1978 -2000 -359 -380
13.33° -1614 -1620 -698 -670
20.00° -1045 -1000 -982 -1000
26.67° -408 -430 -1183 -1240
33.33° 37 100 -1248 -1290
Figure 16-2
88

E x a m p l e 1 7
Hemispherical Shell — Static Loads
Description
This is a hemispherical shell loaded by point loads at the edge as shown in Figure
17-1. The problem solved is identical to the one suggested in Reference [1].
• Three-dimensional shell analysis
Input Data
The computer model used is shown in Figure 17-1. An 8 x 8 mesh of Shell elements
is used on a quarter of the hemispherical shell. Symmetry is used to define the
boundary conditions. A single restraint in the vertical direction is applied at the cen-
ter of the free edge to provide stability.
The input data file for this example is SHELL.
The theoretical lower bound for the displacement under the load in the direction of
the load is 0.0924, where the hole at the center is not present. Reference [1] suggests
a value of 0.094 for comparison of results. The SAP2000 solution gives a value of
the displacement under the load of 0.0937. The comparison is excellent.
83
89

Reference
84
90

85
Example 17 Hemispherical Shell — Static Loads
Figure 17-1
Hemispherical Shell Example
91

E x a m p l e 1 8
Portal with P-delta
Description
These are two two-dimensional, one story, one bay, portal frames fixed at the base
as shown in Figure 18-1. One frame carries a central load of 1000 pounds and the
other carries an eccentric load of the same magnitude. The critical buckling load for
the frame in the symmetrical, non-sway mode is 6082 pounds (2 -1
D
?H =
255
2
2
. π
) and
in the asymmetrical, sway mode is 1784 pounds (2 -1
D
?H =
.748
2
2
π
). The purpose of
this example is to verify the adequacy of the P-Delta algorithm in SAP2000 for
these type of problems. Theoretical results for these problems can be derived using
the stability function approach. Tables for stability functions can be obtained from
References [1].
• P-Delta analysis of frameworks
87
93

Input Data
The two frames are modeled together in SAP2000 using Frame elements. The load-
ing is applied as span loads to the beams of the structures. Pound-inch units are
used.
The theoretical results are computed assuming no axial deformation and no shear
deformation in the members. To duplicate this behavior a large axial area is speci-
fied for the elements and the shear areas are defaulted as zero (program interprets
this to mean that the shear deformation is to be ignored.) It is important to note that
the axial deformations of the members were not forced to be zero by restraining or
constraining the joints. Setting the axial deformation to be zero in this manner also
sets the axial load in the member to be zero. This then completely eliminates the P-
Delta effect from that member.
For the P-Delta analysis the default value of the relative displacement tolerance
(.001) is used and the maximum number of iterations is set at 10 even though the so-
lution converges at a much lower number of iterations. All loads are in a single
Load case and this is used as the P-Delta load combination.
The input data for this example is PORTALPD.
The lateral displacement, joint rotation and member end-moment results for the two
load configurations are compared in Figure 18-2 with theoretical results and with
results for a model in which the P-Delta effect was ignored. The agreement between
the SAP2000 and theoretical results is excellent.
Theoretical values are obtained using the slope-deflection method of analysis by in-
cluding the effect of axial loads in members. In this case the stiffness and carry-over
factor of each member, instead of being constant, are functions of the axial load in
the member. These functions are tabulated in Reference [1].
It is interesting to study the effect of P-Delta for these frames. In the symmetrical
frame (central load), the decrease in the stiffness of the columns due to compressive
axial loads causes a decrease in the beam end moments (top column moments) but
increases the bottom column moments. For the asymmetrical frame (eccentric
load), the same effect is seen in the column that carries the larger axial load. How-
ever, the column with the lesser axial load is now comparatively stiffer and attracts
a larger moment at each end when P-Delta effects are considered.
88
94

Reference
1. Livesley, R. K., and Chandler, D. B.
Stability Functions for Structural Frameworks, Manchester University Press,
UK, 1956.
89
Example 18 Portal with P-delta
Figure 18-1
Portal Frame Example
95

90
QUANTITY
With P-Delta
Without
P-Delta
SAP2000 Theoretical
SAP2000 &
Theoretical
Rotation Joint 2 θ 0.09178 0.09192 0.08620
Moment Joint 1 ( M12 ) 4589.1 4606.6 4166.7
Moment Joint 2 ( M21 ) 8260.4 8254.0 8333.3
Shear Force ( F ) 128.5 128.6 125.0
Frame Under Central Load
QUANTITY
With P-Delta
Without
P-Delta
SAP2000 Theoretical
SAP2000
Theoretical
Lateral Displacement
∆
1.894 1.893 1.385
Rotation Joint 6 θ$ 0.1014 0.1013 0.0924
Rotation Joint 8 θ 0.0367 0.0367 0.0369
Moment Joint 5 ( M56 ) 2550.9 2544.9 2455.4
Moment Joint 6 ( M65 ) 6183.6 6088.6 6919.6
Moment Joint 7 ( M78 ) 4503.5 4456.9 3794.6
Moment Joint 8 ( M87 ) 6124.9 6153.0 5580.4
Shear Force ( F ) 101.6 101.4 93.75
Frame Under Eccentric Load
Figure 18-2
Comparison of Results for a Planar Rigid Portal Frame
96

E x a m p l e 1 9
Pounding of Two Planar Frames —
Nonlinear Time-History Analysis
Description
A two-bay, seven-story plane frame is linked to a one bay four story plane frame us-
ing Nllink Gap elements. The structure experiences pounding due to ground mo-
tion. El Centro 1940 (N-S) record is used in the nonlinear time history analysis.
The geometry of the structure is shown in Figure 19-1.
• Use of uniaxial Nllink gap elements
• Nonlinear time-history analysis
Input Data
A Diaphragm constraint is applied to each floor of the two frames. Kip-inch units
are used.
The joints at column line 3 are connected to the corresponding joints at column line
4 by Nllink Gap elements. The local 1 axes of these elements are in the global X di-
rection, and gap properties are specified for the local 1 direction. The opening dis-
91
97

placement for the gaps is 0.25 inches, corresponding to the distance between the
outer faces of the buildings.
The nonlinear gap stiffness was set to 1000 k/in, an estimate of the stiffness of a
tributary region around the point of contact. The linear effective stiffness, used for
calculating the modes, was set to zero, since the gap elements are normally open.
Care should be taken not to use values of nonlinear stiffness or linear effective stiff-
ness that are too large relative to the stiffness of connecting elements. Overly large
values of stiffness can cause numerical sensitivity, which can reduce the accuracy
and the efficiency of the solution.
The modes were calculated using Ritz vectors, with the ground acceleration and the
nonlinear deformation loads used as starting vectors. All eleven modes of the struc-
ture were requested.
The input data for this example is POUND. The time history of the ground accelera-
tion is given in file ELCN-THU
This example is included as a sample only. A typical results plot is shown in Figure
19-2. It shows the variations of displacement of Column lines 3 and 4 and the link
force at Story level 4. It can be clearly seen that the link force is generated whenever
the two column lines move in phase and their separation is less than the specified
initial opening or if they move towards each other out of phase. For most part the
pounding has the effect of keeping the buildings in phase. For display purposes the
displacements are scaled up by a factor of 100.
92
98

93
Example 19 Pounding of Two Planar Frames — Nonlinear Time-History Analysis
Figure 19-11
Geometry of Two Pounding Frames
99

94
Figure 19-2
Displacements of Pounding Columns and Pounding Force at Story 4
100

E x a m p l e 2 0
Friction-Pendulum Base-Isolated 3D Frame —
Nonlinear Time-History Analysis
Description
This is a two-story, three-dimensional frame with base isolation using friction-pen-
dulum base isolators. The structure is subjected to earthquake motion in two per-
pendicular directions using the Loma Prieta acceleration records.
The geometry of the structure is shown in Figure 20-1.
• Use of biaxial Nllink friction-pendulum elements
• Nonlinear quasistatic time-history analysis
• Nonlinear time-history analysis
Computer Model
The structure is modeled as a reinforced concrete frame with 9 column lines and 12
bays. Kip-inch units are used. The modulus of elasticity is taken to be 3000 ksi. The
self-weight of the concrete is taken as 150 pcf.
95
101

The floor slab is taken to be 8” thick covering all the specified floor bays at the base
and the 1st story levels. At the second story level the corner column as well as the
two edge beams are eliminated together with the floor slab to render this particular
level unsymmetric as depicted in Figure 20-1. A diaphragm constraint is applied to
each story. The floor slab is modeled with Shell Membrane elements. These are
used for the purpose of generating mass only; their stiffness is ignored due to the
diaphragm Constraints.
Friction-pendulum type base isolators of the type described in Reference [1] are
modeled using the SAP2000 Nllink Isolator2 elements.
The isolator properties are defined as follows:
Stiffness in direction 1 (vertical) 1E3
Stiffness in directions 2 and 3 (horizontal) 1E2
Coefficient of friction at fast speed .04
Coefficient of friction at slow speed .03
Parameter determining the variation
of the coefficient of friction with velocity 20
Radius of contact surface in directions 2 and 3 60
A single Load case is defined that models the self-weight of the structure. This will
be applied before the seismic analysis in order to generate the proper frictional re-
sponse in the isolators. This self-weight must be applied as part of the time-history
analysis, as described below.
Seventeen Ritz vectors are requested for the modal analysis, using the two horizon-
tal ground accelerations, the gravity load, and all the nonlinear deformation loads as
the starting load vectors. There are 27 nonlinear deformation loads, one for each of
the three translational degrees of freedom for the nine isolators. However, only
three of the 18 horizontal degrees of freedom are independent due to the diaphragm
constraint. The program will automatically discard 15 dependent starting load vec-
tors. Thus the total number of independent starting load vectors is 15. By listing the
two ground accelerations as first, two Ritz vectors are generated for these two start-
ing load vectors, and one for each of the remaining 13, for a total of 17 modes.
It is very important that the nonlinear deformation loads be used as starting load
vectors in order to capture nonlinear behavior. In this case, the axial load in each
isolator must be adequately modeled since the shear force depends strongly upon it.
Two time-history analyses are performed. The first history applies the self-weight
quasistatically. This history consists of 10 time steps of one second, for a total time
of 10 seconds. The load is increased linearly to full value for the first five seconds,
96
102

and allowed to come to equilibrium for the remaining five seconds. A damping
value of 99% is used for all modes to prevent vibration.
The second history starts from the first history, and applies the seismic acceleration.
This history consists of 2000 time steps of 0.02 seconds, for a total time of 40 sec-
onds. Zero damping is used for all modes since most energy dissipation is expected
to be due to the friction properties of the isolators, with little damage occuring in the
superstructure.
The input data file for this example is ISOLAT2 and the input time history files are
LP-TH0 and LP-TH90.
This example is included as a sample only. No results are available for comparison.
Typical plots are shown for the seismic time history. Figure 20-2 shows the time
variation of input, kinetic, potential (strain), damping, and frictional energies; these
energies do not start at zero since they continue from the self-weight time history.
Figure 20-3 shows the time variation of the displacements of the second floor at
Column line 1. Figure 20-4 shows the interaction diagram for the two shear forces
in the isolator beneath Column line 1. Figure 20-5 shows the force-displacement
plot for motion in the X direction of the isolator beneath Column line 1.
References
1. Zayas, V. and Low, S.
“A Simple Pendulum Technique for Achieving Seismic Isolation,” Earthquake
Spectra, Vol. 6, No. 2, Earthquake Engineering Research Institute, Oakland,
California,1990.
97
Example 20 Friction-Pendulum Base-Isolated 3D Frame — Nonlinear Time-History Analysis
103

98
Figure 20-1
Model of Friction-Pendulum Base-Isolated 3-D Frame
104

99
Example 20 Friction-Pendulum Base-Isolated 3D Frame — Nonlinear Time-History Analysis
Figure 20-2
Variation of Energy during Seismic History
Figure 20-3
Horizontal Displacements at Top of Column 1 during Seismic History
105

100
Figure 20-4
Shear Force Interaction in Isolator under Column 1 during Seismic History
Figure 20-5
Shear Force vs. Deformation in Isolator under Column 1 during Seismic History
106

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